JP6820568B2 - Communication equipment, communication methods and integrated circuits - Google Patents

Description

The present invention relates to an apparatus and method for determining a transmission timing of direct link data transmission in a D2D communication system. More specifically, the present invention relates to user equipment capable of operating in an inter-device (D2D) communication system and capable of performing the methods of the present invention.

Long Term Evolution (LTE: Long Term Evolution)
Third-generation mobile communication systems (3G) based on WCDMA® wireless access technology are being deployed on a wide scale around the world. High-Speed Downlink Packet Access (HSDPA) and High-Speed Uplink Packet Access (HSUPA) are the first steps in enhancing, developing, and evolving this technology. Packet Access)) has been introduced, which provides extremely competitive wireless access technology.

To meet the ever-increasing demand from users and to be competitive with new wireless access technologies, 3GPP has introduced a new mobile communication system called Long Term Evolution (LTE). LTE is designed to meet carrier demand for high-speed data and media transmission and high-capacity voice support over the next decade. The ability to provide high bitrates is an important strategy in LTE.

Work item (WI) specifications for LTE (Long Term Evolution) include E-UTRA (Evolved UMTS Terrestrial Radio Access (UTRA)) and E-UTRAN (Evolved UMTS Terrestrial Radio Access Network (UTRAN)). : Evolved UMTS Radio Access Network), and will eventually be released as Release 8 (LTE Release 8). The LTE system is a packet-based efficient radio access and radio access network that provides all IP-based functionality at low latency and low cost. Detailed system requirements are described in [3]. In LTE, multiple scalable transmit bandwidths (eg, 1.4 MHz, 3.0 MHz, 5.0 MHz, 10.0 MHz, 15.0 MHz, etc., are used to achieve flexible system deployments using a given spectrum. And 20.0 MHz) is specified. Radio access based on OFDM (Orthogonal Frequency Division Multiplexing) is adopted for the downlink. This is because such radio access is inherently less susceptible to multipath interference (MPI) due to its low symbol rate, uses cyclic prefixes (CP), and supports a variety of transmit bandwidth configurations. Because it is possible. For the uplink, wireless access based on SC-FDMA (Single-Carrier Frequency Division Multiple Access) is adopted. This is because, considering that the transmission output of the user equipment (UE: User Equipment) is limited, it is prioritized to provide a wide coverage area rather than improving the peak data rate. Release 8 LTE employs a number of major packet radio access technologies (eg MIMO (Multiple Input Multioutput) Channel Transmission Technology) to achieve a highly efficient control signaling structure.

LTE and E-UTRAN Architecture Figure 1 shows the LTE overall architecture, and FIG. 2 shows the E-UTRAN architecture in more detail.

As can be seen from FIG. 1, the LTE architecture supports interconnecting multiple different radio access networks (RANs) such as UTRAN and GERAN (GSM® EDGE Radio Access Network). The RAN is connected to the EPC via a Serving GPRS Support Node (SGSN). In a 3GPP mobile communication network, a mobile terminal 110 (also called a User Equipment, UE, or device) has a NodeB (NB) in UTRAN and an evolved NodeB (eNB: evolved NodeB) in E-UTRAN access. Attached to the access network via. The entities NB and eNB 120 are known as base stations in other mobile communication networks. Two data packet gateways (serving gateway (SGW) 130 and packet data network gateway 160 (PDN-GW or simply PGW)) are located within the EPS to support the mobility of the user equipment. There is. Assuming E-UTRAN access, the entity eNB 120 is connected to one or more SGWs via a S1-U interface (“U” stands for “user plane”) via a wired line and also S1-MMME. It is connected to the mobility management entity 140 (MME) via an interface via a wired line. The SGSN 150 and MME 140 are also referred to as serving core network (CN) nodes.

As shown in FIG. 2, the E-UTRAN is composed of an evolved NodeB (eNB) 120, and the eNB 120 is a user plane (PDCP / RLC / MAC / PHY) of the E-UTRA toward the user equipment (UE). And terminate the control plane (RRC) protocol. The eNB 120 includes a physical (PHY) layer, a medium access control (MAC) layer, a wireless link control (RLC) layer, and a packet data control protocol (PDCP) layer (these layers are user plane header compression and encryption functions. Includes). In addition, the eNB 120 provides radio resource control (RRC) functionality corresponding to the control plane. The eNB 120 provides radio resource management, admission control, scheduling, negotiated uplink QoS (quality of service) implementation, cell information broadcasting, user plane data and control plane data encryption / decryption, downlink / uplink. Performs many functions such as compression / decompression of user plane packet headers.

A plurality of eNBs are connected to each other by an X2 interface. Furthermore, the eNB is also connected to the EPC (Evolved Packet Core) by the S1 interface, and more specifically, it is connected to the MME (Mobility Management Entity) by the S1-MME. , S1-U is connected to the serving gateway (S-GW: Serving Gateway). The S1 interface supports a many-to-many relationship between the MME / serving gateway and the eNB. While routing and forwarding user data packets, the SGW acts as a mobility anchor for the user plane during handover between eNodeBs, and also an anchor for mobility between LTE and another 3GPP technology (S4). It terminates the interface and acts as a relay for traffic between the 2G / 3G system and the PDN GW). The SGW terminates the downlink data path for the idle user device and triggers paging when the downlink data arrives at the user device. The SGW manages and stores the context of the user equipment (eg, IP bearer service parameters, network internal routing information). In addition, the SGW performs duplication of user traffic in the case of lawful interception.

The MME 140 is the main control node of the LTE access network. The MME is responsible for tracking and paging procedures (including retransmissions) of user equipment in idle mode. The MME is involved in the bearer activation / deactivation process and also selects the SGW of the user equipment during the initial attachment and during the in-LTE handover with the relocation of the core network (CN) node. Also plays a role in The MME is responsible for authenticating the user (by interacting with the HSS). Non-Access Stratum (NAS) signaling is terminated in the MME, which also plays a role in generating a temporary ID and assigning it to the user device. The MME checks the authentication of the user equipment to enter the service provider's Public Land Mobile Network (PLMN) and enforces roaming restrictions on the user equipment. The MME is the end point in the network in the encryption / integrity protection of NAS signaling and manages the security key. Legal interception of signaling is also supported by MME. In addition, the MME provides a control plane function for mobility between the LTE access network and the 2G / 3G access network, terminating the S3 interface from the SGSN. In addition, the MME terminates the S6a interface towards the home HSS for roaming user equipment.

Component Carrier Structure in LTE FIGS. 3 and 4 show the structure of the component carrier in LTE. The downlink component carriers of the 3GPP LTE system are further divided in the time-frequency domain in the so-called subframe. In 3GPP LTE, each subframe is divided into two downlink slots as shown in FIG. 3, where the first downlink slot provides a control channel area (PDCCH area) within the first OFDM symbol. Be prepared. Each subframe consists of a given number of OFDM symbols in the time domain (12 or 14 OFDM symbols in 3GPP LTE (Release 8)), and each OFDM symbol extends over the bandwidth of the component carrier. Therefore, each OFDM symbol is composed of several modulation symbols transmitted by each subcarrier of N ^DL _RB × N ^RB _sc , as also shown in FIG.

For example, assuming a multi-carrier communication system that uses OFDM, for example, as used in 3GPP Long Term Evolution (LTE), the smallest unit of resources that can be allocated by the scheduler is one "resource block". .. A physical resource block is defined as N ^DL _symb contiguous OFDM symbols in the time domain and N ^RB _sc contiguous subcarriers in the frequency domain, as illustrated in FIG. Therefore, in 3GPP LTE (Release 8), the physical resource block consists of N ^DL _simb x N ^RB _sc resource elements corresponding to one slot in the time domain and 180 kHz in the frequency domain (for downlink resource grids). Further details are described, for example, in Section 6.2 of Non-Patent Document 1, which is available on the 3GPP website and is incorporated herein by reference).

Even if a resource block or resource block pair is scheduled, it is possible that some resource elements in it will not be used, but to simplify the terminology used, the entire resource block or resource block pair It shall be assigned. Examples of resource elements that are not actually assigned by the scheduler are reference signals, broadcast signals, synchronization signals, various control signals, or resource elements used for channel transmission.

The number of physical resource blocks in the downlink is determined by the downlink transmission bandwidth set in the cell, and is currently defined in LTE as 6 to 110 (physical) resource blocks ((P) RB). Has been done. In LTE, it is customary to express the bandwidth in Hz (eg 10 MHz) or resource block units, for example in the case of downlink, the cell bandwidth can be expressed in, for example, 10 MHz.

A channel resource can be defined as a "resource block" as exemplified in FIG. 4, and in FIG. 4, a multi-carrier communication system that employs OFDM, for example, as discussed in the LTE work item of 3GPP. Is assumed. More generally, a resource block can be assumed to represent the smallest resource unit in a mobile communication wireless interface that can be allocated by the scheduler. The dimensions of the resource block are time (eg, time slot, subframe, frame, etc. in time division multiplexing (TDM)), frequency (eg, subband, carrier frequency, etc. in frequency division multiplexing (FDM)). ), Code (eg, diffusion code in the case of code division multiplexing (CDM)), antenna (eg, multi-input, multi-output (MIMO)), and any other combination, which is used in mobile communication systems. It depends on the access method.

Data is mapped to physical resource blocks by a pair of virtual resource blocks. A pair of virtual resource blocks is mapped to a pair of physical resource blocks. Two types of virtual resource blocks are defined according to the mapping method to physical resource blocks in the LTE downlink, that is, a localized virtual resource block (LVRB) and a distributed virtual resource block (DVRB). Resource Block). In local transmit modes that use local VRBs, the eNB has full control over which resource blocks are used and how much, and usually uses this control when selecting resource blocks that result in higher spectral efficiency. .. In most mobile communication systems, this results in the use of adjacent physical resource blocks or clusters of adjacent physical resource blocks for transmission to a single user device. This is because the radio channel is coherent in the frequency domain, that is, if one physical resource block provides high spectral efficiency, it is likely that adjacent physical resource blocks will also have high spectral efficiency as well. .. In a distributed transmission mode using a distributed VRB, a physical resource block that conveys data to the same user equipment so that frequency diversity can be obtained by using at least some physical resource blocks that provide sufficiently high spectral efficiency. Is dispersed over the frequency band.

In 3GPP LTE Release 8, downlink control signaling is basically transmitted by the following three physical channels.
Physical control format indicator channel (PCFICH) that indicates the number of OFDM symbols used for control signaling in a subframe (ie, the size of the control channel area).
Physical hybrid ARQ indicator channel (PHICH) that conveys the downlink ACK / NACK associated with uplink data transmission.
Physical downlink control channel (PDCCH) that conveys downlink scheduling quotas and uplink scheduling quotas.

PCFICH is transmitted from a known location within the control signaling domain of the downlink subframe using a known pre-defined modulation and coding scheme. The user equipment decodes the PCFICH in order to obtain information about the size of the control signaling region in the subframe (eg, the number of OFDM symbols). If the user equipment (UE) cannot decode PCFICH, or if an incorrect PCFICH value is obtained, the L1 / L2 control signaling (PDCCH) included in the control signaling area cannot be correctly decoded, resulting in As all resource allocations contained in the PDCCH can be lost.

The PDCCH conveys control information (eg, a scheduling grant that allocates resources for downlink data transmission or uplink data transmission). PDCCH to the user equipment is transmitted with the first one, two, or three OFDM symbols according to the PCFICH in the subframe.

Physical downlink shared channels (PDSCHs) are used to convey user data. The PDSCH is mapped to the remaining OFDM symbols following the PDCCH in one subframe. The PDSCH resource assigned to one user device has a resource block of each subframe as a unit.

A physical uplink shared channel (PUSCH) conveys user data. The physical uplink control channel (PUCCH) is an uplink direction signaling (eg, scheduling request, HARQ acknowledgment (ACK) and negative response (NACK) in response to PDSCH data packets, channel state information. (CSI: channel state information), etc.).

The term "component carrier" refers to a combination of several resource blocks. In future releases of LTE, the term "component carrier" will no longer be used, and instead the terminology will be changed to "cell" to indicate a combination of downlink and optionally uplink resources. The link between the carrier frequency of the downlink resource and the carrier frequency of the uplink resource is indicated in the system information transmitted by the downlink resource.

Further development of LTE (LTE-A)
At the World Radiocommunication Conference 2007 (WRC-07), the frequency spectrum of IMT-Advanced was determined. Although the overall frequency spectrum for IMT-Advanced has been determined, the actual available frequency bandwidth will vary by region and country. However, following the determination of the outline of the available frequency spectrum, the standardization of wireless interfaces has begun in the 3GPP (3rd Generation Partnership Project). At 3GPP TSG RAN # 39 meeting, the description of the items to be examined regarding "Further Advancements for E-UTRA (LTE-Advanced)" was approved. This study item covers the technical elements that should be considered in the evolution and development of E-UTRA (for example, to meet the requirements of IMT-Advanced). In the following, two important technical elements currently under consideration for LTE-A will be described.

Carrier Aggregation in LTE-A to Support Wider Bandwidth The LTE Advanced System can support 100 MHz, while the LTE System can only support 20 MHz. Today, the lack of a wireless spectrum has become a bottleneck in the development of wireless networks, and as a result, it is difficult to find a sufficiently wide spectral band for LTE advanced systems. Therefore, there is an urgent need to find a way to obtain a wider radiospectral band, where a possible answer is carrier aggregation.

In carrier aggregation, two or more component carriers (CCs) are aggregated to support a wide transmit bandwidth of up to 100 MHz. In LTE-Advanced systems, several cells in the LTE system are aggregated into one wider channel, which channels are wide enough for 100 MHz even if these cells in LTE are in different frequency bands. .. The user device can simultaneously receive or transmit one or more component carriers (CCs) depending on their capabilities as follows.
-Release 10 user equipment with receive and / or transmit capability for carrier aggregation (CA) simultaneously receives and transmits on multiple component carriers (CC) corresponding to multiple serving cells. , Or both can be done.
-LTE release 8/9 user equipment can receive on one component carrier (CC) corresponding to only one serving cell and transmit on one component carrier (CC).

Carrier aggregation (CA) is supported for both continuous and discontinuous component carriers, with each component carrier using up to 110 frequency domains using Release 8/9 numerology. Limited to resource blocks.

It is possible to configure user equipment to aggregate different numbers of component carriers with different bandwidths on the uplink and downlink, which are transmitted from the same eNodeB (base station). is there. The number of downlink component carriers that can be configured depends on the downlink aggregation capability of the user equipment. Conversely, the number of uplink component carriers that can be configured depends on the uplink aggregation capabilities of the user equipment. Mobile terminals cannot be configured to have more uplink component carriers than downlink component carriers.

In a typical TDD deployment, the number of component carriers and the bandwidth of each component carrier is the same for the uplink and downlink. Component carriers transmitted from the same eNodeB do not necessarily have to provide the same coverage.

The component carrier is LTE Release 8/9 compatible. However, existing mechanisms (eg, barring) can be used to prevent the release 8/9 user equipment from camping on the component carrier.

The distance between the center frequencies of the continuously aggregated component carriers is a multiple of 300 kHz. This is to maintain compatibility with the 100 kHz frequency raster of 3GPP LTE (Release 8/9) while maintaining the orthogonality of the subcarriers at 15 kHz intervals. Depending on the aggregation scenario, n × 300 kHz spacing can be facilitated by inserting a small number of unused subcarriers between successive component carriers.

The effect of aggregating multiple carriers is only on the MAC layer. The MAC layer requires one HARQ entity for each component carrier to be aggregated, both uplink and downlink. (When SU-MIMO in the uplink is not used) The maximum number of transport blocks per component carrier is one. The transport block and its HARQ retransmissions need to be mapped to the same component carrier.

5 and 6 show a layer 2 structure with carrier aggregation set in the downlink and uplink, respectively. There is a transport channel between the MAC and the first layer (layer 1), and a logical channel between the MAC and the RLC.

When carrier aggregation (CA) is configured, the user equipment has only one RRC connection with the network. During RRC connection establishment / reestablishment / handover, one serving cell provides non-access layer mobility information (eg, tracking area identifier (TAI)), and during RRC connection reestablishment / handover, one serving cell Provide security input. This cell is referred to as the primary cell (PCell). The carrier corresponding to PCell is the downlink primary component carrier (DL PCC) in the downlink and the uplink primary component carrier (UL PCC) in the uplink.

Depending on the capabilities of the user equipment, the secondary cell (SCell) can be set to form a set of serving cells in combination with the PCell. The carrier corresponding to SCell is the downlink secondary component carrier (DL SCC) in the downlink and the uplink secondary component carrier (UL SCC) in the uplink.

Therefore, the set of serving cells set for the user equipment always consists of one PCell and one or more SCells.
− Each SCell can be configured to use uplink resources by user equipment in addition to downlink resources. Therefore, the number of DL SCCs configured is always greater than or equal to the number of UL SCCs, and the SCell cannot be configured to use only uplink resources.
-From the user equipment point of view, each uplink resource belongs to only one serving cell.
-The number of serving cells that can be set depends on the aggregation capability of the UE.
-PCells can only be modified by handover procedures (ie, security key changes and RACH procedures).
-PCell is used to transmit PUCCH.
-PCells, unlike SCells, cannot be deactivated.
-Reestablishment is triggered when Rayleigh fading (RLF) occurs in PCell, but reestablishment is not triggered when Rayleigh fading (RLF) occurs in SCell.
-Non-access layer (NAS) information is obtained from the downlink PCell.

Component carriers can be set and reconfigured by RRC. Activation and deactivation are done via MAC control elements. During intra-LTE handover, the RRC can also add, remove, or reconfigure SCells for use in the target cell. Reconfiguration, addition, and deletion of SCell can be performed by RRC. During the in-LTE handover, the RRC can also add, delete, or reconfigure the SCell to be used with the PCell in the destination cell. When adding a new SCell, dedicated RRC signaling is used to send all the required system information for that SCell (in connection mode), and the user equipment needs to get the system information to be broadcast directly from the SCell. Absent.

When the user equipment is configured to use carrier aggregation, the pair of uplink component carriers and downlink component carriers is always active. The downlink component carrier of this pair is sometimes referred to as the "downlink anchor carrier". The same is true for uplinks.

When carrier aggregation is set, user equipment can be scheduled for multiple component carriers at the same time, but only one random access procedure can be performed at a time. In cross-carrier scheduling, the PDCCH of a component carrier allows the resources of another component carrier to be scheduled. For this purpose, a component carrier identification field (referred to as "CIF") has been introduced in each DCI format.

By linking the uplink component carrier and the downlink component carrier when cross-carrier scheduling is not performed, the uplink component carrier to which the grant is applied can be identified. The link of the downlink component carrier to the uplink component carrier does not necessarily have to be one-to-one. In other words, multiple downlink component carriers can be linked to the same uplink component carrier. On the other hand, one downlink component carrier can be linked to only one uplink component carrier.

RRC states in LTE In the following, the two main states in LTE, "RRC_IDLE" and "RRC_CONNECTED", will be mainly described.

In RRC_IDLE mode, radio is not enabled, but IDs are assigned and tracked by the network. More specifically, the mobile terminal in RRC_IDLE mode performs cell selection and reselection (in other words, determines which cell to camp on). In the cell (re) selection process, the priority of each applicable frequency of each applicable radio access technology (RAT), the quality of the radio link, and the status of the cell (ie, whether the cell is banned or reserved) are Will be considered. The mobile terminal in the RRC_IDLE mode monitors the paging channel to detect an incoming call and further acquires system information. The system information mainly consists of parameters that allow the network (E-UTRAN) to control the (re) selection process of the cell. The RRC specifies control signaling, i.e. paging and system information, applied to mobile terminals in RRC_IDLE mode. The behavior of the mobile terminal in the RRC_IDLE mode is defined in, for example, Section 8.4.2 of Non-Patent Document 2 (incorporated herein by reference).

In the RRC_CONNECTED state, the mobile terminal has an active radio operation with the eNodeB. In E-UTRAN, wireless resources are allocated to mobile terminals so that (unicast) data can be transmitted over a shared data channel. To support this behavior, mobile terminals monitor the corresponding control channels used to indicate the dynamic allocation of shared transmit resources for time and frequency. The mobile terminal provides the network with a report of its buffer status and downlink channel quality and measurement information of adjacent cells so that E-UTRAN can select the most suitable cell for the mobile terminal. These measurement reports include cells that use different frequencies or radio access technology (RAT). Further, the user equipment receives system information mainly composed of the information required to use the transmission channel. User equipment in the RRC_CONCEPTED state can be configured to use a Discontinuous Reception (DRX) cycle to extend the life of its battery. RRC is a protocol for E-UTRAN to control the behavior of a user device in the RRC_CONNECTED state.

Uplink access method in LTE Uplink transmission requires highly power-efficient transmission by a user terminal in order to maximize coverage. As the uplink transmission method of E-UTRA, a method that combines single carrier transmission and FDMA with dynamic bandwidth allocation is selected. The main reason for choosing single-carrier transmission is that it has a lower peak-to-average power ratio (PAPR) compared to multi-carrier signals (OFDMA), which in turn improves power amplifier efficiency and coverage. This is because it is expected (the data rate is high with respect to the given terminal peak power). At each time interval, NodeB allocates the user a unique time / frequency resource for transmitting user data, which ensures orthogonality within the cell. Orthogonal multiple access on the uplink increases spectral efficiency by eliminating in-cell interference. Interference caused by multipath propagation is dealt with in the base station (NodeB) by inserting a cyclic prefix in the transmission signal.

The basic physical resource used to transmit the data consists of a frequency resource of size BW _grant over one time interval (eg, 0.5 ms subframe) (encoded information bits are this resource). Mapped to). The subframe (also referred to as transmission time interval (TTI)) is the minimum time interval for transmitting user data. However, by concatenating the subframes, it is also possible to allocate the frequency resource BW _grant to the user for a time longer than 1 TTI.

Uplink Scheduling Method in LTE As the uplink method, both scheduling controlled (ie, controlled by eNB) access and contention-based access can be used.

In the case of scheduled controlled access, a specific frequency resource (ie, time / frequency resource) of a specific time length for transmitting uplink data is allocated to the user equipment. However, some time / frequency resources can be allocated for contention-based access. Within the contention-based time / frequency resources, the user equipment can transmit without being initially scheduled. One scenario in which a user device makes contention-based access is, for example, random access, that is, when the user device makes the first access to a cell, or to request an uplink resource. It's time to do it.

For scheduled controlled access, the NodeB scheduler allocates unique frequency / time resources to the user for uplink data transmission. More specifically, the scheduler determines:
-User equipment (s) that allow transmission-Physical channel resource (frequency)
-Transport format that mobile terminals should use for transmission (Modulation Coding Scheme (MCS))

The allocation information is signaled to the user equipment via the scheduling grant sent on the L1 / L2 control channel. In the following, for the sake of brevity, this channel will be referred to as an uplink grant channel. The scheduling grant message contains at least information about the portion of the frequency band that the user equipment is allowed to use, the validity period of the grant, and the transport format that the user equipment must use for the upcoming uplink transmission. .. The shortest validity period is one subframe. Grant messages can also include additional information depending on the method selected. Only grants "for each user device" are used as grants granting the right to transmit on the uplink shared channel (UL-SCH) (ie, there is no grant "for each radio bearer in each user device"). .. Therefore, the user equipment needs to allocate the allocated resources among the radio bearers according to some rules (discussed in detail in one of the following sections). Unlike the case of HSUPA, the transport format is not selected on the user equipment side. The eNB determines the transport format based on some information (eg, reported scheduling information and QoS information), and the user equipment must follow the selected transport format.

Procedure for buffer status report / scheduling request in uplink scheduling The normal mode of scheduling is dynamic scheduling, which consists of a downlink allocation message that allocates a downlink transmit resource and an uplink grant message that allocates an uplink transmit resource. .. These messages are usually valid during one particular subframe. These messages are transmitted on the PDCCH using the user device C-RNTI, as already described above. Dynamic scheduling is efficient for service types where the traffic is bursty and the speed is dynamic (such as TCP).

In addition to dynamic scheduling, persistent scheduling is defined, in which the radio resources are set semi-statically for users over a period of more than one subframe. Since it can be assigned to a device, the need for a specific downlink allocation message or uplink grant message through the PDCCH for each subframe is avoided. Persistent scheduling is useful for services such as VoIP where data packets are small, periodic, and nearly constant in size. The PDCCH overhead is significantly reduced compared to dynamic scheduling.

Buffer status reporting (BSR) from the user equipment to the eNB is used to assist the eNodeB in allocating uplink resources (ie, the uplink scheduling described in detail in [2]). In the case of downlink, the eNB scheduler naturally recognizes the amount of data delivered to each user device. However, in the uplink direction, the scheduling decision is made in the eNB, but since the data buffer is in the user equipment, it is buffered from the user equipment to the eNB to indicate the amount of data that needs to be transmitted through UL-SCH. A status report (BSR) must be sent.

In LTE, basically two types of buffer status reports (BSR) are defined, a long BSR and a short BSR. Which buffer status report (BSR) the user device sends is triggered by the available transmit resources in the transport block, the number of groups of logical channels with non-empty buffers, and certain events at the user device. It depends on what is done. The long BSR reports the amount of data in the four logical channel groups, while the short BSR shows the amount of data stored in the buffer for only the highest logical channel group. The reason for introducing the concept of the logical channel group is that when five or more logical channels are set in the user equipment, reporting the buffer state of each logical channel increases the signaling overhead too much. Therefore, the eNB assigns each logical channel to a logical channel group. Preferably, logical channels with the same or similar QoS requirements should be assigned to the same logical channel group.

Whether a short BSR or a long BSR is transmitted by the user equipment is triggered by the available transmit resources in the transport block, the number of groups of logical channels with non-empty buffers, and certain events at the user equipment. It depends on the resource. The long BSR reports the amount of data in the four logical channel groups, while the short BSR shows the amount of data stored in the buffer for only the highest logical channel group.

The reason for introducing the concept of the logical channel group is that when five or more logical channels are set in the user equipment, reporting the buffer state of each logical channel increases the signaling overhead too much. Therefore, the eNB assigns each logical channel to a logical channel group. Preferably, logical channels with the same or similar QoS requirements should be assigned to the same logical channel group.

The buffer status report (BSR) can be triggered, for example, in the case of the next event.
-When the data of a logical channel with a higher priority than the logical channel whose buffer is not empty arrives-In one of the logical channels, the data is available from the state where there was no data to be transmitted before. When-When the retransmission BSR timer expires-When the timing of periodic BSR reporting comes (that is, when the peripheral BSR timer expires)
-When there is extra space in the transport block to store the BSR

To increase the robustness against transmission failures, LTE defines a buffer status report (BSR) retransmission mechanism. When the uplink grant is received, the retransmission BSR timer is activated or restarted. If no uplink grant is received before this timer expires, the user device will trigger the buffer status report again.

When a buffer status report (BSR) is triggered, if the user equipment does not have an uplink resource allocated to include the buffer status report in the transport block (TB), the user equipment will be on the PUCCH (Physical Uplink Control Channel). ) (If set) to send a scheduling request (SR: scheduling request). If the configured PUCCH does not have a dedicated Scheduling request (D-SR) resource, the user device requests a UL-SCH resource to send buffer status report (BSR) information to the eNB. Random access procedure (RACH procedure) is started. However, it should be noted that when transmitting a periodic buffer status report (BSR), the user equipment does not trigger the transmission of a scheduling request (SR).

In addition, scheduling request (SR) transmission enhancements have been introduced in certain scheduling modes, allowing resources to persist at predetermined intervals to save the overhead of L1 / L2 control signaling for transmit grants. Assigned (to persistent) (referred to as semi-persistent scheduling (SPS)). An example of a service that is primarily considered for semi-persistent scheduling is VoIP. During the talk-spurt, the codec generates VoIP packets every 20ms. Therefore, the eNodeB can permanently allocate (persistently) uplink resources or downlink resources every 20 ms and can use these resources to send VoIP packets. Typical semi-persistent scheduling (SPS) benefits in services where traffic behavior can be predicted (ie, the bit rate is constant and packet arrival timing is periodic). If semi-persistent scheduling (SPS) is configured in the uplink direction, the eNodeB can turn off scheduling request (SR) triggering / transmission for a particular logical channel configured, i.e., these. Even if the BSR is triggered by the arrival of data on a specific configured logical channel, the scheduling request (SR) is not triggered. The reason for this type of enhancement is that sending a scheduling request (SR) for a logical channel (a logical channel that carries VoIP packets) that uses resources allocated (semi-permanently) to a semi-persistent is an eNB. It makes no sense in scheduling and should therefore be avoided.

Further details regarding the buffer status reporting (BSR) procedure (particularly the triggering of the buffer status reporting procedure) are described in Chapter 5.4.5 of Non-Patent Document 3 (incorporated herein by reference). ..

Logical channel prioritization The user equipment has an uplink transmission speed control function that manages the sharing of uplink resources among a plurality of wireless bearers. Hereinafter, this uplink transmission speed control function is also referred to as a logical channel prioritization procedure. The logical channel prioritization (LCP) procedure is applied when a new transmission is made, i.e. when a transport block needs to be generated. One proposed method for allocating capacity allocates resources to each bearer in order of priority until each bearer receives an allocation corresponding to its minimum data rate, if more capacity is available. , Assign it to bearers, for example in order of priority.

The logical channel prioritization (LCP) procedure belonging to the user equipment is based on the token bucket model, which is well known in the IP world, as will become clear from the later explanation of the logical channel prioritization (LCP) procedure. It will be carried out. The basic functions of the token bucket model are as follows. Tokens representing the right to send a certain amount of data are periodically added to the bucket at a particular rate. When resources are allocated to a user device, they are allowed to send up to the amount represented by the number of tokens in the bucket. When transmitting data, the user device deletes a number of tokens corresponding to the amount of data transmitted. If the bucket is full, more tokens will be destroyed. Regarding the addition of tokens, the iteration cycle of this process can be assumed to be every TTI, but it is also easy to lengthen this cycle so that tokens are added every second. Basically, instead of adding tokens to the bucket every 1ms, you can add 1000 tokens every second. The logical channel prioritization (LCP) procedure used in Release 8 is described below. Further details of the logical channel prioritization (LCP) procedure are described in Section 5.4.3.1 of Non-Patent Document 4 (incorporated herein by reference).

The RRC controls the scheduling of uplink data by signaling each logical channel. In this signaling, the higher the value of priority, the lower the priority level. The preferred Bit Rate sets a preferred bit rate (PBR: Prioritized Bit Rate). BucketSizeDuration sets the bucket size duration (BSD). The idea behind the preferred bitrate is to support a minimum bitrate for each bearer (including low priority bearers with unguaranteed bitrates (non-GBR)) to avoid resource shortages. That is. Each bearer must at least acquire sufficient resources to achieve a preferred bit rate (PBR).

The user device maintains a variable B _j for each logical channel j. B _j is initialized to 0 when the associated logical channel is established, and is incremented by the product PBR × TTI time length for each TTI (PBR is the preferred bit rate of the logical channel j). However, the value of B _j can not exceed the bucket size, the value of B _j is larger than the bucket size of logical channel j, the value of B _j is set to the bucket size. The bucket size of the logical channel is equal to the preferred bit rate (PBR) x bucket size period (BSD), and the preferred bit rate (PBR) and bucket size period (BSD) are set by the upper layer.

When performing a new transmission, the user equipment performs the following logical channel prioritization procedure.
− The user equipment allocates resources to the logical channel in the following steps.
○ Step 1: Allocate resources to all logical channels for which B _j > 0 in descending order of priority. If the radio bearer's preferred bit rate (PBR) is set to "infinity," the user equipment allocates resources for all data available on that wireless bearer and then has a lower priority. Meet the preferred bit rate (PBR) of the radio bearer (s).
○ Step 2: The user equipment reduces B _j by the total size of the MAC SDU used for the logical channel j in step 1.
Note at this point, it should be noted that the value of B _j can be negative.
○ Step 3: If any resources remain, all logical channels, allocating resources in a strict descending order of priority (regardless of the value of B _j), the data for that logical channel is eliminated or up, Continue until either the Link Grant is exhausted. Logical channels set to the same priority shall be assigned equally.
− In addition, the user equipment also follows the following rules during the above scheduling procedure.
○ If the entire RLC SDU (or SDU that is partially transmitted or RLC PDU that is retransmitted) fits in the remaining resources, the user equipment is that RLC SDU (or SDU that is partially transmitted or retransmitted). RLC PDU) should not be split.
○ When dividing the RLC SDU from the logical channel, the user equipment maximizes the size of the segment so that the grant is used as much as possible.
○ User equipment should maximize the transmission of data.
In the logical channel prioritization procedure, the user equipment considers the following relative priorities in descending order.
-Data from C-RNTI MAC control element or UL-CCCH-MAC control element of buffer status report (BSR) (excluding BSR included for padding)
-MAC control elements of power headroom reporting (PHR) -Data from logical channels (excluding data from UL-CCCH)
-MAC control element of buffer status report (BSR) included for padding

In the case of carrier aggregation (described in the previous section), when the user equipment is required to send multiple MAC PDUs during one TTI, steps 1-3 and related rules apply independently to each grant. Or can be applied to the total capacity of grants. Furthermore, the order in which grants are processed is also left to the implementation of the user equipment. When a user device is required to transmit multiple MAC PDUs during one TTI, it is up to the user device implementation to decide which MAC PDU should include the MAC control element.

Uplink power control Uplink transmission power control in mobile communication systems has an important purpose. Uplink transmit power control minimizes the need to transmit sufficient energy per bit to achieve the required quality of service (QoS), minimizes interference with other users of the system, and of mobile terminals. Balance with the need to maximize battery life. In achieving this goal, the role of power control (PC) is crucial in providing the required signal-to-noise ratio (SINR) while at the same time controlling the interference caused by adjacent cells. The classic idea of power control in the uplink is that all users receive the same signal-to-noise ratio (SINR) (known as full compensation). In 3GPP, instead of this, the use of partial power control (FPC: Fractional Power Control) was adopted in LTE. With this new feature, users with high path loss operate with low signal-to-noise ratio (SINR) requirements and therefore often cause less interference in adjacent cells.

In LTE, detailed power control formulas are specified for the physical uplink shared channel (PUSCH), the physical uplink control channel (PUCCH), and the sounding reference signal (SRS) (Section 5.1 of Non-Patent Document 5). ). The power control formula for each of these uplink signals follows the same basic principle. In each case, the power control expression has two main terms, an open-loop basic operating point derived from static or semi-static parameters signaled by the eNodeB, and dynamics that are updated on a subframe-by-subframe basis. It can be thought of as the sum of offsets.

The basic operating point of the open loop for determining the transmission power per resource block depends on multiple factors such as cell-to-cell interference and cell load. The basic operating point of the open loop consists of two components, a semi-static basic level P ₀ (common power level of all user devices in the cell (measurement unit: dBm)) and an offset unique to the user device. ) And the components of open-loop path loss compensation. The dynamic offset portion of the power per resource block has two additional components: a component that depends on the modulation and encoding method (MCS) used, and an explicit Transmitter Power Control (TPC) command. And, it can be disassembled.

(Referred to as delta _TF in LTE specification, TF represents a "transport format") modulation and coding scheme dependent component (MCS), the data of the information the transmission power per resource block (RB), is transmitted It can be adapted according to the rate.

Another component of dynamic offset is the transmit power control (TPC) command that is specific to the user equipment. This command operates in two modes: cumulative TPC (accumulative TPC) commands (available for PUSCH, PUCCH, and SRS) and absolute TPC commands (available only for PUSCH). be able to. Switching between these two modes for PUSCH is semi-statically set by RRC signaling for each user device (ie, the mode cannot be changed dynamically). For cumulative TPC commands, each TPC command signals a power step relative to a previous level.

Timing Advance
As the LTE uplink transmission method, single carrier frequency division multiple access (SC-FDMA) is selected so that orthogonal multiple access in time and frequency is achieved between a plurality of different user devices transmitting by uplink. ing.

Uplink orthogonality is maintained by ensuring that transmissions from a plurality of different user devices in the cell are time-aligned at the eNB receiver. This avoids the occurrence of in-cell interference both between user devices that are assigned to transmit in successive subframes and between user devices that transmit on adjacent subcarriers. The temporal match of the uplink transmission is achieved by applying a timing advance based on the downlink reception timing in the transmitter of the user equipment. This is shown in FIG. The main role of Timing Advance is to cancel different propagation delays between different user devices.

Timing Advance Procedure When the user equipment is synchronized with the downlink transmission received from the eNB, the initial timing advance is set by the random access procedure. In the random access procedure, the user device sends a random access preamble, and the eNodeB can estimate the uplink timing from this preamble, and the 11 bits included in the random access response (RAR) message. Respond by the initial timing advance command of. In this method, the eNodeB can set the timing advance with a particle size of 0.52 μs within the range of 0 ms to a maximum of 0.67 ms.

After the timing advance for each user device is initially set, the timing advance is updated from time to time in order to cancel the change in the arrival time of the uplink signal in the eNodeB. When deriving a timing advance update command, the eNodeB can measure any uplink signal useful for that purpose. The details of uplink timing measurement in eNodeB are not specified and are left to the implementation of eNodeB.

Timing advance update commands are generated on the eNodeB's MAC (medium access control) layer and sent to user equipment as MAC control elements, which are multiplexed with data on the physical downlink shared channel (PDSCH). Can be transformed into. The particle size of the update command is 0.52 μs, similar to the initial timing advance command in the response to the random access channel (RACH) preamble. The range of the update command is ± 16 μs, and the uplink timing can be changed at intervals equal to the length of the extended cyclic prefix. Update commands are generally not sent more frequently than about every 2 seconds. In fact, even for user equipment traveling at 500 km / h, the change in round trip path length is 278 m / s or less, and the corresponding change in round trip time is 0.93 μs / s, so the frequency is high. No need to update.

Upon receiving the timing advance command, the user device adjusts the timing of its own uplink transmission in PUCCH / PUSCH / SRS of the primary cell. The timing advance command indicates the change in the uplink timing with respect to the current uplink timing as a multiple of 16 Ts. The uplink transmission timing in PUSCH / SRS of the secondary cell is the same as that of the primary cell.

For random access response, the timing advance command _{T A} of 11 _bits, T A = 0, 1, 2,. .. .. Indicates _{N TA} value by the index value of 1282, the adjustment amount in this case the timing _is given by N TA = _{T A} × 16. _NTA is defined in [3].

In another case, the timing advance command _{T A} of 6 bits, the current _{N TA} value _{(N TA, old)} The new _{N TA} value from _{(N TA, new)} adjustments _to, T A = 0, 1, 2. .. .. , Indicated by 63 index value, this _{time, N TA, new = N TA} , is _{old + (T A -31) ×} 16. In this case, adjusting the _NTA value by a positive amount or a negative amount indicates that the uplink transmission timing is advanced or delayed by a given amount, respectively.

When the timing advance command is received in the subframe n, the corresponding adjustment of the timing is applied from the beginning of the subframe n + 6. When the uplink PUCCH / PUSCH / SRS transmissions of the user equipment in the subframe n and the subframe n + 1 overlap due to the timing adjustment, the user equipment transmits the entire subframe n and the overlapping portion of the subframe n + 1. Do not send.

If the downlink reception timing changes and is not corrected, or is only partially corrected by the uplink timing adjustment without the timing advance command as defined in Non-Patent Document 6, the user equipment , Change the _NTA accordingly.

The eNodeB sends periodic timing update commands to all user devices in the cell within a range that maintains the ability of the user device to send data quickly when it arrives in its transmit buffer. Therefore, eNodeB sets a timer for each user device, and the user device restarts this timer each time it receives a timing advance update. This timer is also referred to as a timing advance timer (TAT). If the user device does not receive a new timing advance update by the time the timer expires, it must be considered that the user device's uplink synchronization has been lost (Non-Patent Document 7 (available on the 3GPP website). See also section 5.2) (incorporated herein by reference).

In such cases, the user equipment is not allowed to perform any other uplink transmission of any kind in order to avoid the risk of interference with the uplink transmission from another user equipment.

Further characteristics of the timing advance procedure are described in Non-Patent Document 3 and Non-Patent Document 6 (Section 7.1), which are incorporated herein by reference.

LTE Device to Device (D2D) Neighborhood Services Neighborhood-based applications and services are a new trend in social technology. Areas identified include commercial services and services related to public safety that are of interest to businesses and users. By introducing the Proximity Service (ProSe) feature into LTE, the 3GPP industry can serve this growing market while at the same time several public safety services that use LTE in tandem. Can meet the urgent needs of the community.

Device-to-device (D2D) communication is a technical element in LTE Release 12. Device-to-device (D2D) communication technology can increase spectral efficiency in D2D as an underlay for cellular networks. For example, if the cellular network is LTE, all physical channels that carry data use SC-FDMA in D2D signaling. In D2D communication, user equipment (UEs) transmit data signals to each other through direct links that use cellular resources, without going through a base station. FIG. 7 shows one possible scenario in a D2D compatible communication system.

D2D communication in LTE " D2D communication in LTE" focuses on two areas, discovery and communication, but the present invention is mostly related to the discovery part.

Device-to-device (D2D) communication is a technical element in LTE-A. In D2D communication, user devices use cellular resources to transmit data signals to each other through direct links without going through a base station (BS). The D2D user communicates directly, but remains under the control of the base station (at least when within eNB coverage). Therefore, in D2D, the performance of the system can be improved by reusing cellular resources.

It is assumed that D2D operates in the uplink LTE spectrum (in the case of FDD) or in the uplink subframe of the cell providing coverage (in the case of TDD, except when out of coverage). Moreover, D2D transmission / reception does not use full duplex in a given carrier. From the point of view of the individual user equipment, the given carrier does not use full duplex by D2D signal reception and LTE uplink transmission (ie, D2D signal reception and LTE uplink transmission cannot be performed at the same time).

In D2D communication, when the user device 1 plays a role of transmission (sending side user device or transmitting side terminal), the user device 1 sends data, and the user device 2 (receiving side user device) receives the data. The user device 1 and the user device 2 can change the role of transmission and the role of reception. The transmission from the user device 1 can be received by one or a plurality of user devices (user device 2, etc.).

Regarding the user plane protocol, the contents of the agreement relating to D2D communication (Section 9.2 of Non-Patent Document 8 (incorporated herein by reference)) are shown below.
− PDCP:
○ 1: MD2D broadcast communication data (that is, IP packet) should be treated as normal user plane data.
◯ 1: Header compression / decompression in PDCP can be applied to MD2D broadcast communication data.
■ In D2D broadcast operations related to public safety, U mode is used for header compression in PDCP.
− RLC:
○ 1: RLC UM is used for MD2D broadcast communication.
○ Segmentation and restructuring is supported by RLC UM in layer 2 (L2).
○ The receiving user equipment needs to maintain at least one RLC UM entity per transmitting peer user equipment (peer UE).
○ It is not necessary to configure the receiver's RLC UM entity before receiving the first RLC UM data unit.
○ At present, the necessity of RLC AM or RLC TM in D2D communication for transmitting user plane data is not recognized.
− MAC:
◯ 1: HARQ feedback is not assumed in MD2D broadcast communication.
○ The receiving user device needs to recognize the source ID in order to identify the RLC UM entity of the receiver.
○ The MAC header includes a second layer (L2) destination ID that enables packet filtering in the MAC layer.
○ The second layer (L2) destination ID can be a broadcast address, a group cast address, or a unicast address.
■ Second layer (L2) group cast / unicast: Before passing the received RLC UM PDU by the second layer (L2) destination ID transmitted in the MAC header, even if it is passed to the RLC entity of the receiver. However, it can be discarded.
■ Second layer (L2) broadcast: The receiving user equipment processes all the RLC PDUs received from all the transmitters, reconstructs them, and passes the IP packet to the upper layer.
○ The MAC subheader contains a logical channel ID (LCID) (to distinguish between multiple logical channels).
○ In D2D, at least multiplexing / demultiplexing, priority processing, and padding are useful.

Resource allocation
Scheduling Allocation of Radio Resources FIG. 9 shows the behavior regarding resource allocation in D2D communication. Resource allocation in D2D communication is currently under study, and the current format is described in Section 9.2.3 of Non-Patent Document 8 (incorporated herein by reference).
From the viewpoint of the transmitting user device, the user device corresponding to the neighborhood service (ProSe compatible UE) can operate in the following two modes of resource allocation.
-Mode 1 (eNB schedules resource allocation): The eNodeB or release 10 relay node schedules the exact resources that the user equipment uses to transmit direct communication data and direct communication control information. The user device needs to be in the RRC_CONNECTED state in order to transmit data. Further, the user equipment requests a transmission resource from the eNB, and the eNB schedules a scheduling allocation and a transmission resource for transmitting data. The user device sends a scheduling request (dedicated scheduling request (D-SR) or random access) to the eNB and then a buffer status report (BSR). Based on the buffer status report (BSR), the eNB can determine that the user equipment has data to be transmitted by ProSe direct communication, and can estimate the resources required for the transmission.
-Mode 2 (user device autonomously selects resources): The user device itself selects a resource from the resource pool for transmitting direct communication data and direct communication control information.

Which resource allocation mode the user device uses for D2D data communication is basically determined by the RRC state (ie RRC_IDLE or RRC_CONNECTED) and the coverage state of the user device (ie in or out of coverage). If the user device has a serving cell (ie, the user device is in the RRC_CONNECTED state, or is camping on a particular cell in the RRC_IDLE state), the user device is considered to be in coverage.

Specifically, the following rules regarding resource allocation modes (according to Non-Patent Document 9) apply to user equipment.
-If the user device is out of coverage, the user device can only use mode 2.
-If the user device is within coverage, the user device can use mode 1 if the user device is configured by the eNB to use mode 1.
-If the user device is within coverage, the user device can use mode 2 if the user device is configured by the eNB to use mode 2.
-When the exception condition does not exist, the user device changes from mode 1 to mode 2 or from mode 2 to mode 1 only when the user device is set by the eNB to change the mode. If the user device is within coverage, the user device will only use the mode indicated by the eNB settings, unless one of the following exceptional cases occurs.
-While T311 or T301 is running, the user equipment considers itself to be under exceptional conditions.
-When an exceptional case occurs, the user equipment is allowed to use mode 2 temporarily, even if it is set to use mode 1.

While within the coverage area of an E-UTRA cell, the user equipment only performs ProSe direct communication transmission on the uplink carrier only in the resources allocated by that cell (even if the carrier's resources are pre-existing in UICC, for example). Even if it is set to).

For user equipment in the RRC_IDLE state, the eNB can select one of the following options.
-The eNB provides a mode 2 transmit resource pool in the SIB. A user device that is permitted to perform ProSe direct communication uses these resources in the RRC_IDLE state to perform ProSe direct communication.
-The eNB indicates in the SIB that it supports D2D but does not provide resources for ProSe direct communication. The user equipment needs to enter the RRC_CONNECTED state in order to execute the transmission of ProSe direct communication.

For the user equipment in the RRC_CONNECTED state, the following can be performed.
-A user device in the RRC_CONNECTED state that is allowed to execute ProSe direct communication transmission indicates to the eNB that it wants to execute ProSe direct communication transmission when it needs to execute ProSe direct communication transmission.
-The eNB uses the UE context received from the MME to confirm whether the user device in the RRC_CONNECTED state is allowed to transmit ProSe direct communication.
-The eNB can set a mode 2 resource allocation transmission resource pool that can be used without restriction while the user device is in the RRC_CONCEPTED state for the user device in the RRC_CONNECTED state by dedicated signaling. .. Instead, the eNB may set up a mode 2 resource allocation transmit resource pool for a user device in the RRC_CONNECTED state, which the user device can use only in exceptional cases, by dedicated signaling. If yes, and not in exceptional cases, the user equipment follows mode 1.

In mode 1, the user equipment requests a transmission resource from the eNodeB. The eNodeB schedules scheduling allocations and transmission resources for transmitting data.
-The user device sends a buffer status report (BSR) after sending a scheduling request (dedicated scheduling request (D-SR) or RACH procedure) to the eNodeB, and the eNodeB indicates that the user device is about to execute D2D transmission. , The required amount of resources can be determined based on the buffer status report (BSR).
-In mode 1, the user equipment needs to be RRC-connected to transmit D2D communication.

In the mode 2, a resource pool (time / frequency) is provided to the user equipment, and the user equipment selects a resource for transmitting D2D communication from the resource pool.

FIG. 8 schematically shows transmit and receive resources in overlay (LTE) and underlay (D2D). The eNodeB controls whether the user device applies mode 1 transmission or mode 2 transmission. When the user device recognizes a resource capable of transmitting (or receiving) D2D communication, the user device uses the corresponding resource only for the corresponding transmission / reception. In the example of FIG. 8, the D2D subframe is used only for the purpose of receiving or transmitting a D2D signal. Since the user equipment as the D2D device operates in the half-duplex mode, it can either receive or transmit the D2D signal at any time. Similarly, in the same FIG. 8, subframes other than the D2D subframe can be used for LTE (overlay) transmission and / or reception.

D2D discovery is a procedure / process that identifies other D2D-enabled devices in the vicinity that are of interest to you. For this purpose, a D2D device that wishes to be discovered sends some discovery signal (with a particular network resource), and the receiving user equipment interested in the discovery signal recognizes such a transmitting D2D device. To do. Section 8 of Non-Patent Document 8 describes the current details of the D2D discovery mechanism.

Transmission procedure in D2D communication FIG. 10 schematically shows a transmission procedure in D2D communication. The D2D data transmission procedure differs depending on the resource allocation mode. As described above, in mode 1, the eNB explicitly schedules resources for scheduling allocation and D2D data communication. The following shows a series of steps of the request / authorization procedure in the case of mode 1 resource allocation.
-Step 1 The user equipment sends an SR (scheduling request) to the eNB via PUCCH.
-Step 2 The eNB grants the uplink resource (for the user equipment to send a buffer status report (BSR)) via the PDCCH scrambled by C-RNTI.
-Step 3 The user equipment sends a D2D BSR indicating the state of the buffer via PUSCH.
-Step 4 The eNB grants D2D resources (for the user equipment to send data) via the PDCCH scrambled by D2D-RNTI.
-Step 5 The D2D transmitting side user device transmits the scheduling allocation (SA) / D2D data according to the grant received in step 4.

A scheduling assignment (SA) is a compact (low payload) message containing control information (eg, a pointer to a time-frequency resource for the corresponding D2D data transmission). The content of the scheduling allocation (SA) is basically the grant received in step 4 above. The details of the contents of the D2D grant and scheduling allocation (SA) have not been determined at this time.

D2D discovery
In ProSe Direct Discovery, a ProSe-enabled user device sends an E-UTRA direct radio signal to another nearby ProSe-enabled user device via a PC5 interface. It is defined as the procedure used to use and discover. FIG. 11 schematically illustrates a PC5 interface for direct discovery between devices as described in Section 5.1.1.4 of Non-Patent Document 10 (incorporated herein by reference). ing.

The upper layer handles the announcement of discovery information and the permission of monitoring. For this purpose, user equipment must exchange a predefined signal (referred to as a discovery signal). The user equipment maintains a list of nearby user equipment by periodically checking the discovery signal to establish a communication link when needed. The discovery signal needs to be detected with high reliability even in an environment where the signal-to-noise ratio (SNR) is low. It is necessary to allocate resources for the discovery signal so that the discovery signal can be transmitted periodically.

There are two types of ProSe direct discovery: open and restricted. The open type is when no explicit permission from the discovered user device is required, and the restricted type discovery is performed only when there is an explicit permission from the discovered user device.

ProSe direct discovery can be a stand-alone service enabler on the discovering user device, which is the user device on which the discovering user device is discovered in a particular application. Allows you to use information from. The information transmitted in ProSe direct discovery can be, for example, "find a taxi nearby", "find a coffee shop", "find the nearest police station", and so on. The user device on the discovering side can acquire necessary information through ProSe direct discovery. Further, depending on the information obtained, ProSe direct discovery can be used to perform subsequent operations in the remote communication system (eg, starting ProSe direct communication).

ProSe direct discovery model ProSe direct discovery is based on several discovery models. The model for direct discovery of ProSe is defined in Section 5.3.1.2 of Non-Patent Document 10 (incorporated herein by reference) as follows:

Model A ("I am here")
Model A is also expressed as "I am here" because the announcing user device broadcasts information about itself (such as its ProSe application identification information and ProSe UE identification information) in a discovery message. This is to identify itself and inform other devices in the communication system that it is available.

According to Model A, two roles of ProSe-compatible user equipment involved in ProSe direct discovery are defined. The ProSe-compatible user device can have the functions of the user device on the announcement side and the user device on the monitoring side. The announcing user device announces specific information that can be used by nearby user devices that have permission to discover. The monitoring user device monitors specific information of interest in the vicinity of the announcing user device.

In this model, the announcing user device broadcasts discovery messages at predefined discovery intervals, and the monitoring user device interested in these messages reads and processes the messages.

Model B ("Who is there?" / "Who is there? / Are you there?")
This model defines the following two roles of ProSe-enabled user equipment involved in ProSe direct discovery.
-Discovering user device: This user device sends a request containing specific information about the object that it wants to discover.
-Discovered user equipment: The user equipment that receives the request message can respond with some information related to the request of the discovering user equipment.

Model B is equivalent to "Who is there? / Are you there?" Because the discovering user device has information about another user device for which it wants to receive a response. Is to send. The information to be transmitted can be, for example, information related to the ProSe application ID corresponding to the group. Members of the group can respond to this transmitted information.

According to this model, two roles of the ProSe-compatible user device involved in the direct discovery of ProSe are defined, that is, the user device on the discovery side and the user device on the discovery side. The discovering user device sends a request containing specific information about the object it wants to discover. On the other hand, the discovered user device that has received this request message can respond with some information related to the request of the discovering user device.

The content of the discovery information is transparent to the access layer (AS: Access Stratum), and the access layer (AS) does not recognize the content of the discovery information. Therefore, in the access layer, the various models of ProSe direct discovery are not distinguished, nor are the types of ProSe direct discovery. The ProSe protocol passes only valid discovery information to be announced to the access layer (AS).

The user device can be involved in the announcement and monitoring of the discovery information in both the RRC_IDLE state and the RRC_CONNECTED state according to the eNB settings. The user device announces and monitors discovery information subject to half-duplex constraints.

Discovery Type FIG. 12 is a diagram showing an IDLE mode and a CONNECTED mode when receiving a discovery resource in D2D communication.

D2D communication is controlled by the network (in this case, the carrier manages the switch between direct transmission (D2D) and the conventional cellular link), or the direct link is set up without the control of the carrier. Can be managed by. In D2D, infrastructure mode and ad hoc communication can be combined.

In general, device discovery is required periodically. In addition, the D2D device uses the discovery message signaling protocol to perform device discovery. For example, a D2D-enabled user device can send its own discovery message, another D2D-enabled user device can receive this discovery message, and this information can be used to establish a communication link. The advantage of hybrid networks is that network entities such as eNBs can additionally assist in sending and configuring discovery messages if the D2D device is also within range of the network infrastructure. Coordinating / controlling the transmission and setting of discovery messages by the eNB is also important to prevent interference between D2D messaging and the cellular traffic controlled by the eNB. Furthermore, devices within coverage can assist with ad hoc discovery protocols, even if some of the devices are outside the scope of network coverage.

At least two types of discovery procedures are defined to define the terminology used further in the description.
-Type 1: A resource allocation procedure in which resources for announcing discovery information are allocated without targeting a specific user device, and further characterized by the following.
○ The eNB provides the user equipment with the resource pool settings used to announce the discovery information. The settings can be signaled in the SIB.
○ The user device autonomously selects (s) wireless resources (s) from the indicated resource pool and announces the discovery information.
○ The user device can announce the discovery information with the discovery resource randomly selected during each discovery period.
-Type 2: A resource allocation procedure in which resources for announcing discovery information are allocated to a specific user device, and further characterized by the following.
○ The user device in the RRC_CONNECTED mode can request the resource from the eNB for announcing the discovery information via the RRC. The eNB allocates resources via RRC.
○ Resources are allocated in the resource pool set for the user equipment to be monitored.
According to Type 2 procedures, resources are allocated to semi-persistents, for example for the transmission of discovery signals.
When the user device is in RRC_IDLE mode, the eNB can select one of the following options:
-The eNB can provide a type 1 resource pool in the SIB for announcing discovery information. User devices that are allowed to discover ProSe directly use these resources in RRC_IDLE mode to announce discovery information.
-The eNB can indicate in the SIB that it supports D2D but does not provide the resources to announce the discovery information. The user device needs to enter RRC_CONNECTED mode in order to request a D2D resource for announcing the discovery information.

For user devices in the RRC_CONNECTED state, the user device that is allowed to perform the ProSe direct discovery announcement informs the eNB that it wants to perform the D2D discovery announcement. The eNB then confirms whether the user device is allowed to announce ProSe direct discovery using the UE context received from the MME. The eNB can configure the user equipment via dedicated RRC signaling to use a Type 1 resource pool or a Type 2 dedicated resource for the announcement of discovery information (or no resource). The resources allocated by the eNB are valid until a) the eNB de-configures the resource by RRC signaling, or b) the user device enters IDLE mode.

The receiving user equipment in RRC_IDLE mode and RRC_CONNECTED mode monitors both the allowed Type 1 and Type 2 discovery resource pools. The eNB provides a resource pool configuration in the SIB that is used to monitor discovery information. The SIB can also include discovery resources used to make announcements in adjacent cells.

Radio Protocol Architecture FIG. 13 schematically shows a radio protocol stack (access layer (AS)) for ProSe direct discovery. FIG. 13 needs to be updated.

The access layer (AS) functions as an interface with an upper layer (ProSe protocol). Therefore, the MAC layer receives the discovery information from the upper layer (ProSe protocol). In this case, the IP layer is not used to transmit the discovery information. Further, the access layer (AS) has a scheduling function, that is, the MAC layer determines the radio resource to be used to announce the discovery information received from the upper layer. In addition to this, the access layer (AS) has the function of generating discovery PDUs, that is, the MAC layer can construct a MAC PDU that conveys discovery information and transmit the MAC PDU with the determined radio resource. Pass it to the physical layer. No MAC header is added.

In the user device, the RRC protocol informs the MAC of the discovery resource pool. In addition, the RRC informs the MAC of the Type 2 resources allocated for transmission. There is no need for a MAC header. The discovery MAC header does not include fields based on when performing filtering on the second layer (Layer 2). Filtering found messages at the MAC level is unlikely to save processing or power compared to performing filtering based on ProSe UE ID or ProSe application ID in the upper layers. The receiving MAC passes all the received discovery messages to the upper layer. At this time, the MAC may pass only the correctly received message to the upper layer.

In the following, it is assumed that the first layer (L1) indicates to the MAC layer whether the discovery message is correctly received. Furthermore, it is assumed that the upper layer always passes only valid discovery information to the access layer.

Conventional solutions for allocating discovery resources in D2D systems cannot determine suitable resource patterns or resource settings for allocating resources in a manner suitable for the requested D2D service. Specifically, when a base station allocates resources based on information transmitted by a D2D-enabled device according to common signaling procedures, the period of transmitted resources is too short for the user equipment to fully broadcast the discovery information. Sometimes. As a result, the transmitting user equipment has to request resources again, which increases the signaling overhead in the LTE system.

Further, for example, information regarding the content of the discovery information is transparent to the access layer (AS). Therefore, in the access layer, the various models of ProSe direct discovery are not distinguished, nor are the types of ProSe direct discovery, and in the base station, the model of discovery transmission and the type of preferred procedure for allocating discovery resources. No information is received that is useful in making the decision.

D2D Sync The main role of sync is to allow the receiver to obtain time and frequency references. Such criteria can be used for at least two purposes: 1) Match the frequency correction with the receiver window when detecting the D2D channel, 2) Match the timing and parameters of the transmitter when transmitting the D2D channel. The following channels are currently defined in 3GPP for the purpose of synchronization.
− D2DSS D2D Synchronization Signal
− PD2DSCH Physical D2D Synchronization Channel
− PD2DSS Primary D2D Synchronization Signal
-SD2DSS Secondary D2D Synchronization Signal

In addition, the 3GPP has agreed on the following terminology for synchronization:
D2D Synchronization Source: A node that transmits at least a D2D synchronization signal.
D2D Synchronization Signal: A signal from which a user device can obtain timing and frequency synchronization.

The D2D synchronization source can basically be an eNB or D2D user device.

D2D synchronization can be regarded as a procedure similar to LTE cell search. The following steps are currently being considered within 3GPP to enable both network control and efficient synchronization in partial coverage and out-of-coverage scenarios.

The synchronous ProSe-compatible user device of the receiver periodically searches for the LTE cell (following the LTE mobility procedure) and the D2DSS / PD2DSP transmitted by the SS user device.

Once a suitable cell is found, the user equipment camps on that cell and follows cell synchronization (according to LTE legacy procedures).

Once the appropriate D2DSS / PD2DSP transmitted by the SS user equipment is found, the user equipment synchronizes its receiver with all incoming D2DSS / PD2DSCH (depending on the capabilities of the user equipment) and comes in. Monitor for connections (scheduling quotas). Note that the D2DSS transmitted by the eNodeB D2D synchronization source is Release 8 PSS / SSS. The eNodeB D2D synchronization source has a higher priority than the user equipment D2D synchronization source.

The synchronous ProSe compatible user device of the transmitter periodically searches for the LTE cell (following the LTE mobility procedure) and the D2DSS / PD2DSP transmitted by the SS user device.

Once a suitable cell is found, the user equipment can camp on to that cell and follow cell synchronization to transmit the D2D signal, and the network can configure the user equipment to transmit D2DSS / PD2DSCH according to cell synchronization. ..

If no suitable cell is found, the user equipment checks to see if any of the incoming D2DSS / PD2DSP can be relayed further (ie, has not reached the maximum hop count), and (a) can further relay, enter. When the incoming D2DSS / PD2DSP is found, the user equipment synchronizes its transmitter with the signal and transmits the D2DSS / PD2DSCH accordingly, or (b) further relays the incoming D2DSS / PD2DSP. If not found, the user equipment acts as an independent synchronization source, transmitting D2DSS / PD2DSCH according to any internal synchronization criteria.

Further details of the synchronization procedure in D2D are described in Non-Patent Document 8.

3GPP TS 36.211, “Evolved universal terrestrial radio access (E-UTRA); physical channels and modulations (Release 10)”, version 10.4.0, 2012 TS 25.912 3GPP TS 36.321 V10.5 3GPP TS 36.321 V8 TS 36.213 TS 36.133 3GPP TS 36.321, “Evolved Universal Terrestrial Radio Access (E-UTRA); Medium Access Control (MAC) protocol specification”, version 8.9.0 3GPP TS 36.843vers. 12.0.0 TS 36.300 3GPP TS 23.303 V12.0.0

An exemplary embodiment provides a transmitting terminal, which transmits data to a receiving terminal through a direct link connection in a communication system. The transmitting terminal is configured to determine the transmission timing of the direct link data transmission in the communication system. The transmitting terminal includes a receiving unit, which is configured to receive an uplink control information message from the base station, including a timing command for adjusting the uplink transmission timing value of data transmission to the base station. .. The generation unit is configured to generate direct link timing information based on the uplink transmission timing value used for uplink transmission to the base station, and this direct link timing information is data through the direct link. It can be used to generate a direct link transmission timing value to determine the timing of transmission. The transmission unit transmits the generated direct link timing information to the receiving terminal, and this direct link timing information is used to determine the reception timing of the data received from the transmitting terminal through the direct link in the receiving terminal. It can be used to generate a direct link reception timing value.

Further benefits and advantages of the disclosed embodiments will become apparent from the specification and drawings. These benefits and benefits can be provided individually by the various embodiments and features disclosed herein and in the drawings, and it is not necessary to have all of these benefits and benefits in order to obtain one or more of them. ..

Hereinafter, exemplary embodiments will be described in more detail with reference to the accompanying drawings. Similar or corresponding details in the drawings are numbered the same.

An exemplary architecture of a 3GPP LTE system is shown. It provides an exemplary overview of the entire 3GPP LTE E-UTRAN architecture. FIG. 6 is an exemplary subframe boundary diagram of a downlink component carrier as defined for 3GPP LTE (Release 8/9). FIG. 5 is a diagram of an exemplary downlink resource grid of downlink slots as defined in 3GPP LTE (Release 8/9). It shows the second layer (Layer 2) structure of 3GPP LTE-A (Release 10) with downlink carrier aggregation enabled. It shows the second layer (Layer 2) structure of 3GPP LTE-A (Release 10) with downlink carrier aggregation enabled. It is the schematic which shows the system including the D2D compatible user equipment. It is a schematic diagram which shows the transmission resource and the reception resource in overlay (LTE) and underlay (D2D) in a D2D subframe. It shows the behavior related to resource allocation in D2D communication. The transmission procedure in D2D communication is shown schematically. A schematic diagram of a PC5 interface for direct discovery between devices is shown. It is a figure which showed the IDLE mode and the CONCEPTED mode at the time of receiving a resource for discovery by an exemplary development form. The radio protocol stack (AS) for ProSe direct discovery is shown schematically. It shows a method of controlling the transmission timing for transmitting data from a transmitting user device to a receiving user device through a direct link connection. Shown are sender / receiver user devices in an exemplary evolution. According to the structure shown in FIG. 15, a method of controlling the transmission timing for transmitting data from the transmitting user device to the receiving user device through a direct link connection is shown. According to a further developed form, a method of controlling the transmission timing for transmitting data from the transmitting user device to the receiving user device through a direct link connection is shown.

The following paragraphs describe various exemplary embodiments. For illustration purposes only, most embodiments are wireless with 3GPP LTE (Release 8/9) and LTE-A (Release 10/11/12) mobile communications systems, some of which are described in the Background Techniques section above. It is outlined in relation to the access method. Although these exemplary embodiments can be advantageously used in mobile communication systems such as, for example, the 3GPP LTE-A (Release 10/11/12) communication systems described in the Background Techniques section above. It should be noted that these exemplary embodiments are not limited to use in this particular exemplary communication network.

The term "direct link" as used in the claims and herein is a communication between two D2D user devices that allows direct exchange of data without the involvement of a network. Please be understood as a link (communication channel). In other words, the communication channel is established by bypassing the eNodeB (base station) between two user devices in the communication system that are close enough to exchange data directly. This term is used as a contrast to "LTE link" or "LTE (uplink) traffic" which means data traffic between user devices managed by eNodeB.

The terms "transmitting user equipment" or "transmitting terminal" as used in the claims and the specification are understood as mobile devices capable of transmitting and receiving data. I want to. The adjective "sender" is only intended to articulate a temporary action. In the following description, the transmitting user device for the purpose of discovery transmission may be the announcing user device or the discovering user device (discoverer). This term is used as a contrast to "receiving user equipment" or "receiving terminal", which means a mobile device that temporarily performs an action to receive data. There is. In the following description, the receiving side user device for the purpose of discovery transmission may be a monitoring side user device or a discovered side user device (discoveree).

Some examples will be described in detail below. The following description is not intended to limit the invention and should be understood as merely exemplary embodiments for a deeper understanding of the invention. Those skilled in the art will recognize that the general principles set forth in the claims can be applied to various scenarios in a manner not expressly described herein. Therefore, the following scenarios envisioned to illustrate the various embodiments do not limit the invention to such scenarios.

The present invention is based on the finding that in a D2D communication system, it is important to synchronize the transmission and reception of data transmitted from the transmitting terminal to the receiving terminal via a direct link. Specifically, it is important that the receiving terminal can set a receiving window (more specifically, the FFT window) when receiving data from the transmitting terminal, and the receiving window is the transmitting terminal. Is as close as possible to the timing when the data is transmitted through the direct link connection and the propagation delay between the transmitting terminal and the receiving terminal is added. If the data transmitted through the direct link is not received at the correct timing (ie, the receive FFT window is not placed at the correct timing), the signal-to-noise ratio (SNR) is reduced, which reduces the performance of the data transmission. In particular, if the timing mismatch exceeds the length of the cyclic prefix (ie, the reception is outside the cyclic prefix), the decoding performance will be significantly reduced, for example, it may not be possible to decode the data correctly. is there. In addition to this, in order to reduce intra-cell interference in the communication system, the data transmission through the direct link and the LTE data transmission are synchronized, that is, the LTE data and the direct link data are the same in the base station. It is advantageous if it is received at the same timing (in other words, at the same timing as the data traffic on the uplink between the terminal and the base station).

FIG. 14 shows one possible method for controlling the transmission timing when data is transmitted from the transmitting user device (hereinafter UE1) to the receiving user device (hereinafter UE2) through a direct link connection. .. One solution that can reduce intra-cell interference is in the transmitting user equipment for data transmission through a direct link, the same up that this transmitting user equipment uses for uplink data transmission to the base station. Use link timing. The uplink timing is controlled by the eNB by the timing advance (TA) command as described above in the "timing advance" section, and the UE1 has its own internal timing advance value based on this timing advance (TA) command. Can be adjusted to an 11-bit value (called the _NTA value).

Therefore, according to the solution shown in FIG. 14, the transmitting user device also uses LTE uplink timing for D2D data transmission. Specifically, N _TA value is used to adjust the transmission timing when the UE1 to transmit data to the base station, and a transmission timing for sending data through the direct link, further, the recipient-user It is also used as a reference for synchronizing the FFT windows of the device (ie UE2).

Specifically, UE1 maintains the N _TA value of 11 bits, the N _TA value is used to determine the timing advance relative to the reception timing of the downlink. The timing advance value is sent to the receiving user device (eg, UE2 in this example) in a control message (also referred to as a scheduling allocation (SA) message, but 6 bits). Thus UE1 before sending to the UE2 11 bits of _{N TA} value for the uplink transmission in the scheduling assignment (SA) message, downsampling the _{N TA} value to the 6 bits. As an example of downsampling, UE1 can transmit only the six most significant bits of the uplink _NTA value to UE2.

FIG. 14 shows a plurality of different timings, the eNB timing, the UE1 timing, and the UE2 timing are shown on a horizontal line. In this example, UE1 (sender user equipment) transmits data to UE2 (receiver user equipment) through a direct link. The downlink timing (that is, the time when the eNB signaling including the TA command for adjusting the uplink timing is received by the UE1) is indicated by Rx _eNB @ UE1.

As described above, the UE 1 downsamples the _NTA value determined by itself based on the TA command received from the eNB and the autonomous timing adjustment function, and performs the direct link communication through the direct link (PC5 interface). A direct link scheduling allocation (SA) message (monitored / received by UE2) containing a downsampled _NTA value is transmitted. This direct link SA message _is received in UE2 in Rx D2D _SA @ UE2.

According to this method embodiment, a direct link data, through a link directly from the UE1, and applying the adjusted timing advance on the basis of the _{N TA} value of 11 bits, in other words uplink timing _{(Tx LTE _UE1 = Tx D2D _UE1} ) Is transmitted at. D2D data or direct link data transmitted by UE1 at time _Rx D2D _data @ UE2 are received by the UE2. On the other hand, the UE 2 calculates the time when the data from the UE 1 should arrive based on the downsampled 6-bit _NTA value received in the scheduling allocation (SA) message. Therefore, the timing advance value transmitted to the UE 2 in the scheduling allocation (SA) message is not the same as the timing advance value used by the UE 1, but is only an approximation thereof.

This solution can be problematic at this time, because when based on current technology, UE2 is unable to properly position its receive window in time, which reduces decoding performance and signals. The signal-to-noise ratio (SNR) is reduced. However, with future progress, it is predicted that good performance can be obtained even when the timing advance used by UE2 is only an approximation of the timing advance used by UE1, and the above problems will be alleviated. Will be done.

In conclusion, the solutions described above can reduce carrier-to-carrier interference, because D2D data in the case of direct link communication is transmitted using the same timing advance as in the case of legacy LTE uplink communication. is there. However, at this time, the receiving user equipment (UE2) cannot effectively adjust its receiving FFT window, because the 6-bit _NTA value sent by UE1 in the scheduling allocation (SA) message This is because it is only an approximation of the 11-bit _NTA value used by the UE 1 to transmit D2D data.

The above problem related to the solution described with reference to FIG. 14 is the direct link data transmission of the same timing advance value used by the receiving user device to set the receive FFT window for D2D data. It is solved by providing the transmitting user equipment, which is used in.

FIG. 15 shows a transmitting side / receiving side user device 500 according to this further developed form. The user device or terminal 500 can transmit data to the receiving terminal through a direct link connection in the D2D communication system. The transmitting side terminal 500 is configured to determine the transmission timing of direct link data transmission in the communication system. For this purpose, the transmitting user device 500 includes a receiving unit (540) capable of receiving an uplink message including a timing advance command from the base station. The timing advance command can be a MAC control element, and the user device 500 can use this timing advance command to adjust the uplink transmission timing value for transmitting data to the base station. The received TA command is input to the generation unit 570 either directly or through the control unit, and the generation unit 570 is input with the uplink transmission timing value for controlling the transmission timing in the uplink to the base station 510. Generated based on the TA command.

At the same time, the generation unit 570 directly generates the link timing information based on the uplink transmission timing value. The direct link timing information is used by the transmitting terminal 500 to determine the timing of data transmission to the receiving terminal through the direct link.

The transmitting side terminal 500 transmits the generated direct link timing information to the receiving side terminal 500 by the transmitting unit 560. The receiving terminal uses the transmitted direct link timing information to generate a direct link reception timing value. The timing of direct link data transmission determined at the transmitting terminal is the same as the direct link receiving timing value calculated at the receiving terminal, which is advantageous.

FIG. 16 shows a method of controlling the transmission timing for transmitting data from the transmitting side user device (UE1) to the receiving side user device (UE2) through a direct link connection according to the structure shown in FIG. The TA value used by the UE 1 for the direct link transmission is the same as the TA value transmitted to the UE 2 in the direct link SA. Accordingly, the reception window is determined by the UE2 by using direct link TA value _(TA D2D _UE1), it can be adjusted to match the transmission timing _Rx D2D _data @ UE2 of D2D data.

In one exemplary embodiment of the solution described above, the UE 1 has 11 bits for adjusting the transmission timing of legacy LTE uplink transmissions to the base station, eg, based on an uplink TA command received from an eNB. Generate and maintain the _LTE value of. At the same time, the UE 1 downsamples the 11-bit _NTA value in order to generate 6-bit direct link timing information. The direct link timing information can be generated, for example, by taking the 6 most significant bits of the uplink _NTA value maintained for LTE uplink operation. Next, this direct link timing information is incorporated into, for example, a direct link SA message and transmitted to the UE 2. On the other hand, the UE 1 generates an 11-bit direct link _NTA value based on the direct link timing information. The 11-bit direct link _NTA value can be generated, for example, by adding a series of 0s to the beginning of the direct link timing information. Similarly, the UE 2 extracts 6-bit direct link timing information from the received direct link SA message, and based on the information, appends a series of 0s to the beginning of the signaled direct link timing information. Restore the direct link _NTA value of the bit. Therefore, the direct link _NTA value used by the UE 2 to adjust the receive FFT window is the same as the timing advance value used by the UE 1 to transmit data through the direct link. As further shown in FIG. 16, the UE 2 applies the generated _NTA value to the reception timing of the scheduling allocation (SA) message.

The above idea can be explained by the following example. _{N TA} value of 11 bits for the LTE uplink data transmission to the base _station, N if TA_UPLINK = is 11011011001, six direct link timing downsampled is calculated by considering the most significant bit The information is 110110. In the downsampling of information performed by UE1, some low-order bits are lost and the direct link transmission timing value is given by _{NTA_D2D} = 11011000000. Similarly, the receiving user device (UE2) receives the direct link timing information that conveys the value 110110 by the scheduling allocation (SA) message. Based on this information, the UE 2 can generate a direct link reception timing value by adding a series of 0s to the beginning of the received value. The direct link reception timing value is N _{TA_D2D} = 11011000000.

The above is only an example for explaining how to apply the general concept of the present invention in a concrete implementation. However, of course, the present invention is not limited to this example. For example, the uplink transmission timing value may be shorter than 11 bits or longer than 11 bits. Similarly, direct link timing information can be generated by procedures other than downsampling. Although the direct link timing information having 6 bits has been described, the direct link timing information can be made longer than this. The same applies to the direct link transmission timing value.

Therefore, the timing advance value for determining the transmission timing of the D2D data and the timing advance value for determining the reception timing of the D2D data generated in the UE 1 and the UE 2 are the same, so that the receiving terminal can receive the same data. , A reception FFT window that matches the transmission timing of D2D data can be set. As a matter of course, the direct link timing value calculated in UE1 and UE2 is not the same as the uplink transmission timing value for legacy LTE uplink transmission, but is only an approximate value thereof. This discrepancy can result in inter-carrier interference in LTE uplink transmissions on the eNB receiver under certain conditions, currently from the current technical point of view, because of the uplink for transmitting data to the eNB. This is because the timing is different from the transmission timing for D2D data transmission.

A further development that can reduce carrier-to-carrier interference is a method of implementing both the solution described with reference to FIG. 14 and the solution described with reference to FIGS. 15 and 16.

According to this further development, the base station decides which method to use. Specifically, the base station 510 of the direct link communication system, which is designed to control the timing of direct link data transmission in the communication system, transmits a resource request message for allocating resources for uplink data transmission. It includes a receiving unit, which is designed to receive data from the side terminal 500. The base station generates setting information in the generation unit, and this setting information is transmitted to the transmitting user device 500 or UE1 by the transmitting unit of the base station. The UE 1 uses the received setting information to control the timing of transmission through a direct link.

Specifically, in the transmitting side user device 500, the receiving unit 540 receives the setting information from the base station. After that, the transmitting user device 500 follows the received setting information, for example, in the transmitting unit 560, (1) the generated direct link timing information, or (2) the uplink used for uplink transmission to the base station. Select the link transmission timing value. Based on this selection, the transmitting user device controls the timing of transmission through the direct link.

In case (1), the transmitting user device generates a direct link transmission timing value as described with reference to FIGS. 15 and 16, that is, good decoding performance is ensured but inter-frame interference occurs. Choose an increasing method. This solution can be used when the base station implements an inter-carrier interference (ICI) mitigation technique such as a guard band to mitigate inter-carrier interference (ICI). In addition, this solution can also be used when the base station does not need to consider reducing interference.

In case (2), the transmitting user device also uses the legacy LTE uplink transmission timing for uplink transmission to the base station when transmitting data to the receiving user device via a direct link. In this case, the D2D transmission timing coincides with the LTE uplink transmission timing, which keeps the inter-carrier interference (ICI) low when the data is uplink-transmitted to the base station. At the cost of the advantages of this transmission scheme, the receive FFT window for D2D data transmitted by the transmitting user equipment is not effectively adjusted. Such a solution can be used when protecting LTE uplink transmissions by avoiding additional carrier-to-carrier interference caused by direct link data transmissions is more important than D2D performance. .. For example, if the eNB does not have the means to implement inter-carrier interference (ICI) mitigation techniques such as power control or guard band, such a solution may be advantageous from a network perspective.

According to a further development that solves the problem of reducing interference and obtaining good decoding performance, the transmitting user device receives, for example, a TA command received from a base station to adjust the transmission timing of LTE uplink transmission. The uplink timing advance value _LTE generated based on can be included in the direct link SA message. In other words, according to this evolution, the direct link SA message contains an 11-bit _NTA value, and instead of the downsampled 6-bit uplink transmission timing, this 11-bit _NTA value is the receiver. Signaled to the user device. Therefore, the same timing advance value is used for transmitting and receiving D2D data, which allows the receiving user equipment to accurately adjust the FFT reception window. Furthermore, since the transmission timing of the D2D data is the same as the uplink data transmission timing to the base station, the inter-carrier interference (ICI) for the LTE uplink transmission can be minimized. However, this solution requires sending a scheduling allocation (SA) message containing an 11-bit TA field to the receiving user equipment, which increases the signaling load.

According to a further development, the transmitting user equipment can select which transmission method to use for the D2D transmission timing in the control unit 590 independently of the base station.

The transmitting terminal includes a control unit 590, and the control unit 590 particularly adjusts the timing for transmitting data through the direct link based on (1) the generated direct link timing information, or (2). ) Whether to adjust based on the uplink transmission timing information used for uplink transmission to the base station is selected based on a predefined selection criterion. These two options are the same as those described above herein and will not be repeated herein.

As a selection criterion, compare the length of the cyclic prefix for uplink transmission to the base station with the length of the cyclic prefix for direct link transmission, or whether the transmitting terminal is in a connected state. It can include determining if it is idle.

Specifically, if the length of the cyclic prefix in the case of uplink transmission (LTE WAN) to the base station is different from the length of the cyclic prefix in the case of direct link transmission (D2D transmission), the inter-carriers in the cell. Interference (ICI) is high, and the base station needs to implement measures (guard band, etc.) to reduce the interference. In this case, since the transmitting side user device has already set a guard band for reducing inter-carrier interference (ICI), the method (1) is selected and the direct link timing is signaled to the receiving side user device. The information can be used to decide to adjust the transmission timing of the D2D data transmission. In this solution, the receiving user equipment can accurately adjust the FFT reception window, which provides good decoding performance in exchange for high interference. In this case, the high interference during uplink transmission is mitigated, for example, by a guard band.

On the other hand, if the length of the cyclic prefix in the case of uplink transmission (LTE WAN) to the base station and the length of the cyclic prefix in the case of direct link transmission (D2D transmission) are the same, The transmitting user device can directly determine the link transmission timing according to the method (2). In this case, the base station does not have to implement or use measures to reduce inter-carrier interference (ICI), and therefore can choose a transmission timing control method for D2D transmission that can reduce inter-frame interference. For this purpose, the transmitting user equipment can use the LTE uplink transmission timing value to determine the timing of data transmission through the direct link.

Finally, as a further exemplary embodiment, if the sender user device cannot determine the length of the cyclic prefix when it is an LTE WAN, the sender user device determines the transmission timing through the direct link. It can be controlled according to 1).

Alternatively or additionally, the transmitting user device can determine which method to use to control the timing of the direct link transmission based on the RRC state. When the transmitting user device is in the RRC_CONNECTED state, the transmitting user device can generate a direct link transmission timing value using the direct link timing information, and this transmission timing value can be used to generate a direct link transmission timing value through the direct link. The timing of data transmission is determined (method 2). Instead, when the transmitting user device is in the RRC_IDLE state, the transmitting user device can use 0 as the timing advance value for direct link transmission. Specifically, when the transmitting user device is in the IDLE mode, the TA command is not received from the base station because the RRC connection with the base station is not established, and therefore the transmitting user device does not receive any uplink transmission timing. It also has no advance value. Therefore, the transmitting user device in the RRC_IDLE mode cannot match the timing of the direct link transmission with the timing of the LTE uplink transmission. As a result, according to an exemplary embodiment, the sending user equipment in RRC_IDLE mode has a downlink timing (ie, when a scheduling allocation (SA) message is received) to transmit data over a direct link. use.

According to a further embodiment, the position of the data reception FFT window is determined based on the reception timing of the scheduling allocation (SA) message. Specifically, the direct link timing information included in the scheduling allocation (SA) message received from the transmitting user device in the receiving user device is used as the reference timing for determining the position of the receiving FFT window. More specifically, the receiving user equipment applies the timing advance value generated based on the direct link timing information received in the scheduling allocation (SA) message to the receiving timing of SA. Therefore, the receiving user equipment can include a storage unit that stores the reception timing of the scheduling allocation (SA) message from the transmitting user equipment, for example, in a variable. The stored receive timing is used for the purpose of calculating the position of the receive FFT window for receiving D2D data. Instead, D2DSS / PD2DSCH can be used as the timing reference. FIG. 17 shows how to set the position of the receive window for D2D data according to the method above.

According to another embodiment, a separate timing advance timer (TAT) and / or TAT value for D2D can be set for the transmitting terminal capable of transmitting data via a direct link. This timing advance timer (TAT) value can be set to infinity, for example. When set to infinity, as a result, the transmitting user equipment always goes through the direct link, even if the timing advance timer (TAT) for LTE uplink transmission has expired and LTE uplink transmission to the base station is not allowed. You will be able to send data. In such a case, the transmitting user device can determine the transmission timing of the direct link data transmission according to the _latest available _NTA value stored in the storage unit of the transmitting user device.

Instead, the transmitting user device can use a timing advance equal to 0 for the timing of transmitting the direct link data. In other words, the sending user equipment can use the same transmission timing that is used to transmit the scheduling allocation (SA) message or control information message through the direct link.

According to another embodiment, the transmitting terminal capable of transmitting data through the direct link can also follow a timing alignment timer (Timing Alignment Timer) used for controlling the LTE uplink transmission timing. More specifically, when the timing adjustment timer (TAT) timer has expired and the user device is not allowed to perform LTE uplink transmission to the base station, the transmitting user device sends the direct link data through the direct link. It is also not permitted to make transmissions and / or discovery announcements. The TAT timer needs to be restarted first by receiving the TA command. In resource allocation mode 1, the transmitting user equipment triggers a random access procedure before sending any uplink transmission to the base station (eg, a dedicated scheduling request on the PUCCH) or any data transmission over a direct link. Need to do. Similarly, according to another embodiment, when the transmitting user device is configured to use resource allocation mode 2 for D2D data communication, if the timing adjustment timer expires, scheduling allocation through a direct link. Random access procedures can be triggered or executed before sending a message or data.

In summary, according to one embodiment, there is provided a transmitting terminal, which transmits data to a receiving terminal through a direct link connection in a communication system. The transmitting terminal is configured to determine the transmission timing of the direct link data transmission in the communication system. The transmitting terminal includes a receiving unit, which is configured to receive an uplink control information message from the base station, including a timing command for adjusting the uplink transmission timing value of data transmission to the base station. .. The generation unit is configured to generate direct link timing information based on the uplink transmission timing value used for uplink transmission to the base station, and the direct link timing information is data transmission through the direct link. Can be used to generate a direct link transmission timing value to determine the timing of. The transmission unit transmits the generated direct link timing information to the receiving terminal, and this direct link timing information is used to determine the reception timing of the data received from the transmitting terminal through the direct link in the receiving terminal. It can be used to generate a direct link reception timing value.

At the transmitting terminal, the generation unit can be configured to downsample the uplink transmission timing information value used for uplink transmission to the base station, and the direct link timing information is this downsampled uplink. This is the transmission timing value. The downsampled uplink transmission timing value can contain n most significant bits of the uplink transmission timing information value used for uplink transmission to the base station, where n is a predefined value. is there.

Furthermore, the timing of data transmission through the direct link can be given by the direct link transmission timing value, and the direct link transmission timing value is a receiving terminal for determining the reception timing of the data received through the direct link. It can be equal to the direct link reception timing value, which is generated in.

In the transmitting terminal, the timing of data transmission through the direct link can be given by the uplink transmission timing information value used for the uplink transmission to the base station.

According to a further advantageous development, the receiving unit at the transmitting terminal is further configured to receive the setting information from the base station, and the transmitting unit is a direct link transmission timing value generated according to the received setting information. It is configured to use timing information or received downlink uplink timing information values to schedule / control transmission timing through a direct link.

The transmitting terminal can further include a control unit, which uses the uplink transmission timing information value used for uplink transmission to the base station as the transmission timing for transmitting data through the direct link. Whether to use the generated direct link transmission timing value timing information is selected based on a predefined selection criterion.

As selection criteria, (1) the length of the cyclic prefix in the case of uplink transmission to the base station is compared with the length of the cyclic prefix in the case of direct link transmission, or (2) the transmitting terminal. It is advantageous to include determining whether is in a connected or idle state.

At the transmitting terminal, the direct link timing information is generated based on the reception timing of the control information message and the uplink transmission timing value of data transmission to the base station.

An advantageous embodiment provides a base station for use in a direct link communication system, which is configured to control the time scheduling of direct link data transmission in the communication system. This base station includes a receiving unit, which is configured to receive a resource request message for scheduling allocation of resources for uplink data transmission from a transmitting terminal. The generation unit is configured to generate setting information for setting timing information for scheduling / controlling transmission timing through a direct link by a transmitting terminal. The transmission unit transmits the setting information to the transmitting terminal.

A further advantageous embodiment provides a receiving terminal, which receives data from a transmitting terminal directly through a link connection in a communication system. This receiving terminal is a receiving unit that receives the direct link timing information generated in the transmitting terminal based on the uplink transmission timing value used for the uplink transmission to the base station from the transmitting terminal. , Is equipped. The generation unit generates a direct link reception timing value based on the received direct link timing information. The receiving unit controls the receiving timing of the data received from the transmitting terminal through the direct link based on the generated direct link receiving timing value.

In this receiving terminal, the direct link timing information is the downsampled uplink transmission timing value, and the generation unit adds a predefined number of 0 bits to the beginning of the downsampled timing information. It is configured to do.

According to one advantageous embodiment, the direct link reception timing value is equal to the direct link transmission timing value generated in the transmitting terminal for determining the timing of data transmission through the direct link.

A further advantageous embodiment provides a communication method in which the transmission timing of direct link data transmission is controlled by a transmitting terminal in a communication system. This method
A step of receiving an uplink control information message from a base station in a receiving unit including a timing command for adjusting an uplink transmission timing value of data transmission to a base station, and
A step of generating direct link timing information in the generation unit based on the uplink transmission timing value used for uplink transmission to the base station, and this direct link timing information is the timing of data transmission through the direct link. Can be used to generate a direct link transmission timing value to determine, steps and,
It is a step of transmitting the generated direct link timing information to the receiving side terminal in the transmitting unit, and in the receiving side terminal, this direct link timing information controls the receiving timing of the data received from the transmitting side terminal through the direct link. Can be used to generate a direct link receive timing value for
The step of transmitting data to the receiving terminal through the direct link in the transmission unit using the generated direct link transmission timing value transmission timing determined by the generated direct link timing information.
including.

This communication method is a step of downsampling the received uplink transmission timing value used for uplink transmission to the base station, and the direct link timing information is based on the downsampled uplink transmission timing value. Can further include steps, which are generated by The downsampled timing information can include, for example, n most significant bits of the uplink transmission timing value, where n is a predefined value.

In the above-mentioned communication method, the timing of data transmission through the direct link is given by the direct link transmission timing value, and the direct link transmission timing value is a reception for determining the reception timing of the data received through the direct link. It is equal to the direct link reception timing value generated at the side terminal.

The timing of data transmission through the direct link can be given by the uplink transmission timing information value used for the uplink transmission to the base station.

The above-mentioned communication method is
A step of receiving setting information from a base station, wherein the setting information is preferably included in the control information.
A step of controlling the transmission timing through the direct link based on the generated direct link transmission timing value or the uplink transmission timing value according to the received setting information.
It is advantageous to further include.

In this method, for example, whether to use the uplink transmission timing value or the direct link transmission timing value for the purpose of controlling the transmission timing of the direct link data transmission is based on a predefined selection criterion. Can be selected in the selection unit.

As selection criteria, (1) the length of the cyclic prefix in the case of uplink transmission to the base station is compared with the length of the cyclic prefix in the case of transmission through a direct link, or (2) the transmitting terminal. It is advantageous to include determining whether is in a connected or idle state.

A further advantageous embodiment provides a communication method in which the transmission timing of direct link data transmission is controlled by a receiving terminal in a communication system. This method
A step of receiving the direct link timing information generated in the transmitting terminal based on the uplink transmission timing value used for the uplink transmission to the base station from the transmitting terminal in the receiving unit, and
A step of generating a direct link reception timing value in the generation unit based on the received direct link timing information, and
A step of controlling the reception timing of data received from the transmitting terminal through the direct link in the receiving unit based on the generated direct link reception timing value.
including.

In this communication method, when the direct link timing information is generated based on the downsampled uplink transmission timing value, a predefined number of 0 bits is added to the beginning of the direct link timing information in the generation unit. Additional steps can be included.

A further advantageous embodiment is a communication method in which the transmission timing of direct link data transmission in a communication system is controlled by a base station.
A step of receiving a resource request message for scheduling allocation of resources for transmitting uplink data to a base station from a transmitting terminal in a receiving unit, and
A step of generating setting information in the generation unit for setting the timing information for controlling the transmission timing through the direct link by the transmitting terminal, and
The step of transmitting the generated setting information in the transmission unit and
Provides communication methods, including.

Another aspect of the invention relates to implementing the various embodiments and aspects described above using hardware and software. In this regard, the present invention provides user equipment (mobile terminals) and eNodeBs (base stations). The user equipment is adapted to perform the methods described herein. Further, the eNodeB evaluates the IPMI set quality of each user device from the IPMI set quality received from the user device, and when its own scheduler schedules different user devices, the IPMI of those different user devices It has a means, which makes it possible to consider the setting quality.

It is further recognized that various embodiments of the present invention can be implemented or implemented using computing devices (processors). The computing device or processor may be, for example, a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic device. Various embodiments of the present invention may also be implemented or embodied by a combination of these devices.

In addition, various embodiments of the invention can also be implemented by software modules. These software modules are executed by the processor or directly in the hardware. It is also possible to combine software modules and hardware implementations. The software module may be stored in any kind of computer-readable storage medium, such as RAM, EPROM, EEPROM, flash memory, registers, hard disks, CD-ROMs, DVDs, and the like.

Furthermore, it should be noted that the individual features of a plurality of different embodiments of the present invention may be the subject of another invention, either individually or in any combination.
Those skilled in the art will appreciate that the invention presented in a specific embodiment can be devised with enormous variations or modifications without departing from the broadly defined concept or scope of the invention. Let's do it. Therefore, embodiments of the present invention are intended to be exemplary in all respects and are not intended to limit the invention.

Claims (15)

A communication device for device-to-device communication.
From the base station apparatus receives the timing advance value of the uplink to the base station apparatus by an index value to the timing advance command indicating the (N _TA value) (T _A command), the T _A command transmission timing of the uplink The receiver, which is a command for adjusting
A control unit that sets direct link timing advance information indicating a direct link reception timing adjustment value in the inter-device communication using the uplink _NTA value.
A transmitter that transmits a control message used for scheduling allocation of the direct link, including the set direct link timing advance information, to another communication device through the direct link.
Equipped with
And the transmission unit, the case of using the transmission to the uplink to the base station apparatus Timing Alignment Timer (TAT) has expired, after receiving the timing advance command (T _A command) from the base station apparatus Perform transmission through the direct link,
Communication device. If the communication device is in RRC_CONNECTED state, the control unit, the sets of the direct link timing advance information by using the N _TA value, when the communication device is in RRC_IDLE state, the control unit, the direct link Set timing advance information to zero,
The communication device according to claim 1. When the communication device cannot match the transmission timing of the direct link with the transmission timing of the uplink to the base station device, the control unit sets the direct link timing advance information to zero.
The communication device according to claim 1. If the communication device is in RRC_CONNECTED state, and the transmission unit, based on the direct link timing advance information set using the N _TA value, and transmits the direct link data, said communication device is in RRC_IDLE state In the case, the transmission unit transmits the direct link data based on the direct link timing advance information set to zero.
The communication device according to any one of claims 1 to 3. The transmission unit transmits the direct link data to the other communication device based on the reception timing adjustment value of the direct link indicated by the direct link timing advance information.
The communication device according to any one of claims 1 to 3. The direct link timing advance information is indicated by an 11-bit value.
The communication device according to any one of claims 1 to 5. The direct link timing advance information included in the transmitted control message is used in the other communication device to adjust the reception timing of the direct link data transmitted from the communication device.
The communication device according to any one of claims 1 to 3. A communication method for device-to-device communication.
From the base station apparatus receives the timing advance value of the uplink to the base station apparatus by an index value to the timing advance command indicating the (N _TA value) (T _A command), the T _A command transmission timing of the uplink Is a command to adjust
Using the _NTA value of the uplink, the direct link timing advance information indicating the reception timing adjustment value of the direct link in the inter-device communication is set.
A control message used for scheduling allocation of the direct link, including the set direct link timing advance information, is transmitted to another communication device through the direct link.
Wherein when the to the base station apparatus used for uplink transmission Timing Alignment Timer (TAT) has expired, transmits through the direct link from the base station device after receiving the timing advance command (T _A command) To carry out,
Communication method. In the setting, when the inter-device communication is performed in RRC_CONNECTED state, the setting of the direct link timing advance information is performed by using the N _TA value, when the inter-device communication is performed in RRC_IDLE state, Set the direct link timing advance information to zero,
The communication method according to claim 8. In the inter-device communication, when the transmission timing of the direct link cannot be matched with the transmission timing of the uplink to the base station apparatus, the direct link timing advance information is set to zero.
The communication method according to claim 8. When the communication apparatus that performs communication between the device is in the RRC_CONNECTED state, on the basis of the said direct link timing advance information set using the N _TA value, and transmits the direct link data communication apparatus for performing communication between the device Is in the RRC_IDLE state, the direct link data is transmitted based on the direct link timing advance information set to zero.
The communication method according to any one of claims 8 to 10. The direct link data is transmitted to the other communication device based on the reception timing adjustment value of the direct link indicated by the direct link timing advance information.
The communication method according to any one of claims 8 to 10. The direct link timing advance information is indicated by an 11-bit value.
The communication method according to any one of claims 8 to 12. The direct link timing advance information included in the transmitted control message is used in the other communication device to adjust the reception timing of the direct link data.
The communication method according to any one of claims 8 to 10. From the base station apparatus receives the timing advance value of the uplink to the base station apparatus by an index value to the timing advance command indicating the (N _TA value) (T _A command), the T _A command transmission timing of the uplink Is a command to adjust the processing and
Using the _NAT value of the uplink, the process of setting the direct link timing advance information indicating the reception timing adjustment value of the direct link in the inter-device communication, and
Timing used for transmitting the uplink to the base station device by transmitting a control message used for scheduling assignment of the direct link to another communication device through the direct link, including the set direct link timing advance information. If Alignment Timer (TAT) has expired, the process of implementing the transmission through the direct link from the base station device after receiving the timing advance command (T _a command),
Integrated circuit to control.