JP5890673B2 - Wireless communication system and base station - Google Patents

Description

  The present invention relates to a radio communication system and a base station, and more particularly to allocation of radio resources in the radio communication system and the base station.

  As a world standard wireless communication system, LTE (Long Term Evolution) system is standardized by 3GPP (3rd Generation Partnership Project). In LTE, a transmission bandwidth in radio communication between a base station and a mobile terminal is assigned with a resource block (RB) as a minimum unit. The bandwidth of the resource block is 180 kHz. The base station schedules radio resources to be allocated to each mobile terminal every subframe (1 ms).

  In the LTE system, the base station performs scheduling in consideration of the priority of the QCI (QoS Class Identifier) type of the connected bearer. In addition, when multiple bearers of the same QCI type are connected, priority is given in consideration of the radio section quality between the base station and the target mobile terminal of each bearer, the transmission request data size, and the average throughput when performing allocation. Determine the degree. Specifically, the priority is determined by the ratio of the maximum transmission data size (however, the upper limit is the transmission request data size) that can be estimated from the radio section quality and the average throughput. Based on these priorities, the base station allocates optimal resources to each mobile terminal according to the priority order.

  The radio quality is measured using a reference signal for both the uplink, which is data transmission from the mobile terminal to the base station, and the downlink, which is data transmission from the base station to the mobile terminal. The downlink radio quality is determined by the mobile terminal measuring SINR with respect to a reference signal transmitted from the base station to the mobile terminal. The mobile terminal feeds back the radio quality to the base station by transmitting the measured SINR to the base station in correspondence with the CQI (Channel Quality Indicator). The mobile terminal broadcasts CQI to the base station at a constant cycle. The uplink radio quality is determined by measuring the SINR of the reference signal transmitted from the mobile terminal to the base station (see, for example, Non-Patent Document 1).

  The base station schedules radio resources that are not allocated to each mobile terminal based on the radio quality at the latest notification time. Thereby, a radio | wireless communication band can be utilized efficiently.

3GPP TS 36.213 V9.2.0 (2010-06), “Physical layer procedures”

  By the way, in the communication standard of the LTE system, the frequency, the communication time, the size and the type of the packet of communication data, etc. are detailed regarding the function of allocating radio resources in the base station to the mobile terminal that requests communication Is not stipulated. On the other hand, there are three radio resource allocation methods depending on the type of data to be communicated. That is, there are a dynamic allocation algorithm that dynamically allocates, a semi-persistent allocation algorithm that performs semi-fixed allocation, and a persistent allocation algorithm that allocates fixed allocation. Basically, Dynamic Allocation Algorithm is used in the case of normal data communication. However, an appropriate algorithm can be used according to the status of the data to be transmitted and the radio resource to be allocated.

  In particular, in LTE, a Semi-Persistent Allocation Algorithm is used during Voice Packet communication such as voice call. The Voice Packet is a packet that is always generated, although the packet size is smaller than that of a packet normally used for browsing on the Internet or performing file transfer. Hereinafter, a protocol that is applied when assigning a packet that is generated in a small amount but always occurs, such as Voice Packet, using the Semi-Persistent Allocation Algorithm will be described. Hereinafter, unless otherwise specified, the case of uplink communication will be described.

  First, when transmitting a normal packet in uplink communication, (1) the base station allocates a specific band of radio resources at the start of packet transmission, and notifies the mobile terminal of information on the band allocated in this way. To do. When the information on the allocated bandwidth is notified to the mobile terminal, (2) the mobile terminal transmits data at a constant period according to the notified information. (3) The base station secures a specific band allocated at the start of packet transmission for the mobile terminal to be communicated during a certain period of time transmitted by the mobile terminal, Do not assign to terminals. In this way, a normal packet can be transmitted in uplink communication.

  However, in normal packet uplink communication started as described above, packet loss or the like occurs due to factors such as deterioration of the radio wave condition of the transmission path, and an error occurs in the packet received by the base station. Is also envisaged. In the following, a description will be given of processing performed when packet transmission is incorrect during normal packet transmission as described above.

  When an error in packet transmission is detected in the base station that has received the packet transmitted by the mobile terminal, first, (1) the base station notifies the mobile terminal that the packet transmission is incorrect. Along with this processing, (2) the base station secures a specific band of radio resources in accordance with the retransmission timing for retransmission of the packet in which the transmission error is detected. (3) When notified that the packet transmission is incorrect, the mobile terminal retransmits the packet in which the transmission error is detected after 8 subframes from the previous packet transmission. In this way, even if a normal packet cannot be correctly transmitted in uplink communication, it is possible to perform retransmission processing of the packet that has not been correctly transmitted.

  The feature of the Semi-Persistent Allocation Algorithm is that control information (allocated bandwidth information, etc.) is notified to the mobile terminal only at the start of data transmission, and control information is not notified during communication for a certain period thereafter. Thereby, compared with the case where control information is always notified, the resource for transmitting control information can be saved considerably.

  On the other hand, data transmission at a fixed period and data transmission at the time of retransmission when a packet transmission error occurs are generally autonomously performed by the mobile terminal according to the notification from the base station. For this reason, the base station must also synchronize with the mobile terminal that performs processing autonomously and perform control such as storage and processing autonomously. Therefore, as the number of mobile terminals to be processed increases, the processing load for various controls in the base station increases at an accelerated rate, and the memory consumption for storing various information also increases. This is not in line with the concept that the Semi-Persistent Allocation Algorithm tries to save resources for transmitting control information.

  In addition, when packets are transmitted at a fixed period, for example, when the same bandwidth is allocated to other mobile terminals due to loss of control information or delay of control timing due to deterioration of the transmission path, the Semi-Persistent Allocation Algorithm The transmission content of the secured mobile terminal becomes interference. Further, the fact that packets are transmitted at a constant period also in other base stations existing around a certain base station means that there is a possibility of causing constant interference. In other words, when each of the arranged base stations independently applies the Semi-Persistent Allocation Algorithm, if the same frequency is used at the same timing as that of the adjacent cell, interference is constantly generated and transmission efficiency is reduced.

  Therefore, an object of the present invention made in view of such circumstances is to allocate radio resources without increasing the processing load of the base station while avoiding interference when transmitting packets from the mobile terminal to the base station. To provide a wireless communication system and a base station.

The invention according to the first aspect to achieve the above object is
In a radio communication system that allocates radio resources for data transmission from a mobile terminal to a base station,
The base station determines whether the data transmitted from the mobile terminal is a new packet, a retransmission packet to compensate for a transmission error, or a packet for which allocation has already been reserved, and the determination together with, it allocates radio resources to the data transmission according to,
A radio resource is allocated to data transmission by the new packet after a radio resource is allocated to data transmission by the packet reserved for the allocation and the retransmission packet .

The invention according to a second aspect is the wireless communication system according to the first aspect,
The base station divides an area to which the radio resource is allocated into an area in which the allocation is dynamically changed and an area in which the allocation is fixed at a certain period, and the allocation is fixed at a certain period. In the area, the radio resources are allocated.

The invention according to the third aspect, in a wireless communication system according to the first aspect,
The base station allocates the radio resource by shifting a predetermined offset amount from the radio resource allocation in the base station adjacent to the base station.

The invention according to the fourth aspect for achieving the above object is as follows:
A base station that allocates radio resources for data transmission from a mobile terminal,
Determine whether the data transmitted from the mobile terminal is a new packet, a retransmission packet to compensate for a transmission error, or a packet that has already been reserved, and according to the determination, Allocate radio resources for data transmission ,
A radio resource is allocated to data transmission by the new packet after a radio resource is allocated to data transmission by the packet reserved for the allocation and the retransmission packet .

The invention according to a fifth aspect is the base station according to the fourth aspect ,
The area to which the radio resource is allocated is divided into an area in which the allocation is dynamically changed and an area in which the allocation is fixed at a constant period. Allocate resources.

The invention according to a sixth aspect is the base station according to the fourth aspect ,
The radio resource is allocated by shifting a predetermined offset amount from the radio resource allocation in the base station adjacent to the base station.

  According to the present invention, when a packet is transmitted from a mobile terminal to a base station in a radio communication system and a base station, radio resources can be allocated without increasing the processing load of the base station while avoiding interference.

It is a figure which shows schematic structure of the radio | wireless communications system which concerns on one Embodiment of this invention. It is a figure which shows schematic structure of the mobile terminal which concerns on one Embodiment of this invention. It is a figure which shows schematic structure of the base station which concerns on one Embodiment of this invention. 3 is a flowchart illustrating resource allocation in the uplink according to an embodiment of the present invention. It is a figure which shows the example of the allocation area | region in the uplink which concerns on one Embodiment of this invention.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a radio communication system according to an embodiment of the present invention. The mobile terminal 100 and the base station 200 perform data communication by wireless communication.

  FIG. 2 is a schematic configuration diagram of the mobile terminal 100. The mobile terminal 100 includes a wireless communication unit 110 and a control unit 120.

  The wireless communication unit 110 performs wireless communication with the base station 200. The radio communication unit 110 receives downlink data transmitted from the base station 200 and transmits uplink data to the base station 200. The control unit 120 controls and manages the entire mobile terminal 100 including each functional unit of the mobile terminal 100.

  FIG. 3 is a schematic configuration diagram of the base station 200. The base station 200 includes a wireless communication unit 210, a control unit 220, and a storage unit 230.

  The wireless communication unit 210 performs wireless communication with the mobile terminal 100. The radio communication unit 210 receives uplink data transmitted from the mobile terminal 100 and transmits downlink data to the mobile terminal 100.

  The control unit 220 is a block that controls the entire base station 200 and includes a terminal state determination unit 221 and a scheduler 222.

  Based on the information received from the mobile terminal 100, the terminal state determination unit 221 determines the type of data packet that the mobile terminal 100 intends to transmit to the base station 200 through uplink communication. That is, the terminal state determination unit 221 determines whether the data transmitted from the mobile terminal 100 is a new packet, a retransmission packet to compensate for a transmission error, or a packet that has already been reserved. To do. Here, the “new packet” is a packet of data initially transmitted from the mobile terminal 100, and the “already reserved packet” is the data transmitted from the mobile terminal 100 for the second time and thereafter. Packet.

  The scheduler 223 schedules radio resources to be allocated for radio communication between the mobile terminal 100 and the base station 200. At this time, the scheduler 223 according to the present embodiment allocates radio resources to data transmission according to the determination of the packet type by the terminal state determination unit 221.

  The storage unit 230 stores various information such as information on the mobile terminal 100 that performs communication, the type of packet determined by the terminal state determination unit 221, and the result of the scheduler 223 assigning radio resources. Even when the scheduler 223 schedules radio resources, the radio resources can be scheduled based on information such as the type of packet stored in the storage unit 230.

  Next, in the present embodiment, a process in which the base station 200 allocates radio resources to various packets will be described. In the following description, the radio communication system according to the present embodiment will be described assuming a case where radio resources are allocated to data transmission from the mobile terminal 100 to the base station 200. That is, hereinafter, a case where uplink communication is performed using the above-described Semi-Persistent Allocation Algorithm will be described.

  FIG. 4 is a flowchart illustrating resource allocation in the uplink according to an embodiment of the present invention.

  The radio resource allocation processing according to the present embodiment starts when the mobile terminal 100 is notified of an allocation request by Semi-Persistent scheduling to the base station 200. When the mobile terminal 100 is notified of an allocation request based on Semi-Persistent scheduling, the terminal state determination unit 221 determines whether or not there is a packet for which allocation has already been reserved in the data transmitted from the mobile terminal 100. (Step S11). If there is a packet whose assignment is already reserved in step S11, the scheduler 222 assigns radio resources to data transmission by the packet whose assignment is reserved (step S12).

  After step S12 or when there is no packet reserved for allocation in step S11, the terminal state determination unit 221 determines whether there is a retransmission packet for compensating for a transmission error in the data transmitted from the mobile terminal 100. Is determined (step S13). If there is a retransmission packet in step S13, the scheduler 222 allocates radio resources to data transmission by the retransmission packet (step S14).

  After step S14 or when there is no retransmission packet in step S13, the terminal state determination unit 221 determines whether or not there is a new packet to start transmission in the data transmitted from the mobile terminal 100. (Step S15). If there is a new packet in step S15, the scheduler 222 allocates radio resources to data transmission by the new packet (step S16).

  After step S16 or when there is no new packet in step S15, the radio resource allocation processing according to the present embodiment ends.

  As described above, in this embodiment, the base station 200 determines whether the data transmitted from the mobile terminal 100 is a new packet, a retransmission packet to compensate for a transmission error, or a packet whose allocation has already been reserved. It is determined whether it is due to. Then, the base station 200 allocates radio resources to the data transmission according to the determination. At this time, it is preferable that the base station 200 allocates radio resources to data transmission by a new packet after allocating radio resources to data transmission by a packet reserved for retransmission and a retransmission packet. By processing in this way, DCI (Downlink Control Information), which is control information used for downlink communication, needs to be transmitted only when radio resources are allocated for data transmission by a new packet, and needs to be transmitted in other cases. Will disappear.

  Further, according to the present embodiment, even if the number of processing target mobile terminals increases, the amount of processing load does not increase because the number increases, so the amount of processing load can be made constant. There is no additional memory consumption associated with the increase. Further, according to the present embodiment, even if an exceptional situation occurs, for example, when the DCI is not achieved, the base station and the mobile terminal are hesitant, wireless communication is automatically performed so as to avoid interference. Resources can be allocated.

  FIG. 5 is a diagram illustrating an example of resource allocation areas in the uplink according to an embodiment of the present invention.

  As shown in FIG. 4, in this embodiment, as illustrated in FIG. 4, in response to each allocation request, data transmission by various packets is performed for radio resources in a region where each subframe number (Subframe Number) is specified. An example of assignment is shown. In FIG. 5, the vertical direction represents a subframe number, and the horizontal direction represents an index of a physical resource block. The region shown in FIG. 5 is repeated with a period of 20 subframes. Therefore, uplink communication according to the allocation area shown in FIG. 5 is performed semi-persistently. This avoids allocation collisions and interference within each base station.

  In FIG. 5, the hatched area from the upper right to the lower left represents an area to which data transmission by a new packet is allocated by Semi-Persistent scheduling. In this area, radio resources are allocated to data transmission by the above-mentioned “new packet” or “already reserved packet”. An area hatched with diagonal lines from upper left to lower right represents an area to which data transmission by a retransmitted packet is assigned by Semi-Persistent scheduling. Further, the area not hatched with diagonal lines represents an area to which data transmission by other packets is assigned. As described above, when notified that the packet transmission is incorrect, the mobile terminal 100 retransmits the packet in which the transmission error is detected after 8 sub frames from the previous packet transmission. Therefore, also in the base station 200, as shown in FIG. 5, after 8 subframes from the time of new packet transmission, the retransmitted packet is placed in an area that matches the timing at which the packet in which the transmission error is detected is retransmitted. Data transmission by is assigned.

  In the “other packet areas” shown in FIG. 5, allocation using the Semi-Persistent Allocation Algorithm and allocation using the Dynamic Allocation Algorithm can be mixed. However, if a portion where the area to which the radio resource is allocated changes dynamically and an area where the area does not change dynamically are mixed, the processing load increases. Therefore, in the present embodiment, the control unit 220 manages in advance a region where the allocation is dynamically changed and a region other than that, and performs semi-persistent allocation in a region where the allocation is not dynamically changed. It is preferable to perform assignment using an algorithm. As described above, in this embodiment, the base station 200 divides an area to which radio resources are allocated into an area in which the allocation is dynamically changed and an area in which the allocation is fixed at a certain period. It is preferable to allocate radio resources in a region where the frequency is fixed at a constant period.

  In the above description, the description has been given focusing on one specific base station 200, but a plurality of other base stations that form surrounding cells are usually adjacent to the base station 200. . In the LTE system, these adjacent base stations can communicate with the base station 200 using the X2 interface. Therefore, the base station 200 can determine the offset amount of the radio resource allocation as shown in FIG. 5 via the adjacent base station and the X2 interface. For example, the control unit 220 can shift the pattern of the region shown in FIG. That is, even when each base station to which radio resources are allocated applies the Semi-Persistent Allocation Algorithm independently, the base station 200 can perform radio resource allocation so as to automatically avoid interference. As described above, in this embodiment, it is preferable that the base station 200 allocates radio resources by shifting a predetermined offset amount from radio resource allocation in other base stations adjacent to the base station 200. is there. Thereby, it is avoided that the allocation of radio resources in the base station 200 interferes with the allocation of radio resources in other neighboring base stations.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, functions included in each member, each means, each step, etc. can be rearranged so as not to be logically contradictory, and a plurality of means, steps, etc. can be combined or divided into one. Is possible.

  Further, in the above-described embodiments, description has been made assuming LTE as the mobile communication system, but the present invention is not limited to this, and radio resource allocation is performed according to the radio quality between the mobile terminal and the base station. The present invention can be similarly applied to any wireless communication system that changes the above.

DESCRIPTION OF SYMBOLS 100 Mobile terminal 110 Wireless communication part 120 Control part 200 Base station 210 Wireless communication part 220 Control part 221 Terminal state determination part 222 Scheduler 230 Storage part

Claims (6)

In a radio communication system that allocates radio resources for data transmission from a mobile terminal to a base station,
The base station determines whether the data transmitted from the mobile terminal is a new packet, a retransmission packet to compensate for a transmission error, or a packet for which allocation has already been reserved, and the determination together with, it allocates radio resources to the data transmission according to,
A radio communication system , wherein a radio resource is allocated to data transmission by the new packet after a radio resource is allocated to data transmission by the packet reserved for the allocation and the retransmission packet .   The base station divides an area to which the radio resource is allocated into an area in which the allocation is dynamically changed and an area in which the allocation is fixed at a certain period, and the allocation is fixed at a certain period. The radio communication system according to claim 1, wherein the radio resource is allocated in a region.   The radio communication system according to claim 1, wherein the base station allocates the radio resource by shifting a predetermined offset amount from radio resource allocation in a base station adjacent to the base station. A base station that allocates radio resources for data transmission from a mobile terminal,
Determine whether the data transmitted from the mobile terminal is a new packet, a retransmission packet to compensate for a transmission error, or a packet that has already been reserved, and according to the determination, Allocate radio resources for data transmission ,
A base station , wherein a radio resource is allocated to data transmission by the new packet after a radio resource is allocated to data transmission by the packet reserved for the allocation and the retransmission packet . The area to which the radio resource is allocated is divided into an area in which the allocation is dynamically changed and an area in which the allocation is fixed at a constant period. The base station according to claim 4 , which allocates resources. The base station according to claim 4 , wherein the radio resource is allocated by shifting a predetermined offset amount from radio resource allocation in a base station adjacent to the base station.

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