JP5063467B2 - Wireless communication system, wireless base station, wireless terminal, and wireless communication method - Google Patents

Description

  The present invention relates to a radio communication system, a radio base station, a radio terminal, and a radio communication method that perform packet transfer between radio base stations at the time of handover.

  Conventionally, adaptive modulation is known as one of techniques for improving communication speed in a wireless communication system. In adaptive modulation, a modulation scheme with a high communication speed is used when radio quality (SNR, etc.) is high, and a modulation scheme with a low communication speed is used when radio quality is low.

  In a wireless communication system using adaptive modulation, in order to improve communication efficiency, the size of data to be transmitted (hereinafter referred to as transmission data size) is often adjusted according to the modulation scheme. Specifically, a small transmission data size is used when a low-speed modulation scheme is used, and a large transmission data size is used when a high-speed modulation scheme is used.

  On the other hand, the wireless terminal performs a so-called handover in which the connection destination is switched to a wireless base station with better conditions during movement or the like. A wireless communication system that transfers packets between wireless base stations during such a handover has been proposed (see Non-Patent Document 1).

  Specifically, a handover source radio base station (hereinafter referred to as a handover source base station) transmits a first packet composed of data addressed to a radio terminal and a first header to a handover destination radio base station (hereinafter referred to as a handover destination). To the base station).

The handover destination base station transmits a second packet constituted by the first packet and the first header received from the handover source base station to the wireless terminal. As a result, untransmitted data can be transmitted to the wireless terminal at the handover source base station, and data loss is reduced.
“Overview for Ultra Mobile Broadband (UMB) Air Interface Specification (3GPP2 C.S0084-000-0)”, [online], [Search April 15, 2008], http://www.3gpp2.org/Public_html /specs/C.S0084-000-0_v2.0_070904.pdf

  However, in a wireless communication system that performs packet transfer between wireless base stations at the time of handover, since the first header and the second header are added to the data addressed to the wireless terminal, the ratio of the header to the data addressed to the wireless terminal, That is, there is a problem that the overhead increases.

  Further, in a radio communication system that performs packet transfer between radio base stations at the time of handover, there is the following problem when each radio base station adjusts the transmission data size according to the modulation scheme.

  Specifically, the radio quality between the handover source base station and the radio terminal is low, and the radio quality between the handover destination base station and the radio terminal is often high. In this case, the handover source base station transfers the first packet having a small size to the handover destination base station. Therefore, even if the handover destination base station can use a high-speed modulation scheme, there is a problem that the second packet having a large size cannot be transmitted and communication efficiency cannot be improved.

  Therefore, the present invention has been made to solve the above-described problems, and each wireless base station adjusts the transmission data size according to the modulation method in a system configuration in which packets are transferred between wireless base stations at the time of handover. In this case, an object is to provide a radio communication system, a radio base station, a radio terminal, and a radio communication method capable of improving communication efficiency while reducing overhead.

In order to solve the above-described problems, the present invention has the following aspects. First, according to a first aspect of the present invention, when a wireless terminal is handed over, a first packet having a size corresponding to a first wireless quality with the wireless terminal is sequentially transferred to a handover destination of the wireless terminal. a first radio base station, a handover destination of the radio terminal, have a, a second radio base station a second packet of a size corresponding to the second radio quality is transmitted to the radio terminal between said radio terminal and, wherein the first packet includes the data addressed to the wireless terminal, a first header, wherein the second packet is a first packet from the first radio base station, wherein the first header and the see contains different and including a second header a header of a protocol, a second radio base station, the payload portion is a portion excluding the second header in the second packet, from the first radio base station a plurality of said first paths of If it is possible to include the Tsu bets, the payload portion including a plurality of said first packet transmitted to the wireless terminal, the wireless terminal of the second packet received from the second radio base station If more than the first packet in the payload portion, is summarized in that to obtain a plurality of said first packet from said payload portion.

  According to such a wireless communication system, when each wireless base station adjusts the transmission data size according to the modulation method in a system configuration in which packets are transferred between wireless base stations at the time of handover, communication is performed while reducing overhead. Efficiency can be improved.

A second aspect of the present invention relates to the first aspect of the present invention, wherein the first radio base station is information indicating a communication state of the first radio base station at the time of handover of the radio terminal. The communication state information capable of specifying the size of the first packet is transmitted to the second radio base station, and the second radio base station can be included in the payload portion based on the communication state information. after determining the number of the first packet, receiving the first packet number that is the determination from the first radio base station then, the including the first packet number that is the determination to the payload portion and gist that you send to the wireless terminal.

  A third aspect of the present invention relates to the second aspect of the present invention, wherein the communication status information is at least one of the first radio quality, the first modulation scheme, or the size of the first packet. The gist is to include information.

A fourth aspect of the present invention relates to the second aspect of the present invention, wherein the second radio base station sends a notification message indicating the handover of the radio terminal during the handover of the radio terminal. When the first radio base station receives the notification message from the second radio base station, the first radio base station includes the communication status information in a response message to the notification message, and sends the response message to the first radio base station. The gist is to transmit to two radio base stations.

The fifth aspect of the present invention relates to the first aspect of the present invention, the second radio base station, said with inclusion of plurality of the first packet in the payload portion, the payload portion a plurality of the First Predetermined information indicating inclusion of a packet is included in the second header and transmitted to the wireless terminal, and the wireless terminal transmits the predetermined information in the second header of the second packet received from the second wireless base station. if it contains information, and subject matter to be determined to contain a plurality of the first packet in the payload portion.

A sixth aspect of the present invention relates to the first aspect of the present invention, the second radio base station, as well as include a plurality of the first packet in the payload portion, the plurality of the first packet of each size information indicating the size included in the payload portion is transmitted to the wireless terminal, the wireless terminal, based on the size information included in the payload portion, and acquires a plurality of said first packet from said payload portion This is the gist.

Seventh aspect of the present invention relates to the first aspect of the present invention, the wireless terminal, when acquiring the plurality of the first packets from the payload portion, included in each of the plurality of the first packet The gist is to perform reception processing of the plurality of first packets based on the first header.

Eighth aspect of the present invention is capable of communicating with the handover source for sequentially transferring the first packet including the data and the first header destined wireless terminal, said first packet from said handover source, the first a radio base station of the handover destination to send the header of different protocols and including a second header, the second packet including the wireless terminal and a header, the first packet, the wireless terminal and the handover source having a first size corresponding to the radio quality between the second packets have a size corresponding to the second radio quality between the radio base station and the radio terminal, the radio base station , if the payload portion is a portion excluding the second header in the second packet, it is possible to include a plurality of the first packets from the handover source, the payload Including a plurality of said first packet in a portion to increase the transmission to the wireless terminal.

A ninth aspect of the present invention is a radio terminal that performs a handover from a first radio base station to a second radio base station, and the first radio base station performs the handover at the time of handover of the radio terminal. A packet having a size corresponding to a first wireless quality between the wireless terminal and the first packet including data addressed to the wireless terminal and a first header is sequentially transferred to a handover destination of the wireless terminal; The second radio base station is a packet having a size corresponding to the second radio quality with the radio terminal, and the first packet from the first radio base station is different from the first header. send a header of the protocol, the second packet including the wireless terminal, the wireless terminal may contain multiple of the first packet in the payload portion of the second packet received from the second radio base station The above From payload portions to obtain a plurality of said first packet, and summarized in that executes reception processing based on the first header included in each of the plurality of the first packets the obtained.

According to a tenth aspect of the present invention, when a wireless terminal is handed over, the first wireless device sequentially transfers a first packet having a size corresponding to the first wireless quality with the wireless terminal to a handover destination of the wireless terminal. A base station and a second radio base station that is a handover destination of the radio terminal and transmits a second packet of a size according to a second radio quality between the radio terminal and the radio terminal; wherein the first packet includes data of the addressed wireless terminal, a first header, wherein the second packet is a first packet from the first radio base station, different protocol than the first header and including a second header headers, the a radio communication method used in including a wireless communication system, the second radio base station, which is the portion excluding the second header in the second packet payload portion If it is possible to include a plurality of said first packet from said first radio base station, and transmitting including the plurality of the first packet in the payload portion to the wireless terminal, the wireless terminal , if it contains a plurality of the first packet in the payload portion of the second packet received from the second radio base station, further comprising the steps of: obtaining a plurality of said first packet from said payload portion The gist.

  According to the present invention, when each radio base station adjusts the transmission data size according to the modulation method in a system configuration in which packets are transferred between radio base stations at the time of handover, communication efficiency is improved while reducing overhead. A wireless communication system, a wireless base station, a wireless terminal, and a wireless communication method can be provided.

  Next, an embodiment of the present invention will be described with reference to the drawings. Specifically, (1) schematic configuration of radio communication system, (2) detailed configuration of radio communication system, (3) details of downlink packet processing operation in radio base station, (4) details of adaptive modulation and size adjustment processing , (5) Operation of the wireless communication system, (6) Actions and effects, (7) Other embodiments will be described. In the description of the drawings in the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.

(1) Schematic Configuration of Radio Communication System First, a schematic configuration of a radio communication system, specifically (1.1) overall schematic configuration and (1.2) schematic configuration of a radio base station will be described.

(1.1) Overall Schematic Configuration FIG. 1 is an overall schematic configuration diagram of a wireless communication system 10 according to the present embodiment.

  As shown in FIG. 1, the radio communication system 10 includes a radio base station 1A (first radio base station), a radio base station 1B (second radio base station), a radio terminal 2, an access gateway 3, and a network 4. In the present embodiment, the wireless communication system 10 has a configuration based on 3GPP2 UMB Air Interface (hereinafter simply referred to as “UMB system”), which is one of wide-area IP broadband systems capable of high-speed communication.

  In the wireless communication system 10, adaptive modulation that dynamically switches a modulation class (modulation method) according to wireless quality is introduced for the purpose of increasing the communication speed. In this embodiment, a reception SINR (Signal to Interference plus Noise power Ratio) is used as the radio quality. In adaptive modulation, an appropriate modulation method is selected from a plurality of modulation methods such as BPSK (Binary Phase Shift Keying) and 24QAM (Quadrature Amplitude Modulation).

  In the wireless communication system 10, the transmission data size is set according to the modulation method in order to improve communication efficiency. Specifically, the transmission data size is set small under a situation where a modulation class with a low communication speed is used, and the transmission data size is set large under a situation where a modulation class with a high communication speed is used.

  The radio base station 1A, the radio base station 1B, and the access gateway 3 are connected to each other via a backbone network (not shown). The radio base station 1 </ b> A and the radio base station 1 </ b> B can communicate with the network 4 via the access gateway 3. Also, the radio base station 1A and the radio base station 1B can perform wired communication (that is, communication between base stations) with each other.

  The radio base station 1A and the radio base station 1B execute radio communication with the radio terminal 2 located in the communicable area (cell). The radio terminal 2 compares the reception quality of radio signals (for example, pilot signals) transmitted by the radio base station 1A and the radio base station 1B and connects to the higher reception quality. In the example of FIG. 1, the wireless terminal 2 is moving from the communicable area of the wireless base station 1A toward the communicable area of the wireless base station 1B, and switches the connection destination from the wireless base station 1A to the wireless base station 1B. Perform a handover.

  Here, data addressed to the radio terminal 2 remains in the radio base station 1A and the communication path between the radio base station 1A and the access gateway 3. Therefore, the radio base station 1A becomes a relay station (anchor) between the access gateway 3 and the radio base station 1B, and transfers untransmitted data to the radio terminal 2 to the radio base station 1B using inter-base station communication. Thereby, a handover with less data loss is realized.

  Specifically, the handover source radio base station 1A adds control data used for control of downlink communication with the radio terminal 2 as a first header to the data destined for the radio terminal 2, and addresses the radio terminal 2. The first packet including the data and the first header is sequentially transferred to the radio base station 1B. Here, the size of the first packet (transmission data size) is a size corresponding to the first modulation scheme corresponding to the first radio quality between the radio terminal 2 and the radio base station 1A.

  In addition, the handover destination radio base station 1B adds control data used for control of downlink communication with the radio terminal 2 as a second header to the first packet received from the radio base station 1A. And a second packet including the second header is transmitted to the wireless terminal 2. The size (transmission data size) of the second packet is a size corresponding to the second modulation scheme corresponding to the second radio quality between the radio terminal 2 and the radio base station 1B.

  In the UMB system, a radio base station that functions as a relay station between the access gateway 3 and the radio base station 1B, such as the radio base station 1A, is referred to as a DAP (Data Attachment Point), and is actually wireless like the radio base station 1B. A radio base station that transmits a downlink packet to the terminal 2 is referred to as FLSE (Forward Link Serving eBS), and a radio base station that actually receives an uplink packet from the radio terminal 2 such as the radio base station 1B is referred to as RLSE (Reverse Link Serving eBS). ). In some cases, FLSE and RLSE are different radio base stations.

  In the UMB system, the following (a) to (c) are assumed as a method for switching the DAP from the handover source radio base station 1A to the handover destination radio base station 1B. (A) A method of switching the DAP from the radio base station 1A to the radio base station 1B after a certain period of time has elapsed since the handover. (B) A method of switching the DAP from the radio base station 1A to the radio base station 1B when there is no user data traffic for transmission / reception. (C) A method of switching DAP from the radio base station 1A to the radio base station 1B when transmission of unprocessed / untransmitted data to the radio base station 1B is completed in the radio base station 1A. Thus, by switching the DAP from the radio base station 1A to the radio base station 1B, the DAP and FLSE / RLSE become the same radio base station.

  In the following embodiment, a case will be described in which the radio base station 1A is DAP and the radio base station 1B is FLSE in downlink communication (forward link). A case where the second radio quality between the radio terminal 2 and the radio base station 1B is higher than the first radio quality between the radio terminal 2 and the radio base station 1A will be mainly described. That is, the size (transmission data size) of the second packet transmitted by the radio base station 1B is sufficiently larger than the size (transmission data size) of the first packet transmitted by the radio base station 1A.

  FIG. 2 is a diagram for explaining a schematic configuration of the wireless terminal 2.

  In the UMB system, a plurality of communication modules exist in the wireless terminal 2 in accordance with the number of wireless base stations with which communication is performed. In FIG. 2, the communication module 20A is a communication module corresponding to the radio base station 1A. The communication module 20B is a communication module corresponding to the radio base station 1B.

  The communication module 20B receives the second packet via the radio section, executes the reception process according to the first header inserted by the radio base station 1B, and then stores the first packet obtained by the reception process in the communication module 20A. Forward. The communication module 20A performs a reception process based on the second header inserted by the radio base station 1A in the same manner as when receiving the packet directly from the radio base station 1A with respect to the first packet transferred from the communication module 20B.

  As described above, the wireless terminal 2 performs the protocol processing of the communication module 20A corresponding to the handover source radio base station 1A via the communication module 20B corresponding to the handover destination radio base station 1B during the handover. Such a method has an advantage in terms of uniformizing and unifying reception processing (communication module).

  In the UMB system, IP tunneling technology represented by IETF RFC3931 Layer Two Tunneling Protocol-Version 3 (L2TPv3) and IETF RFC2784 Generic Routing Encapsulation (GRE) is adopted. Specifically, GRE is adopted for the user data bearer between the radio base station 1A and the access gateway 3, and L2TPv3 is adopted for the user data bearer between the radio base station 1A and the radio base station 1B.

(1.2) Schematic Configuration of Radio Base Station FIG. 3 is a schematic configuration diagram showing a schematic configuration of the radio base station 1A. Since the schematic configuration of the radio base station 1B is the same as that of the radio base station 1A, description of the schematic configuration of the radio base station 1B is omitted.

  As illustrated in FIG. 3, the radio base station 1A includes an RF unit 101, a control unit 102, an I / F unit 103, and a storage unit 104.

  The RF unit 101 includes an LNA, a power amplifier, an up converter, a down converter, and the like, and transmits and receives radio signals. The I / F unit 103 is wired to the radio base station 1B and the access gateway 3 via a router or the like.

  The control unit 102 is configured by a CPU, for example, and controls various functions provided in the radio base station 1A. Further, the control unit 102 executes processing according to various protocols described later.

  The storage unit 104 is configured by a memory, for example, and stores various types of information used for control and the like in the radio base station 1A. In addition, the storage unit 104 stores in advance a table (see FIG. 8) in which the radio quality (reception SINR), the modulation class, and the transmission data size are associated with each other.

(2) Detailed Configuration of Radio Communication System Next, a detailed configuration of the radio communication system 10 will be described. FIG. 4 is a functional block configuration diagram showing detailed configurations of the radio base station 1A, the radio base station 1B, and the radio terminal 2. 4 also serves as a protocol stack diagram according to the UMB system.

  As shown in FIG. 4, the radio base station 1A includes an APP unit 11A, an IRTP unit 12A, an RLP unit 13A, an SP unit 14A, an RP unit 15A, and a PCP / MAC / PHY unit 16A. The radio base station 1B includes an APP unit 11B, an IRTP unit 12B, an RLP unit 13B, an SP unit 14B, an RP unit 15B, and a PCP / MAC / PHY unit 16B.

  The communication module 20A of the wireless terminal 2 includes an APP unit 21A, an IRTP unit 22A, an RLP unit 23A, an SP unit 24A, an RP unit 25A, and a PCP / MAC / PHY unit 26A. The communication module 20B of the wireless terminal 2 includes an APP unit 21B, an IRTP unit 22B, an RLP unit 23B, an SP unit 24B, an RP unit 25B, and a PCP / MAC / PHY unit 26B.

  The APP unit 11A, the APP unit 11B, the APP unit 21A, and the APP unit 21B execute processing based on APP (Application Protocol) in the UMB system. APP is a protocol having a plurality of standard protocols such as IP (Internet Protocol), ROHC (RObust Header Compression), and EAP (Extensible Authentication Protocol).

  The IRTP unit 12A, the IRTP unit 12B, the IRTP unit 22A, and the IRTP unit 22B execute processing based on IRTP (Inter-Route Tunneling Protocol) in the UMB system. IRTP is a protocol having an inter-base station transfer function and an inter-module transfer function in a wireless terminal.

  The RLP unit 13A, the RLP unit 13B, the RLP unit 23A, and the RLP unit 23B execute processing based on RLP (Radio Link Protocol) in the UMB system. RLP is a protocol having a fragment and reconstruction / retransmission control function. Specifically, RLP defines a SAR (Segmentation And Reassembly) sub-protocol that performs fragmentation and reassembly, and a QN (Quick Nak) sub-protocol that performs retransmission control. Note that the RLP unit 13A, the RLP unit 13B, the RLP unit 23A, and the RLP unit 23B also have a function of executing encryption / decryption of a data fragment generated by a fragment.

  The RLP unit 13A, the RLP unit 13B, the RLP unit 23A, and the RLP unit 23B include the PCP / MAC / PHY unit 16A, the PCP / MAC / PHY unit 16B, the PCP / MAC / PHY unit 26A, and the PCP / MAC / PHY unit 26B. , Information on the modulation class in use is notified. The RLP unit 13A, the RLP unit 13B, the RLP unit 23A, and the RLP unit 23B execute a fragment to which the transmission data size corresponding to the modulation class is applied based on the notified information.

  The SP unit 14A, the SP unit 14B, the SP unit 24A, and the SP unit 24B execute processing based on SP (Stream Protocol) in the UMB system. SP is a protocol that distributes data fragments generated by fragments into respective streams (packet streams). Here, in the UMB system, for example, the following uses are defined as a stream. Stream 0: Broadcast Signaling on forward link and Reserved on reverse link, Stream 1: Best Effort Delivery Signaling, Stream 2: Reliable Delivery Signaling, Stream 3: Broadcast Inter Route Tunneling on forward link and Reserved on reverse link, Stream 4: Best Effort Delivery Inter Route Tunneling etc.

  The RP unit 15A, RP unit 15B, RP unit 25A, and RP unit 25B execute processing based on RP (Route Protocol) in the UMB system. RP is a protocol for selecting a communication path (service route) between a wireless terminal and a wireless base station.

  The RLP, SP, and RP protocols described above are protocols in the radio link layer (RLC) defined by the UMB system.

  PCP / MAC / PHY unit 16A, PCP / MAC / PHY unit 16B, PCP / MAC / PHY unit 26A and PCP / MAC / PHY unit 26B are PCP / MAC / PHY (Packet Consolidation Protocol / MAC / PHY) in the UMB system. Process based on. PCP / MAC / PHY is a protocol having a function of encapsulating upper packets and wirelessly transmitting them.

  The PCP / MAC / PHY unit 16A, the PCP / MAC / PHY unit 16B, the PCP / MAC / PHY unit 26A, and the PCP / MAC / PHY unit 26B execute wireless communication using adaptive modulation. That is, the PCP / MAC / PHY unit 16A, the PCP / MAC / PHY unit 16B, the PCP / MAC / PHY unit 26A, and the PCP / MAC / PHY unit 26B measure the radio quality (reception SINR) and correspond to the radio quality. Select the modulation class. That is, the higher the radio quality, the faster the modulation class is selected.

(3) Details of Downlink Packet Processing Operation in Radio Base Station Next, details of the downlink packet processing operation in the radio base station 1A and the radio base station 1B will be described.

(3.1) Operation pattern 1
FIG. 5 is a diagram for explaining an operation pattern 1 of the downlink packet processing operation executed by the radio base station 1A and the radio base station 1B. In the operation pattern 1, a case will be described in which the first radio quality between the radio terminal 2 and the radio base station 1A is higher than the second radio quality between the radio terminal 2 and the radio base station 1B.

  The APP unit 11A of the radio base station 1A generates an upper layer packet illustrated in FIG. The APP unit 11A passes the generated upper layer packet to the RLP unit 13A.

  As shown in FIG. 5B, the RLP unit 13A divides (fragments) the upper layer packet to generate RLP fragment data, and encrypts the generated RLP fragment data. Here, the RLP fragment data is data addressed to the wireless terminal 2.

At the time of fragmentation, the RLP unit 13A sets the size of the RLP fragment data according to the first modulation scheme (modulation class) corresponding to the first radio quality between the radio base station 1A and the radio terminal 2. . Further, as shown in FIG. 5C, the RLP unit 13A adds an RLP header (RLP _A ) to the encrypted RLP fragment data to generate an RLP packet. The RLP header (RLP _A ) includes information indicating the start point and end point of RLP fragment data, a sequence number used for retransmission processing, and the like. The RLP packet generated by the RLP unit 13A is passed to the SP unit 14A.

As shown in FIG. 5D, the SP unit 14A adds an SP header (SP _A ) to the RLP packet generated by the RLP unit 13A to generate an SP packet. The SP header (SP _A ) includes information used for distribution to the stream according to the use of the RLP packet. The SP packet generated by the SP unit 14A is passed to the RP unit 15A.

As shown in FIG. 5E, the RP unit 15A adds an RP header (RP _A ) to the SP packet generated by the SP unit 14A to generate an RP packet. Then, the RP unit 15A transfers the RP packet to the radio base station 1B using inter-base station communication.

The RLP header (RLP _A ), the SP header (SP _A ), and the RP header (RP _A ) constitute a first header added to data addressed to the wireless terminal 2. Further, the RP packet constitutes a first packet including data addressed to the wireless terminal 2 and a first header.

  The transferred RP packet is transferred to the IRTP unit 12B of the radio base station 1B. As shown in FIG. 5F, the IRTP unit 12B adds an IRTP header indicating that the radio base station 1A is the transmission source to the RP packet. As a result, an IRTP packet is generated. In the wireless terminal 2, internal transfer between the communication module 20A and the communication module 20B is executed based on the IRTP header. The IRTP packet is passed to the RLP unit 13B.

  As shown in FIG. 5G, the RLP unit 13B divides (fragments) the IRTP packet to generate RLP fragment data, and encrypts the generated RLP fragment data. At that time, the RLP unit 13B sets the size of the RLP fragment data according to the second modulation scheme (modulation class) corresponding to the second radio quality between the radio base station 1B and the radio terminal 2.

Further, as shown in FIG. 5H, the RLP unit 13B adds an RLP header (RLP _B ) to the encrypted RLP fragment data to generate an RLP packet. The RLP packet generated by the RLP unit 13B is passed to the SP unit 14B.

As shown in FIG. 5 (i), the SP unit 14B adds an SP header (SP _B ) to the RLP packet generated by the RLP unit 13B to generate an SP packet. The SP packet generated by the SP unit 14B is passed to the RP unit 15B.

As shown in FIG. 5 (j), the RP unit 15B adds an RP header (RP _B ) to the SP packet generated by the SP unit 14B to generate an RP packet. The RP packet generated by the SP unit 14B is passed to the PCP / MAC / PHY unit 16B.

Here, the IRTP header, RLP header (RLP _B ), SP header (SP _B ), and RP header (RP _B ) constitute the second header. Also, the RP packet generated by the RP unit 15B constitutes a second packet including the first packet and the second header.

  The PCP / MAC / PHY unit 16B performs predetermined protocol processing on the RP packet shown in FIG. 5 (k), and then transmits the RP packet to the wireless terminal 2 via the wireless section.

(3.2) Operation pattern 2
FIG. 6 is a diagram for explaining an operation pattern 2 of the downlink packet processing operation executed by the radio base station 1A and the radio base station 1B. In operation pattern 2, a case will be described in which the second radio quality between the radio terminal 2 and the radio base station 1B is higher than the first radio quality between the radio terminal 2 and the radio base station 1A. In addition, the description which overlaps with the operation pattern 1 is abbreviate | omitted.

  As shown in FIG. 6A, the RP unit 15A of the radio base station 1A sequentially transfers RP packets (first packets) to the radio base station 1B. The transferred RP packet is transferred to the IRTP unit 12B of the radio base station 1B.

  Here, as shown in FIG. 6B, the size of the IRTP payload which is the payload portion excluding the second header in the second packet is larger than the size of the RP packet (first packet). When the size of the IRTP payload (payload portion) is larger than the size of the RP packet (first packet), the IRTP unit 12B determines whether or not a plurality of RP packets can be included in the IRTP payload. Here, it is determined that a plurality of RP packets can be included in the IRTP payload. That is, in this embodiment, the IRTP unit 12B constitutes a determination unit.

  When the IRTP unit 12B determines that a plurality of RP packets can be included in the IRTP payload, the IRTP unit 12B includes a plurality of RP packets in the IRTP payload. In the example of FIG. 6B, the IRTP unit 12B includes three RP packets in the IRTP payload. That is, in this embodiment, the IRTP unit 12B constitutes a packet processing unit.

By including a plurality of RP packets in the IRTP payload in this way, one second header (IRTP header, RLP header (RLP _B ), SP header (SP _B ), and RP header (RP _B ) is added to the plurality of RP packets. )). That is, the overhead can be reduced as compared with the case where one second header is added to one RP packet. In addition, as the number of RP packets included in the IRTP payload increases, the overhead can be significantly reduced.

  The IRTP unit 12B combines a plurality of RP packets and sandwiches an offset field at the boundary between the RP packets. The offset field consists of size information indicating the size of each RP packet. As a result, the wireless terminal 2 easily acquires the RP packet.

  Then, the IRTP unit 12B adds an IRTP header to the IRTP payload. As shown in FIG. 7, the IRTP header is information on an ID (route ID, pilot ID, base station ID) indicating a transfer source base station (in this case, the wireless base station 1A). In this embodiment, a new combined bit is provided in the IRTP header field. The combined bit is predetermined information indicating whether or not the IRTP packet is a combination of a plurality of transfer packets from the handover source base station. In the example of FIG. 7, when the combined bit is 0, it indicates that there is no connection, and when the combined bit is 1, it indicates that there is a connection.

  Next, as illustrated in FIG. 6C, the RLP unit 13B omits the division (fragment) of the IRTP packet and performs only the encryption. Note that the RLP unit 13B sets the size of the second packet and the IRTP payload according to the second modulation scheme (modulation class) corresponding to the second radio quality between the radio base station 1B and the radio terminal 2. Have

Furthermore, as shown in FIG. 6D, the RLP unit 13B adds an RLP header (RLP _B ) to the encrypted RLP fragment data to generate an RLP packet. As shown in FIG. 6E, the SP unit 14B adds an SP header (SP _B ) to the RLP packet generated by the RLP unit 13B to generate an SP packet. As shown in FIG. 6F, the RP unit 15B adds an RP header (RP _B ) to the SP packet generated by the SP unit 14B to generate an RP packet. As described above, the IRTP header, RLP header (RLP _B ), SP header (SP _B ), and RP header (RP _B ) constitute the second header.

  The PCP / MAC / PHY unit 16B performs predetermined protocol processing on the RP packet illustrated in FIG. 6F, and then transmits the RP packet to the wireless terminal 2 through the wireless section.

(4) Details of Adaptive Modulation and Size Adjustment Processing Next, details of adaptive modulation and size adjustment processing will be described. FIG. 8 is a diagram illustrating a configuration example of a table in which radio quality (reception SINR), a modulation class, and a transmission data size are associated with each other.

  In the example of FIG. 8, a total of nine modulation classes of modulation classes 0 to 8 are prepared. Modulation class 8 is the fastest modulation class, and modulation class 0 is the slowest modulation class. Specifically, 24QAM is used in modulation class 8, and π / 2-BPSK is used in modulation class 0.

In each modulation class, a threshold for radio quality (reception SINR) is defined. For example, when the radio quality (reception SINR) exceeds the threshold SINR ₈ , the modulation class 8 is applied. Modulation class 7 is applied when the radio quality (received SINR) is below threshold SINR ₈ and above threshold SINR ₇ . Similarly, modulation class 6 is applied when the radio quality (received SINR) is below threshold SINR ₇ and above threshold SINR ₆ .

Each modulation class is associated with a transmission data size. Specifically, the transmission data size (SIZE ₈ ) corresponding to the modulation class 8 is the maximum, and the transmission data size (SIZE ₀ ) corresponding to the modulation class 0 is the minimum.

(5) Operation of Radio Communication System Next, with reference to FIG. 9 to FIG. 12, the operation of the radio communication system 10, specifically, (5.1) Overall schematic operation, (5.2) Radio base station The operation flow and (5.3) the operation flow of the wireless terminal will be described.

(5.1) Overall Schematic Operation FIG. 9 is a sequence diagram showing the overall schematic operation of the radio communication system 10.

  In step S11, the radio base station 1A and the radio terminal 2 are being connected, and the radio base station 1A transmits a downlink packet to the radio terminal 2.

  In step S12, the radio terminal 2 executes a handover from the radio base station 1A to the radio base station 1B.

  In step S13, the radio base station 1B transmits to the radio base station 1A an IPT-Notification message (handover notification message) notifying that the radio terminal 2 has been handed over to the radio base station 1B.

  In step S14, the radio base station 1A transmits to the radio base station 1B an IPT-Notification Ack message that is an acknowledgment message for the IPT-Notification message. Here, the radio base station 1B transmits Link Adaptation Info (communication state information) included in the IPT-Notification Ack message.

  Here, Link Adaptation Info is information on a modulation class (first modulation scheme) used by the radio base station 1A. Thereby, the IRTP unit 12B of the radio base station 1B determines in advance whether or not a plurality of RP packets can be included in the IRTP payload, and determines the number of RP packets that can be included in the IRTP payload. It can be determined (predicted) in advance. However, the information is not limited to the information on the modulation class (first modulation scheme) as described above, but may be information on the size of the first packet.

  In step S15, the radio base station 1A transfers the downlink packet to be transmitted to the radio terminal 2 to the radio base station 1B.

  In step S16, the radio base station 1B transmits the downlink packet transferred from the radio base station 1A to the radio terminal 2. At that time, the radio base station 1A includes a plurality of RP packets in the IRTP payload based on the Link Adaptation Info included in the IPT-Notification Ack message received in step S14.

  FIG. 10 is a diagram illustrating a message configuration example of the IPT-Notification Ack message.

  As shown in FIG. 10, in the IPT-Notification Ack message according to the present embodiment, a Link Adaptation Info field is added to the IPT-Notification Ack message according to the normal UMB system. The Link Adaptation Info field stores the above-mentioned Link Adaptation Info.

(5.2) Operation Flow of Radio Base Station FIG. 11 is a flowchart showing a downlink packet processing operation in the radio base station 1B.

  In step S101, the radio base station 1B receives the downlink packet and determines whether the packet is transferred from another radio base station (step S102). If it is a downlink packet transferred from another radio base station, the process proceeds to step S103. If it is not a downlink packet transferred from another radio base station, that is, the process that is received from the access gateway 3 proceeds to step S104. In step S104, normal processing is performed by the RLP unit 13B, the SP unit 14B, and the RP unit 15B.

  In step S103, the IRTP unit 12B of the radio base station 1B determines whether there is an IRTP packet being assembled. If there is an IRTP packet being assembled, the process proceeds to step S105. If there is no IRTP packet being assembled, the process proceeds to step S104. In step S105, the IRTP unit 12B sets the combined bit to 1.

  In step S104, the IRTP unit 12B determines whether or not Link Adaptation Info has been received from the radio base station 1A. If Link Adaptation Info has been received, the process proceeds to step S107. If Link Adaptation Info has not been received, the process proceeds to step S106. In step S106, the IRTP unit 12B waits for an IPT-Notification Ack message.

  In step S107, the IRTP unit 12B determines the number “n” of RP packets that can be included in the IRTP payload based on the Link Adaptation Info. For example, if the IRTP payload size is A and the RP packet size is B, the value obtained by dividing A by B can be “n”.

  In step S108, the IRTP unit 12B attaches an IRTP header to the IRTP payload.

  In step S109, the IRTP unit 12B stores the above-described offset and RP packet in the IRTP payload, and increments the transmission counter (adds 1). Note that the initial value of the transmission counter is zero. In other words, unless the last RP packet arrives, the above-described process of storing the offset and RP packet in the IRTP payload is repeated until the transmission counter reaches “n”.

  In step S110, the IRTP unit 12B determines whether or not the transmission counter has reached “n” or the last RP packet. If any of these conditions is satisfied, the process proceeds to step S111.

  In step S111, the SP unit 14B executes SP processing. In step S112, the RP unit 15B executes the RP process. In step S113, the PCP / MAC / PHY unit 16B transmits the packet (second packet) to the wireless terminal 2.

(5.3) Operation Flow of Wireless Terminal FIG. 12 is a flowchart showing a downlink packet processing operation in the communication module 20B of the wireless terminal 2.

  In step S201, the PCP / MAC / PHY unit 26B receives the packet (second packet).

In step S202, the RP unit 25B executes a packet reception process based on the RP header (RP _B ).

In step S203, the SP unit 24B executes a packet reception process based on the SP header (SP _B ).

In step S204, the RLP unit 23B performs packet reception processing based on the RLP header (RLP _B ).

  In step S205, the IRTP unit 22B determines whether there is an IRTP header, that is, whether the packet has been transferred between base stations. If there is no IRTP header, the packet is passed to the APP unit 21B. If there is an IRTP header, the process proceeds to step S206.

  In step S206, the IRTP unit 22B determines whether or not the combined bit in the IRTP header is 1 (ON). If the combined bit is 1 (ON), the process proceeds to step S207. If the combined bit is 0 (OFF), the process proceeds to step S208.

  In step S207, the IRTP unit 22B deletes the IRTP header. Further, the IRTP unit 22B cuts out the RP packet from the IRTP payload using the offset in the IRTP payload.

  In step S208, the IRTP unit 22B deletes the IRTP header and obtains an RP packet.

  In step S209, the IRTP unit 22B passes the RP packet to the RP unit 25A of the communication module 20A. The RP packet reaches the upper application layer after normal RP, SP, and RLP processing.

(6) Operation and Effect As described above, according to the present embodiment, by including a plurality of RP packets (first packets) in the IRTP payload (payload portion), a large amount of data can be obtained in one second packet. Since transmission is possible, it is possible to effectively use radio resources and improve communication efficiency. In addition, one second header (IRTP header, RLP header (RLP _B ), SP header (SP _B ), and RP header (RP _B )) is sufficient for a plurality of RP packets (first packets). The overhead can be reduced.

  According to the present embodiment, the IRTP unit 12B determines the number “n” of RP packets (first packets) that can be included in the IRTP payload based on the Link Adaptation Info, and the determined number “n”. Since the RP packet is included in the IRTP payload as soon as it is received from the radio base station 1A, transmission delay can be suppressed.

  According to the present embodiment, since the Link Adaptation Info includes information on either the modulation class or the transmission data size in the radio base station 1A, the IRTP unit 12B easily specifies the transmission data size in the radio base station 1A. be able to.

  According to the present embodiment, the radio base station 1A transmits an IPT-Notification Ack message including Link Adaptation Info. Thereby, when a handover occurs, Link Adaptation Info can be immediately notified to the radio base station 1B. In addition, since existing messages specified in the UMB system are used to notify Link Adaptation Info, the amount of traffic can be reduced and the processing load can be reduced compared to the case where a dedicated message is newly provided. Can do.

  According to the present embodiment, the IRTP unit 12B includes a combined bit “1” (predetermined information) indicating that a plurality of RP packets (first packet) are included in the IRTP payload in the IRTP header (second header). If the combined bit is “1”, the IRTP unit 22B of the wireless terminal 2 determines that the IRTP payload includes a plurality of RP packets. Therefore, the IRTP unit 22B can confirm that the IRTP payload includes a plurality of RP packets without inspecting the IRTP payload.

  According to the present embodiment, the IRTP unit 12B includes an offset (size information) indicating the size of each RP packet (first packet) in the IRTP payload. The IRTP unit 22B of the wireless terminal 2 acquires a plurality of RP packets from the IRTP payload based on the offset included in the IRTP payload. Thereby, a plurality of RP packets can be easily acquired from the IRTP payload.

  According to the present embodiment, the communication module 20A of the wireless terminal 2 executes reception processing of a plurality of RP packets based on the first header included in each of the plurality of RP packets acquired from the IRTP payload. Therefore, even when a plurality of RP packets are collected, normal reception processing can be realized.

(7) Other Embodiments As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the embodiment described above, the communication state information is information on either the modulation class or the transmission data size in the radio base station 1A, but instead of the information on the modulation class or the transmission data size, the radio state information in the radio base station 1A Information on quality (radio quality between the radio base station 1B and the radio terminal 2) may be used.

  In this case, the radio base station 1B can derive the transmission data size in the radio base station 1A from the radio quality in the radio base station 1A using the table described above. As described above, the communication state information may be any information as long as it is information that can specify the transmission data size in the radio base station 1A.

  Further, the communication status information is not limited to including information on any of radio quality, modulation class, or transmission data size in the radio base station 1A, and may include all of these information.

  In the above-described embodiment, a total of nine modulation classes of modulation classes 0 to 8 are prepared. However, the number is not limited to nine, and ten or more or eight or less modulation classes may be prepared. Further, although 24QAM is used in the modulation class having the highest communication speed, it is not limited to 24QAM, and higher-speed 64QAM may be used.

  In the embodiment described above, the received SINR is used as the radio quality. However, the received SINR is not limited to the received SINR, and a received signal strength indicator (RSSI) or a received BER (Bit Error Rate) may be used.

  In the above-described embodiment, the configuration based on the UMB system has been described. However, the present invention is not limited to the UMB system, and the present invention is applied to any radio communication system that uses adaptive modulation and transfers packets between radio base stations at the time of handover. Is possible.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

1 is an overall schematic configuration diagram of a wireless communication system according to an embodiment of the present invention. It is a figure for demonstrating schematic structure of the radio | wireless terminal which concerns on embodiment of this invention. It is a schematic block diagram which shows schematic structure of the wireless base station which concerns on embodiment of this invention. It is a functional block block diagram which shows the detailed structure of the wireless base station and wireless terminal which concern on embodiment of this invention. It is a figure for demonstrating the operation pattern 1 of the downlink packet processing operation which concerns on embodiment of this invention. It is a figure for demonstrating the operation pattern 2 of the downlink packet processing operation which concerns on embodiment of this invention. It is a figure which shows the structural example of the IRTP header which concerns on embodiment of this invention. It is a figure which shows the structural example of the table which matched radio | wireless quality (reception SINR), the modulation class, and the transmission data size. It is a sequence diagram which shows the whole schematic operation | movement of the radio | wireless communications system concerning embodiment of this invention. It is a figure which shows the message structural example of the IPT-Notification Ack message which concerns on embodiment of this invention. It is a flowchart which shows the processing operation | movement of the downlink packet in the wireless base station which concerns on embodiment of this invention. It is a flowchart which shows the processing operation | movement of the downlink packet in the communication module of the radio | wireless terminal which concerns on embodiment of this invention.

Explanation of symbols

1A, 1B ... wireless base station, 2 ... wireless terminal, 3 ... access gateway, 4 ... network, 10 ... wireless communication system, 11A, 11B, 21A, 21B ... APP part, 12A, 12B, 22A, 22B ... IRTP part, 13A, 13B, 23A, 23B ... RLP unit, 14A, 14B, 24A, 24B ... SP unit, 15A, 15B, 25A, 25B ... RP unit, 16A, 16B, 26A, 26B ... PCP / MAC / PHY unit, 20A, 20B ... Communication module 101 ... RF unit 102 ... Control unit 103 ... I / F unit 104 ... Storage unit

Claims (10)

During handover of a wireless terminal, a first radio base station to the first packet of a size corresponding to the first radio quality sequentially transferred to the handover destination of the radio terminal between said radio terminal,
A second wireless base station that is a handover destination of the wireless terminal and transmits a second packet having a size corresponding to a second wireless quality with the wireless terminal to the wireless terminal ;
Wherein the first packet includes the data of the addressed wireless terminal, a first header, a,
It said second packet, said first packet from said first radio base station, seen including and a including a second header headers different protocols from the first header,
If the second radio base station, the payload portion is a portion excluding the second header in the second packet, it is possible to include a plurality of said first packet from said first radio base station, including a plurality of said first packet to the payload portion is transmitted to said wireless terminal,
The wireless terminal, the second case that includes a plurality of said first packet to the payload portion of the received second packet from the radio base station, a radio communication system for acquiring a plurality of said first packet from said payload portion . The first radio base station transmits communication status information that indicates a communication status of the first radio base station and can specify a size of the first packet at the time of handover of the radio terminal. To the base station,
The second radio base station, based on the communication state information, the payload after determining the number of the first packet that can be included in part, the decision to said first said first packet number received from the radio base station then, the wireless communication system of claim 1 wherein the first packet number that is the determination included in the payload part that sends to the wireless terminal.   The wireless communication system according to claim 2, wherein the communication state information includes at least one piece of information among the first wireless quality, the first modulation scheme, or the size of the first packet. The second radio base station, when the handover of the radio terminal, and sends a notification message indicating a handover of the wireless terminal to the first radio base station,
When the first radio base station receives the notification message from the second radio base station, the first radio base station includes the communication state information in a response message to the notification message and transmits the response message to the second radio base station. The wireless communication system according to claim 2. The second radio base station, said with inclusion of plurality of the first packet in the payload portion, said including predetermined information which indicates that including a plurality of said first packet to the payload portion to the second header radio Send it to your device ,
The wireless terminal, when said predetermined information is included in the second header of the received second packet from the second radio base station, according to claim determines that includes a plurality of said first packet to the payload portion The wireless communication system according to 1. The second radio base station, as well as include a plurality of the first packet in the payload portion, and sends the size information indicating the size of each of the plurality of the first packets to the wireless terminal included in the payload part,
The wireless terminal, on the basis of the said size information included in the payload part, a wireless communication system according to claim 1 for obtaining a plurality of said first packet from said payload portion. The wireless terminal, when acquiring the plurality of the first packets from the payload portion, based on said first header included in each of the plurality of the first packet, executes the process of receiving the plurality of first packet The wireless communication system according to claim 1. It is possible to communicate with a handover source that sequentially transfers a first packet including data addressed to a wireless terminal and a first header, and includes a header of a protocol different from the first packet from the handover source and the first header. A handover destination radio base station that transmits a second packet including a second header to the radio terminal,
The first packet has a size according to a first radio quality between the radio terminal and the handover source, and the second packet is a second radio between the radio terminal and the radio base station. have a size in accordance with the quality,
If the radio base station, the payload portion is a portion excluding the second header in the second packet, it is possible to include a plurality of the first packets from the handover source, a plurality in the payload part the radio base station to be transmitted to the wireless terminal, including the first packet. A wireless terminal that performs a handover from a first wireless base station to a second wireless base station,
The first radio base station is a packet of a size corresponding to the first radio quality with the radio terminal at the time of handover of the radio terminal, the data addressed to the radio terminal, a first header, Are sequentially transferred to the handover destination of the wireless terminal,
The second radio base station is a packet having a size corresponding to the second radio quality with the radio terminal, and the first packet from the first radio base station is different from the first header. A second packet including a protocol header to the wireless terminal;
The wireless terminal may comprise a plurality of the first packet in the payload portion of the second packet received from the second radio base station, to obtain a plurality of said first packet from said payload portion, the obtained wireless terminal for performing a reception process on the basis of the first header included in each of the plurality of the first packets. A first radio base station that sequentially transfers a first packet of a size corresponding to a first radio quality with the radio terminal to a handover destination of the radio terminal at the time of handover of the radio terminal;
A second wireless base station that is a handover destination of the wireless terminal and transmits a second packet having a size corresponding to a second wireless quality with the wireless terminal to the wireless terminal;
Wherein the first packet includes the data of the addressed wireless terminal, a first header, a,
Said second packet, said first and said first packet from the radio base station, a radio communication method used and header including second header of different protocols, to including a wireless communication system from the first header Because
If the second radio base station, the payload portion is a portion excluding the second header in the second packet, it is possible to include a plurality of said first packet from said first radio base station, transmitting to the wireless terminal including a plurality of said first packet to the payload portion,
A step wherein the wireless terminal, to get a case, a plurality of the first packets from the payload portion includes a plurality of said first packet to the payload portion of the second packet received from the second radio base station,
A wireless communication method comprising:

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