JP2012151878A - Radio communication system, radio base station, radio terminal, and radio communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the overhead of packets transmitted/received between a radio base station at the handover target and a radio terminal when packets are transferred between radio base stations during handover.SOLUTION: A radio terminal 2 includes: a first communication module 20A which inserts an RLP header (A), an SP header (A), and an RP header (A) into a packet to be transmitted to a first radio base station 1A as the handover source; and a second communication module 20B which inserts an RLP header (B), an SP header (B), and an RP header (B) into a packet to be transmitted to a second radio base station 1B as the handover target. The second communication module 20B skips insertion of the RLP header (B), the SP header (B), and the RP header (B) into a packet transferred by the first communication module 20A and transmits to the second radio base station 1B the packet transferred by the first communication module 20A.

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 of the radio terminal.

  Conventionally, a wireless terminal performs a so-called handover in which a connection destination is switched to a wireless base station with better conditions during movement or the like. During such a handover, a packet transmitted / received by a wireless terminal is transferred between a handover source radio base station (hereinafter referred to as a first radio base station) and a handover destination radio base station (hereinafter referred to as a second radio base station). A wireless communication system for transferring has been proposed.

  As a wireless communication system that employs such a system, for example, UMB (Ultra Mobile Broadband) whose standard is being developed in 3GPP2 (Third Generation Partnership Project 2) can be cited (for example, see Non-Patent Document 1).

  In downlink communication, the wireless terminal receives from the second wireless base station a packet transferred from the first wireless base station to the second wireless base station. At that time, each of the first radio base station and the second radio base station inserts downlink control data used for downlink communication control (for example, retransmission control or fragment) with the radio terminal as a packet header.

  Then, the radio terminal executes packet reception processing based on each downlink control data inserted in the packet received from the second radio base station. Such a method is advantageous in terms of uniformizing and unifying packet reception processing.

  Further, in uplink communication, the radio terminal transmits, to the packet transmitted to the second radio base station, uplink control data used for controlling uplink communication with the first radio base station, and the second radio base station. Uplink control data used for uplink communication control is inserted as a header.

“Overview for Ultra Mobile Broadband (UMB) Air Interface Specification (3GPP2 C.S0084-000-0)”, [online], [searched on March 17, 2008], <URL: http: //www.3gpp2. org / Public_html / specs / C.S0084-000-0_v2.0_070904.pdf>

  However, since each of the first radio base station and the second radio base station inserts the downlink control data into the packet in the downlink communication, the control data (header) of the packet transmitted from the second radio base station to the radio terminal The overhead, which is a proportion, increases.

  Also in uplink communication, the radio terminal is transmitted from the radio terminal to the second radio base station in order to insert uplink control data corresponding to each of the first radio base station and the second radio base station into the packet. Packet overhead increases.

  Thus, in a conventional wireless communication system that performs packet transfer between wireless base stations at the time of handover of a wireless terminal, packets transmitted and received between the second wireless base station (handover destination wireless base station) and the wireless terminal There was a problem that the overhead increased.

  Therefore, the present invention has been made to solve the above-described problem, and in a system configuration in which packet transfer is performed between radio base stations at the time of handover of a radio terminal, between the radio base station that is the handover destination and the radio terminal. An object of the present invention is to provide a wireless communication system, a wireless base station, a wireless terminal, and a wireless communication method that can reduce the overhead of packets transmitted and received by the wireless communication.

  In order to solve the above-described problem, a first radio base station (first radio base station 1A), a second radio base station (second radio base station 1B) capable of communicating with the first radio base station, A wireless communication system (wireless communication system 10) including a wireless terminal (wireless terminal 2) that switches a connection destination from a first wireless base station to the second wireless base station, wherein the first wireless base station For the packet to be transmitted to the terminal, first downlink control data (RLP header (A), SP header (A), RP header (used for controlling downlink communication between the wireless terminal and the first wireless base station) ( A)) is inserted into the first downlink control data insertion unit (RLP unit 13A, SP unit 14A, RP unit 15A) and the packet in which the first downlink control data is inserted at the time of switching the connection destination Second radio base station A packet transfer unit (RP unit 15A) for transferring, and the second radio base station controls downlink communication between the radio terminal and the second radio base station for a packet to be transmitted to the radio terminal 2nd downlink control data insertion part (RLP part 13B, SP part 14B, RP part 15B) which inserts the 2nd downlink control data (RLP header (B), SP header (B), RP header (B)) used for And a packet transmission unit (PCP / MAC / PHY unit 16B) that transmits the packet transferred by the first radio base station to the radio terminal, and the second downlink control data insertion unit includes the first downlink control data insertion unit, The insertion of the second downlink control data into the packet transferred by the radio base station is omitted, and the radio terminal is inserted into the packet received from the second radio base station. It may be required to perform the packet reception processing based on the first downlink control data.

  According to this, in a system configuration that performs packet transfer between radio base stations at the time of handover of a radio terminal, packets transmitted and received between the radio base station that is the handover destination (ie, the second radio base station) and the radio terminal A wireless communication system capable of reducing overhead can be provided.

  The wireless terminal is provided corresponding to the first wireless base station, and performs a packet reception process based on the first downlink control data (first communication module 20A), A second downlink reception processing unit (second communication module 20B) that is provided corresponding to the second radio base station and executes packet reception processing based on the first downlink control data or the second downlink control data; When the second radio base station transmits the packet transferred by the first radio base station to the radio terminal, the packet transmitted to the radio terminal is transferred by the first radio base station A downlink transfer information insertion unit (IRTP unit 12B) for inserting downlink transfer information (IRTP header (B)) indicating the packet, and the second downlink reception processing unit includes: Packet reception processing based on the first downlink control data inserted in the packet received from the second radio base station when the downlink transfer information is inserted in the packet received from the second radio base station And the first downlink reception processing unit omits the packet reception processing based on the first downlink control data when the second downlink reception processing unit executes packet reception processing based on the first downlink control data. It is good also as doing a summary.

  The first radio base station further includes a first downlink retransmission processing unit (RLP unit 13A) that executes a first downlink retransmission process for retransmitting a packet that the radio terminal has failed to receive to the radio terminal, 2 The radio base station includes a second downlink retransmission processing unit (RLP unit 13B) that executes a second downlink retransmission process for retransmitting a packet that the radio terminal has failed to receive to the radio terminal, and the second downlink retransmission process. The unit acquires the first downlink retransmission control information (RLP information) used for the first downlink retransmission process from the first downlink retransmission processing unit at the time of switching the connection destination, and acquires the acquired first downlink retransmission control. The second downlink retransmission processing unit executes the second downlink retransmission processing by using the first downlink retransmission control information by the second downlink retransmission processing unit. If the first It may be required to omit the Ri retransmission process.

  In addition, the wireless terminal failed to receive a first downlink retransmission request unit (RLP unit 13A) that executes a first downlink retransmission request that requests the first downlink retransmission processing unit to retransmit a packet that has failed to be received. A second downlink retransmission request unit (RLP unit 13B) that executes a second downlink retransmission request for requesting retransmission of the packet to the second downlink retransmission processing unit, wherein the second downlink retransmission request unit includes the connection destination At the time of switching, second downlink retransmission control information (RLP information) used for the first downlink retransmission request is acquired from the first downlink retransmission request unit, and the second downlink retransmission control information is acquired using the acquired second downlink retransmission control information. When the second downlink retransmission request unit executes the second downlink retransmission request by using the second downlink retransmission control information, the first downlink retransmission request unit executes the first downlink retransmission request. Omitting the request It may be used as the subject matter of the present invention.

  In addition, the first radio base station includes a first downlink fragment processing unit (RLP unit 23A) that executes a first downlink fragment process for decomposing user data (APP data) to be transmitted to the radio terminal and generating a packet. The second radio base station includes a second downlink fragment processing unit (RLP unit 23B) that performs a second downlink fragment process for decomposing user data (APP data) to be transmitted to the radio terminal and generating a packet. And the second downlink fragment processing unit may omit the second downlink fragment processing when the connection destination is switched.

  In order to solve the above-described problems, the present invention has the following aspects. First, a first aspect of the present invention includes a first radio base station (first radio base station 1A) and a second radio base station (second radio base station 1B) capable of communicating with the first radio base station. A wireless communication system (wireless communication system 10) including a wireless terminal (wireless terminal 2) that switches a connection destination from the first wireless base station to the second wireless base station, wherein the wireless terminal For packets to be transmitted to the radio base station, first uplink control data (RLP header (A), SP header (A), RP, used for controlling uplink communication between the radio terminal and the first radio base station) The first transmission processing unit (first communication module 20A) for inserting the header (A)) and the uplink direction between the radio terminal and the second radio base station for the packet to be transmitted to the second radio base station Second uplink control data used for communication control (RLP header (B), SP header (B), RP header (B)) are inserted, and the first transmission processor is connected to the connection destination. At the time of switching, the packet in which the first uplink control data is inserted is transferred to the second transmission processing unit, and the second transmission processing unit transfers the packet transferred by the first transmission processing unit to the second transmission processing unit. The second radio base station transmits the packet received from the radio terminal while transmitting to the two radio base stations and omitting the insertion of the second uplink control data into the packet transferred by the first transmission processing unit. Is transferred to the first radio base station.

  According to such an aspect, in a system configuration that performs packet transfer between radio base stations at the time of handover of a radio terminal, transmission / reception is performed between the radio base station that is the handover destination (ie, the second radio base station) and the radio terminal. It is possible to provide a wireless communication system capable of reducing packet overhead.

  A second aspect of the present invention relates to the sixth aspect of the present invention, wherein the first radio base station performs a first uplink reception processing unit (RLP unit) that performs packet reception processing based on the first uplink control data. 13A, SP unit 14A, RP unit 15A), and the second radio base station performs a second uplink reception processing unit (RLP) that performs packet reception processing based on the first uplink control data or the second uplink control data. 13B, SP unit 14B, RP unit 15B), and the second transmission processing unit transmits the packet transferred by the first transmission processing unit to the second radio base station. An uplink transfer information insertion unit (IRTP) for inserting uplink transfer information (IRTP header (B)) indicating the packet transferred by the first transmission processing unit to the packet transmitted to the base station 22B), and when the uplink transfer information is inserted in the packet received from the wireless terminal, the second uplink reception processing unit is inserted in the packet received from the wireless terminal. Packet reception processing based on uplink control data is executed, and the first uplink reception processing unit, when the second uplink reception processing unit executes packet reception processing based on the first uplink control data, the first uplink control The gist is to omit the packet reception processing based on the data.

  A third aspect of the present invention relates to the sixth aspect of the present invention, wherein the first transmission processing unit retransmits a packet that the first radio base station failed to receive to the first radio base station. A first uplink retransmission processing unit (RLP unit 23A) that performs one uplink retransmission processing, wherein the second transmission processing unit retransmits a packet that the second radio base station has failed to receive to the second radio base station; A second uplink retransmission processing unit (RLP unit 23B) for executing the second uplink retransmission processing to be performed, and the second uplink retransmission processing unit is used for the first uplink retransmission processing when the connection destination is switched. 1 uplink retransmission control information (RLP information) is acquired from the first uplink retransmission processing unit, the second uplink retransmission process is executed using the acquired first uplink retransmission control information, and the first uplink retransmission processing unit The second uplink retransmission processing unit When performing the second uplink retransmission processing using the retransmission control information, and summary of omitting the first uplink retransmission processing.

  A fourth aspect of the present invention relates to the eighth aspect of the present invention, wherein the first radio base station requests a first uplink retransmission request to request the first uplink retransmission processing unit to retransmit a packet that has failed to be received. And the second radio base station executes a second uplink retransmission request for requesting the second uplink retransmission processing unit to retransmit a packet that has failed to be received. A second uplink retransmission request unit (RLP unit 13B) that performs second uplink retransmission control information (RLP information) used for the first uplink retransmission request when the connection destination is switched. ) From the first uplink retransmission request unit, execute the second uplink retransmission request using the second uplink retransmission control information, and the first uplink retransmission request unit includes the second uplink retransmission request unit Using the second uplink retransmission control information, When performing uplink retransmission request, and the gist of omitting the first uplink retransmission request.

  A fifth aspect of the present invention relates to the sixth aspect of the present invention, wherein the first transmission processing unit generates a packet by decomposing user data (APP data) transmitted to the first radio base station. A first uplink fragment processing unit (RLP unit 23A) that performs first uplink fragment processing is provided, and the second transmission processing unit decomposes user data (APP data) to be transmitted to the second radio base station and packet The second uplink fragment processing unit (RLP unit 23B) that executes the second uplink fragment processing for generating the second uplink fragment processing unit omits the second uplink fragment processing at the time of switching the connection destination. The gist is to do.

  Further, when the connection destination of the wireless terminal (wireless terminal 2) is switched, the wireless terminal and the other wireless base station are switched from the other wireless base station (first wireless base station 1A) that is the switching destination of the connection destination. Receiving the packet in which the first downlink control data (RLP header (A), SP header (A), RP header (A)) used for the downlink communication control is inserted, and switching destination of the connection destination A second downlink control used for controlling downlink communication between the radio terminal and the radio base station for a packet to be transmitted to the radio terminal. The downlink control data insertion unit (RLP unit 13B, SP unit 14B, RP unit 15B) for inserting data (RLP header (B), SP header (B), RP header (B)) and the other radio base station Roll A packet transmission unit (PCP / MAC / PHY unit 16B) for transmitting the transmitted packet to the radio terminal, wherein the downlink control data insertion unit is configured to transmit the packet for the packet transferred by the other radio base station. It is good also as a summary to omit insertion of 2 downlink control data.

  The sixth aspect of the present invention provides a connection destination from the first radio base station (first radio base station 1A) to the second radio base station (second radio base station 1B) capable of communicating with the first radio base station. A first uplink used for controlling uplink communication between the radio terminal and the first radio base station for a packet to be transmitted to the first radio base station. A first transmission processing unit (first communication module 20A) for inserting control data (RLP header (A), SP header (A), RP header (A)), and a packet to be transmitted to the second radio base station. On the other hand, the second uplink control data (RLP header (B), SP header (B), RP header (B)) used for controlling uplink communication between the radio terminal and the second radio base station is inserted. 2 transmission processing unit (second communication module 20B) The first transmission processing unit transfers the packet in which the first uplink control data is inserted to the second transmission processing unit at the time of switching the connection destination, and the second transmission processing unit includes: Transmitting the packet transferred by the first transmission processing unit to the second radio base station, and omitting insertion of the second uplink control data into the packet transferred by the first transmission processing unit. The gist.

  For the packet to be transmitted to the wireless terminal (wireless terminal 2) and the wireless terminal, first downlink control data (RLP header (A), SP header ( A), a first radio base station (first radio base station 1A) that inserts an RP header (A)) and a packet that can communicate with the first radio base station and is to be transmitted to the radio terminal, A second radio base station (second radio base) that inserts second downlink control data (RLP header (B), SP header (B), RP header (B)) used for controlling downlink communication with the radio terminal. Station 1B), wherein the wireless terminal switches the connection destination from the first wireless base station to the second wireless base station, and the first wireless base station connects to the connection At the time of the previous switching, Transferring the packet in which one downlink control data is inserted to the second radio base station; and the second radio base station transmits the second downlink control data for the packet transferred by the first radio base station. The second wireless base station transmitting the packet transferred by the first wireless base station to the wireless terminal, and the wireless terminal from the second wireless base station. And a step of executing a packet reception process based on the first downlink control data inserted in the received packet.

  According to a seventh aspect of the present invention, a first radio base station (first radio base station 1A), a second radio base station (second radio base station 1B) capable of communicating with the first radio base station, For packets to be transmitted to the first radio base station, first uplink control data (RLP header (A), SP header (A), RP header (used for controlling uplink communication with the first radio base station) ( A)) is inserted into the first transmission processing unit (first communication module 20A) and the packet to be transmitted to the second radio base station is used to control uplink communication with the second radio base station. A wireless terminal (wireless terminal 2) having a second transmission processing unit (second communication module 20B) for inserting second uplink control data (RLP header (B), SP header (B), RP header (B)) A wireless communication method using the wireless terminal, wherein the wireless terminal The step of switching the connection destination from the first radio base station to the second radio base station, and the first transmission processing unit, when switching the connection destination, the packet in which the first uplink control data is inserted A step of transferring to the second transmission processing unit; a step of the second transmission processing unit omitting insertion of the second uplink control data into the packet transferred by the first transmission processing unit; A transmission processing unit transmitting the packet transferred by the first transmission processing unit to the second radio base station; and the second radio base station receiving the packet received from the radio terminal in the first And a step of transferring to the radio base station.

  According to the present invention, a wireless communication system capable of reducing the overhead of packets transmitted and received between a handover destination wireless base station and a wireless terminal in a system configuration for transferring packets between wireless base stations at the time of handover of the wireless terminal. , A wireless base station, a wireless terminal, and a wireless communication method can be provided.

1 is an overall schematic configuration diagram of a wireless communication system according to an embodiment of the present invention. It is a schematic block diagram which shows schematic structure of the 1st radio base station which concerns on embodiment of this invention. It is a schematic block diagram which shows schematic structure of the radio | wireless terminal which concerns on embodiment of this invention. It is a figure for demonstrating the 1st communication module and 2nd communication module of the radio | wireless terminal which concern on embodiment of this invention. It is a functional block block diagram which shows the detailed structure of the 1st radio base station which concerns on embodiment of this invention, a 2nd radio base station, and a radio | wireless terminal. It is a figure which shows the structure of the packet used in the radio | wireless communications system which concerns on embodiment of this invention. It is a conceptual diagram for demonstrating the whole schematic operation | movement in the downlink communication of the radio | wireless communications system which concerns on embodiment of this invention. It is a sequence diagram which shows the whole operation | movement of the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows the example which added the field for RP information to the last part of IPT-Notification. It is a figure which shows the example which added the field for RLP information to the last part of IPT-Notification Ack. It is a flowchart which shows the operation | movement in the downlink communication of the 2nd wireless base station which concerns on embodiment of this invention. It is a flowchart which shows the operation | movement in the downlink communication of the 2nd communication module of the radio | wireless terminal which concerns on embodiment of this invention. It is a flowchart which shows the operation | movement in the uplink communication of the 2nd communication module of the radio | wireless terminal which concerns on embodiment of this invention. It is a flowchart which shows the operation | movement in the uplink communication of the 2nd wireless base station which concerns on embodiment of this invention. 6 is a flowchart illustrating a packet retransmission operation executed by an RLP unit according to the embodiment of the present invention.

  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) packet configuration, (4) operation of radio communication system, (5) action and effect, (6 ) 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 the radio communication system 10, specifically, (1.1) overall schematic configuration, (1.2) schematic configuration of a radio base station, (1.3) A schematic configuration of the wireless terminal 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 first radio base station 1A, a second radio base station 1B, 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.

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

  The first radio base station 1A and the second radio base station 1B perform radio communication with the radio terminal 2 located in the communicable area. The radio terminal 2 compares the reception quality of broadcast signals (so-called pilot signals) transmitted by the first radio base station 1A and the second radio base station 1B and connects to the higher reception quality.

  In the example of FIG. 1, the wireless terminal 2 moves from the communicable area of the first radio base station 1A toward the communicable area of the second radio base station 1B, and the second radio base station 1A A handover for switching the connection destination to the base station 1B is executed.

  Here, downlink packets to be transmitted to the radio terminal 2 remain in the first radio base station 1A and the communication path between the first radio base station 1A and the access gateway 3. Therefore, the first radio base station 1A serves as a relay station (anchor) between the access gateway 3 and the second radio base station 1B, and performs communication between base stations for packets not transmitted to the radio terminal 2 to the second radio base station 1B. Use and transfer.

  Thereby, a handover with less packet loss is realized. In addition, the time for establishing a communication path between the access gateway 3 and the second radio base station 1B is shortened, and high-speed handover is realized.

  In uplink communication, the second radio base station 1B transfers the uplink packet received from the radio terminal 2 to the first radio base station 1A using inter-base station communication. The first radio base station 1A relays the uplink packet received from the second radio base station 1B to the access gateway 3. In the UMB system, as an option, the second radio base station 1B can relay the upstream packet directly to the access gateway 3 without going through the first radio base station 1A.

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

  In the UMB system, the second radio base station 1B gives information indicating the handover source first radio base station 1A to the packet scheduled to be transmitted by the first radio base station 1A, and the second radio base station 1B The packet is handled as a normal packet to be transmitted, and is transmitted to the wireless terminal 2 after performing predetermined processing.

  Specifically, each of the first radio base station 1A as the handover source and the second radio base station 1B as the handover destination inserts control data used for controlling downlink communication with the radio terminal 2 as a packet header. . In the following, the control data (header) inserted into the packet by the first radio base station 1A as the handover source is referred to as “first downlink control data” as appropriate, and the control is inserted into the packet by the second radio base station 1B as the handover destination. The data (header) is appropriately referred to as “second downlink control data”.

  In the UMB system, the following methods (a) to (c) are assumed as a method for switching the DAP from the first radio base station 1A as the handover source to the second radio base station 1B as the handover destination.

(A) Method for switching DAP from first radio base station 1A to second radio base station 1B after a certain period of time has passed since handover (b) When there is no user data traffic for transmission / reception, DAP is switched to first radio base station (C) When transmission of unprocessed / untransmitted data to the second radio base station 1B is completed in the first radio base station 1B, the DAP is switched to the first radio base station 1B. Method of Switching from Station 1A to Second Radio Base Station 1B In this way, by switching DAP from first radio base station 1A to second radio base station 1B, DAP and FLSE become the same radio base station.

  In the following embodiment, a case will be described in which the first radio base station 1A is DAP and the second radio base station 1B is FLSE in downlink communication (forward link). Also, a case will be described in which the first radio base station 1A is DAP and the second radio base station 1B is RLSE in uplink communication (reverse link).

  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 first radio base station 1A and the access gateway 3, and L2TPv3 is adopted for the user data bearer between the first radio base station 1A and the second radio base station 1B. Is done.

(1.2) Schematic Configuration of Radio Base Station FIG. 2 is a schematic configuration diagram showing a schematic configuration of the first radio base station 1A. Since the schematic configuration of the second radio base station 1B is the same as that of the first radio base station 1A, description of the schematic configuration of the second radio base station 1B is omitted.

  As illustrated in FIG. 2, the first 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 second 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 first 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 information used for control and the like in the first radio base station 1A. In addition, the storage unit 104 includes a buffer unit 104 a that temporarily stores data to be transmitted to and received from the wireless terminal 2.

(1.3) Schematic Configuration of Radio Terminal FIG. 3 is a schematic configuration diagram showing a schematic configuration of the radio terminal 2.

  As illustrated in FIG. 3, the wireless terminal 2 includes an RF unit 201, an operation unit 202, a control unit 203, an audio codec unit 204, a microphone 205, a speaker 206, a display unit 207, and a storage unit 208.

  The RF unit 201 includes an LNA, a power amplifier, an up converter, a down converter, and the like, and transmits and receives radio signals. The control unit 203 is configured by a CPU, for example, and controls various functions provided in the wireless terminal 2. The control unit 203 executes processing according to various protocols described later. The storage unit 208 is configured by a memory, for example, and stores various types of information used for control in the wireless terminal 2 and the like. The storage unit 208 includes a buffer unit 208a that temporarily stores data to be transmitted / received to / from the first radio base station 1A or the second radio base station 1B.

  The display unit 207 displays an image received via the control unit 203 and displays operation details (such as an input telephone number and an address). The operation unit 202 is configured by a numeric keypad, function keys, and the like, and is an interface used for inputting user operation details.

  The microphone 205 collects sound and inputs sound data based on the collected sound to the control unit 203 via the sound codec unit 204. The speaker 206 outputs audio based on the audio data acquired from the control unit 203 via the audio codec unit 204.

  The audio codec unit 204 is, for example, an audio codec method G.264. 729. G. 729 is a method of sampling (sampling) an analog telephone band (3.4 kHz≈4 kHz) signal at 8 kHz and realizing a transmission rate of 8 kbps, and has an adaptability in communication using a narrow band transmission path. . Such a communication method has a characteristic of transmitting packets with a small data size at short intervals.

(2) Detailed Configuration of Radio Communication System Next, a detailed configuration of the radio communication system 10, specifically, (2.1) UMB system overview, (2.2) Detailed configuration of a handover source radio base station, (2 .3) A detailed configuration of the handover destination radio base station, (2.4) a detailed configuration of the radio terminal will be described.

(2.1) UMB System Overview FIG. 4 is a diagram for explaining the first communication module 20A and the second communication module 20B 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 the present embodiment, the first communication module 20A is a communication module corresponding to the first radio base station 1A. The second communication module 20B is a communication module corresponding to the second radio base station 1B.

  In downlink communication, the second communication module 20B receives a packet from the second radio base station 1B via a radio section, and internally transfers the packet to the first communication module 20A. In the wireless terminal 2, during the handover, the protocol of the first communication module 20A corresponding to the first radio base station 1A as the handover source is passed through the second communication module 20B corresponding to the second radio base station 1B as the handover destination. Process.

  In uplink communication, the first communication module 20A inserts control data (header) for the first radio base station 1A into the packet. The second communication module 20B inserts control data (header) for the second radio base station 1B into the packet. Hereinafter, the control data (header) inserted by the first communication module 20A is appropriately referred to as “first uplink control data”, and the control data (header) inserted by the second communication module 20B in the packet is appropriately referred to as “second uplink control data”. Referred to as “data”.

  The first communication module 20A internally transfers a packet to be transmitted to the first radio base station 1A to the second communication module 20B. The second communication module 20B transmits the packet transferred from the first communication module 20A to the second radio base station 1B via the radio section.

  FIG. 5 is a functional block configuration diagram showing detailed configurations of the first radio base station 1A, the second radio base station 1B, and the radio terminal 2. FIG. 5 also serves as a protocol stack diagram according to the UMB system.

  As shown in FIG. 5, the first 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 second 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 first 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 second 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-module transfer function in the wireless terminal 2.

  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 packet division (fragment), reconstruction, and downlink retransmission control functions. Specifically, RLP defines a SAR (Segmentation And Reassembly) sub-protocol that performs packet division and reassembly, and a QN (Quick Nak) sub-protocol that performs retransmission control.

  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 the divided upper packets to 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 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.

(2.2) Detailed Configuration of Handover Source Radio Base Station The detailed configuration of the handover source first radio base station 1A will be described with reference to FIG.

  In downlink communication, the RLP unit 13A, the SP unit 14A, and the RP unit 15A are used for controlling downlink communication between the radio terminal 2 and the first radio base station 1A for packets to be transmitted to the radio terminal 2. 1st downlink control data insertion part which inserts 1 downlink control data (RLP header (A), SP header (A), and RP header (A)) is comprised.

  The RP unit 15A configures a packet transfer unit that transfers a packet in which the RLP header (A), the SP header (A), and the RP header (A) are inserted to the second radio base station 1B at the time of handover of the radio terminal 2. To do.

  Furthermore, in downlink communication, the RLP unit 13A configures a first downlink retransmission processing unit that executes a first downlink retransmission process for retransmitting a packet that the wireless terminal 2 has failed to receive to the wireless terminal 2. Further, the RLP unit 13A constitutes a first downlink fragment processing unit that executes a first downlink fragment process for decomposing user data (APP data) to be transmitted to the wireless terminal 2 and generating a packet.

  On the other hand, in the uplink communication, the RLP unit 13A, the SP unit 14A, and the RP unit 15A receive the first uplink control data (RLP header (A), SP header ( A first uplink reception processing unit that performs packet reception processing based on A) and the RP header (A)) is configured.

  In uplink communication, the RLP unit 13A constitutes a first uplink retransmission request unit that executes a first uplink retransmission request that requests the RLP unit 23A to retransmit a packet that has failed to be received.

(2.3) Detailed Configuration of Handover Destination Radio Base Station Next, with reference to FIG. 5, a detailed configuration of the second radio base station 1B that is the handover destination will be described.

  In the downlink communication, the RLP unit 13B, the SP unit 14B, and the RP unit 15B are provided with second downlink control data (RLP header (B), RLP header (B), used for controlling downlink communication between the radio terminal 2 and the second radio base station 1B. A second downlink control data insertion unit for inserting the SP header (B) and the RP header (B)) is configured. The PCP / MAC / PHY unit 16B constitutes a packet transmission unit that transmits the packet transferred by the first radio base station 1A to the radio terminal 2.

  At the time of handover of the radio terminal 2, the RLP unit 13B, the SP unit 14B, and the RP unit 15B perform second downlink control data (RLP header (B), SP header (B) for the packet transferred by the first radio base station 1A. And RP header (B)) are omitted.

  When transmitting the packet transferred by the first radio base station 1A to the radio terminal 2 at the time of handover of the radio terminal 2, the IRTP unit 12B transfers the packet transmitted to the radio terminal 2 by the first radio base station 1A. A downlink transfer information insertion unit for inserting downlink transfer information (IRTP header (B)) indicating that the received packet is received.

  In the downlink communication, the RLP unit 13B configures a second downlink retransmission processing unit that executes a second downlink retransmission process of retransmitting a packet that the wireless terminal 2 has failed to receive to the wireless terminal 2.

  At the time of handover of the radio terminal 2, the RLP unit 13B acquires the first downlink retransmission control information (RLP information) used for the first downlink retransmission process from the RLP unit 13A, and uses the acquired first downlink retransmission control information. The second downlink retransmission process is executed.

  Note that the RLP unit 13A omits the first downlink retransmission process when the RLP unit 13B executes the second downlink retransmission process using the first downlink retransmission control information.

  In addition, the RLP unit 13B configures a second downlink fragment processing unit that executes a second downlink fragment process for decomposing user data (APP data) to be transmitted to the wireless terminal 2 and generating a packet. Here, the RLP unit 13B omits the second downlink fragment processing at the time of handover of the radio terminal 2.

  On the other hand, in the uplink communication, the RLP unit 13B, the SP unit 14B, and the RP unit 15B have the first uplink control data (RLP header (A), SP header (A) and RP header (A)) or second uplink control data. A second uplink reception processing unit that performs packet reception processing based on (RLP header (B), SP header (B), and RP header (B)) is configured.

  The RLP unit 13B, the SP unit 14B, and the RP unit 15B have the first uplink control data (RLP) inserted in the packet received from the wireless terminal 2 when the uplink transfer information is inserted into the packet received from the wireless terminal 2. Packet reception processing based on the header (A), the SP header (A), and the RP header (A)) is executed.

  The RLP unit 13A, the SP unit 14A, and the RP unit 15A are connected to the RLP unit 13B, the SP unit 14B, and the RP unit 15B. ) Is executed, the packet reception process based on the first uplink control data is omitted.

  In uplink communication, the RLP unit 13B configures a second uplink retransmission request unit that executes a second uplink retransmission request that requests the RLP unit 23B to retransmit a packet that has failed to be received.

  The RLP unit 13B acquires the second uplink retransmission control information (RLP information) used for the first uplink retransmission request from the RLP unit 13A during the handover of the radio terminal 2, and uses the second uplink retransmission control information to obtain the second An uplink retransmission request is executed.

  The RLP unit 13A omits the first uplink retransmission request when the RLP unit 13B executes the second uplink retransmission request using the second uplink retransmission control information.

(2.4) Detailed Configuration of Wireless Terminal The detailed configuration of the wireless terminal 2 will be described with reference to FIG.

  In downlink communication, the first communication module 20A includes a first downlink reception processing unit that performs packet reception processing based on first downlink control data (RLP header (A), SP header (A), and RP header (A)). Configure.

  The second communication module 20B includes first downlink control data (RLP header (A), SP header (A) and RP header (A)) or second downlink control data (RLP header (B), SP header (B) and A second downlink reception processing unit that executes packet reception processing based on the RP header (B)) is configured.

  When the downlink transfer information (IRTP header (B)) is inserted in the packet received from the second radio base station 1B, the second communication module 20B is inserted in the packet received from the second radio base station 1B. Packet reception processing based on the first downlink control data (RLP header (A), SP header (A), and RP header (A)) is executed.

  When the second communication module 20B executes the packet reception process based on the first downlink control data (RLP header (A), SP header (A), and RP header (A)), the first communication module 20A 1 Packet reception processing based on downlink control data (RLP header (A), SP header (A), and RP header (A)) is omitted.

  In downlink communication, the RLP unit 23A of the first communication module 20A constitutes a first downlink retransmission request unit that executes a first downlink retransmission request that requests the RLP unit 13A to retransmit a packet that has failed to be received. The RLP unit 23B constitutes a second downlink retransmission request unit that executes a second downlink retransmission request that requests the RLP unit 13B to retransmit a packet that has failed to be received.

  The RLP unit 23B acquires the second downlink retransmission control information (RLP information) used for the first downlink retransmission request from the RLP unit 23A during the handover, and uses the acquired second downlink retransmission control information to perform the second downlink retransmission. Execute the request. Then, the RLP unit 23A omits the first downlink retransmission request when the RLP unit 23B executes the second downlink retransmission request using the second downlink retransmission control information.

  On the other hand, in uplink communication, the first communication module 20A is used for controlling uplink communication between the radio terminal 2 and the first radio base station 1A for a packet to be transmitted to the first radio base station 1A. A first transmission processing unit for inserting uplink control data (RLP header (A), SP header (A), and RP header (A)) is configured.

  The second communication module 20B, for the packet to be transmitted to the second radio base station 1B, uses second uplink control data (RLP header (RLP header)) used for controlling uplink communication between the radio terminal 2 and the second radio base station 1B. B), a second transmission processing unit for inserting the SP header (B) and the RP header (B)).

  The first communication module 20A transmits a packet in which the first uplink control data (RLP header (A), SP header (A), and RP header (A)) is inserted during the handover of the radio terminal 2 to the second communication module 20B. Forward to.

  The second communication module 20B transmits the packet transferred by the first communication module 20A to the second radio base station 1B, and also transmits second uplink control data (RLP header (BLP) for the packet transferred by the first communication module 20A. ), Insertion of SP header (B) and RP header (B)) is omitted.

  When the IRTP unit 22B transmits the packet transferred by the first communication module 20A to the second radio base station 1B, the packet transferred by the first communication module 20A with respect to the packet transmitted to the second radio base station 1B An uplink transfer information insertion unit for inserting uplink transfer information (IRTP header (B)) indicating that

  The RLP unit 23A of the first communication module 20A constitutes a first uplink retransmission processing unit that executes a first uplink retransmission process for retransmitting a packet that the first radio base station 1A failed to receive to the first radio base station 1A. . The RLP unit 23B of the second communication module 20B constitutes a second uplink retransmission processing unit that executes a second uplink retransmission process of retransmitting a packet that the second radio base station 1B failed to receive to the second radio base station 1B. .

  The RLP unit 23B acquires the first uplink retransmission control information (RLP information) used for the first uplink retransmission process from the RLP unit 23A during the handover, and uses the acquired first uplink retransmission control information to perform the second uplink retransmission. Execute the process. When the RLP unit 23B executes the second uplink retransmission process using the first uplink retransmission control information, the RLP unit 23A omits the first uplink retransmission process.

  The RLP unit 23A constitutes a first uplink fragment processing unit that executes a first uplink fragment process for decomposing user data (APP data) to be transmitted to the first radio base station 1A and generating a packet. The RLP unit 23B constitutes a second uplink fragment processing unit that executes a second uplink fragment process for decomposing user data (APP data) to be transmitted to the second radio base station 1B and generating a packet. The RLP unit 23B omits the second uplink fragment processing at the time of handover.

(3) Packet Configuration FIG. 6 is a diagram illustrating a packet configuration used in the wireless communication system 10.

  The RLP unit 13A and the RLP unit 13B divide (fragment) APP data as shown in FIG. 6A, add an RLP header to the divided data, and generate an RLP packet shown in FIG. 6B. In the RLP header, data indicating the start point and end point of fragmented data, a sequence number used for retransmission processing, and the like are inserted.

  The SP unit 14A and the SP unit 14B add an SP header to the RLP packet shown in FIG. 6B to generate the SP packet shown in FIG. In the SP header, data used for distribution to a stream according to the use of the RLP packet is inserted.

  The RP unit 15A and the RP unit 15B add an RP header to the SP packet illustrated in FIG. 6C to generate the RP packet illustrated in FIG. Data for identifying the service route is inserted into the RP header.

  Furthermore, the IRTP unit 12B adds an IRTP header indicating the handover source first radio base station 1A. As a result, the total of RLP header, SP header, RP header, and IRTP header is 3 bytes to 33 bytes.

(4) Operation of Radio Communication System Next, the operation of the radio communication system 10, specifically, (4.1) Overall schematic operation of the radio communication system, (4.2) Overall operation sequence of the radio communication system, ( 4.3) Detailed operation in downlink communication, (4.4) Detailed operation in uplink communication, and (4.5) Retransmission operation will be described.

(4.1) Overall Schematic Operation of Radio Communication System FIG. 7 is a conceptual diagram for explaining the overall schematic operation of the radio communication system 10 in downlink communication.

  The first radio base station 1A gives various headers (RLP header (A), SP header (A) and RP header (A)) for the first radio base station 1A to the IP payload received from the access gateway 3, Transfer to the second radio base station 1B.

  The second radio base station 1B that has received this packet copies the RLP header (A), the SP header (A), and the RP header (A) to copy two sets of the RLP header (A), the SP header (A), and the RP. While generating the header (A), one of them is deleted, and a set of RLP header (A), SP header (A), and RP header (A) is added to the packet and transmitted to the wireless terminal 2.

(4.2) Overall Operation Sequence of Radio Communication System FIG. 8 is a sequence diagram showing the overall operation of the radio communication system 10. Specifically, FIG. 8 shows an operation example in downlink communication.

  In step S101, the radio terminal 2 is connected to the first radio base station 1A and receives a downlink packet from the first radio base station 1A.

  In step S102, the radio terminal 2 hands over from the first radio base station 1A to the second radio base station 1B.

  In step S103, the second radio base station 1B transmits IPT-Notification for notifying the handover of the radio terminal 2 to the first radio base station 1A.

In step S104, the first radio base station 1A transmits IPT-NotificationAck, which is a confirmation response to IPT-Notification, to the second radio base station 1B.

  IPT-Notification and IPT-Notification Ack are messages defined in 3GPP2 IOS (Interoperability Specification). In this embodiment, RLP information and RP information are exchanged between the first radio base station 1A and the second radio base station 1B using IPT-Notification and IPT-NotificationAck. Specifically, the first radio base station 1A uses the second radio base station to transmit, as RLP information, a transmission sequence number indicating the transmission order of packets, a packet for which no reception acknowledgment (ACK) is obtained from the radio terminal 2, and the like. Transmit to station 1B.

  FIG. 9 shows an example in which a field for RP information is added to the last part of IPT-Notification. FIG. 10 shows an example in which a field for RLP information is added to the last part of the IPT-NotificationAck.

  In step S105, the second radio base station 1B stores the RLP information of the first radio base station 1A.

  In step S106, the first radio base station 1A transfers the downlink packet # 1 addressed to the radio terminal 2 to the second radio base station 1B. Here, “# 1” represents a transmission sequence number. In step S107, the second radio base station 1B transmits the downlink packet # 1 received from the first radio base station 1A to the radio terminal 2. The first radio base station 1A and the second radio base station 1B store the transmitted packets in the buffer unit 104a until receiving an ACK from the radio terminal 2.

  In step S108, the first radio base station 1A transfers the downlink packet # 2 addressed to the radio terminal 2 to the second radio base station 1B. In step S109, the second radio base station 1B transmits the downlink packet # 2 received from the first radio base station 1A to the radio terminal 2. Here, it is assumed that the wireless terminal 2 has failed to receive the downlink packet # 2 transmitted by the second wireless base station 1B.

  In step S110, the first radio base station 1A transfers the downlink packet # 3 addressed to the radio terminal 2 to the second radio base station 1B. In step S111, the second radio base station 1B transmits the downlink packet # 3 received from the first radio base station 1A to the radio terminal 2.

  In step S112, the wireless terminal 2 detects the missing transmission sequence number # 2, and transmits ATReceiverStatus (NAK) requesting retransmission of the downlink packet # 2 to the second wireless base station 1B.

  In step S113, the second radio base station 1B retransmits the downlink packet # 2 to the radio terminal 2 in response to the retransmission request for the downlink packet # 2. Here, it is assumed that the retransmitted downlink packet # 2 is normally received by the wireless terminal 2.

  In step S114, the radio terminal 2 transmits ATReceiverStatus (ACK) to the second radio base station 1B. In step S115, the second radio base station 1B transfers the ATReceiverStatus (ACK) received from the radio terminal 2 to the first radio base station 1A.

  In step S116 and step S117, the first radio base station 1A and the second radio base station 1B clear the transmission buffer.

(4.3) Detailed Operation in Downlink Communication Next, detailed operation in downlink communication, specifically, (4.3.1) Operation of Second Radio Base Station in Downlink Communication, (4.3. 2) The operation of the wireless terminal in downlink communication will be described.

(4.3.1) Operation of Second Radio Base Station in Downlink Communication FIG. 11 is a flowchart showing the operation of the second radio base station 1B in downlink communication. Here, when the APP data of the first radio base station 1A is sent to the radio terminal 2 via the RLP unit 13A, the SP unit 14A, the RP unit 15A, and the PCP / MAC / PHY unit 16A, a handover occurs, A case will be described where two wireless base stations 1B are to be routed.

  In step S401, the second radio base station 1B receives the downlink packet.

  In step S402, the second radio base station 1B determines whether or not the downlink packet received in step S401 has been transferred from another radio base station. When the packet is not a downlink packet transferred from another radio base station, that is, for a packet received directly from the access gateway 3, normal protocol processing is executed by the RLP unit 13B, SP unit 14B, and RP unit 15B (step S410). ). In normal protocol processing, the RLP unit 13B executes the above-described second downlink fragment processing and the like.

  If the downlink packet received in step S401 is transferred from another radio base station, the process proceeds to step S403.

  In step S403, the RLP unit 13B of the second radio base station 1B receives the RP packet from the RP unit 15A of the first radio base station 1A. The RLP unit 13B copies the RLP header (A) and deletes one, and acquires RLP information (first downlink retransmission control information from the RLP unit 13A of the first radio base station 1A so that it can respond to retransmission. To do.

  Here, the RLP unit 13B stores that the received downlink packet is a downlink packet transferred from the first radio base station 1A. Further, the RLP unit 13B omits the second downlink fragment process described above (step S404).

  In step S405, the RLP unit 13B determines whether or not RLP information (first downlink retransmission control information) has been received from the RLP unit 13A of the first radio base station 1A. If the RLP information has not been received, the RLP unit 13B requests the RLP unit 13A to notify the RLP information (step S406).

  In step S407, the SP unit 14B copies the SP header (A) and deletes one of them. In step S408, the RP unit 15B copies the RP header (A) and deletes one of them.

  In step S409, the IRTP unit 12B inserts downlink transfer information (IRTP header (B)) indicating a downlink packet transferred by the first radio base station 1A.

  In step S411, the PCP / MAC / PHY unit 16B transmits the downlink packet to the wireless terminal 2.

(4.3.2) Operation of Radio Terminal in Downlink Communication FIG. 12 is a flowchart showing the operation of the second communication module 20B of the radio terminal 2 in downlink communication.

  In step S501, the PCP / MAC / PHY unit 26B of the second communication module 20B receives the downlink packet.

  In step S502, the IRTP unit 22B determines whether downlink transfer information (IRTP header (B)) is inserted in the downlink packet received in step S501. When the downlink transfer information (IRTP header (B)) is not inserted, normal protocol processing is executed by the RLP unit 23B, SP unit 24B, and RP unit 25B (step S510). When the downlink transfer information (IRTP header (B)) is inserted, the IRTP unit 22B removes the downlink transfer information (IRTP header (B)) and passes the downlink packet to the RP unit 25B (step S503).

  In step S504, the RP unit 25B removes the RP header (A). Further, since the RP unit 25B is a packet in which the downlink packet has been transferred between the radio base stations, the RP unit 25B performs necessary processing in cooperation with the RP unit 25A of the first communication module 20A.

  In step S505, the SP unit 24B removes the SP header (A). In steps S506 to S508, the RLP unit 23B performs retransmission control (retransmission request) on behalf of the RLP unit 23A. At this time, it is assumed that RLP information (second downlink retransmission control information) necessary for retransmission control is notified from the RLP unit 23A when a handover occurs.

  In step S506, the RLP unit 23B determines whether or not a retransmission request is necessary. If a retransmission request is necessary, the RLP unit 23B requests the second radio base station 1B to retransmit the downlink packet (step S508).

  In step S507, the downlink packet is transferred to the first communication module 20A. However, since necessary processing in the RP / SP / RLP has already been performed, it is directly transmitted to the APP unit 21A.

(4.4) Detailed operation in uplink communication Next, detailed operation in uplink communication, specifically, (4.4.1) Operation of radio terminal in uplink communication, (4.4.2) Uplink An operation of the second radio base station in the direction communication will be described.

(4.4.1) Operation of Radio Terminal in Uplink Communication FIG. 13 is a flowchart showing the operation of the second communication module 20B of the radio terminal 2 in the uplink communication.

  In step S601, the RLP unit 23B of the second communication module 20B receives the uplink packet.

  In step S602, the RLP unit 23B determines whether or not the uplink packet received in step S601 is transferred from another communication module (the first communication module 20A in the present embodiment). When the packet is not an uplink packet transferred from the first communication module 20A, that is, for the packet received from the APP unit 21B, normal protocol processing is executed by the RLP unit 23B, SP unit 24B, and RP unit 25B (step S610). .

  If the downlink packet received in step S601 has been transferred from the first communication module 20A, the process proceeds to step S603. In step S603, the RLP unit 23B stores information indicating that the data has been transferred from the first communication module 20A.

  In step S604, the RLP unit 23B copies the RLP header (A) and deletes one, and acquires RLP information (first uplink retransmission control information from the RLP unit 23A of the first communication module 20A, and supports retransmission. In addition, the RLP unit 23B omits the above-described second uplink fragment processing (step S604).

  In step S605, the RLP unit 23B determines whether or not RLP information (first uplink retransmission control information) has been received from the RLP unit 23A of the first communication module 20A. When the RLP information has not been received, the RLP unit 23B requests the RLP unit 23A to notify the RLP information (step S606).

  In step S607, the SP unit 24B copies the SP header (A) and deletes one of them. In step S608, the RP unit 25B copies the RP header (A) and deletes one of them.

  In step S609, the IRTP unit 22B inserts uplink transfer information (IRTP header (B)) indicating that the packet is an uplink packet transferred by the first communication module 20A.

  In step S610, the PCP / MAC / PHY unit 26B transmits the uplink packet to the second radio base station 1B.

(4.4.2) Operation of Second Radio Base Station in Uplink Communication FIG. 14 is a flowchart showing the operation of the second radio base station 1B in uplink communication.

  In step S701, the PCP / MAC / PHY unit 16B of the second radio base station 1B receives the uplink packet.

  In step S702, the IRTP unit 12B determines whether or not uplink transfer information (IRTP header (B)) is inserted in the uplink packet received in step S701. When the uplink transfer information (IRTP header (B)) is not inserted, normal protocol processing is executed by the RLP unit 13B, SP unit 14B, and RP unit 15B (step S710). When the uplink transfer information (IRTP header (B)) is inserted, the IRTP unit 12B removes the uplink transfer information (IRTP header (B)) and passes the uplink packet to the RP unit 15B (step S703).

  In step S704, the RP unit 15B removes the RP header (A). Further, since the RP unit 15B is a packet in which the uplink packet has been transferred between the communication modules, the RP unit 15B performs necessary processing in cooperation with the RP unit 15A of the first radio base station 1A.

  In step S705, the SP unit 14B removes the SP header (A). In steps S706 to S708, the RLP unit 13B performs retransmission control (retransmission request) on behalf of the RLP unit 13A. At this time, it is assumed that RLP information (second uplink retransmission control information) necessary for retransmission control is notified from the RLP unit 13A when a handover occurs.

  In step S706, the RLP unit 13B determines whether or not a retransmission request is necessary. If a retransmission request is necessary, the RLP unit 13B requests the wireless terminal 2 to retransmit the downlink packet (step S708).

  In step S707, the downlink packet is transferred to the first radio base station 1A, but since necessary processing in RP / SP / RLP has already been performed, it is directly transmitted to the APP unit 11A.

(4.5) Retransmission Operation FIG. 15 is a flowchart showing a packet retransmission operation executed by the RLP unit 13A, the RLP unit 13B, the RLP unit 23A, and the RLP unit 23B.

(4.5.1) Retransmission operation on the receiving side FIG. 15A shows a retransmission operation (retransmission request) of the RLP unit (RLP unit 13A, RLP unit 13B, RLP unit 23A or RLP unit 23B) at the time of packet reception. It is a flowchart.

  In step S201, the RLP unit receives the RLP packet.

  In step S202, the RLP unit determines whether or not the sequence number of the received RLP packet is greater than V (R) that is the sequence number expected to be received next.

  When the sequence number of the received RLP packet is larger than V (R), the RLP unit transmits a retransmission request message (NAK) to the packet transmission source (step S203). When the sequence number of the received RLP packet is equal to or less than V (R), the RLP unit transmits an ACK to the packet transmission source (step S204).

(4.5.2) Transmission side retransmission operation FIG. 15B shows a retransmission operation (retransmission processing) of the RLP unit (RLP unit 13A, RLP unit 13B, RLP unit 23A or RLP unit 23B) during packet transmission. It is a flowchart.

  In step S301, the RLP unit detects that a retransmission request message has been received or an ACK has not been received for a certain period of time since the packet transmission (timer timeout).

  In step S302, the RLP unit acquires a packet to be retransmitted from the transmission buffer, and retransmits the acquired packet.

(5) Operation and Effect As described above, in the downlink communication, the RLP unit 13B, the SP unit 14B, and the RP unit 15B of the second radio base station 1B perform the first processing on the packet transferred by the first radio base station 1A. 2. Insertion of downlink control data (RLP header (B), SP header (B), and RP header (B)) is omitted. Therefore, it is possible to reduce the overhead of packets transmitted and received between the second radio base station 1B and the radio terminal 2.

  In the present embodiment, the second communication module 20B of the wireless terminal 2 uses the second wireless base station 1B when the downlink transfer information (IRTP header (B)) is inserted in the packet received from the second wireless base station 1B. The packet receiving process based on the first downlink control data (RLP header (A), SP header (A), and RP header (A)) inserted in the packet received from is executed. Then, in the first communication module 20A of the wireless terminal 2, the second communication module 20B executes packet reception processing based on the first downlink control data (RLP header (A), SP header (A), and RP header (A)). In this case, the packet reception process based on the first downlink control data (RLP header (A), SP header (A), and RP header (A)) is omitted. For this reason, the processing load of the wireless terminal 2 can be reduced.

  In downlink communication, the RLP unit 13B of the second radio base station 1B acquires the first downlink retransmission control information (RLP information) from the RLP unit 13A at the time of handover of the radio terminal 2, and acquires the acquired first downlink retransmission control information. The second downlink retransmission process is executed using The RLP unit 13A of the first radio base station 1A omits the first downlink retransmission process when the RLP unit 13B executes the second downlink retransmission process using the first downlink retransmission control information.

  Further, the RLP unit 23B of the second communication module 20B acquires the second downlink retransmission control information (RLP information) from the RLP unit 23A at the time of handover, and uses the acquired second downlink retransmission control information to perform the second downlink retransmission. Execute the request. Then, the RLP unit 23A of the first communication module 20A omits the first downlink retransmission request when the RLP unit 23B executes the second downlink retransmission request using the second downlink retransmission control information.

  In this way, retransmission control at the RLP level in downlink communication is not performed by the first radio base station 1A and the first communication module 20A, but by the second radio base station 1B and the second communication module 20B. Implemented by: Accordingly, it is not necessary to transfer the packet again between the first radio base station 1A and the second radio base station 1B during the retransmission operation, and high-speed retransmission is possible. Furthermore, resources (for example, IP data) for inter-base station transfer accompanying retransmission can be reduced. Further, during the retransmission operation, the packet transfer between the first communication module 20A and the second communication module 20B becomes faster, and unnecessary packet transfer becomes unnecessary.

  In the present embodiment, the RLP unit 13B of the second radio base station 1B omits the second downlink fragment process at the time of handover of the radio terminal 2. Accordingly, the second radio base station 1B can relay the packet received from the first radio base station 1A to the radio terminal 2 at high speed.

  In the present embodiment, in the uplink communication, the second communication module 20B transmits the packet transferred by the first communication module 20A to the second radio base station 1B, and the packet transferred by the first communication module 20A. The insertion of the second uplink control data (RLP header (B), SP header (B), and RP header (B)) is omitted. Therefore, it is possible to reduce the overhead of packets transmitted and received between the second radio base station 1B and the radio terminal 2.

  In this embodiment, in uplink communication, the RLP unit 13A, SP unit 14A and RP unit 15A of the first radio base station 1A are connected to the RLP unit 13B, SP unit 14B and RP unit 15B of the second radio base station 1B. When performing packet reception processing based on one uplink control data (RLP header (A), SP header (A), and RP header (A)), first uplink control data (RLP header (A), SP header (A) And packet reception processing based on the RP header (A)) is omitted. For this reason, the processing load of the first radio base station 1A can be reduced.

  In the present embodiment, in uplink communication, the RLP unit 23B of the second communication module 20B acquires the first uplink retransmission control information (RLP information) from the RLP unit 23A of the first communication module 20A, and acquires the acquired first uplink The second uplink retransmission process is executed using the retransmission control information. When the RLP unit 23B executes the second uplink retransmission process using the first uplink retransmission control information, the RLP unit 23A omits the first uplink retransmission process.

  Further, the RLP unit 13B of the second radio base station 1B acquires the second uplink retransmission control information (RLP information) from the RLP unit 13A, and executes the second uplink retransmission request using the second uplink retransmission control information. The RLP unit 13A of the first radio base station 1A omits the first uplink retransmission request when the RLP unit 13B executes the second uplink retransmission request using the second uplink retransmission control information.

  Thus, retransmission control at the RLP level in uplink communication is not performed by the first radio base station 1A and the first communication module 20A, but by the second radio base station 1B and the second communication module 20B. Implemented by: Accordingly, it is not necessary to transfer the packet again between the first radio base station 1A and the second radio base station 1B during the retransmission operation, and high-speed retransmission is possible. Furthermore, resources (for example, IP data) for inter-base station transfer accompanying retransmission can be reduced. Further, during the retransmission operation, the packet transfer between the first communication module 20A and the second communication module 20B becomes faster, and unnecessary packet transfer becomes unnecessary.

  Furthermore, in uplink communication, the RLP unit 23B of the second communication module 20B omits the second uplink fragment process. For this reason, the second communication module 20B can relay the packet received from the first communication module 20A to the second radio base station 1B at high speed.

  As described above, according to the present embodiment, redundant headers (control data) can be reduced in handover of the UMB system. Since packets used for real-time communication such as VoIP have a smaller packet size than other types of packets, it is particularly effective to reduce headers (control data).

(6) 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 above-described embodiment, the second radio base station 1B copies the RLP header (A), the SP header (A), and the RP header (A) by copying two sets of the RLP header (A) and SP in the downlink communication. The header (A) and the RP header (A) are generated, and one of the RLP header (A), the SP header (A) and the RP header (A) is deleted, but the RLP header (A) and the SP header (A ) And RP header (A) need not be copied and deleted.

  Similarly, the second communication module 20B copies two sets of RLP header (A) and SP header (A) by copying the RLP header (A), SP header (A), and RP header (A) in uplink communication. And RP header (A) are generated and one RLP header (A), SP header (A) and RP header (A) are deleted, but RLP header (A), SP header (A) and RP header are deleted. It is not necessary to copy and delete (A).

  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 can be applied to any system that transfers packets between radio base stations at the time of handover.

  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.

DESCRIPTION OF SYMBOLS 1A ... 1st wireless base station, 1B ... 2nd 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 unit, 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 section, 20A ... first communication module, 20B ... second communication module, 101 ... RF section, 102 ... control section, 103 ... I / F section, 104 ... storage section, 104a ... buffer section, 201 ... RF , 202 ... operation unit, 203 ... control unit, 204 ... voice codec unit, 205 ... microphone, 206 ... speaker, 207 ... display unit, 208 Storage unit, 208a ... buffer unit

Claims (7)

A radio communication system including a first radio base station, a second radio base station that can communicate with the first radio base station, and a radio terminal that switches a connection destination from the first radio base station to the second radio base station Because
The wireless terminal is
A first transmission processing unit for inserting first uplink control data used for controlling uplink communication between the radio terminal and the first radio base station for a packet to be transmitted to the first radio base station;
A second transmission processing unit that inserts second uplink control data used for controlling uplink communication between the radio terminal and the second radio base station for a packet to be transmitted to the second radio base station; ,
The first transmission processing unit transfers the packet in which the first uplink control data is inserted to the second transmission processing unit at the time of switching the connection destination,
The second transmission processing unit transmits the packet transferred by the first transmission processing unit to the second radio base station, and also controls the second uplink control for the packet transferred by the first transmission processing unit. Skip data insertion,
The wireless communication system, wherein the second wireless base station transfers the packet received from the wireless terminal to the first wireless base station. The first radio base station includes a first uplink reception processing unit that performs packet reception processing based on the first uplink control data,
The second radio base station includes a second uplink reception processing unit that performs packet reception processing based on the first uplink control data or the second uplink control data,
When the second transmission processing unit transmits the packet transferred by the first transmission processing unit to the second radio base station, the second transmission processing unit performs the first transmission on the packet transmitted to the second radio base station. An uplink transfer information insertion unit for inserting uplink transfer information indicating that the packet has been transferred by the processing unit;
The second uplink reception processing unit is based on the first uplink control data inserted in the packet received from the wireless terminal when the uplink transfer information is inserted in the packet received from the wireless terminal Execute packet reception processing,
The first uplink reception processing unit omits the packet reception processing based on the first uplink control data when the second uplink reception processing unit executes the packet reception processing based on the first uplink control data. The wireless communication system according to 1. The first transmission processing unit includes a first uplink retransmission processing unit that executes a first uplink retransmission process of retransmitting a packet that the first radio base station has failed to receive to the first radio base station,
The second transmission processing unit includes a second uplink retransmission processing unit that performs a second uplink retransmission process of retransmitting a packet that the second radio base station has failed to receive to the second radio base station,
The second uplink retransmission processing unit acquires the first uplink retransmission control information used for the first uplink retransmission process from the first uplink retransmission processing unit at the time of switching the connection destination, and acquires the acquired first uplink retransmission processing unit. Performing the second uplink retransmission process using retransmission control information;
2. The first uplink retransmission processing unit omits the first uplink retransmission processing when the second uplink retransmission processing unit executes the second uplink retransmission processing using the first uplink retransmission control information. The wireless communication system according to 1. The first radio base station includes a first uplink retransmission request unit that executes a first uplink retransmission request that requests the first uplink retransmission processing unit to retransmit a packet that has failed to be received,
The second radio base station includes a second uplink retransmission request unit that executes a second uplink retransmission request for requesting the second uplink retransmission processing unit to retransmit a packet that has failed to be received,
The second uplink retransmission request unit obtains second uplink retransmission control information used for the first uplink retransmission request from the first uplink retransmission request unit when the connection destination is switched, and performs the second uplink retransmission control. Performing the second uplink retransmission request using information,
4. The first uplink retransmission request unit omits the first uplink retransmission request when the second uplink retransmission request unit executes the second uplink retransmission request using the second uplink retransmission control information. The wireless communication system according to 1. The first transmission processing unit includes a first uplink fragment processing unit that performs a first uplink fragment processing for decomposing user data to be transmitted to the first radio base station and generating a packet,
The second transmission processing unit includes a second uplink fragment processing unit that performs a second uplink fragment processing for generating a packet by decomposing user data to be transmitted to the second radio base station,
The radio communication system according to claim 1, wherein the second uplink fragment processing unit omits the second uplink fragment processing when the connection destination is switched. A wireless terminal that switches a connection destination from a first wireless base station to a second wireless base station that can communicate with the first wireless base station,
A first transmission processing unit for inserting first uplink control data used for controlling uplink communication between the radio terminal and the first radio base station for a packet to be transmitted to the first radio base station;
A second transmission processing unit that inserts second uplink control data used for controlling uplink communication between the radio terminal and the second radio base station for a packet to be transmitted to the second radio base station; ,
The first transmission processing unit transfers the packet in which the first uplink control data is inserted to the second transmission processing unit at the time of switching the connection destination,
The second transmission processing unit transmits the packet transferred by the first transmission processing unit to the second radio base station, and also controls the second uplink control for the packet transferred by the first transmission processing unit. A wireless terminal that skips data insertion. A first radio base station;
A second radio base station capable of communicating with the first radio base station;
A first transmission processing unit that inserts first uplink control data used for controlling uplink communication with the first radio base station for a packet to be transmitted to the first radio base station; and the second radio base A radio communication method using a radio terminal having a second transmission processing unit for inserting second uplink control data used for control of uplink communication with the second radio base station for a packet to be transmitted to a station Because
The wireless terminal switching a connection destination from the first wireless base station to the second wireless base station;
The first transmission processing unit transferring the packet in which the first uplink control data is inserted to the second transmission processing unit when the connection destination is switched;
The second transmission processing unit omitting insertion of the second uplink control data into the packet transferred by the first transmission processing unit;
The second transmission processing unit transmitting the packet transferred by the first transmission processing unit to the second radio base station;
And a step in which the second radio base station transfers the packet received from the radio terminal to the first radio base station.

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