JP5427433B2 - Communication system, radio base station, and communication method - Google Patents

Description

  The present invention has a radio base station and a plurality of radio terminals, and simultaneously transmits packets including a plurality of code blocks obtained by dividing a bit string that is the same information from the radio base station to a plurality of radio terminals. The present invention relates to a system, a radio base station in the communication system, and a communication method in the communication system.

  When multicast communication in which the same information is simultaneously transmitted from a radio base station to a plurality of radio terminals is performed, hybrid automatic retransmission (HARQ) may be employed. This HARQ improves the error detection capability in a wireless terminal by combining automatic retransmission (ARQ) and error detection using a forward error detection code (FEC).

  Specifically, the radio base station transmits the same bit string a plurality of times simultaneously to a plurality of radio terminals. On the other hand, a plurality of wireless terminals combine the same bit strings received a plurality of times, and determine the value of each bit from the combination result. Thereby, a time diversity effect is obtained and the error detection capability is improved.

  Also, the radio base station may transmit a bit string divided into units called code blocks of a predetermined length for the convenience of arithmetic processing by a decoder in the receiving apparatus.

  For example, in the technique described in Patent Document 1, the transmission apparatus divides a bit string of information into a plurality of blocks. Next, the transmission apparatus adds a CRC (Cyclic Redundancy Check) bit string, which is an error detection code, to each block to generate a code block. Further, the transmission device encodes the code block and transmits it. On the other hand, the receiving apparatus performs decoding for each code block, and further detects an error in the information bit string included in the code block based on the CRC bit string included in the code block.

JP 2005-295192 A

  However, in the technique described in Patent Document 1 described above, even when an error occurs only in an information bit string in one code block in one radio terminal, the radio base station retransmits all code blocks. ing. For this reason, efficient retransmission control cannot be performed.

  In view of the above problems, an object of the present invention is to provide a communication system, a radio base station, and a communication method that enable efficient retransmission control according to communication quality of code blocks in a plurality of radio terminals. To do.

In order to solve the above-described problems, the present invention has the following features. A first feature of the present invention is that the wireless base station (wireless base station 1) and a plurality of wireless terminals (wireless terminals 2A to 2D) have the same information from the wireless base station to the plurality of wireless terminals. A communication system (wireless communication system 10) for simultaneously transmitting a packet including a plurality of code blocks obtained by dividing a bit string, wherein the wireless base station includes the code block and redundant bits for error detection A packet transmission unit (radio communication unit 106) for transmitting a plurality of transmission unit packets to the plurality of radio terminals, wherein the plurality of radio terminals receive the plurality of transmission unit packets from the radio base station ; It obtains the likelihood of the code blocks based on redundant bit corresponding to the transmission unit packets for each of the transmission unit packet, the radio base a likelihood of each of the transmission unit packet And a communication quality transmission unit to be transmitted to (the wireless communication unit 206), the radio base station, said plurality of said communication quality reception unit for receiving the likelihood of each transmission unit packet from the wireless terminal (wireless communication unit 106 ) And the likelihood for each transmission unit packet from the plurality of wireless terminals is totaled for each transmission unit packet to obtain a total value, and the plurality of transmissions are set to a ratio according to the reciprocal of the total value. A retransmission transmission unit setting unit (transmission unit setting unit 162) that sets a transmission unit of a retransmission packet corresponding to each of the unit packets, and a retransmission packet of a transmission unit corresponding to the set ratio and summarized in that obtaining Bei packet retransmission unit that transmits to the terminal a (wireless communication unit 106).

  According to such a communication system, the transmission-side radio base station extracts a plurality of packets each consisting of a code block and error detection redundant bits for each transmission unit at the time of transmission, and combines them. A transmission packet is generated and simultaneously transmitted to a plurality of wireless terminals. On the other hand, the plurality of radio terminals on the receiving side measure and transmit the communication quality for each code block included in the received first transmission packet. Furthermore, the radio base station sets a transmission unit for retransmission for each code block based on the communication quality for each code block measured by a plurality of radio terminals. At this time, the radio base station sets a transmission unit at the time of retransmission for each code block so as to have a ratio corresponding to the degree of deterioration of communication quality for each code block from a plurality of radio terminals. Therefore, for each code block, the transmission unit at the time of retransmission differs according to the communication quality measured by a plurality of wireless terminals, thereby enabling efficient retransmission control.

According to a second aspect of the present invention, there is provided a radio base station that simultaneously transmits a packet including a plurality of code blocks obtained by dividing a bit string that is the same information to a plurality of radio terminals. A packet transmission unit that transmits a plurality of transmission unit packets composed of redundant bits for detection to the plurality of wireless terminals, and a communication quality reception unit that receives the likelihood for each transmission unit packet from the plurality of wireless terminals; Then, the likelihood for each transmission unit packet from the plurality of wireless terminals is summed for each transmission unit packet to obtain a total value, and the plurality of transmission unit packets are set to a ratio according to the reciprocal of the total value. transmission unit and retransmitted at transmission unit setting unit for setting the plurality of wireless end the retransmission packet transmission unit in accordance with the ratio in which the set of retransmission packets corresponding to the respective And summarized in that and a packet retransmission unit to be transmitted to.

  Such a radio base station generates a first transmission packet by extracting and combining a plurality of packets composed of code blocks and redundant bits for error detection for each transmission unit at the time of transmission, and simultaneously generating a plurality of packets. To the wireless terminal. Further, the radio base station sets a transmission unit at the time of retransmission, which is a transmission unit at the time of retransmission, for each code block based on the communication quality for each code block measured by a plurality of radio terminals. At this time, the radio base station sets a transmission unit at the time of retransmission for each code block so as to have a ratio corresponding to the degree of deterioration of communication quality for each code block from a plurality of radio terminals. Therefore, for each code block, the transmission unit at the time of retransmission differs according to the communication quality measured by a plurality of wireless terminals, thereby enabling efficient retransmission control.

A third aspect of the present invention is according to the second aspect of the present invention, indicating that the reception of all the code blocks of said plurality of transmission units packets from said plurality of wireless terminals is not completed successfully A notification receiving unit (wireless communication unit 106) that receives either an abnormality notification or a normal notification indicating that reception of all code blocks in the plurality of transmission unit packets from the plurality of wireless terminals has been normally completed. ), And the packet retransmitting unit is one of the plurality of wireless terminals when the abnormality notification is received from any of the plurality of wireless terminals, or within a predetermined time from transmission by the packet transmitting unit. The gist is to transmit the retransmission packet when the normal notification from the receiver is not received.

A fourth feature of the present invention relates to the third feature of the present invention, wherein when the normal notification is received from any one of the plurality of wireless terminals, a wireless terminal other than the wireless terminal that is the transmission source of the normal notification is provided. The gist is to set a wireless terminal as a transmission destination of the retransmission packet .

  Such a wireless base station does not need to receive retransmission because it excludes the wireless terminal that has successfully received all the code blocks in the first transmission packet from the transmission destination of the second transmission packet. The second transmission packet is not transmitted to the wireless terminal, and unnecessary reception processing is prevented from occurring in the wireless terminal.

A fifth feature of the present invention includes a plurality of code blocks obtained by dividing a bit string that is the same information from the radio base station to the plurality of radio terminals, having a radio base station and a plurality of radio terminals. A communication method in a communication system for simultaneously transmitting packets, wherein the wireless base station transmits a plurality of transmission unit packets comprising the code block and redundant bits for error detection to the plurality of wireless terminals; The plurality of wireless terminals receiving the plurality of transmission unit packets from the wireless base station; and the plurality of wireless terminals are configured to determine the likelihood of the code block based on the redundant bits corresponding to the transmission unit packets. determining a degree for each of the transmission unit packet, said plurality of wireless terminals, transmitting a likelihood of each of the transmission unit packet to the radio base station A step that, the radio base station, receiving the likelihood of each transmission unit packets from the plurality of radio terminals, the radio base station, for each of the transmission unit packets from the plurality of wireless terminals The likelihood is summed for each transmission unit packet to obtain a total value, and the transmission unit of the retransmission packet corresponding to each of the plurality of transmission unit packets is set to have a ratio corresponding to the reciprocal of the total value. a step, the radio base station, and summarized in that and transmitting the retransmission packet transmission unit in accordance with the ratio in which the set to the plurality of wireless terminals.

  According to the present invention, it is possible to perform efficient retransmission control according to the communication quality of code blocks in a plurality of wireless terminals.

1 is an overall schematic configuration diagram of a communication system according to an embodiment of the present invention. It is a schematic block diagram of the radio base station which concerns on embodiment of this invention. It is a functional block block diagram of the control part in the wireless base station which concerns on embodiment of this invention. 1 is an overall schematic configuration diagram of a wireless terminal according to an embodiment of the present invention. It is a functional block diagram of the control part in the radio | wireless terminal which concerns on embodiment of this invention. It is a sequence diagram which shows operation | movement of the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows the production | generation process of the HARQ packet which concerns on embodiment of this invention. It is a figure which shows an example of the CRC check which concerns on embodiment of this invention. It is a figure which shows the structure of the HARQ packet for resending which concerns on embodiment of this invention. It is a figure which shows an example of the CRC recheck which concerns on embodiment of this invention. It is a figure which shows an example of the likelihood detection which concerns on embodiment of this invention. It is a figure which shows the other structure of the HARQ packet for resending which concerns on embodiment of this invention. It is a figure which shows an example of likelihood redetection which concerns on embodiment of this invention.

  Next, an embodiment of the present invention will be described with reference to the drawings. Specifically, (1) the configuration of the communication system, (2) the operation of the communication system, (3) the operation and effect, and (4) 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) Configuration of Communication System First, the configuration of a communication system according to an embodiment of the present invention will be described in the order of (1.1) overall schematic configuration of communication system and (1.2) configuration of communication apparatus.

(1.1) Overall Schematic Configuration of Communication System FIG. 1 is an overall schematic diagram of a radio communication system according to an embodiment of the present invention. A radio communication system 10 illustrated in FIG. 1 includes a radio base station 1, a radio terminal 2A, a radio terminal 2AB, and a radio terminal 2AC. In FIG. 1, radio terminals 2A to 2C are located in a cell 3 provided by the radio base station 1.

  The radio base station 1 simultaneously transmits HARQ packets including a plurality of code blocks obtained by dividing a bit string, which is the same information, to the radio terminals 2A to 2C by multicast communication.

(1.2) Configuration of Radio Base Station (1.2.1) Schematic Configuration of Radio Base Station FIG. 2 is a schematic configuration diagram of the radio base station 1. As illustrated in FIG. 2, the wireless base station 1 includes a control unit 102, a storage unit 103, a wired communication unit 104, a wireless communication unit 106, and an antenna 108.

  The control unit 102 is configured by a CPU, for example, and controls various functions provided in the radio base station 1. The storage unit 103 is configured by a memory, for example, and stores various types of information used for control and the like in the radio base station 1.

  The wired communication unit 104 communicates with a gateway server or the like in an upper network (not shown). The wireless communication unit 106 transmits and receives wireless signals via the antenna 108.

(1.2.2) Detailed Configuration of Radio Base Station Next, a detailed configuration of the radio base station 1, specifically, a functional block configuration of the control unit 102 will be described. FIG. 3 is a functional block configuration diagram of the control unit 102 of the radio base station 1.

  As shown in FIG. 3, the control unit 102 includes a CRC adding unit 152, a code block generating unit 154, FEC encoders 156-1, 156-2, and 156-3, and rate matching units 158-1, 158-2, and 158-. 3, a code block combining unit 160, a transmission unit setting unit 162, and a transmission destination setting unit 164.

  The CRC adding unit 152 inputs a bit string of information. Next, the CRC adding unit 152 adds a CRC bit string to the information bit string to generate a transmission target bit string. Further, the CRC adding unit 152 outputs the transmission target bit string to the code block generating unit 154.

  The code block generation unit 154 inputs a transmission target bit string. Next, the code block generation unit 154 divides the transmission target bit string into blocks (code blocks) having a predetermined length. Here, the code block generation unit 154 divides the transmission target bit string into three code blocks (code blocks # 1 to # 3) having a predetermined length.

  Further, the code block generation unit 154 outputs the code block # 1 to the FEC encoder 156-1. The code block generation unit 154 outputs the code block # 2 to the FEC encoder 156-2 and outputs the code block # 3 to the FEC encoder 156-3.

  The FEC encoder 156-1 receives the code block # 1 and performs encoding. Furthermore, the FEC encoder 156-1 outputs the encoded code block # 1 to the subsequent rate matching unit 158-1. Similarly, the FEC encoder 156-2 performs encoding of the input code block # 2, and outputs the encoded code block # 2 to the subsequent rate matching unit 158-2. Similarly, the FEC encoder 156-3 encodes the input code block # 3 and outputs the encoded code block # 3 to the subsequent rate matching unit 158-3. The coded code blocks # 1 to # 3 include their own identification information.

  The rate matching unit 158-1 receives the encoded code block # 1. Next, rate matching section 158-1 adds redundant bit # 1 for error detection, which is a CRC bit string, to encoded code block # 1, and generates transmission target packet # 1. Furthermore, the rate matching unit 158-1 extracts the first transmission unit, which is the transmission unit set by the transmission unit setting unit 162, from the transmission target packet # 1, and outputs the first transmission unit to the code block combining unit 160.

  Similarly, the rate matching unit 158-2 inputs the encoded code block # 2, and adds an error detection redundant bit # 2 that is a CRC bit string to the encoded code block # 2. The transmission target packet # 2 is generated. Further, rate matching section 158-2 extracts transmission target packet # 2 for each second transmission unit, which is the transmission unit set by transmission unit setting section 162, and outputs it to code block combining section 160. Similarly, rate matching section 158-3 inputs encoded code block # 3 and adds error detection redundancy bit # 3, which is a CRC bit string, to encoded code block # 3. Thus, transmission target packet # 3 is generated. Further, rate matching section 158-3 extracts transmission target packet # 3 for each third transmission unit, which is the transmission unit set by transmission unit setting section 162, and outputs the extracted packet to code block combining section 160. Note that the redundant bit includes identification information of the encoded code block to which the redundant bit is added.

  The transmission unit setting unit 162 sets the first to third transmission units described above. Specifically, the transmission unit setting unit 162 has the same length as the first transmission unit to the third transmission unit at the first transmission to the wireless terminals 2A to 2C, and the first transmission unit to the third transmission unit. The first transmission unit to the third transmission unit are set so that the total length of the packets becomes the packet length of the HARQ packet having a fixed length.

  Also, the transmission unit setting unit 162 transmits the communication quality of the code blocks # 1 to # 3 from the wireless terminals 2A to 2C (described later) via the antenna 108 and the wireless communication unit 106 during retransmission to the wireless terminals 2A to 2C. , The ratio of the first transmission unit to the third transmission unit becomes a ratio according to the degree of deterioration of the communication quality of the code blocks # 1 to # 3 from the wireless terminals 2A to 2C, and The first transmission unit to the third transmission unit are set so that the total length of the first transmission unit to the third transmission unit becomes the packet length of the HARQ packet having a fixed length.

  The code block combining unit 160 extracts the first transmission unit packet extracted from the transmission target packet # 1, the second transmission unit packet extracted from the transmission target packet # 2, and the transmission target packet # 3. The issued third transmission unit packets are input and combined to generate a HARQ packet. Further, the code block combining unit 160 outputs the generated HARQ packet to the transmission destination setting unit 164.

  The transmission destination setting unit 164 sets the wireless terminals 2A to 2C existing in the cell 3 as transmission destinations as transmission destinations of HARQ packets at the time of initial transmission to the wireless terminals 2A to 2C. Further, the transmission destination setting unit 164 adds the set transmission destination information to the HARQ packet and then outputs the information to the wireless communication unit 106. The HARQ packet is transmitted to the wireless terminals 2A to 2C, which are set transmission destinations, via the wireless communication unit 106 and the antenna 108.

  Further, the transmission destination setting unit 164, when retransmitting to the wireless terminals 2A to 2C, ACK indicating that the HARQ packet has been normally received in the wireless terminals 2A to 2C via the antenna 108 and the wireless communication unit 106, or When the wireless terminal 2A to 2C receives a NACK indicating that the HARQ packet has not been normally received, the wireless terminal that is the ACK transmission source is excluded from the transmission destination, and only the wireless terminal that is the NACK transmission source is the transmission destination. Set as. Further, as described above, the transmission destination setting unit 164 adds the set transmission destination information to the HARQ packet and outputs the HARQ packet to the wireless communication unit 106. The HARQ packet is transmitted to the wireless terminal that is the set transmission destination via the wireless communication unit 106 and the antenna 108.

(1.3) Configuration of Radio Terminal (1.3.1) Schematic Configuration of Radio Terminal FIG. 4 is a schematic configuration diagram of the radio terminal 2A. As illustrated in FIG. 4, the wireless terminal 2A includes a control unit 202, a storage unit 203, a wireless communication unit 206, an antenna 208, a monitor 210, a microphone 212, a speaker 214, and an operation unit 216. The wireless terminals 2AB and 2C have the same configuration as the wireless terminal 2A.

  The control unit 202 is configured by a CPU, for example, and controls various functions provided in the wireless terminal 2A. The storage unit 203 is configured by a memory, for example, and stores various information used for control and the like in the wireless terminal 2A.

  The wireless communication unit 206 transmits and receives wireless signals via the antenna 208.

  The monitor 210 displays an image received via the control unit 202 and displays operation details (such as an input telephone number and an address). The microphone 212 collects sound and outputs sound data based on the collected sound to the control unit 202. The speaker 214 outputs sound based on the sound data acquired from the control unit 202.

  The operation unit 216 is configured by a numeric keypad, function keys, and the like, and is an interface used for inputting user operation details.

(1.3.2) Detailed Configuration of Wireless Terminal Next, a detailed configuration of the wireless terminal 2A, specifically, a functional block configuration of the control unit 202 will be described. FIG. 5 is a functional block configuration diagram of the control unit 202 of the wireless terminal 2A. Note that the control units 202 of the wireless terminals 2B and 2C have the same configuration as the control unit 202 of the wireless terminal 2A.

  As shown in FIG. 5, the control unit 202 includes a code block dividing unit 252, rate dematching units 254-1, 254-2, and 254-3, FEC decoders 256-1, 256-2, and 256-3, communication quality. A measurement unit 258, a code block combination unit 260, and a CRC check unit 262 are included.

  The code block division unit 252 receives the HARQ packet from the radio base station 1 via the antenna 208 and the radio communication unit 206. Next, the code block dividing unit 252 adds the identification information of the encoded code block included in the encoded code block in the HARQ packet and the redundant bit included in the redundant bit in the HARQ packet. The identification information of the coded code block is detected.

  Next, the code block dividing unit 252 extracts the packet of the first transmission unit including the encoded code block # 1 including the identification information of the encoded code block # 1 and the redundant bit # 1 from the HARQ packet, Output to the rate dematching unit 254-1.

  Similarly, the code block dividing unit 252 extracts a packet of the second transmission unit including the encoded code block # 2 including the identification information of the encoded code block # 2 and the redundant bit # 2 from the HARQ packet, The data is output to the rate dematching unit 254-2. Further, similarly, the code block dividing unit 252 extracts a packet of the third transmission unit including the encoded code block # 3 including the identification information of the encoded code block # 3 and the redundant bit # 3 from the HARQ packet. And output to the rate dematching unit 254-3.

  The rate dematching unit 254-1 receives the first transmission unit packet and extracts the code block # 1 and the redundant bit # 1 from the first transmission unit packet. Further, the rate dematching unit 254-1 outputs the code block # 1 to the FEC decoder 256-1 and the communication quality measurement unit 258, and outputs the redundant bit # 1 to the communication quality measurement unit 258.

  Similarly, the rate dematching unit 254-2 receives the second transmission unit packet, and extracts the code block # 2 and the redundant bit # 2 from the second transmission unit packet. Further, the rate dematching unit 254-2 outputs the code block # 2 to the FEC decoder 256-2 and the communication quality measurement unit 258, and outputs redundant bit # 2 to the communication quality measurement unit 258. Similarly, the rate dematching unit 254-3 inputs the third transmission unit packet, and extracts the code block # 3 and the redundant bit # 3 from the third transmission unit packet. Further, the rate dematching unit 254-3 outputs the code block # 3 to the FEC decoder 256-3 and the communication quality measurement unit 258, and outputs redundant bit # 3 to the communication quality measurement unit 258.

  The communication quality measuring unit 258 receives the code block # 1 and the redundant bit # 1 from the rate dematching unit 254-1. Similarly, the communication quality measurement unit 258 receives the code block # 2 and redundant bit # 2 from the rate dematching unit 254-2, and receives the code block # 3 and redundant bit # 3 from the rate dematching unit 254-3. Enter.

  Next, the communication quality measurement unit 258 detects an error (CRC check) of the code block # 1 based on the redundant bit # 1 that is a CRC bit string and detects an error of the code block # 2 based on the redundant bit # 2 that is a CRC bit string And error detection of code block # 3 based on redundant bit # 3, which is a CRC bit string. Further, the communication quality measuring unit 258 outputs the error detection results of the code blocks # 1 to # 3 to the wireless communication unit 206 as the communication quality of the code blocks # 1 to # 3. The communication qualities of the code blocks # 1 to # 3 are transmitted to the radio base station 1 via the radio communication unit 206 and the antenna 208.

  Also, the communication quality measurement unit 258 outputs an ACK indicating normal reception to the radio communication unit 206 when the error detection results of the code blocks # 1 to # 3 all indicate that there is no error. To do. Also, the communication quality measurement unit 258 confirms that the radio communication unit 206 has not received the error normally if any of the error detection results of the code blocks # 1 to # 3 indicates that there is an error. NACK is output. ACK or NACK is transmitted to the radio base station 1 via the radio communication unit 206 and the antenna 208.

  The FEC decoder 256-1 receives the code block # 1 and performs decoding. Further, the FEC decoder 256-1 outputs the decoded code block # 1 to the code block combining unit 260. Similarly, the FEC decoder 256-2 decodes the input code block # 2, and outputs the decoded code block # 2 to the code block combining unit 260. Further, similarly, the FEC decoder 256-3 decodes the input code block # 3 and outputs the decoded code block # 3 to the code block combining unit 260.

  The code block combining unit 260 inputs the code blocks # 1 to # 3 after decoding. Next, the code block combining unit 260 combines the decoded code blocks # 1 to # 3 to generate a transmission target bit string. Further, the code block combining unit 260 outputs the generated transmission target bit string to the CRC check unit 262.

  The CRC check unit 262 inputs a transmission target bit string. Next, the CRC check unit 262 extracts an information bit string and a CRC bit string from the transmission target bit string, and performs error detection of the information bit string based on the CRC bit string. Further, the CRC check unit 262 outputs an information bit string when no error is detected.

(2) Operation of Radio Communication System FIG. 6 is a sequence diagram showing operations of the radio base station 1 and the radio terminals 2A to 2C constituting the radio communication system 10.

  In step S101, the radio base station 1 generates a HARQ packet.

  FIG. 7 is a diagram illustrating a HARQ packet generation process. In the following, it is assumed that the block which is the minimum transmission unit has a length L. In the first step shown in FIG. 7A, the radio base station 1 divides the transmission target bit string into code blocks # 1 to # 3 having a length of 2L.

  In the second step shown in FIGS. 7B1 to 7B3, the radio base station 1 adds four redundant bits # 1 which are CRC bit strings of length L to the code block # 1, and has a length of 6L. A transmission target packet # 1 is generated. Similarly, the radio base station 1 adds four redundant bits # 2, which are CRC bit strings of length L, to the code block # 2, generates a transmission target packet # 2 of length 6L, and stores it in the code block # 3. Four redundant bits # 3, which is a CRC bit string having a length L, are added to generate a transmission target packet # 3 having a length 6L.

  In the third step shown in FIG. 7C, the transmission unit setting unit 162 in the wireless terminal sets the first to third transmission units to 4L which is 1/3 of the packet length of the HARQ packet. Further, the radio base station 1 extracts and combines the packets of the first transmission unit to the third transmission unit, which are blocks of 4L from the beginning of the transmission target packets # 1 to # 3, and combines them. 12L HARQ packet # 1 is generated.

  Again, referring back to FIG. In step S102, the radio base station 1 simultaneously transmits the same HARQ packet to the radio terminals 2A to 2C that are transmission destinations by multicast communication. The radio terminals 2A to 2C receive the HARQ packet.

  In step S103, the communication quality measurement unit 258 in the radio terminals 2A to 2C measures the communication quality (CRC check) of each code block included in the HARQ packet.

  FIG. 8 is a diagram illustrating an example of a CRC check in step S103. The communication quality measuring unit 258, from the HARQ packet shown in FIG. 7 (c), as shown in FIGS. 8 (a) to 8 (c), the first transmission unit packet consisting of the code block # 1 and the redundant bit # 1 Then, the second transmission unit packet composed of code block # 2 and redundant bit # 2 and the third transmission unit packet composed of code block # 3 and redundant bit # 3 are extracted.

  Further, the communication quality measuring unit 258 performs a CRC check on the code block # 1 based on the redundant bit # 1. Similarly, the communication quality measuring unit 258 performs a CRC check on the code block # 2 based on the redundant bit # 2, and performs a CRC check on the code block # 3 based on the redundant bit # 3.

  In FIG. 8, the result of the CRC check for the code block # 1 is NG in the radio terminals 2A and 2B, that is, an error is detected in the code blocks # 1 and # 2, and OK in the radio terminal 2C. That is, no error is detected in code block # 1. The CRC check result for code block # 2 is NG for the wireless terminal 2A and OK for the wireless terminals 2B and 2C. Also, the CRC check result for code block # 3 is OK in any of the wireless terminals 2A to 2C.

  Again, referring back to FIG. In step S104, the communication quality measurement unit 258 in the radio terminals 2A to 2C determines whether there is no error in all code blocks based on the CRC check result in step S103, in other words, all code blocks. It is determined whether or not it has been received normally.

  Here, as shown in FIG. 8, in the wireless terminal 2A, the result of the CRC check for code blocks # 1 and # 2 is NG, the result of the CRC check for code block # 3 is OK, and the code block # 1 and # 2 are not received normally. In this case, in step S105, the radio terminal 2A sends a NACK, a CRC check result NG indicating the communication quality of the code block # 1, and a CRC check indicating the communication quality of the code block # 2 to the radio base station 1. The result NG and the CRC check result OK which is the communication quality of the code block # 3 are transmitted.

  In the wireless terminal 2B, the CRC check result of the code block # 1 is NG, the CRC check results of the code blocks # 2 and # 3 are OK, and the code block # 1 is normally received. Absent. In this case, in step S105, the radio terminal 2B sends a NACK, a CRC check result indicating the communication quality of the code block # 1, NG, and a CRC check indicating the communication quality of the code block # 2 to the radio base station 1. The result OK and the CRC check result OK which is the communication quality of the code block # 3 are transmitted.

  In the wireless terminal 2C, the result of the CRC check for the code blocks # 1 to # 3 is OK, and all the code blocks # 1 to # 3 are normally received. In this case, in step S105, the radio terminal 2C transmits ACK to the radio base station 1, and ends a series of operations.

  On the other hand, in step S105, the radio base station 1 determines the communication quality of the NACK and code blocks # 1 to # 3 from the radio terminal 2A, the communication quality of the NACK and code blocks # 1 to # 3 from the radio terminal 2B, ACK from the wireless terminal 2C is received.

  In step S106, the radio base station 1 determines whether or not a NACK from the radio terminals 2A to 2C has been received, or whether or not an ACK has not been received within a predetermined time.

  When the NACK from the radio terminals 2A to 2C is not received and the ACK from the radio terminals 2A to 2C is received within a predetermined time, the radio base station 1 ends a series of operations.

  Here, the radio base station 1 receives NACKs from the radio terminals 2A and 2B and receives ACKs from the radio terminal 2C. In this case, in step S107, the radio base station 1 generates a retransmission HARQ packet.

  FIG. 9 is a diagram illustrating a configuration of a HARQ packet for retransmission. In FIG. 9, as shown in FIG. 8, the CRC check result for code block # 1 is NG for wireless terminals 2A and 2B, and OK for wireless terminal 2C, and the CRC check result for code block # 2 is wireless This is an example of a case where the terminal 2A is NG, the wireless terminals 2B and 2C are OK, and the CRC check result for code block # 3 is OK in the wireless terminals 2A to 2C.

  In this case, retransmission of code blocks # 1 and # 2 is necessary, and retransmission of code block # 3 is not necessary.

  The transmission unit setting unit 162 in the radio base station 1 calculates a representative level of communication quality for the code blocks # 1 and # 2. Specifically, the transmission unit setting unit 162 sets the representative level to NG when at least one of the CRC check results in the wireless terminals 2A and 2B is NG. In FIG. 8, since the CRC check result in the wireless terminal 2A and the CRC check result in the wireless terminal 2B are both NG for the code block # 1, the transmission unit setting unit 162 determines the communication quality for the code block # 1. The representative level is NG. In FIG. 8, since the CRC check result in the wireless terminal 2A is NG for the code block # 2, the transmission unit setting unit 162 sets the representative level of communication quality for the code block # 2 to NG.

  Further, as shown in FIG. 9A, the transmission unit setting unit 162 corresponds to the fact that the representative levels of communication quality for the code blocks # 1 and # 2 are both NG, The second transmission unit is set to 6L, which is 1/2 of the packet length of the HARQ packet. Next, the transmission unit setting unit 162 in the radio base station 1 extracts 6L from the block next to the last block among the blocks that have been transmitted immediately before the transmission target packet # 1. Similarly, the transmission unit setting unit 162 in the radio base station 1 extracts 6L from the block next to the last block among the blocks that have been transmitted immediately before the transmission target packet # 2. Further, the radio base station 1 combines the packet of the first transmission unit and the packet of the second transmission unit, which are 6L blocks extracted from the transmission target packets # 1 and # 2, to retransmit 12L in length. HARQ packet # 2 is generated.

  Alternatively, the transmission unit setting unit 162 in the radio base station 1 calculates the average level of communication quality for the code blocks # 1 and # 2. Specifically, the transmission unit setting unit 162 calculates the average level as 0 when the CRC check result in the wireless terminals 2A and 2B is OK, and 1 when it is NG. In FIG. 8, since the CRC check result in the wireless terminal 2A and the CRC check result in the wireless terminal 2B are both NG for the code block # 1, the transmission unit setting unit 162 determines the communication quality for the code block # 1. The average level is (1 + 1) / 2 = 1. In FIG. 8, for code block # 2, since the CRC check result at wireless terminal 2A is NG, the CRC check result at wireless terminal 2A is NG, and the CRC check result at wireless terminal 2B is OK, transmission unit setting section 162 The average level of communication quality for code block # 2 is (1 + 0) /2=0.5.

  Further, as shown in FIG. 9B, the transmission unit setting unit 162 has an average communication quality level of 1 for the code block # 1, and an average communication quality level of 0.5 for the code block # 2. Accordingly, the ratio between the first transmission unit and the second transmission unit is 1: 0.5, that is, 2: 1. Here, since the packet length of the HARQ packet is 12L, the transmission unit setting unit 162 sets the first transmission unit to 8L and sets the second transmission unit to 4L. Next, the transmission unit setting unit 162 in the radio base station 1 extracts 8L from the block next to the last block among the blocks that have been transmitted immediately before the transmission target packet # 1. Similarly, the transmission unit setting unit 162 in the radio base station 1 extracts 4L from the block next to the last block among the blocks that have been transmitted immediately before the transmission target packet # 2. Furthermore, the radio base station 1 combines the first transmission unit, which is a block corresponding to 8L extracted from the transmission target packet # 1, and the second transmission unit, which is a block corresponding to 4L extracted from the transmission target packet # 2. As a result, a retransmission HARQ packet # 2 having a length of 12L is generated.

  Again, referring back to FIG. In step S108, the radio base station 1 sets the transmission destination of the retransmission HARQ packet to the radio terminals 2A and 2B.

  Further, in step S109, the radio base station 1 simultaneously transmits the same retransmission HARQ packet to the radio terminals 2A to 2C as transmission destinations by multicast communication. The radio terminals 2A and 2B receive the retransmission HARQ packet.

  In step S110, the communication quality measurement unit 258 in the radio terminals 2A and 2B measures the communication quality (CRC) of each code block included in the HARQ packet received in step S102 and the HARQ packet for retransmission received in step S109. Recheck).

  FIG. 10 is a diagram illustrating an example of CRC recheck in step S110. FIG. 10 shows an example in which the retransmission HARQ packet # 2 is the one shown in FIG.

  As shown in FIG. 10 (a1), the communication quality measuring unit 258 in the wireless terminals 2A and 2B receives the code block # 1 and redundant bit # 1 received in step S102, and the code block # 1 received in step S109. And redundant bit # 1. Here, code block # 1 and one of redundant bits # 1 have been received twice. In this case, the communication quality measurement unit 258 in the wireless terminals 2A to 2C combines the Euclidean distances of the bits at the same position for the two code blocks # 1 and the two redundant bits # 1, and uses the combined value of the Euclidean distances. Based on the code block # 1 and redundant bit # 1 received twice, the bits are determined. Further, the communication quality measuring unit 258 in the wireless terminals 2A to 2C performs CRC recheck on the code block # 1 based on the redundant bit # 1. Here, in both the wireless terminals 2A and 2B, the result of the CRC recheck of the code block # 1 is OK.

  Similarly, the communication quality measurement unit 258 in the wireless terminals 2A and 2B combines the code block # 2 and the redundant bit # 2 received in step S102 and step S109 as shown in FIG. 10 (a2). Next, the communication quality measurement unit 258 in the radio terminals 2A to 2C determines each bit of the code block # 2 and the redundant bit # 2 received twice. Further, the communication quality measurement unit 258 in the wireless terminals 2A to 2C performs CRC recheck on the code block # 2 based on the redundant bit # 2. Here, in both the wireless terminals 2A and 2B, the result of the CRC recheck of the code block # 2 is OK.

  Again, referring back to FIG. In step S111, the radio terminals 2A and 2B check whether all code blocks have no errors based on the CRC recheck result in step S110, in other words, whether all code blocks have been normally received. Determine whether.

  Here, as shown in FIG. 10, in both the wireless terminal 2A and the wireless terminal 2B, the result of the CRC check of the code blocks # 1 and # 2 is OK, and all the code blocks are received normally. . In this case, in Step S112, the radio terminals 2A and 2B transmit ACK, and the radio base station 1 receives the ACK. This completes a series of operations.

  On the other hand, if there is a code block that has not been normally received, the radio terminals 2A and 2B again transmit NACK and code block communication quality to the radio base station 1, as in step S105. The operation is performed, and then the operations after step S106 are repeated.

(3) Operation / Effect According to the radio communication system 10 according to the embodiment of the present invention, the radio base station 1 on the transmission side generates a plurality of transmission target packets including code blocks and redundant bits for error detection. . Further, the radio base station 1 generates a HARQ packet by combining each transmission target packet for each predetermined transmission unit, and simultaneously transmits the same HARQ packet to the radio terminals 2A to 2C by multicast communication.

  On the other hand, the receiving-side wireless terminals 2A to 2C take out a predetermined transmission unit of each transmission target packet included in the received HARQ packet and include it in the transmission target packet based on redundant bits included in the transmission target packet. CRC check is performed on the code block to be transmitted, and the result is transmitted as the communication quality for each code block included in the transmission target packet.

  Furthermore, the radio base station 1 sets a transmission unit for retransmission for each code block based on the CRC check results from the radio terminals 2A to 2C. At this time, the radio base station 1 has the same transmission unit of the transmission target packet including each code block whose CRC check result is NG in any of the radio terminals 2A to 2C, and the total of the transmission units. A HARQ packet for retransmission is generated by combining the packets of transmission units extracted from the respective transmission target packets by setting the length to be the packet length of the HARQ packet having a fixed length. Furthermore, the radio base station 1 transmits the HARQ packet for retransmission to a radio terminal that has not normally received the code block. On the other hand, the radio base station 1 sets the transmission unit of the transmission target packet including the code block in which the CRC check results from all the radio terminals 2A to 2C are OK to zero. That is, the radio base station 1 does not retransmit a code block normally received by all the radio terminals 2A to 2C.

  Therefore, for each code block, the transmission unit at the time of retransmission differs according to the communication quality of the code block measured by each of the radio terminals 2A to 2C, and efficient retransmission control is possible.

  Also, the radio base station 1 transmits the retransmission HARQ packet only to the radio terminal that has not normally received the code block, and unnecessary reception processing occurs in the radio terminal that does not need to receive the retransmission. It is prevented.

(4) 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 communication quality measurement unit 258 in the wireless terminals 2A to 2C performs the CRC check of the code blocks # 1 to # 3 based on the redundant bits # 1 to # 3 that are CRC bit strings. When # 1 to # 3 are not CRC bit strings, the likelihoods of code blocks # 1 to # 3 based on these redundant bit strings # 1 to # 3 are detected, and the likelihood is used as the communication quality of code blocks # 1 to # 3. Also good. FIG. 11 is a diagram illustrating an example of likelihood detection of code blocks # 1 to # 3.

  Further, the transmission unit setting unit 162 in the radio base station 1 calculates the total likelihood value for each of the radio terminals 2A to 2C for each of the code blocks # 1 to # 3, and the first transmission unit to the third transmission unit. The ratio of transmission units is a ratio according to the reciprocal of the total likelihood value of code blocks # 1 to # 3, and the total length of the first transmission unit to the third transmission unit is a fixed length. You may make it set the 1st transmission unit thru | or the 3rd transmission unit so that it may become a packet length.

  For example, a case is considered in which, when the likelihood of a code block in a wireless terminal is 0.8 or more, it is considered that the code block has been normally received in the wireless terminal.

  As shown in FIG. 11, for code block # 1, the likelihood at radio terminal 2A is 0.2, the likelihood at radio terminal 2B is 0.2, and the likelihood at radio terminal 2C is 0.8. For code block # 2, the likelihood at radio terminal 2A is 0.2, the likelihood at radio terminal 2B is 0.6, the likelihood at radio terminal 2C is 0.8, and code block # 3 It is assumed that the likelihood at the wireless terminal 2A is 0.1, the likelihood at the wireless terminal 2B is 0.7, and the likelihood at the wireless terminal 2C is 0.8.

  In this case, the radio terminal 2A sends NACK, the likelihood 0.2 of the code block # 1, the likelihood 0.2 of the code block # 2, and the likelihood of the code block # 3 to the radio base station 1. Send 0.1. Also, the radio terminal 2B transmits NACK, a likelihood of 0.2 for the code block # 1, a likelihood of 0.6 for the code block # 2, and a likelihood of 0 for the code block # 3 to the radio base station 1. .7 is transmitted. In addition, the wireless terminal 2 </ b> C transmits ACK to the wireless base station 1.

  The transmission unit setting unit 162 in the radio base station 1 has a total value 0 of the likelihood 0.2 of the code block # 1 from the radio terminal 2A and the likelihood 0.2 of the code block # 1 from the radio terminal 2B. .4 is calculated. Further, the transmission unit setting unit 162 calculates a total value 0.8 of the likelihood 0.2 of the code block # 2 from the wireless terminal 2A and the likelihood 0.6 of the code block # 2 from the wireless terminal 2B. To do. Further, the transmission unit setting unit 162 calculates a total value 0.8 of the likelihood 0.1 of the code block # 3 from the wireless terminal 2A and the likelihood 0.7 of the code block # 3 from the wireless terminal 2B. To do.

  Further, the transmission unit setting unit 162 sets the ratio of the first transmission unit to the third transmission unit to 1 / 0.4: 1 / 0.8: 1 / 0.8, which is the ratio of the reciprocal of the total likelihood value. That is, 2: 1: 1. Alternatively, the transmission unit setting unit 162 sets the ratio of the first transmission unit to the third transmission unit to 1 / (0.4 / 2): 1 / (0.8 / 2): 1 / (0.8 / 2), that is, 2: 1: 1. When the length of the HARQ packet is 12L, the first transmission unit is 6L, and the second transmission unit and the third transmission unit are 3L.

  After that, the radio base station 1 generates a retransmission HARQ packet by combining the first transmission unit of the transmission target packet # 1, the second transmission unit of the transmission target packet # 2, and the third transmission unit of the transmission target packet # 3. To the wireless terminals 2A and 2B. FIG. 12 is a diagram illustrating a configuration of a HARQ packet for retransmission when the first transmission unit is 6L, and the second transmission unit and the third transmission unit are 3L.

  The communication quality measurement unit 258 in the wireless terminals 2A and 2B that has received the retransmission HARQ packet measures the communication quality of each code block included in the already received HARQ packet and the newly received retransmission HARQ packet ( Likelihood redetection).

  FIG. 13 is a diagram illustrating an example of likelihood redetection. As shown in FIG. 13 (a1), the communication quality measurement unit 258 in the wireless terminals 2A and 2B receives the already received code block # 1 and redundant bit # 1, and the newly received code block # 1 and redundant bit. Combine with # 1. Here, code block # 1 and one of redundant bits # 1 have been received twice. In this case, the communication quality measurement unit 258 in the wireless terminals 2A and 2B combines the Euclidean distances of the bits at the same position for the two code blocks # 1 and the two redundant bits # 1, and uses the combined value of the Euclidean distances. Based on the code block # 1 and redundant bit # 1 received twice, the bits are determined. Furthermore, the communication quality measurement unit 258 in the wireless terminals 2A and 2B detects the likelihood of the code block # 1 based on the redundant bit # 1.

  Further, as shown in FIG. 13 (a2), the communication quality measurement unit 258 in the wireless terminals 2A and 2B includes the already received code block # 2 and redundant bit # 2, and the newly received redundant bit # 2. And the likelihood of the code block # 2 is detected based on the redundant bit # 2. Similarly, the communication quality measuring unit 258 in the wireless terminals 2A and 2B, as shown in FIG. 13 (a3), already received code block # 3 and redundant bit # 3, and newly received redundant bit # 3. And the likelihood of code block # 3 is detected based on redundant bit # 3.

  Thereafter, the wireless terminals 2A and 2B determine whether or not all code blocks are error-free based on the result of likelihood redetection, in other words, whether or not all code blocks have been normally received. . For example, in the example of FIG. 13, the likelihoods of the code blocks # 1 to # 3 are all 0.8, and it is determined that they are normally received.

  When all the code blocks are normally received, the radio terminals 2A and 2B transmit ACK, and the radio base station 1 receives the ACK. On the other hand, when there is a code block that has not been normally received, the radio terminals 2A and 2B transmit NACK and likelihood that is code block communication quality to the radio base station 1.

  Further, the transmission unit setting unit 162 in the radio base station 1 uses the minimum value of the likelihoods of the radio terminals 2A to 2C for each of the code blocks # 1 to # 3 as a representative value, and uses the first transmission unit. Or the ratio of the third transmission unit is a ratio corresponding to the inverse of the representative value of the likelihood of the code blocks # 1 to # 3, and the total length of the first transmission unit to the third transmission unit is a fixed length. The first transmission unit to the third transmission unit may be set so as to be the packet length of the HARQ packet.

  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.

  The communication system, communication apparatus, and communication method of the present invention are capable of efficient retransmission control according to the communication quality of code blocks in a plurality of wireless terminals, and are useful as communication systems and the like.

  DESCRIPTION OF SYMBOLS 1 ... Wireless base station, 2A thru | or 2C ... Wireless terminal, 3 ... Cell, 10 ... Wireless communication system, 102 ... Control part, 103 ... Memory | storage part, 104 ... Wired communication part, 106 ... Wireless communication part, 108 ... Antenna, 152 ... CRC addition part, 154 ... code block generation part, 156-1, 156-2, 156-3 ... FEC encoder, 158-1, 158-2, 158-3 ... rate matching part, 160 ... code block combination part, 162 ... Transmission unit setting unit, 164 ... Transmission destination setting unit, 202 ... Control unit, 203 ... Storage unit, 206 ... Wireless communication unit, 208 ... Antenna, 210 ... Monitor, 212 ... Microphone, 214 ... Speaker, 216 ... Operation unit 252: Code block division unit 254-1, 254-2, 254-3 Rate dematching unit 256-1, 256-2, 256-3 ... FEC Coder, 258 ... communication quality measurement unit, 260 ... code block combining unit, 262 ... CRC checker

Claims (5)

A communication system including a radio base station and a plurality of radio terminals, and simultaneously transmitting packets including a plurality of code blocks obtained by dividing a bit string that is the same information from the radio base station to the plurality of radio terminals. There,
The radio base station includes a packet transmission unit for transmitting a plurality of transmission units packets consisting of said coding blocks and redundancy bits for error detection to the plurality of wireless terminals,
The plurality of radio terminals receive the plurality of transmission unit packets from the radio base station , obtain the likelihood of the code block based on redundant bits corresponding to the transmission unit packets for each transmission unit packet, and A communication quality transmitter that transmits the likelihood of each transmission unit packet to the radio base station;
The radio base station is
A communication quality receiving unit that receives likelihood for each transmission unit packet from the plurality of wireless terminals;
The likelihood for each transmission unit packet from the plurality of wireless terminals is summed for each transmission unit packet to obtain a total value, and the ratio of the plurality of transmission unit packets is set to a ratio according to the reciprocal of the total value . Retransmission transmission unit setting unit for setting a transmission unit of a retransmission packet corresponding to each ,
Communication system to obtain Bei a packet retransmission unit for transmitting the retransmission packet transmission unit in accordance with the ratio in which the set to the plurality of wireless terminals. A wireless base station that simultaneously transmits a packet including a plurality of code blocks obtained by dividing a bit string that is the same information to a plurality of wireless terminals,
A packet transmitter for transmitting a plurality of transmission unit packets composed of the code block and redundant bits for error detection to the plurality of wireless terminals;
A communication quality receiving unit that receives likelihood for each transmission unit packet from the plurality of wireless terminals;
The likelihood for each transmission unit packet from the plurality of wireless terminals is summed for each transmission unit packet to obtain a total value, and the ratio of the plurality of transmission unit packets is set to a ratio according to the reciprocal of the total value . Retransmission transmission unit setting unit for setting a transmission unit of a retransmission packet corresponding to each ,
A radio base station comprising: a packet retransmission unit that transmits a retransmission packet in a transmission unit corresponding to the set ratio to the plurality of radio terminals. Anomaly notification indicating that reception of all code blocks in the plurality of transmission unit packets from the plurality of wireless terminals is not normally completed, or in the plurality of transmission unit packets from the plurality of wireless terminals A notification receiving unit that receives any of the normal notifications indicating that the reception of all the code blocks has been normally completed;
The packet retransmission unit receives the normal notification from any of the plurality of wireless terminals when the abnormality notification is received from any of the plurality of wireless terminals, or within a predetermined time from transmission by the packet transmission unit. The radio base station according to claim 2, wherein when the notification is not received, the retransmission packet is transmitted. A transmission destination setting unit configured to set a wireless terminal other than the wireless terminal that is the transmission source of the normal notification as a transmission destination of the retransmission packet when the normal notification is received from any of the plurality of wireless terminals; The radio base station according to claim 3 provided. In a communication system having a radio base station and a plurality of radio terminals, and simultaneously transmitting packets including a plurality of code blocks obtained by dividing a bit string that is the same information from the radio base station to the plurality of radio terminals A communication method,
The radio base station transmitting a plurality of transmission unit packets comprising the code block and redundant bits for error detection to the plurality of radio terminals;
The plurality of wireless terminals receiving the plurality of transmission unit packets from the wireless base station;
The plurality of wireless terminals , for each transmission unit packet, obtaining a likelihood of the code block based on the redundant bits corresponding to the transmission unit packet ;
The plurality of wireless terminals transmitting the likelihood of each transmission unit packet to the wireless base station;
The wireless base station receiving the likelihood for each transmission unit packet from the plurality of wireless terminals;
The radio base station, the plurality of calculated total value the likelihood of the transmission per unit packet by summing for each of the transmission unit packet from the wireless terminal, wherein such that the ratio corresponding to a reciprocal of the sum Setting a retransmission packet transmission unit corresponding to each of a plurality of transmission unit packets ;
The wireless base station transmitting a retransmission packet of a transmission unit according to the set ratio to the plurality of wireless terminals ;
A communication method comprising:

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