JP2009044708A - Radio communication system, radio terminal and radio base station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a HARQ radio communication system reducing a data-transmission delay resulting from a sub-packet retransmission by adjusting the sub-packet retransmission period. <P>SOLUTION: In the radio communication system in which a packet is transmitted and received with the HARQ method between a base station and multiple radio mobile stations, each of the base station and the multiple radio mobile stations has: a packet transmission circuit for transmitting subpackets in predetermined intervals; a packet reception circuit for repeating decoding processing by combining a newly received subpacket and a previously received former subpacket until an original packet is successfully decoded; and a HARQ control equipped with a function of, for packet communication whose data length is short, transmitting a subpacket or response from the packet transmission circuit in retransmission interval that is shortened from the retransmission interval of the normal mode. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a radio communication system, and more particularly to a radio communication system for cellular communication adopting a hybrid automatic repeat request (HARQ), a radio terminal and a radio base station applied thereto.

  In the fourth generation mobile communication system, HARQ has attracted attention as a data retransmission method. In HARQ, a packet including transmission data and, for example, an error detection code (redundant bit) generated by turbo coding is divided into a plurality of radio subpackets in order to increase resistance in a radio channel. Are transmitted and received in units of subpackets. Usually, data is transmitted in the first subpacket, and redundant bits are transmitted in the subsequent subpacket. When the data transmission node transmits the subpacket, it waits for a response from the data reception node and determines the subpacket to be transmitted next. The data receiving node returns an ACK (Acknowledgement) to the data transmitting node when the received subpacket is successfully decoded, and returns a NAK (Negative Acknowledgement) when the decoding fails. At this time, the data receiving node waits for the next subpacket to be received in a state where the received subpacket that has failed in decoding is stored.

  When the data transmission node receives the NAK from the data reception node with respect to the first subpacket, the data transmission node transmits the second subpacket. When the data receiving node receives the second subpacket, it combines the first and second subpackets and tries to decode the received data. That is, using the error detection code (redundant bit) received in the second subpacket, an attempt is made to decode the data portion of the received first subpacket. The data receiving node returns ACK or NAK to the data transmitting node according to the decoding result.

  When the data transmission node receives the NAK from the data reception node as a response to the second subpacket, the data transmission node transmits the third subpacket. When the error detection code (redundancy bit) is divided into a plurality of subpackets, the remaining part of the error detection code is transmitted in the third subpacket. In this case, the data receiving node that has received the third subpacket combines the first, second, and third subpackets and attempts to decode the received data.

  The HARQ data transmission node has a repetition function for retransmitting a packet that has already been transmitted when a NAK is received for the last subpacket. Therefore, when the NAK is received for the last subpacket, the data transmitting node retransmits the already transmitted subpackets in order from the first subpacket, and the ACK is received from the data receiving node. Wait for. In this specification, transmission of a subpacket performed by a data transmission node when a NAK is received is referred to as retransmission regardless of whether the subpacket is new or already transmitted.

  When receiving the ACK from the data receiving node, the data transmitting node determines that the packet transmission is successful, and transmits a new data packet to be transmitted next to the data receiving node in the above-described subpacket format. When the NAK return from the data receiving node is repeated and the number of retransmissions of the subpacket reaches a predetermined limit, the data transmission node stops the subpacket retransmission operation. In this case, packet transmission has failed, and an upper layer of the data receiving node determines whether to request packet retransmission or discard the received packet.

  In this way, in the HARQ scheme in which a transmission packet including redundant bits is divided into several subpackets and transmitted, if the radio channel condition is good, data reception is performed before all the redundant bits are received. The node succeeds in restoring the received data, and as a result, data communication using the radio resource effectively becomes possible. In HARQ, a dedicated channel for transmitting ACK / NAK information is prepared in a physical layer, for example, a group of channels composed of OFDM (Orthogonal Frequency Division Multiplexing) subcarriers, and the above-described subpacket retransmission control is speeded up. ing.

  A wireless system using HARQ has been proposed in, for example, IEEE 802.20, which is a standardization organization, and a data retransmission control system is defined in IEEE C802.20-06 / 04 (Non-patent Document 1). 3GPP, which is a standardization organization, has proposed a radio scheme using HARQ as LTE (Long Term Evolution). In 3GPP TR 25.814 V7.0.0 (2006-06) (Non-patent Document 2), A data retransmission control method in the above wireless system is defined. In addition, 3GPP2, which is a standardization organization, has proposed an OFDMA (Orthogonal Frequency Division Multiple Access) radio scheme using HARQ as LBC (Loosely Backwards Compatible), and 3GPP2 C30-200660731-040R4 (Non-patent Document 3). Thus, a data retransmission control method in the above wireless system is defined.

IEEE C802.20-06 / 04. 3GPP TR 25.814 V7.0.0 (2006-06). 3GPP2 C30-20060731-040R4.

  For example, in 3GPP2 LBC (Loosely Backwards Compatible), a unit time width called a “frame” is defined in a radio section, a subpacket transmission period from a data transmission node to a data reception node, and a data reception node to a data transmission node ACK / NAK response timing is specified in units of the frame. For example, in the case of a communication mode in which a subpacket is transmitted from the base station at a period of 8 frames, each wireless terminal processes the received subpacket within a 4-frame period with the frame (0th frame) received as a reference. Then, ACK / NAK is returned to the data transmission node in the fifth frame. The base station finishes the ACK / NAK process and the next subframe transmission preparation within the next two frame periods, and transmits the next subframe in the eighth frame.

  The base station communicates with a plurality of terminals in a time division manner by transmitting subpackets in different frames for each terminal. In a communication mode in which subpackets are transmitted in a period of 8 frames, the base station can communicate with 8 terminals on the same data channel. A combination of frames at regular intervals for assigning different communication time zones for each terminal is called interlace. The base station controls communication with each terminal based on the interlace number. In LBC, in addition to the 8-interlace communication mode, for example, a system configuration of a 6-interlace mode and a 5-interlace mode has been studied, but the interlace mode can be uniquely set in the system.

  In HARQ, the subpacket retransmission period includes, for example, demodulation processing of received data required at the data receiving node, time required for decoding processing, decoding processing of received ACK / NAK required at the data transmitting node, and scheduling of data transmission It depends on the time required for the transmission data encoding process. In the case of the 8-interlace described above, 4 frame periods are secured in the data receiving node and 2 frame periods are secured in the data transmitting node as the data processing time. Although the data processing time varies depending on the size of the transmitted / received subpacket, in the above-described LBC example, even when the maximum-sized subpacket is transmitted in each frame period, each node on the data transmission side and the data reception side The sub-packet retransmission period is determined so as to ensure a sufficient processing time.

  However, if a retransmission cycle is set according to the maximum size sub-packet, if a short-size sub-packet that requires a short processing time is received, a dead time occurs between transmissions of the next sub-packet, resulting in a data transmission delay. There is a problem that becomes larger. For example, a VoIP (Voice over IP) service for making a voice call via an IP (Internet Protocol) network has a stricter requirement regarding data delay than a best effort service such as FTP (File Transfer Protocol). Since the VoIP packet has a relatively small packet size, if a packet is transmitted / received at a retransmission cycle that matches the time required for processing the maximum packet, an unnecessarily long waiting time occurs. For this reason, when the wireless environment deteriorates and the number of retransmissions of subpackets increases, the data transmission delay may increase and service quality may deteriorate.

  An object of the present invention is to provide a wireless communication system in which a sub-packet retransmission period is made appropriate and data transmission delay caused by sub-packet retransmission is reduced.

  In order to achieve the above object, the wireless communication system of the present invention is configured to perform HARQ control in which a base station and a wireless terminal device perform subpacket retransmission at a period shorter than a standard period for data communication in which a packet size is a predetermined value or less. It is characterized by having a function.

More specifically, the present invention relates to a wireless communication system in which a packet is transmitted and received by a hybrid automatic repeat request (HARQ) method between a base station and a plurality of wireless terminals.
A wireless transmission / reception circuit, a packet transmission circuit that divides a packet with redundant bits added into a plurality of subpackets and outputs each subpacket to the wireless transmission / reception circuit at a predetermined cycle, and receives a subpacket from the wireless transmission / reception circuit A packet receiving circuit that repeats the decoding process by combining the newly received sub-packet and the received previous sub-packet until the original packet is successfully decoded, and as a response to the received sub-packet, A control unit that generates an ACK if the packet is successfully decoded by the receiving circuit, generates a NAK if the packet is unsuccessful, and returns the response at a predetermined timing via the packet transmission circuit;
A function in which the control unit provided in the base station and at least one wireless terminal transmits a subpacket or a response from the packet transmission circuit in a retransmission cycle shorter than the retransmission cycle in the standard mode in packet communication with a short data length. It has the HARQ control part provided with.

In the wireless communication system of the present invention, the packet transmission circuit includes, for example, orthogonal frequency division multiplexing (OFDM) in which a channel for subpacket transmission and a channel for response transmission are formed by subcarrier groups having different frequencies. The packet receiving circuit is composed of an OFDM type receiving circuit.
The control mode in which the retransmission cycle is shortened is applied to, for example, VoIP voice packet communication. When performing HARQ control in the retransmission cycle shortening mode, the base station and the terminal negotiate to shorten the retransmission cycle prior to data transmission.

  If the size of the received packet is small, the data receiving node can decode the received packet in a short time and return an ACK / NAK response at a timing earlier than the ACK / NAK transmission timing (frame) in the standard mode. If the transmission data is short, the redundant code added to it is also short. Accordingly, since the size of the second and third subpackets following the first subpacket including the transmission data can be shortened, when the data transmission node receives the NAK response from the data reception node, the transmission timing of the next subpacket Can be expedited.

  In the conventional HARQ wireless communication system, the base station allocates different frames for each terminal and transmits / receives subpackets and ACK / NAK responses. However, in the wireless communication system of the present invention, the base station operates in the retransmission cycle shortening mode. A frame in which the terminal in the middle transmits an ACK / NAK response overlaps a frame (time zone) in which another terminal operating in the standard mode transmits an ACK / NAK response. One feature of the wireless communication system of the present invention is that the base station and each terminal have a function of multiplexing a plurality of ACK / NAKs having different HARQ control modes on the ACK / NAK transmission channel.

  According to the present invention, in packet transmission with a packet length of a predetermined value or less, the retransmission cycle of the subpacket can be shortened. Therefore, real-time data such as VoIP is transmitted with reduced transmission delay, It becomes possible to prevent deterioration of communication quality.

  Hereinafter, as an embodiment of the present invention, an orthogonal frequency division multiplexing (OFDM) cellular radio communication system having the HARQ control function of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, a cellular radio communication system generally includes a plurality of base stations 10 (10A to 10C), a plurality of radio terminal devices 30 (30-1 to 30-6), and a wired line. And a base station control device 20 connected to the station 10. The base station control device 20 is connected to the network NW. The network NW includes a public telephone network and an Internet network, and is connected to other terminal devices that can be a communication partner of a wireless terminal device (hereinafter simply referred to as a terminal) 30, various information providing servers, a call terminal server, and the like. ing. However, the network NW may be configured with a LAN. Each terminal 30 is connected to the base station device 10 by radio, and can communicate with other devices connected to the network NW via the base station device 10 and the base station control device 20.

2A to 2E are diagrams for schematically explaining a data transmission operation in a data transmission node of a HARQ (Hybrid Automatic Repeat Request) method.
FIG. 2A shows data D that can be transmitted in one frame period. For example, redundant bits RB for error correction generated from data D by encoding such as a turbo code are added to data D, resulting in a data packet as shown in FIG. Actually, each data packet includes a header indicating information such as a destination address and a source address. Here, however, the header portion is treated as a part of the data D in order to simplify the drawing and description. This is omitted from the drawings.

  In HARQ, as shown in FIG. 2C, transmission of the same data packet is repeated a plurality of times (repetition). FIG. 2D shows a subpacket transmitted in the wireless section. Here, each data packet shown in FIG. 2C is divided into three, and subpackets P0 to P5 having a predetermined format in the radio section are generated. As shown in FIG. 2E, the subpackets P0 to P5 are transmitted in a predetermined cycle in order from the first subpacket. FIG. 2E shows that when a NAK response is received from the data receiving node with respect to the transmitted subpacket, the subpacket is transmitted at a cycle of 4 frames from the data transmitting node.

FIGS. 3A to 3F are diagrams showing, in a time series, changes in the amount of information applied to the next data decoding process when decoding of received data fails in the HARQ data receiving node. is there.
FIG. 3A shows a state in which data D is received in the first subpacket P0.

  In normal ARQ, when the data receiving node fails to receive the data D, the data receiving node notifies the upper layer, and the upper layer makes a retransmission request for the data D to the data transmitting node. On the other hand, in the HARQ data receiving node, when reception of the data D fails, the data reception processing unit (physical layer to MAC layer) returns a NAK to the data transmitting node, and FIG. C), the redundant bits following the data D are received in the subpackets P1 and P2, combined with the data (and redundant bits) extracted from the already received subpacket P0 (Incremental Redundancy), and received. Attempt to decrypt data D.

  As shown in FIG. 3C, when data D cannot be decoded even when all redundant bits RB are received, the data receiving node is the same as the already received subpacket groups P0 to P2 by repetition. The contents subpackets P3 to P5 are sequentially received, and decoding of the received data D can be attempted with the synthesized packets as shown in FIGS. 3D to 3F (Chase Combining). Therefore, the power of the received code is equivalently increased, and the success rate of data decoding can be increased.

FIG. 4 shows an example of a communication sequence for HARQ control in the downlink (forward link) from the base station 10 to the terminal 30.
In LBC, since data transmission is performed by OFDMA, it is necessary to specify, for terminal 30, an OFDMA subcarrier used for data transmission, that is, a frequency resource. For this reason, when the base station 10 transmits the first subpacket to the terminal 30 using the forward link data channel: F-DCH (Forward Link Data Channel), the forward link common control channel: F-SCCH (Forward Link). Forward link assignment message transmitted by Shared Control Channel): A frequency resource for a forward link data channel (downlink data transmission channel) is specified using FLAM (Forward Link Assignment Message) (SQ11). In LBC, Non-sticky Assignment mode (or Non-persistent Assignment mode) that changes the frequency resource in units of packets and Sticky Assignment mode (or changes the frequency resource until packet transmission failure reaches a certain number of times) (or Persistent Assignment mode).

  The terminal 30 that has received the first subpacket returns ACK when the data D is successfully decoded from the received subpacket, and returns NAK when the decoding is unsuccessful (SQ12). The response message ACK / NAK is transmitted to the base station 10 through a reverse link ACK channel: R-ACKCH (Reverse Link Acknowledgment Channel).

  SQ12 in FIG. 4 shows a case where the terminal 30 fails to decode received data and returns a NAK. The base station 10 that has received the NAK transmits the second subpacket to the F-DCH in a predetermined frame determined by the interlace number associated with the terminal 30 (SQ13). The terminal 30 that has received the second subpacket combines the first and second subpackets and attempts to decode the received data D. If the data is successfully decoded at this stage, the terminal 30 returns an ACK to the base station 10 through the R-ACKCH (SQ14). If data decoding fails, the terminal 30 returns a NAK to the base station 10 through the R-ACKCH, and the third subpacket is retransmitted from the base station 10.

  When receiving the ACK from the terminal 30, the base station 10 completes the retransmission control for one transmission packet. When the NAK return from the terminal is repeated and the number of retransmissions of the subpacket reaches the predetermined limit for the same data packet, the base station 10 stops the retransmission of the subpacket. In this case, the data packet fails to be transmitted, and the terminal 20 executes a communication procedure such as discarding the packet received so far or requesting retransmission of the packet to the packet transmission source device according to the determination of the upper layer.

  FIG. 5 shows an example of a communication sequence for HARQ control in the uplink (reverse link) from the terminal 30 to the base station 10.

  In LBC, the base station 10 specifies uplink frequency resources (OFDM subcarriers) used by the terminal 30 for data transmission. Therefore, the terminal 30 that wants to transmit a data packet requests the base station 10 to allocate resources through a reverse link request channel R-REQCH (Reverse Link Request Channel) (SQ21). When the base station 10 receives the resource assignment request from the terminal 30, the base station 10 uses a reverse link assignment message (RLAM) transmitted to the requesting terminal 30 on the F-SCCH, using the reverse link assignment message (RLAM). Notifies the uplink frequency resource to be used (SQ22).

  When receiving the RLAM, the terminal 30 divides the transmission packet to which redundant bits are added by encoding into a plurality of subpackets, and uses a reverse link data channel: R-ODCH (Reverse Link Data Channel) with frequency resources specified by the base station. The first subpacket is transmitted through (OFDMA Data Channel) (SQ23). The base station 10 decodes the first subpacket received from the terminal 30, and returns ACK to the terminal 30 if decoding is successful and NAK if decoding fails (SQ24). A response message indicating ACK / NAK is transmitted to the terminal through a forward link ACK channel: F-ACKCH (Forward Link Acknowledgment Channel). SQ24 in FIG. 5 shows a case where the base station 10 fails to decode received data in the first subpacket and returns a NAK to the terminal 30.

  The terminal 30 that has received the NAK transmits the second subpacket to the base station 10 through the R-ODCH (SQ25). In the illustrated example, the base station 10 combines the first and second subpackets, successfully decodes the received data, and returns an ACK to the terminal (SQ26). When receiving the ACK from the base station 10, the terminal 30 completes the packet transmission.

  If NAK return from the base station is repeated and the number of retransmissions of the subpacket reaches a predetermined limit, the terminal 30 stops the retransmission of the subpacket. In this case, the data packet fails to be transmitted, and the base station 10 discards the packet received so far, or requests the terminal 30 to retransmit the same packet, based on the determination of a layer higher than the physical layer and the MAC layer. The communication procedure is executed.

  FIG. 6 shows a relationship between an interlace number 51 in HABC retransmission control of LBC and a frame number 52 used for data transmission and ACK / NAK transmission. Here, as an example of the prior art, HARQ control fixed to an 8-interlace mode in which a subpacket is transmitted in a period of 8 frames between the base station 10 and a terminal will be described. In FIG. 6, F0, F1, F2,... Shown in the column of the frame number 52 represent the frames that are the transmission time zones of each subpacket and ACK / NAK along the time axis.

  For example, the base station 10 transmits a subpacket to the terminal 30-j associated with the interlace number j (j = 0 to 8) in the frame Fi (i = 1, 2, 3,...). Upon transmission, the terminal 30-j completes the demodulation processing and decoding processing of the received data D within the four frame periods T1 of the frames Fi + 1 to Fi + 4, and the decoding result is successful for the base station 10 in the frame Fi + 5. A response message (ACK / NAK) indicating whether or not is returned. In FIG. 6, for example, with interlace number 0, the first subpacket P0 is transmitted in frame F0, and the ACK / NAK response is returned in frame F5.

  The base station completes the ACK / NAK decoding process, transmission data encoding process, and scheduling within the two-frame period T2 of the frames Fi + 6 to Fi + 7. If a NAK has been received, the next subpacket is retransmitted to the terminal 30-j in the frame Fi + 8. With interlace number 0, the second subpacket is transmitted in frame F8.

Also for the second subpacket, as in the case of the first subpacket, ACK / NAK is returned at the fifth frame and the next subpacket is retransmitted at the eighth frame, starting from the frame F8.
Conventionally, the above-described fixed frame period HARQ control is performed on both the downlink (forward link) from the base station 10 to the terminal 30 and the uplink (backward link) from each terminal 30 to the base station 10. ing.

FIG. 7 shows, as an embodiment of the present invention, HARQ subpacket retransmission control is executed in a control mode in which the 8-frame period is set to the standard control mode and the subpacket retransmission period is shortened to 4 frame periods in a specific interlace. The relationship between the interlace number 51 and the frame number 52 is shown.
When the length of the packet transmitted in the wireless section is short, such as a voice data packet transmitted by VoIP, the data processing time T1 required at the data receiving node can be reduced. Retransmission control in a control mode with a shortened retransmission cycle is advantageous in avoiding data transmission delay.

  In the illustrated example, a control mode in which the retransmission period of a subpacket is shortened to a 4-frame period is applied to data communication with interlace number 0. If the subpacket length is short, the decoding process on the data receiving node side can be completed in a short time, so that the response timing of ACK / NAK can be advanced compared to the standard mode. Therefore, when the data receiving node operating in the control mode with a shortened retransmission cycle receives the first subpacket P0 in the frame F0, the data receiving node completes the demodulating process and the decoding process of the received data within the period of the frames F0 and F1, A response message (ACK / NAK) is returned in frame F2.

  The subpacket data transmission node processes the response message within the period of frames F2 and F3, and when the response message is NAK, transmits the subpacket P1 in the next frame F4. Also for the subpacket P1, a response message is returned with the same time schedule as that of the subpacket P0, and the HARQ retransmission control of the 4-frame cycle is repeated until the data reception node successfully decodes the received data.

  When data is transmitted from the base station 10 to a specific terminal 30-j with a reduced subpacket retransmission period, the retransmission period is shortened prior to data transmission between the base station 10 and the terminal 30-j. To confirm that the retransmission cycle shortening mode is applied to packet transmission and response return. The same applies when data is transmitted from the terminal to the base station via the uplink.

  The retransmission control mode applied to the communication can be designated from the terminal side or the base station side in a communication parameter exchange procedure executed between the base station and the terminal prior to the communication, for example, a call connection procedure. The retransmission period may be shortened by a resource allocation request from the terminal shown in FIG. In addition, when performing packet communication in which the subpacket size is less than or equal to a predetermined value in the wireless section, retransmission is performed in advance to both the base station and the terminal so that a control mode with a shortened subpacket retransmission period is automatically selected. A control mode automatic setting function may be provided.

  In FIG. 7, sub-packet retransmission control with an 8-frame period is set as a standard mode, and sub-packet retransmission control with a 4-frame period is set as a cycle shortening mode. It can be decided arbitrarily.

  The frequency resource for data transmission is determined by the base station and notified to the terminal by FLAM transmitted to the F-SCCH described with reference to FIGS. In the non-sticky assignment mode (non-persistent assignment mode), the base station notifies the terminal of frequency resources by FLAM at the time of transmission of the first subpacket every time a packet is transmitted. In Sticky Assignment mode (Persistent Assignment mode), unless the number of packet transmission failures reaches a predetermined value, packet transmission is repeated a plurality of times using a specific frequency resource designated by the base station to the terminal. Therefore, in the non-sticky assignment mode, the retransmission control mode in units of packets is specified by specifying the retransmission period (or retransmission control mode) of the subpacket in a specific field in the FLAM transmitted from the base station to the terminal. Can be switched.

FIG. 8 is a block diagram showing an embodiment of the radio terminal device 30 to which HARQ retransmission control according to the present invention is applied.
The terminal 30 includes a radio transmission / reception circuit 310 connected to the antenna 311, an OFDM transmission circuit 320 and an OFDM reception circuit 330 connected to the radio transmission / reception circuit 310, and OFDM control connected to these OFDM transmission / reception circuits 320 and 330. The unit 300 and the protocol processing unit 31, the processor 32 connected to the bus 39, the memory 33, the audio CODEC 34, the display unit 35 and the input unit 36, and the speaker 37 and the microphone 38 connected to the CODEC 34. In the memory 33, various control routines and application programs executed by the processor 32 are prepared.

  The terminal user performs screen selection, selection of a telephone number and a destination address, data input, and transmission / reception operation using the input operation buttons and the display unit 35 prepared in the input unit 36. The voice input from the microphone 38 is converted into encoded voice data by the CODEC 34. The encoded audio data output from the CODEC 34 and the transmission data read from the memory 33 are converted into transmission packets by the protocol processing unit 31 and input to the OFDM transmission circuit 320.

  The OFDM transmission circuit 320 converts the transmission packet into a subpacket and outputs it to the wireless transmission / reception circuit 310. The radio transmission / reception circuit 310 converts the transmission subpacket into a signal in the radio section, amplifies power, and transmits the signal from the antenna 311 to the base station 10. A received signal from the base station 10 received by the antenna 311 is converted into a baseband symbol by the wireless transmission / reception circuit 310 and then input to the OFDM reception circuit 330.

The OFDM receiving circuit 330 executes the decoding process of the received data described with reference to FIG. The reception data decoded by the OFDM reception circuit 330 is output to the reception buffer on the CODEC 34 or the memory 33 via the protocol processing unit 31. The CODEC 34 converts the received encoded audio signal into an analog audio signal and outputs the analog audio signal to the speaker 38. The reception data stored in the reception buffer is processed by the processor 32 and transferred to a specific file area on the memory 33 or the display unit 35 according to the application.
The OFDM control unit 300 performs HARQ retransmission control described with reference to FIGS. 2, 3, and 7 in cooperation with the OFDM transmission circuit 320 and the OFDM reception circuit 330.

FIG. 9 shows an embodiment of the OFDM control unit 300, the OFDM transmission circuit 320, and the OFDM reception circuit 330.
The OFDM transmission circuit 320, for example, turbo-encodes transmission data, generates a transmission packet with redundant bits, and converts the transmission packet output from the encoder 321 into a plurality of subpackets, and performs OFDM control unit 300. , A repetition unit 322 that outputs cyclically in order from the first subpacket, a subpacket (data channel signal) output from the repetition unit 322, and a control channel output from the OFDM control unit 300, A modulator 323 that modulates a pilot channel signal, a subcarrier mapping unit 324 that maps modulation symbol sequences output from the modulator 323 to predetermined OFDM subcarriers, and a subcarrier mapping unit 324, respectively. Connected inverse discrete Fourier transform IDFT) unit 325, and a data symbol output from IDFT unit 325, for example, a synchronization symbol required by a receiving circuit of a base station, such as a CP (Continuous Pilot), and other control symbols are added to a radio transmission / reception circuit A control symbol adding unit 326 that outputs to 310 and a CDM multiplexing unit 327 are included.

  The CDM multiplexing unit 327 multiplexes a plurality of types of signals transmitted by the OFDM control unit 300 through the CDMA channel. The output of CDM multiplexing section 327 is input to IDFT section 325 together with the output of subcarrier mapping section 324.

  On the other hand, the OFDM receiver circuit 330 receives a plurality of predetermined subcarriers from a discrete Fourier transform (DFT) unit 331 that performs Fourier transform on the received baseband symbol input from the radio transceiver circuit 310 and an output of the DFT unit 331. From the subcarrier demapping unit 332 that extracts the upper signal sequence, the demodulator 333 that demodulates the signal sequence of the data channel, control channel, and pilot channel output from the subcarrier demapping unit 332, and the demodulator 333 A de-repetition unit 334 that combines sub-packets output as a demodulated symbol sequence of the data channel in the order of reception, a decoder 335 that decodes received data from the output of the de-repetition unit 334, and an error connected to the decoder 335 A detection unit 336.

  The error detection unit 336 detects whether or not the decoding of the received data has been successfully performed by the decoder 335, notifies the detection result to the OFDM control unit 300, and transfers the received data that has been successfully decoded to the protocol processing unit 31. .

The OFDM control unit 300 includes a communication control unit 301 and a HARQ control unit 302.
The communication control unit 301 is input with a plurality of demodulated symbol sequences of control channels and pilot channels output in parallel from the demodulator 333. The communication control unit 301 detects a resource allocation message (FLAM, RLAM) transmitted from the base station 10 from a demodulated symbol sequence of F-SCCH, which is one of the control channels, and HARQ indicates the resource allocation information indicated by the FLAM, RLAM. In addition to notifying the control unit 302, the ACK / NAK transmitted by the base station 10 is extracted from the demodulation symbol sequence of the F-ACKCH that is one of the control channels, and this is notified to the HARQ control unit 302. In addition, the communication control unit 301 generates a resource allocation request to be transmitted to the base station 10 and other information, and outputs the request to the modulator 323.

  The HARQ control unit 302 performs HARQ control based on the resource allocation information notified from the base station 10 via the communication control unit 301. When receiving data, the HARQ control unit 302 generates ACK / NAK according to the decoding result determination signal output from the error detection unit 336, and outputs this to the modulator 323. Further, at the time of data transmission, the repetition unit 322 is controlled in accordance with ACK / NAK notified from the base station 10 via the communication control unit 301. When NAK is received, retransmission is performed until the number of retransmissions reaches a limit value. The subpacket is retransmitted at a predetermined frame timing according to the control mode.

FIG. 10 shows main channels and transmission information transmitted from the terminal 30 to the base station 10 on the uplink (reverse link).
The subcarrier mapping unit 324 receives from the modulator 323, for example, a control channel: R-ODCCH (Reverse OFDMA Dedicated Control Channel) modulation symbol sequence, a pilot channel: R-DPICH (Reverse Dedicated Pilot Channel) modulation symbol sequence, A modulation symbol string of ACK channel: R-ACKCH (Reverse Acknowledge Channel) and a data channel: modulation symbol string of R-ODCH (Reverse OFDM Data Channel) are supplied. These modulation symbol sequences are input to the IDFT unit 325 together with the CDM multiplexed signal output from the CDM multiplexing unit 327.

  From the CDM multiplexing unit 327, a CDMA pilot channel: R-PICH (Reverse Pilot Channel), R-CDCH (Reverse CDMA Data Channel), R-ACH (Reverse Access Channel), R-CDCCH (Reverse CDMA Dedicated Control Channel) The signal is supplied. The resource allocation request channel shown in FIG. 5 is transmitted by the R-ODCCH or R-CDCCH.

FIG. 11 shows an embodiment of the OFDM control unit 100, the OFDM transmission circuit 120, and the OFDM reception circuit 130 of the base station 10.
The OFDM transmission circuit 120 turbo-encodes transmission data and generates a transmission packet with redundant bits, and each of the transmission packets output from the encoder 121 is converted into a plurality of subpackets, and the OFDM control unit 100 A plurality of repetition units 122 that cyclically output in order from the first sub-packet, sub-packets (data channel signals) output from the repetition unit 122, and control channels output from the OFDM control unit 100 A modulator 123 that modulates a pilot channel signal, a subcarrier mapping unit 124 that maps modulation symbol sequences output from the modulator 123 to predetermined subcarriers of OFDM, and a subcarrier mapping unit 124. Connected inverse discrete Fourier Radio transmission / reception by adding synchronization symbols and other control symbols required by the receiving circuit of the terminal such as CP (Continuous Pilot) to the data symbols output from the exchange (IDFT) unit 125 and the IDFT unit 125 And a control symbol adding unit 126 that outputs the circuit 110. The repetition unit 122 corresponds to the interlace number, and the OFDM control unit 100 selects a different repetition unit for each frame period.

  On the other hand, the OFDM receiver circuit 130 includes a discrete Fourier transform (DFT) unit 131 that performs a Fourier transform on the received baseband symbol input from the radio transceiver circuit 110, and a plurality of pre-specified subcarriers from the output of the DFT unit 131. A subcarrier demapping unit 132 that extracts the upper signal sequence, a demodulator 133 that demodulates the data channel, control channel, and pilot channel signal sequences output from the subcarrier demapping unit 132, and a demodulator 133, respectively. Connected to a plurality of depreciation units 134 that combine the sub-packets output as a demodulated symbol sequence of the data channel in the order of reception, a decoder 135 that decodes received data from the output of the depreciation unit 134, and a decoder 135 Connected to the error detection unit 136 and the DFT unit 131. Consisting of CDM separation unit 137 Metropolitan.

  The de-repetition unit 134 also corresponds to the interlace number, and the OFDM control unit 100 selects a different de-repetition unit for each frame period. The error detection unit 136 detects whether or not the received data has been successfully decoded by the decoder 135, notifies the OFDM control unit 100 of the detection result, and transfers the received data that has been successfully decoded to a protocol processing unit (not shown). To do.

  The base station OFDM control unit 100 includes a communication control unit 101, a HARQ control unit 102, and a management table 103. In the management table 13, for example, interlace management information and frequency resource (subcarrier) management information are stored.

  The communication control unit 101 includes a plurality of demodulated symbol sequences of control channels and pilot channels output in parallel from the demodulator 133, a CDMA reception signal output from the CDM separation unit 137, and transmission / reception from the protocol control unit A control signal is input. When the communication control unit 101 extracts the ACK / NAK transmitted from the terminal from the demodulated symbol sequence of the R-ACKCH, the communication control unit 101 notifies the HARQ control unit 102 of this.

  When the communication control unit 101 detects the resource allocation request REQ transmitted by the terminal 30 from the demodulated symbol sequences of the R-ODCCH and the R-CDCCH, the communication control unit 101 refers to the management table 103 and generates an RLAM indicating resource allocation information. When a data transmission request is received from the protocol control unit, a FLAM is generated. These resource allocation messages are notified to the HARQ control unit 102 and transmitted from the HARQ control unit 102 to the terminal at a predetermined timing. Also, the communication control unit 101 generates a pilot signal to be transmitted to the terminal and various control channel information, and outputs the pilot signal to the modulator 123.

  The HARQ control unit 102 starts HARQ retransmission control based on the FLAM and RLAM notified from the communication control unit 101, and the repetition unit 122 and the delay unit that differ for each frame period according to the interlace information indicated by the management table 103. The pitting unit 134 is selected. The HARQ control unit 102 generates ACK / NAC according to the determination signal of the decoding result output from the error detection unit 136 when receiving data from the terminal, and generates a predetermined frame according to the interlace information indicated by the management table 103. Output to the modulator 123 during the period. Further, at the time of data transmission, the repetition unit 322 is controlled in accordance with ACK / NAK notified from the terminal via the communication control unit 101. When NAK is received, the control mode is set until the number of retransmissions reaches the limit value. The subpacket is retransmitted at a predetermined frame timing.

FIG. 12 shows main channels and transmission information transmitted from the base station 10 to each terminal 30 on the downlink (forward link).
The subcarrier mapping unit 124 is supplied with modulation symbols of a pilot channel and a control channel from the modulator 123 in addition to a modulation symbol string of a data channel: F-DCH (Forward Data Channel).

  The pilot channel includes, for example, an F-CPICH (Forward Common Pilot Channel) shared by all terminals and an individual F-DPICH (Forward Dedicated Pilot Channel) of each terminal. Examples of the control channel include an ACK transmission channel: F-ACKCH (Forward Acknowledge Channel), an RLAM / FLAM transmission channel: F-SCCH (Forward Shared Control Channel), and a PQI transmission channel: F-PQICH (Forward Pilot). Quality Indication Channel) and interference information transmission channels: F-FOSICH (Forward Fast Other Sector Indication Channel) and F-IOTCH (Forward Interference over Thermal Channel).

  FIG. 13 shows a format of FLAM and RLAM transmitted from the base station 10 to the terminal 30. In the present invention, the HARQ retransmission control mode can be specified by a specific field provided in FLAM and RLAM.

  The FLAM and RLAM 60 are a block type field 61 that indicates the type of message, a flag field 62 that indicates whether the resource allocation mode is Sticky Assignment mode or Non-sticky Assignment mode, and a channel that indicates the identifier of the frequency resource allocated to the terminal. An ID field 63, a field 64 indicating the packet format, a flag field 65 indicating whether or not the extended transmission mode is set, and a flag field 66 indicating whether or not the additional allocation is set.

  In the present invention, a flag (HARQ cycle flag) field 67 indicating whether or not to execute subpacket retransmission control at a shortened cycle is added to the FLAM and RLAM 60. For example, a terminal that has received FLAM or RLAM in which the flag field 67 is set to “1” performs HARQ retransmission control with a base station in a control mode in which the retransmission cycle is shortened. On the other hand, the base station 10 associates with the interlace number in the management table 103, the terminal identifier, the allocated frequency resource, the retransmission cycle (or the HARQ cycle flag indicating whether or not the control mode is the cycle shortening mode), and The relationship with an ACK identifier (ACK ID) described later is stored. When FLAM and RLAM 60 are transmitted to a certain terminal 30-j, the HARQ control unit 102 associates the interlace number assigned to the terminal 30-j with the management table 103, and the control mode specified in the flag field 67. The retransmission cycle is stored, and thereafter, communication with the terminal 30-j is performed at the retransmission cycle indicated by the management table 103.

  Returning to FIG. 7, in the HARQ control of interlace number 0 with a shortened retransmission cycle, the data receiving node that has received the subpacket P0 transmits the ACK / NAK response that was returned in the frame F5 in the standard mode. It is returned by F2, and the next subpacket is received by frame F4. In this case, the frame F4 matches the transmission time zone of the subpacket with interlace number 4. Accordingly, when transmitting data from the base station 10 to the terminal, the base station may invalidate the interlace number 4 while executing the retransmission control in the shortened mode with the interlace number 0.

  Further, as shown in the frame F6, when the retransmission control in the shortened mode is performed with any interlace number, a plurality of ACK / NAK responses are generated within the same frame period. Therefore, the base station side needs to be able to multiplex and transmit the ACK / NAK response in the standard mode and the ACK / NAK response in the cycle shortening mode. Multiplexing of ACK / NAK responses is required for each of the downlink and uplink.

  When the retransmission cycle is shortened in downlink data transmission, it is necessary to multiplex ACK / NAK responses transmitted from a plurality of terminals on the R-ACKCH. Here, in order to facilitate understanding of the present invention, a ACK / NAK transmission method of a conventional system in which standard mode HARQ control is executed in all terminals will be described with reference to FIG.

  In OFDM, modulated symbols are transmitted on multiple subcarriers with a predetermined carrier spacing. For example, in the case of an OFDMA system with 512 subcarriers, a frequency band composed of subcarriers f (0) to f (511) is divided into 32 regions each having 16 subcarriers, and each region is defined as an “OFDMA tile”. To do. The base station 10 assigns one or a plurality of OFDMA tiles to each terminal, and each terminal transmits data using OFDMA using a subcarrier group of the assigned OFDMA tile.

  FIG. 14B shows one OFDMA tile 70. The OFDMA tile 70 shown here has the size of 16 subcarriers shown in the frequency direction and 8 OFDM symbols shown in the time direction.

  The terminal 30 performs OOK (On-Off Keying) modulation with the ACK corresponding to the on state and the NAK corresponding to the off state. The R-ACKCH is transmitted using four subtiles 71-1 to 71-4 having a size of “8 subcarriers” × “2OFDM symbols” indicated by bold lines in FIG. The terminal 30 maps the OOK-modulated ACK / NAK response to the subtiles 71-1 to 71-4 using the 16-point DFT precoder 340 shown in FIG. Of the 16 channel inputs of the DFT precoder 340, 8 channels are used for ACK / NAK response, and the remaining 8 channels are left free. In this case, the terminal can transmit eight ACK IDs with one subtile 71. An empty channel can be used, for example, for interference estimation or for ACK / NAK response in MIMO (Multiple-Input Multiple-Output).

Diversity gain can be obtained by repeatedly transmitting a plurality of subtiles to which ACK / NAK responses are mapped, such as 71-1 to 71-4.
In the illustrated example, the four subtiles 71-1 to 71-4 for R-ACKCH occupy half of the OFDMA tile 70. The four subtiles 71-1 to 71-4 are collectively referred to as “R-ACKCH tile” 710.

  In downlink data transmission, when performing subpacket retransmission in a control mode with a shortened retransmission cycle, the base station 10 uses the F-ACKCH to transmit a standard mode ACK / NAK response and a retransmission cycle shortened mode ACK / NAK response. Need to be multiplexed. The base station 10 modulates each ACK / NAK response and then maps it to the OFDMA tile with a 16-point DFT precoder.

  FIG. 15 shows an example of a modulation scheme of an ACK / NAK response in F-ACKCH. In the example shown here, F-ACKCH has four signal points. A signal point 1001 indicates ACK, and a signal point 1004 indicates NAK. A signal point 1003 indicates De-assign indicating the deallocation of frequency resources notified to the terminal by RLAM, and a signal point 1002 indicates an ACK response and De-assign simultaneously.

  The modulated ACK / NAK response is mapped to an OFDMA tile by a 16-point DFT precoder 127, for example, as shown in FIG. As shown in FIG. 17, the OFDMA tile 80 is composed of OFDMA slots 81 of “16 subcarriers” × “8 OFDM symbols”. The ACK / NAK response is CDM (Code Division Multiplexing) multiplexed by orthogonal spreading codes and transmitted using an F-ACKCH segment 83 composed of 4 × 4 F-ACKCH slots indicated by hatching. In addition, in order to obtain frequency diversity gain, the F-ACKCH segment 83 is transmitted in a plurality of OFDMA tiles. In FIG. 17, reference numeral 84 denotes a pilot signal OFDMA slot.

  When the terminal 30 returns an ACK / NAK response to the data transmitted from the base station 10 by reducing the retransmission period of the subpacket on the downlink, conventionally, as described with reference to FIG. A maximum of 8 ACK IDs could be transmitted with one R-ACKCH tile. The maximum number of ACK IDs that can be transmitted simultaneously is determined by the number of OFDMA tiles used in the OFDMA system. For example, in the above-described 512 subcarrier OFDMA system, up to 32 OFDMA tiles of 16 subcarriers are formed. Therefore, when one OFDMA tile of each terminal is allocated, 32 ACK IDs can be simultaneously transmitted. May be used. In this case, it is necessary to prepare four R-ACKCH tiles in the 512 subcarrier OFDMA system.

  However, when a plurality of OFDMA tiles are assigned to a terminal that requires a high transmission rate, the terminal can actually transmit and receive each data packet using the plurality of OFDMA tiles simultaneously. The number of ACK IDs used may be less than the maximum value of 32. In this case, the ACK ID that is in an unused state can be used for an ACK / NAK response returned in the retransmission cycle shortening mode.

  FIG. 18 shows an example of the usage status of the ACK ID. Here, since the OFDMA tiles with tile IDs “0” and “1” are allocated to different terminals, ACK IDs: “0” and “1” are respectively used for subpackets transmitted with these OFDMA tiles. ACK / NAK response is returned. The OFDMA tiles with tile IDs “2” and “3” are assigned to the same terminal. In this case, since two OFDMA tile IDs: “2” and “3” are applied to one subpacket, an ACK / NAK response can be returned using one ACK ID: “2”.

  In the illustrated example, four OFDMA tiles with tile IDs “4” to “7” are assigned to the same terminal, and one packet is assigned an OFDMA tile ID: “4”, “5”, “6”, It is transmitted using “7”. Therefore, the ACK / NAK response to this packet can be returned using one ACK ID: “4”.

  In the example of FIG. 18, ACK ID = “3”, “5”, “6”, and “7” are unused even though a total of 8 OFDMA tiles have already been assigned to the terminal. . Therefore, for example, an ACK ID having the smallest ID value can be sequentially selected from the ACK IDs in the unused state, and this can be assigned for an ACK / NAK response in the retransmission cycle shortening mode. In the state, the terminal in the retransmission cycle shortening mode can return ACK / NAK using ACK ID: “3”.

  The base station 10 knows which ACK ID is used for the ACK / NAK response in each interlace for which HARQ control is performed in the retransmission cycle of the standard mode. Therefore, when an ACK / NAK response is transmitted with ACK ID = 3 in an interlace whose retransmission cycle is shortened, the base station can detect that this ACK / NAK response is transmitted in the retransmission cycle shortening mode. At this time, the ACK / NAK response transmitted with ACK ID = 3 is compared to the ACK / NAK response in the standard mode transmitted with ACK ID “0”, “1”, “2”, “4”. There is no adverse effect.

In the present invention, when the retransmission period of a subpacket is shortened in downlink data transmission, an ACK / NAK response in a shortened mode returned by the R-ACKCH is different from an ACK / NAK response in the standard mode. You can use tiles.
For example, FIG. 19 illustrates an example of an R-ACKCH tile arrangement method in which the vertical axis (frequency) represents OFDM subcarriers and the horizontal axis represents time. Here, four R-ACKCH tiles 710-1 to 710-4 are prepared using four OFDMA tiles 70 (70-1, 70-3, 70-5, 70-7). .

  In the present embodiment, four different subtiles 71A to 71D are transmitted in each R-ACKCH tile 710-i (i = 1 to 4). As shown on the right side of FIG. 19, each subtile 71 is transmitted four times by switching the R-ACKCH tiles 710-1 to 710-4 to be used at each transmission.

  Each subtile 71 has a size of 8 subcarriers × 2 OFDM symbols and can transmit 8 ACK IDs, as described with reference to FIG. Accordingly, in the example illustrated in FIG. 19, a total of 32 ACK IDs can be transmitted by the four R-ACKCH tiles 710-1 to 710-4. As shown in the figure, the frequency diversity effect is obtained by switching the R-ACKCH tile to be used and repeating the transmission of each subtile.

  In this embodiment, apart from the R-ACKCH tile 710-i (i = 1 to 4) used for the ACK / NAK response in the standard mode, the OFDMA tile 70-9 uses the ACK / NAK response in the retransmission cycle shortening mode. A fifth R-ACKCH tile 720 to be used is prepared.

When applying the retransmission cycle shortening mode to data transmission addressed to a specific terminal 30-j, the base station 10 assigns the R-ACKCH tile 720 for the retransmission cycle shortening mode to the terminal 30-j. The terminal 30-j returns an ACK / NAK response using the R-ACKCH tile 720 allocated from the base station. In the illustrated example, sub-tiles 71-1 to 71-4 included in the R-ACKCH tile 720 can be used to transmit up to eight ACK IDs for ACK / NAK responses in the retransmission cycle shortening mode. The R-ACKCH tile 720 obtains time diversity gain by repeatedly transmitting the same subtile four times.
In this example, since the R-ACKCH tile different from the ACK / NAK response in the standard mode is used for the ACK / NAK response in the retransmission cycle shortening mode, there is no possibility of adversely affecting other terminals.

When the retransmission cycle shortening mode is applied to downlink data transmission, the terminal may return an ACK / NAK response using an ACK channel that is idle for interference estimation using R-ACKCH. Good.
For example, as shown in FIG. 20, among the 16 channels input of the DFT precoder 340, 8 channels are used for the ACK / NAK response in the standard mode, and the remaining 8 channels in the idle state are used in the retransmission cycle shortening mode. Used for ACK / NAK response. In this case, since the channels to be used are different, the base station side can clearly distinguish whether the received response is in the standard mode or the shortened mode.
The eight channels used for the ACK / NAK response in the retransmission cycle shortening mode have been vacant conventionally for use for interference estimation and MIMO. Therefore, when these channels are used for ACK / NAK responses as in this embodiment, interference estimation may be affected. However, although the ACK / NAK response is spread by the DFT precoder 340, since the channels are orthogonal, there is no possibility that this embodiment has an adverse effect on the ACK / NAK response in the standard mode.

FIG. 21 shows another embodiment of the ACK / NAK response transmitter when the retransmission cycle shortening mode is applied to downlink data transmission. In this embodiment, I / Q (In-phase / Quadrature) multiplexing of the ACK / NAK response in the standard mode and the ACK / NAK response in the retransmission cycle shortening mode is performed on the R-ACKCH.
In the terminal 30, the ACK / NAK response in the standard mode is OOK modulated by the modulation circuit 342A, and the ACK / NAK response in the retransmission cycle shortening mode is OOK modulated by the modulation circuit 342B and then input to the I / Q multiplexing circuit 342. To do. The ACK / NAK response in the standard mode is I / Q multiplexed in correspondence with the I channel (in-phase channel), and the ACK / NAK response in the retransmission cycle shortening mode is associated with the Q channel (orthogonal channel).

The I / Q multiplexed ACK / NAK response is input as one ACK ID to the DFT precoder 340 described with reference to FIG. In this embodiment, the base station 10 that receives the R-ACHCH demodulates each of the I channel and the Q channel and obtains an ACK / NAK response.
In the prior art described in FIG. 14, it is not necessary to consider the phase in modulation / demodulation of the ACK / NAK response. However, in this embodiment, ACK / NAK responses having different retransmission periods are transmitted in the I channel and the Q channel. For this reason, the reception side needs to demodulate the R-ACHCH reception signal in consideration of the phase.

In the present invention, the ACK / NAK response in the standard mode and the ACK / NAK response in the retransmission cycle shortening mode may be CDM multiplexed using a CDM multiplexing unit orthogonal spreading code as shown in FIG.
For example, the ACK / NAK response in the retransmission period shortening mode and the ACK / NAK response in the standard mode generated by the HARQ control unit 302 of the terminal 30 illustrated in FIG. 9 are separated into separate modulators 323-i constituting the modulator 323. , 323-j, and modulated by the signal point arrangement shown in FIG. The ACK / NAK response in the standard mode and the ACK / NAK response in the retransmission period shortening mode output from the modulator 323 are CDM multiplexed by the orthogonal spreading code in the CDM multiplexing unit 328 and then supplied to the OFDMA subcarrier mapping 324. To do.

Since the base station 10 notifies the terminal of F-ACKCH resource information (frequency and time) in a predetermined cycle, the base station 10 uses the notification to notify the terminal of the standard mode ACK / A spreading code applied to the NAK response and a spreading code applied to the ACK / NAK response in the retransmission cycle shortening mode are allocated.
When the ACK / NAK response in the standard mode and the ACK / NAK response in the retransmission cycle shortening mode are CDM multiplexed with different spreading codes (orthogonal spreading codes) as in this embodiment, the ACK / NAK response in the standard mode is affected. Therefore, it is possible to transmit an ACK / NAK response in the retransmission cycle shortening mode.

  When transmitting an ACK / NAK response from the base station, for example, since the F-ACKCH segment 83 described with reference to FIG. 17 includes four F-ACKCH slots 82, the base station uses one F-ACKCH segment. Up to four ACK / NAK responses can be sent using the ACKCH segment. Apart from the standard mode, when the number of ACK / NAK responses to be transmitted from the base station increases due to the occurrence of the ACK / NAK response in the retransmission cycle shortening mode, the number of F-ACKCH segments 83 may be increased.

Next, a method of determining a subpacket retransmission period applied to communication between a base station and a terminal in the wireless communication system of the present invention will be described.
Prior to data transmission, the base station and the terminal need to be aware of the HARQ subpacket retransmission control mode. For the retransmission control mode for subpackets to be applied to HARQ, the base station or terminal on the data transmission side selects, for example, either the retransmission cycle standard mode or the retransmission cycle shortening mode according to the type of transmission data, and selects What is necessary is just to notify a receiving side apparatus of a result.

  FIG. 23 shows an embodiment of a retransmission cycle determination routine executed on the data transmission side. Here, the transmission side apparatus determines (811) whether or not the transmission data is for voice. When transmitting voice data, the retransmission cycle shortening mode is selected (812). Otherwise, the retransmission cycle standard mode is selected (813), and the selection result is notified to the partner device (814).

  The subpacket retransmission control mode (retransmission cycle standard mode / retransmission cycle shortening mode) in HARQ is determined, for example, in a call connection sequence executed prior to data communication, and the base station and terminal until the call is terminated. However, data may be transmitted and received in the same retransmission control mode. In this case, in the process of executing the call connection sequence, the communication control unit 101 of the base station stores the relationship between the identifier of the wireless terminal and the retransmission control mode (or retransmission period) in the management table 103, and sends it to the terminal. / When allocating downlink communication resources, the interlace according to the retransmission cycle is determined by referring to the management table, and the HARQ control unit 102 is configured to communicate with the terminal according to the retransmission cycle and the interlace. That's fine.

  When making a call from a terminal connected to the base station, the terminal notifies the base station of a desired retransmission control mode, for example, in a retransmission control mode designation field defined in advance in the call connection control message. On the other hand, when the terminal becomes the called side, the base station may notify the terminal of the retransmission control mode using the retransmission control mode designation field defined in advance in the call connection control message.

  As described above, in HARQ, resources are allocated in units of transmission packets, so the retransmission control mode may be determined for each transmission packet. For example, when a data packet is transmitted from a terminal to a base station, the terminal requests the base station to allocate an uplink frequency resource in a form in which a retransmission control mode is designated by R-REQCH, and the base station performs the retransmission control. An uplink frequency resource is allocated according to the mode. Conversely, when a data packet is transmitted from the base station to the terminal, the base station determines the retransmission control mode according to the data type of the transmission packet, and the retransmission control mode and the downlink frequency resource are determined by the FLAM described in FIG. Notify the terminal.

FIG. 24 shows another embodiment of a retransmission cycle determination routine executed on the data transmission side.
In this embodiment, the data transmission side device compares the size of the transmission packet with the threshold (821), and if the packet size is equal to or smaller than the threshold, selects the retransmission cycle shortening mode (822). The retransmission cycle standard mode is selected (823), and the selection result is notified to the partner apparatus (824). If a common packet size threshold is held in advance by the data transmission side device and the reception side device before data communication, for example, at the time of call connection, it is not necessary to notify the partner device of the retransmission cycle mode selection result. good. When the selection result is not notified, the receiving side apparatus can determine whether the received packet is transmitted in the retransmission cycle standard mode or the retransmission cycle shortened mode by comparing the received packet size with a threshold value. .

  When the terminal and the base station transmit / receive a subpacket in the retransmission cycle shortening mode, for example, in the interlace number 0 shown in FIG. 7, the receiving-side apparatus transmits an ACK / NAK for the subpacket received in the frame F0 to the frame F2. It is necessary to reply with. In this case, the threshold applied to the determination step 821 in FIG. 24 is determined by the packet size that can be demodulated and decoded within the period of the frames F0 to F1 by the receiving device.

FIG. 25 shows still another embodiment of the retransmission cycle determination routine.
For example, even when the terminal selects the retransmission cycle shortening mode based on the type of transmission data or the packet size, the retransmission cycle standard mode must be applied depending on the communication situation between the base station and another terminal. There may not be.
In this embodiment, the communication control section 101 of the base station that has received the notification of the subpacket retransmission control mode from the terminal determines the type of the notified retransmission control mode (831), and the terminal desires the retransmission cycle standard mode. If yes, the retransmission cycle standard mode is selected as the application mode (834). If the terminal desires the retransmission cycle shortening mode, the communication control unit 101 refers to the management table 103 to determine the uplink traffic situation (832), and sets the retransmission cycle shortening mode for communication with the terminal. If applicable, the retransmission cycle shortening mode is selected (833), and if not applicable, the retransmission cycle standard mode is selected (834).

  When the retransmission control mode desired by the terminal is notified by, for example, an uplink resource allocation request transmitted on the R-REQCH, the communication control unit 101 allocates the retransmission control mode selected in step 833 or 834 above to the resource allocation. Along with the result, the terminal is notified by FLAM. In this embodiment, each terminal performs HARQ control by applying the retransmission control mode selected on the base station side.

  In this embodiment, the applicability of the retransmission cycle shortening mode can be determined by referring to the management table 103 based on, for example, whether there is an empty interlace to which the resending cycle shortening mode can be applied. As is apparent from the relationship between interlace number 0 and interlace number 4 in FIG. 7, when the retransmission cycle shortening mode is applied, one terminal occupies two interlace frames and transmits / receives data. Become. Therefore, a threshold value indicating an upper limit may be set in advance for the number of interlaces to which the retransmission cycle shortening mode can be applied, and HARQ control in the retransmission cycle shortening mode may be executed within the threshold range. Further, the retransmission cycle shortening mode may be permitted when the empty interlace is equal to or greater than a predetermined threshold.

  As is clear from the above embodiments, according to the present invention, in the wireless cellular communication, the HARQ retransmission cycle is shortened as necessary, and the retransmission control in the cycle shortening mode is performed in addition to the retransmission control in the standard mode. Since it can be selectively executed, data transfer with a small transmission delay can be realized according to the service type.

The figure which shows the cellular radio | wireless communications system to which this invention is applied. The figure for demonstrating schematically the data transmission operation | movement of a HARQ system. The figure which showed the change of the information amount applied to the data decoding process of a HARQ system in time series. The figure which shows an example of the communication sequence of HARQ resending control in the downlink which goes to the terminal 30 from the base station 10. FIG. The figure which shows an example of the communication sequence of HARQ resending control in the uplink which goes to the base station 10 from the terminal 30. FIG. The figure which shows the relationship between the interlace number 51 and the frame number 52 in the HARQ retransmission control of LBC. The figure which shows the relationship between the interlace number 51 and the frame number 52 in the case of performing HARQ resending control in the control mode which shortened the resending cycle of the subpacket. The block diagram which shows one Example of the radio | wireless terminal apparatus 30 to which the HARQ retransmission control by this invention is applied. The figure which shows one Example of the OFDM control part 300, the OFDM transmission circuit 320, and the OFDM receiving circuit 330 of FIG. The figure which shows the main channel and transmission information which are transmitted to the base station 10 from the terminal 30 by an uplink. The figure which shows one Example of the OFDM control part 100 of the base station 10, the OFDM transmission circuit 120, and the OFDM receiving circuit 130. The figure which shows the main channel and transmission information which are transmitted to each terminal 30 from the base station 10 in a downlink. 4 is a format diagram of FLAM and RLAM transmitted from the base station 10 to the terminal 30. FIG. The figure for demonstrating the transmission method of ACK / NAK of the conventional system with which standard mode HARQ control is performed in all the terminals. The figure which shows an example of the modulation system of the ACK / NAK response in F-ACKCH. The figure which shows an example of a structure of the transmission part of the ACK / NAK response in a base station. The figure for demonstrating the relationship between an ACK / NAK response and an OFDMA tile. The figure which shows an example of the usage condition of ACK ID. The figure which shows an example of the arrangement | positioning method of R-ACKCH tile. The figure for demonstrating an example of the transmission method of the ACK / NAK response of the resending cycle shortening mode in a terminal. The figure for demonstrating the other example of the transmission method of the ACK / NAK response of the resending cycle shortening mode in a terminal. The figure for demonstrating the further another example of the transmission method of the ACK / NAK response of the resending cycle shortening mode in a terminal. The figure which shows one Example of the resending period determination routine of HARQ. The figure which shows the other Example of the resending period determination routine of HARQ. The figure which shows further another Example of the resending period determination routine of HARQ.

Explanation of symbols

10: base station, 20: base station control device, 30: wireless terminal device, 31: protocol processing unit, 110, 310: wireless transmission / reception circuit, 100, 300: OFDM control unit,
101, 301: Communication control unit, 102, 302: HARQ control unit, 103, management table, 120, 320: OFDM transmission circuit, 121, 321: encoder
122, 322: repetition unit, 123, 323: modulator,
124, 324: subcarrier mapping unit, 125, 325: IDFT unit,
126, 326: control symbol adding unit, 327: CDM multiplexing unit,
130, 330: OFDM receiving circuit, 131, 331: DFT section,
132, 332: subcarrier demapping unit, 133, 333: demodulator,
134, 334: De-repeat part, 135, 335: Decoder,
136, 336: error detection unit, 127, 328: CDM multiplexing unit,
340: DFT precoder.

Claims (16)

A wireless communication system that transmits and receives packets between a base station and a plurality of wireless terminals using a hybrid automatic repeat request (HARQ) scheme,
Each of the base station and each wireless terminal
A wireless transceiver circuit;
A packet transmission circuit that divides a packet with redundant bits added into a plurality of subpackets, and outputs each subpacket to the wireless transmission / reception circuit at a predetermined period;
A packet receiving circuit that repeats the decoding process by combining the newly received subpacket and the received previous subpacket until the original packet is successfully decoded when the subpacket is received from the wireless transceiver circuit;
As a response to the reception subpacket, ACK is generated when the reception circuit succeeds in decoding the packet, NAK is generated when the packet is unsuccessful, and the response is returned at a predetermined timing via the packet transmission circuit. With
A function in which the control unit provided in the base station and at least one wireless terminal transmits a subpacket or a response from the packet transmission circuit in a retransmission cycle shorter than the retransmission cycle in the standard mode in packet communication with a short data length. A wireless communication system comprising: a HARQ control unit comprising: The packet transmission circuit is composed of an orthogonal frequency division multiplexing (OFDM) type transmission circuit in which the channel for subpacket transmission and the channel for response transmission are formed by subcarrier groups having different frequencies.
The wireless communication system according to claim 1, wherein the packet receiving circuit comprises an OFDM type receiving circuit.   The HARQ control unit stores HARQ control mode information for specifying the retransmission cycle in association with an interlace identification number indicating a relationship between a time frame for sub-packet transmission and a time frame for response transmission. The wireless communication system according to claim 2, further comprising a management table, wherein a retransmission period of the subpacket or response packet from the transmission circuit is controlled according to the management table. The HARQ control unit of the wireless terminal is
In a channel group for response transmission from the wireless terminal to the base station, a response identification number that is not used in the data transmission in the standard mode is applied, and a response to the data transmission with the shortened retransmission cycle is returned. The wireless communication system according to claim 2 or claim 3, wherein The HARQ control unit of the wireless terminal is
In the channel group for response transmission from the wireless terminal to the base station, the standard mode data transmission uses a channel that is idle for interference estimation, and is used for data transmission with a shortened retransmission cycle. The wireless communication system according to claim 2 or 3, wherein a response is returned. The HARQ control unit of the wireless terminal is
A response to the data transmission in the standard mode and a response to the data transmission in which the retransmission period is shortened are orthogonally multiplexed and transmitted to one channel of a channel group for response transmission from the wireless terminal to the base station. The wireless communication system according to claim 2, wherein the wireless communication system is a wireless communication system. HARQ control unit of the base station,
A response to the data transmission in the standard mode and a response to the data transmission in which the retransmission cycle is shortened are orthogonally multiplexed on one channel of the channel group for response transmission from the base station to any one of the wireless terminals. The radio communication system according to claim 2, wherein the radio communication system transmits the data.   Issued when the base station issues a resource assignment message for an uplink data channel issued in response to a resource assignment request from any one of the wireless terminals or the first subpacket addressed to any one of the wireless terminals 8. The radio communication system according to claim 2, wherein the downlink data channel resource allocation message includes information indicating whether the retransmission cycle is a standard mode or a shortened mode. A wireless terminal that transmits / receives a packet to / from a base station by a hybrid automatic repeat request (HARQ) method,
A wireless transceiver circuit;
A packet transmission circuit that divides a packet with redundant bits added into a plurality of subpackets, and outputs each subpacket to the wireless transmission / reception circuit at a predetermined period;
A packet receiving circuit that repeats the decoding process by combining the newly received subpacket and the received previous subpacket until the original packet is successfully decoded when the subpacket is received from the wireless transceiver circuit;
As a response to the reception subpacket, ACK is generated when the reception circuit succeeds in decoding the packet, NAK is generated when the packet is unsuccessful, and the response is returned at a predetermined timing via the packet transmission circuit. With
In the packet communication with a short data length, the control unit includes a HARQ control unit having a function of transmitting a subpacket or a response from the packet transmission circuit at a retransmission cycle shorter than the retransmission cycle of the standard mode. A wireless terminal. The HARQ controller is
In a channel group for response transmission from the wireless terminal to the base station, a response identification number that is not used in the data transmission in the standard mode is applied, and a response to the data transmission with the shortened retransmission cycle is returned. The wireless terminal according to claim 9. The HARQ controller is
In the channel group for response transmission from the wireless terminal to the base station, the standard mode data transmission uses a channel that is idle for interference estimation, and is used for data transmission with a shortened retransmission cycle. The wireless terminal according to claim 9, wherein a response is returned. The HARQ controller is
A response to the data transmission in the standard mode and a response to the data transmission in which the retransmission period is shortened are orthogonally multiplexed and transmitted to one channel of a channel group for response transmission from the wireless terminal to the base station. The wireless terminal according to claim 9, wherein: A wireless base station that transmits / receives a packet to / from a plurality of wireless terminals by a hybrid automatic repeat request (HARQ) method,
A wireless transceiver circuit;
A packet transmission circuit that divides a packet with redundant bits added into a plurality of subpackets, and outputs each subpacket to the wireless transmission / reception circuit at a predetermined period;
A packet receiving circuit that repeats the decoding process by combining the newly received subpacket and the received previous subpacket until the original packet is successfully decoded when the subpacket is received from the wireless transceiver circuit;
As a response to the reception subpacket, ACK is generated when the reception circuit succeeds in decoding the packet, NAK is generated when the packet is unsuccessful, and the response is returned at a predetermined timing via the packet transmission circuit. With
In the packet communication with a short data length, the control unit includes a HARQ control unit having a function of transmitting a subpacket or a response from the packet transmission circuit at a retransmission cycle shorter than the retransmission cycle of the standard mode. A wireless base station. The HARQ controller is
When a response having a response identification number that is not used in data transmission in the standard mode is received in the channel group for response transmission from each wireless terminal, the response is transmitted as a response to data transmission in which the retransmission cycle is shortened. The radio base station according to claim 13, wherein the radio base station is determined. The HARQ controller is
When a response is received on a channel that is idle for interference estimation in the data transmission in the standard mode among the channel group for response transmission from each wireless terminal, the retransmission period of the response is shortened The radio base station according to claim 13, wherein the radio base station is determined to be a response to data transmission. The HARQ controller is
A response to the data transmission in the standard mode and a response to the data transmission with a shortened retransmission cycle are orthogonally multiplexed and transmitted to one channel of the channel group for response transmission toward each wireless terminal. The radio base station according to claim 13.

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