JP5284383B2 - Mobile station apparatus and communication control method - Google Patents

Description

The present invention relates to a mobile station apparatus and a communication control method.

  In the ARQ (Automatic Repeat Request) method, which is one of error correction methods, when there is an error in a received data frame, the receiving side transmits a retransmission request for the data frame to the transmitting side. The transmitting side identifies a data frame to be retransmitted based on the received retransmission request and retransmits it to the receiving side. For this reason, to improve the error correction efficiency by the ARQ scheme, it is considered effective to reduce the number of retransmissions of the data frame, shorten the time from when a retransmission request is received until the data frame is retransmitted, etc. It is done.

  In this regard, Patent Document 1 below discloses a technique for improving system throughput by reducing the number of retransmissions of a data frame in a wireless transmission apparatus to which hybrid ARQ is applied.

JP 2004-253828 A

  Since a certain processing time (hereinafter referred to as a reference required time) is required from reception of a retransmission request to retransmission of a data frame, in particular, TDMA / TDD (Time Division Multiple Access / Time Division Duplex) Communication), it may be difficult to retransmit a data frame using a transmission frame that immediately follows the frame that received the retransmission request. Therefore, in the conventional ARQ applied to the TDMA / TDD system, in order to ensure sufficient time for the retransmission process of the data frame, the data frame is uniformly transmitted using the transmission frames after the frame after receiving the retransmission request. I try to resend. As a result, there is a problem that whenever a data frame error occurs, a retransmission delay of 1 TDMA frame or more always occurs.

  The present invention has been made in view of the above-described conventional problems, and provides a communication device and a data frame retransmission method that can favorably shorten the time from when a retransmission request is received until a data frame is retransmitted. For the purpose.

To achieve the above object, the mobile station apparatus according to the present invention, have a row communicates with the base station apparatus by the TDD system, according to the reception confirmation information transmitted from the base station apparatus, said base station by an automatic retransmission scheme A mobile station device that transmits retransmission data to a device, wherein the number of frames from reception of the reception confirmation information to transmission of retransmission data is based on a position in a reception frame of a reception slot including the reception confirmation information It is characterized by making decisions .

1 is an overall configuration diagram of a mobile communication system according to an embodiment of the present invention. It is a functional block diagram of the mobile station apparatus which concerns on embodiment of this invention. It is a figure which shows an example of a timing difference information storage part. It is a figure which shows an example of the time slot structure by TDMA / TDD, and the subchannel structure by OFDMA. It is a figure explaining the resending timing of a data frame. It is a flowchart which shows the process which acquires the timing difference information in a mobile station apparatus. It is a flowchart which shows the data frame transmission (including resending) process in a mobile station apparatus.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an overall configuration diagram of a mobile communication system according to an embodiment of the present invention. As shown in the figure, the mobile communication system 1 includes a base station apparatus 10 and a plurality of mobile station apparatuses 12 (three here).

  Each mobile station apparatus 12 performs wireless communication with the base station apparatus 10, and is, for example, a portable mobile phone, a portable information terminal, and a communication card. Here, data is transmitted / received to / from the base station apparatus 10 by the TDD method, and multiplex communication is performed by the TDMA method and the OFDMA method. Furthermore, the base station apparatus 10 includes an adaptive array antenna as will be described later, and using this adaptive array antenna, space division is performed with each of the plurality of mobile station apparatuses 12 in the same time slot and the same carrier frequency. Multiplex communication is performed by a multiplex (SDMA: Space Division Multiple Access) method. Thus, bidirectional communication with a plurality of mobile station apparatuses 12 is performed with extremely high frequency utilization efficiency.

  FIG. 4 is a diagram illustrating an example of a time slot configuration (for one TDMA frame) based on TDMA / TDD and a subchannel configuration based on OFDMA. As shown in the figure, the downlink (radio transmission path from the base station apparatus 10 to the mobile station apparatus 12) and the uplink (radio transmission path from the mobile station apparatus 12 to the base station apparatus 10) each have four times. It consists of slots. Each time slot is composed of 28 subchannels, one of which is used as a control channel (CCH) and the remaining 27 subchannels are used as communication channels (TCH). .

  The base station apparatus 10 allocates at least some of the subchannels (27 subchannels × 4 slots) used as communication channels in the downlink and uplink to each mobile station apparatus 12. . Specifically, as shown in FIG. 4, one anchor subchannel (ASCH) is allocated, and one or a plurality of extra subchannels (ESCH) are assigned to each mobile station device 12 as necessary. Assign to.

  The ASCH is a subchannel determined when a link is established (communication start) and notified to each mobile station apparatus 12 using the CCH, and is mainly used for transmitting / receiving control information such as MAP information and ACK information. It is what is done. The MAP information is a bit string composed of 108 bits indicating one or a plurality of ESCHs used in the next TDMA frame (next uplink frame and downlink frame) that has received the MAP information. Specifically, the bit corresponding to the ESCH assigned to the mobile station apparatus 12 in the next TDMA frame is indicated by “1”, and other subchannels (ASCH, ESCH assigned to other mobile station apparatuses 12 and free subchannels) The bit corresponding to is indicated by “0”. The ACK information stores the sequence number of the data frame received in the uplink and ACK (Acknowledge: Acknowledge) or NACK (Negative Acknowledge: Negative Acknowledge) indicating the presence or absence of an error in the data frame. is there. In particular, when the ACK information is NACK, the ACK information means a data frame retransmission request.

  On the other hand, the ESCH is a subchannel that is determined after link establishment and is specified by MAP information notified to each mobile station measure 12 using the ASCH, and is mainly used for transmission / reception of communication data. As shown in FIG. 4, ASCH and ESCH are the same subchannels in the downlink slot and uplink slot (DL # 1 and UL # 1, DL # 2 and UL # 2,...) Corresponding to the slot numbers. Assigned to.

  FIG. 2 is a functional block diagram of the mobile station device 12. As shown in the figure, the mobile station apparatus 12 includes an antenna 20, a radio communication unit 22, a signal processing unit 24, a modem unit 26, a data buffer 28, an external I / F unit 32, a data input unit 34, and data frame retransmission control. The unit 36 and the storage unit 46 are included.

  The radio communication unit 22 includes a low noise amplifier, a down converter, and an up converter, down-converts a radio signal from the base station apparatus 10 received by the antenna 20 and outputs the radio signal to the signal processing unit 24. The transmission signal input from the signal processing unit 24 is up-converted into a radio signal, amplified to a transmission output level, and transmitted from the antenna 20.

  The signal processing unit 24 performs symbol synchronization and removal of a guard interval (GI) signal on the signal input from the wireless communication unit 22 to obtain a baseband OFDM signal, and outputs the baseband OFDM signal to the modulation / demodulation unit 26 To do. Also, a guard interval signal is added to the baseband OFDM signal input from the modem unit 26 and output to the radio communication unit 22.

  The modem unit 26 includes an A / D converter, an FFT unit, a channel estimation unit, and a demapping unit. The baseband OFDM signal input from the signal processing unit 24 is OFDM demodulated, and the obtained received data frame is converted. The data is output to the data buffer 28. Specifically, after A / D converting the baseband OFDM signal, FFT is performed in the FFT unit to obtain each subcarrier component of the OFDM symbol. Next, after performing a predetermined channel estimation process or the like, referring to the subchannel allocation status stored in the channel information storage unit 48, a plurality of subchannels (one ASCH and (1 or a plurality of ESCH) subcarrier components are concatenated to generate a symbol string. Then, the received data frame obtained by decoding the symbol string is output to the data buffer 28.

  The modulation / demodulation unit 26 includes a symbol mapping unit, an IFFT unit, and a D / A converter. The modulation / demodulation unit 26 performs OFDM modulation on the transmission data frame input from the data buffer 28 (transmission queue 30), and obtains the obtained baseband OFDM signal. Is output to the signal processing unit 24. Specifically, referring to the allocation status of the subchannels stored in the channel information storage unit 48, the transmission data frame is divided and a plurality of subchannels (one ASCH and 1 or 1) allocated from the base station apparatus 10 are divided. A plurality of ESCH) transmission data is generated. Next, the generated transmission data of each subchannel is converted into a symbol string by symbol mapping, and the symbol string is distributed to each subcarrier of the subchannel. Then, the IFFT unit performs IFFT and outputs a baseband OFDM signal obtained by D / A conversion to the signal processing unit 24.

  The data buffer 28 is configured to include a transmission queue 30, and temporarily stores the received data frame from the base station apparatus 10 input from the modem unit 26, and receives the received data obtained by connecting these frames. Are sequentially output to a host device (not shown) via the external I / F unit 32. In addition, data input from the data input unit 34 such as a transmission data frame and a numeric keypad input to each mobile station device 12 input from the host device via the external I / F unit 32 is temporarily stored and transmitted. A transmission data frame is generated from the data and sequentially output to the modem unit 26 via the transmission queue 30.

  The transmission queue 30 holds transmission data frames in a first-in first-out (FIFO) list structure. A transmission data frame or a retransmission data frame input from the data frame retransmission control unit 36 is added to the transmission queue 30 for each TDMA frame. The earliest data frame in the transmission queue 30 is extracted for each TDMA frame and output to the modem unit 26.

  The storage unit 46 includes a memory, and includes a channel information storage unit 48 and a timing difference information storage unit 50.

  The channel information storage unit 48 stores subchannels (one ASCH and one or a plurality of ESCHs) allocated from the base station apparatus 10. Since ASCH is a subchannel for transmitting ACK information, the slot position of ASCH indicates the reception timing (reception slot) of ACK information.

  The timing difference information storage unit 50 stores timing difference information indicating a timing difference satisfying a condition for the reference required time in association with information indicating the reception timing of NACK. Here, the reference required time is a minimum time required for a process from receiving a NACK until a data frame is retransmitted (hereinafter referred to as a data frame retransmission process), for example, the slowest process execution speed. It is set based on the mobile station apparatus 12 (lowest processing capability). Also, the timing difference that satisfies the reference required time is a timing difference between the NACK reception timing and the data frame retransmission timing related to the NACK, which is equal to or longer than the reference required time and as close as possible to the reference required time. It is a timing difference having time. Note that the NACK reception timing may be specified by a NACK reception slot, and the data frame retransmission timing may be specified by a transmission slot of a retransmission data frame or a transmission frame including the transmission slot.

  FIG. 3 is a diagram illustrating an example of the timing difference information storage unit 50. As shown in the figure, timing difference information (timing 1, timing 2) is stored in the timing difference information storage unit 50 in association with the slot position of ASCH (sub-channel transmitting ACK information). This indicates the correspondence between the slot position of the ASCH indicating the reception slot of NACK and the transmission frame indicating the timing for retransmitting the data frame related to the NACK. It is set so as to minimize the reference required time required for the frame retransmission process. That is, the information shown in the timing difference information storage unit 50 shown in FIG. 3 is the optimum transmission that minimizes the data frame retransmission processing time while ensuring the reference required time for each slot position of the ASCH indicating the NACK reception slot. A frame is shown. Therefore, for example, when NACK is received in “first slot” (the slot position of ASCH is “first slot”), if a data frame is retransmitted in the next frame (timing 1) of the reception slot, Data frame retransmission processing is shortened the most.

  The data frame retransmission control unit 36 includes a retransmission request acquisition unit 38, a data frame retransmission timing determination unit 40, a transmitted buffer 42, and a retransmission data frame selection unit 44, and is a retransmission transmitted from the base station apparatus 10. In response to the request, retransmission of the data frame related to the retransmission request is controlled.

  The retransmission request acquisition unit 38 acquires ACK information for each TDMA frame from the reception data output from the data buffer 28 and acquires the reception timing (reception slot) of the ACK information.

  The data frame retransmission timing determination unit 40 determines the timing difference between the NACK reception timing and the data frame retransmission timing related to the NACK based on the NACK reception timing so as to approach the reference required time required for the data frame retransmission processing. The retransmission timing (transmission slot or transmission frame) of the data frame related to NACK is determined.

  FIG. 5 is a diagram for explaining the retransmission timing of the data frame specified by the data frame retransmission timing determination unit 40. As shown in FIG. 5A, when the slot position of the ASCH indicating the NACK reception slot is the first slot, the data frame retransmission timing determination unit 40 sets the next transmission frame of the NACK reception slot as the data frame retransmission timing. decide. This is based on the design / experimental results that any mobile station apparatus 12 can complete the data frame retransmission process within the time of about 3 slots from the NACK reception slot to the next transmission frame. It is. In this case, the data frame retransmission processing time can be shortened by at least 1 TDMA frame compared to the conventional case. On the other hand, as shown in FIG. 4B, when the slot position of the ASCH (NACK reception slot) is the fourth slot, the data frame retransmission timing determination unit 40 determines the transmission frame after the NACK reception slot as the data frame retransmission timing. Determine as. This is based on the design / experimental results that it is difficult for all the mobile station devices 12 to complete the data frame retransmission processing within the time from the NACK reception slot to the next transmission frame (almost 0 slot). It is.

  The data frame retransmission timing determination unit 40 reads the timing difference information from the timing difference information storage unit 50 in association with the slot position of the ASCH indicating the NACK reception slot, and also reads the timing difference information read from the NACK reception slot. Based on the above, the retransmission timing (transmission frame) of the data frame related to the NACK may be determined.

  The transmitted buffer 42 temporarily stores at least a part of the plurality of data frames transmitted to the base station apparatus 10 in association with the sequence numbers of the respective data frames. The earliest data frame in the transmission queue 30 is transmitted for each TDMA frame, and is extracted from the transmission queue 30 together with the transmission and stored in the transmitted buffer 42.

  When the NACK is stored in the ACK information acquired by the retransmission request acquisition unit 38, the retransmission data frame selection unit 44 retransmits from the transmitted buffer 42 based on the sequence number of the data frame stored in the ACK information. A data frame to be selected is selected and added to the transmission queue 30. When ACK is stored in the ACK information, the data frame related to the sequence number of the data frame stored in the ACK information is deleted from the transmitted buffer 42.

  Here, the operation of the mobile station apparatus 12 will be described.

  FIG. 6 is a flowchart showing processing for acquiring timing difference information at the start of communication. As shown in the figure, when communication is started, the channel information storage unit 48 stores one ASCH and one or a plurality of ESCHs allocated from the base station apparatus 10. Next, the data frame retransmission timing determination unit 40 acquires the slot position of the ASCH from the channel information storage unit 48 (S100). Further, timing difference information is acquired from the timing difference information storage unit 50 in association with the acquired slot position of the ASCH (S102).

  FIG. 7 is a flowchart showing data frame transmission (including retransmission) in the mobile station apparatus 12. As shown in the figure, first, in the uplink frame, the data frame including the transmission packet received from the host device is stored in the data buffer 28 (S200). Then, the data frame is added to the transmission queue 30 (S202). Next, the earliest data frame is extracted from the transmission queue 30, and the data frame is converted into a transmission signal and transmitted to the base station apparatus 10 (S204). Then, the transmitted data frame is stored in the transmitted buffer 42 in association with the sequence number (S206).

  Next, reception data from the base station apparatus 10 is acquired in the downlink frame. The retransmission request acquisition unit 38 acquires ACK information from the received data, and determines whether the value stored in the ACK information is ACK or NACK (S208). When the value is ACK, the retransmission data frame selection unit 44 deletes the corresponding data frame from the transmitted buffer 42 based on the sequence number of the data frame stored in the ACK information (S210). Then, it is determined whether or not the data transmission is completed (S212). If the transmission is not completed, the processes after S202 are executed in the next uplink frame.

  On the other hand, when the value stored in the ACK information is SACK in S208, the data frame retransmission timing determination unit 40 receives the NACK reception slot acquired by the retransmission request acquisition unit 38 and the timing difference information acquired in S102. Based on the above, the transmission frame of the data frame related to the NACK is determined (S214). Next, the retransmission data frame selection unit 44 selects a data frame to be retransmitted from the transmitted buffer 42 based on the sequence number of the data frame stored in the ACK information (S216), and the data frame is selected in S214. It adds to the transmission queue 30 so that it may transmit in the determined transmission frame (S218). Then, the processing after S204 is executed in the next uplink frame.

  According to the above embodiment, based on the reception timing (reception slot) of NACK so that the time from when a NACK is received until the data frame related to the NACK is retransmitted approaches the reference required time required for the data frame retransmission process. Thus, the retransmission timing (transmission frame) of the data frame related to the NACK is determined. For this reason, it is possible to satisfactorily shorten the time from the reception of NACK to the retransmission of the data frame.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation implementation is possible. For example, in the above description, the present invention is applied to a mobile station apparatus in a mobile communication system using both SDMA, TDMA / TDD, and OFDMA. However, the present invention uses an automatic retransmission request method for TDMA / TDD and data frames. Applicable to all communication devices to be adopted.

  Moreover, in the said embodiment, although the mobile station apparatus 12 showed the structure which resends a data frame according to the data frame resending request | requirement from the base station apparatus 10, the position of the mobile station apparatus 12 and the base station apparatus 10 is switched. It goes without saying that the present invention may be applied to other configurations and configurations each having both functions of a retransmission request and a data frame retransmission.

  DESCRIPTION OF SYMBOLS 1 Mobile communication system, 10 Base station apparatus, 12 Mobile station apparatus, 20 Antenna, 22 Wireless communication part, 24 Signal processing part, 26 Modulation / demodulation part, 28 Data buffer, 30 Transmission queue, 32 External I / F part, 34 Data Input unit, 36 data frame retransmission control unit, 38 retransmission request acquisition unit, 40 data frame retransmission timing determination unit, 42 transmitted buffer, 44 retransmission data frame selection unit, 46 storage unit, 48 channel information storage unit, 50 timing difference information Memory part.

Claims (2)

There line communication with a base station apparatus by the TDD system, according to the reception confirmation information transmitted from the base station apparatus, a mobile station apparatus transmits the retransmission data to the base station apparatus by an automatic retransmission scheme,
A mobile station apparatus that determines the number of frames from when the reception confirmation information is received to when retransmission data is transmitted based on a position in a reception frame of a reception slot including the reception confirmation information . A communication control method in a mobile station apparatus that communicates with a base station apparatus by a TDD scheme and transmits retransmission data to the base station apparatus by an automatic retransmission scheme in accordance with reception confirmation information transmitted from the base station apparatus,
A communication control method, comprising: determining a number of frames from reception of the reception confirmation information to transmission of retransmission data based on a position in a reception frame of a reception slot including the reception confirmation information.

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