JP4906750B2 - Mobile station and communication control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile station in which occurrence of a wrong determination of a signal reported from the base station to the mobile station can be reduced and frequency of occurrence of retransmission can be reduced, and to provide a base station and a communication control method. <P>SOLUTION: Each time a retransmission control signal is received from a base station, a signal determination section 213 compares a soft determination value calculated from the retransmission control signal with a predetermined threshold to determine whether the retransmission control signal indicates ACK or NACK and in accordance with a determination result (ACK or NACK) received from the signal determination section 213 and contents of a transmission instruction received from a transmission instruction receiving section 212, a control section 203 controls retransmission of a radio transfer block. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a mobile station, a base station, and a communication control method in a communication system in which a mobile station communicates with a counterpart station via a base station.

  In the conventional mobile communication system composed of a base station and a plurality of mobile stations as shown in FIG. 15, in the uplink in which packets are transmitted from the mobile station to the base station, the base station is transmitted from the mobile station. By measuring the channel quality according to the reception state of the known signal, a packet transmission method corresponding to the channel quality is determined, and this transmission method is notified to the mobile station. And the mobile station implement | achieves highly efficient data transmission, implement | achieving a predetermined | prescribed error rate by transmitting a packet according to the transmission method notified from the base station.

  Specifically, the mobile station implements a predetermined error rate by adaptively changing the modulation scheme and coding rate. For example, when the channel quality is good or when moving at low speed, 64QAM (Quadrature Amplitude Modulation) with a large number of modulation levels is set for the modulation method, and the coding rate is as high as “1”. Set a numeric value. Also, when the channel quality is poor, or when moving at medium speed or high speed, QPSK (Quadrature Phase Shift Keying) with a small number of modulation levels is set for the modulation method, and the coding rate is “0.25”. By setting a low numerical value like this, packet transmission resistant to noise and interference is realized, although the transmission efficiency is inferior to the above case. As described above, the mobile station realizes data transmission according to the change of the propagation environment by changing the modulation method and the coding rate according to the channel quality.

  In addition, wideband transmission is desirable for high-speed data transmission, but in wideband multipath environments, the power strength (line quality) of transmission signals from individual mobile stations due to the effect of frequency selective fading. Varies greatly in the frequency axis direction. Since this change situation is independent for each mobile station, it is effective for efficient data transmission that the base station grasps the state of each mobile station and performs transmission control (scheduling) on the frequency axis. Are known. Such control is generally performed according to a method called “water injection theorem”. By performing scheduling based on this water injection theorem, for example, the base station selects and selects a mobile station with good channel quality for each band (frequency block) obtained by dividing the entire band into predetermined frequencies. Since the frequency block can be allocated to the mobile station, the system throughput can be improved.

  As described above, it is possible to improve system throughput by performing scheduling based on the water injection theorem at the base station, but since a mobile communication system transmits packets via radio, even if scheduling is performed, an error will not necessarily occur. It is not always possible to transmit a packet without it. It is conceivable that scheduling is performed with a target error rate determined on the assumption that an error occurs in a packet due to noise or interference. In this case, if the target error rate is set to 0.1%, for example, 1 High-quality data transmission can be expected because an error occurs in a packet only once every 10,000 times. However, since a packet transmission method that is resistant to errors must be selected, redundancy is increased and system throughput is increased. Will also decline.

  Therefore, in a conventional mobile communication system, an error rate is determined in advance during scheduling (for example, 10%), and a certain level of error is compensated by retransmission, thereby realizing efficient and high-quality data transmission. HARQ (Hybrid Automatic Repeat reQuest) is used as a technique for retransmitting a packet in which an error has occurred. In HARQ, a mobile station transmits a packet to a base station using setting values (modulation scheme and error rate) scheduled at the base station, and the base station decodes the packet. As a result, CRC (Cyclic Redundancy Check) is obtained. ) Is transmitted to the mobile station if it is normal, NACK (Negative ACKnowledge) is transmitted to the mobile station if the CRC is abnormal. On the other hand, when the mobile station receives ACK from the base station, it transmits the next packet, and when it receives NACK, it retransmits the already transmitted packet.

  On the other hand, in the uplink of Universal Terrestrial Radio Access (UTRA) standardized by 3GPP (3rd Generation Partnership Project), which is a standardization organization of the third generation mobile communication system, Single carrier FDMA (Rec) is adopted as Single carrier FDMA (Rec). The scheduler uses an OFDM (Orthogonal Frequency Division Multiplexing) subcarrier group called a frequency block as a transmission control unit, and can allocate one or more continuous frequency blocks to a mobile station.

  In Evolved UTRA, a mobile station transmits a packet using a frequency block allocated from a base station. In this case, as a result of decoding the packet transmitted from the mobile station at the base station, when the CRC becomes abnormal and the NACK is notified to the mobile station, the scheduler assigns a frequency block different from the initial transmission for retransmission. Therefore, scheduling can be performed while avoiding degradation of channel quality due to frequency selective fading. Therefore, in Evolved UTRA, it is possible to reduce the possibility of repeated retransmissions with poor channel quality.

  However, when the mobile station is at a low speed or stopped, the fluctuation in channel quality on the frequency is small, so it is not always necessary to change the frequency blocks for initial transmission and retransmission. Therefore, when the scheduler notifies the mobile station of the frequency block allocation information for each retransmission, the control information increases, and downlink radio resources cannot be used effectively. In response to this problem, Non-Patent Document 1 discloses the following two retransmission methods for exchanging control information between the base station and the mobile station at the time of retransmission.

  First, the first retransmission method will be described with reference to FIG. Hereinafter, this first retransmission method is referred to as “Non-adaptive HARQ”. First, the base station notifies the mobile station of a transmission instruction indicating a data transmission method. Here, it is assumed that this transmission instruction includes information on a frequency block (RB) to be transmitted by the mobile station. In FIG. 16, the mobile station is notified to transmit a packet using RB1 and RB2.

  First, the mobile station transmits (initially transmits) a packet using RB1 and RB2 (see (2) in the figure) according to the transmission instruction notified from the base station (see (1) in the figure). The base station decodes the packet received from the mobile station, and notifies the mobile station of NACK when the CRC is abnormal. Here, the base station determines that the frequency used by the mobile station for retransmission and the frequency used for initial transmission may be the same, or the frequency used for the second and subsequent retransmissions, and the frequency used for the previous retransmission. And NACK may be notified to the mobile station (see (3) in the figure). When the mobile station receives a NACK from the base station, the mobile station does not receive a transmission instruction and retransmits it to the base station using RB1 and TB2 which are the same frequency blocks as the initial transmission (see (4) in the figure).

  Next, the second retransmission method will be described with reference to FIG. Hereinafter, this second method is referred to as “Adaptive HARQ”. The operation from when the base station notifies the mobile station of the transmission instruction until the base station notifies the mobile station of NACK is the same as the operation described in Non-adaptive HARQ, and thus the description is omitted. To do.

  The base station decodes the packet received from the mobile station, and notifies the mobile station of NACK when the CRC is abnormal. Here, when changing the frequency used by the mobile station for packet transmission, the base station notifies the mobile station of a transmission instruction to notify the change of the frequency block together with NACK ((3) in the figure, (Refer to (4)). In the example of FIG. 17, the base station notifies the mobile station that RB3 and RB4 are used instead of RB1 and RB2 used for the initial transmission by a transmission instruction.

  On the other hand, since the mobile station has received the NACK and the transmission instruction from the base station, the mobile station retransmits the packet using frequency blocks RB3 and RB4 different from the initial transmission (see (5) in the figure). Thus, in Non-adaptive HARQ, it is not necessary to notify control information from the base station to the mobile station for each retransmission, so that downlink radio resources can be used effectively. In addition, in Adaptive HARQ, even when the channel quality is deteriorated due to frequency selective fading, packets can be retransmitted in a frequency block different from the frequency block used in the past, so that high quality data transmission can be expected.

  Further, as described in Non-Patent Document 2, PHICH (Physical Hybrid Automatic Repeat Indicator Channel), which is a physical channel for notifying a retransmission control signal (ACK or NACK), repeatedly codes data, Transmit to mobile station without adding CRC. In addition, a PDCCH (Physical Downlink Control Channel), which is a physical channel for notifying a transmission instruction, applies a convolutional code to data and adds a CRC.

  Here, Non-Patent Document 3 describes the target error rates of PHICH and PDCCH as 10 ^ -3 to 10 ^ -4 and 10 ^ -2, respectively. In this case, assuming that the packet transmission cycle is 1 ms, an error occurs once every 1 to 10 seconds in PHICH, and an error occurs once in 100 ms in PDCCH. For example, when a mobile station erroneously detects an ACK even though the base station has notified NACK, the mobile station does not retransmit the packet, so that a packet dropout occurs in the base station, leading to a decrease in service quality. appear. As a method for dealing with such a problem, as in Patent Document 1, the reliability of ACK is estimated based on the channel quality of a known signal (pilot signal), and when the reliability is equal to or less than a threshold, ACK is overwritten on NACK. Thus, a technique for preventing a packet loss due to the mobile station not retransmitting is disclosed.

3GPP TS36.300 v8.3.0 "Overall description; Stage2" 3GPP TS36.212 “Multiplexing and channel coding (Release 8)” 3GPP R2-072104 “LS on target quality on L1 / L2 control channel, RAN WG1” JP 2004-64691 A

  By the way, Patent Document 1 describes a case where NACK is erroneously detected as ACK, but no consideration is given to a case where ACK is erroneously detected as NACK. The reason is that if ACK is erroneously detected as NACK, even if the transmitting side retransmits the packet, the receiving side detects duplication of the packet, and notifies the transmitting side that transmitted the packet again with ACK. This is because it returns to normal processing and does not have a significant effect on system throughput.

  In conventional communication systems using code division multiplexing such as HSDPA (High Speed Downlink Access) and HSUPA (High Speed Uplink Packet Access), transmission packets are spread over a wide band using spreading codes. The same band is always used on the frequency. For this reason, the above-described erroneous detection does not cause the problem described below.

  However, in a communication system using frequency division multiplexing such as Evolved UTRA, a mobile station transmits a packet using a frequency block notified from a base station, and therefore the frequency used every time a packet is transmitted is different. Occurs. Therefore, the following problems may occur.

  FIG. 18 is a diagram showing a communication state in the conventional mobile communication system shown in FIG. 15, and shows a configuration in which mobile station A and mobile station B communicate with a base station. First, the base station notifies the mobile station A of a transmission instruction for instructing various transmission methods such as frequency block information (RB1, RB2) used during transmission (see (1) in the figure). The mobile station A transmits a packet using RB1 and RB2 in accordance with the transmission instruction notified from the base station (see (2) in the figure). The base station decodes the packet received from the mobile station A, and notifies the mobile station A of ACK if the CRC is normal (see (3) in the figure). Thereafter, radio resources are not newly allocated to the mobile station A, and no new transmission instruction is notified.

  Further, it is assumed that the base station notifies the mobile station B of a transmission instruction including frequency block information (RB1, RB2) at the same time as the transmission of the ACK to the mobile station A (4). The mobile station A decodes the PHICH transmitted from the base station and determines whether the retransmission control signal is ACK or NACK. Here, when mobile station A erroneously determines ACK as NACK, mobile station A determines that it is Non-adaptive HARQ because it has not received notification of a transmission instruction, and uses RB1 and RB2 similar to those at the time of transmission in (2). To retransmit the packet (see (5) in the figure).

  On the other hand, since mobile station B has newly received a transmission instruction in (4), it transmits a packet using RB1 and RB2 (see (6) in the figure). As a result, the base station receives packets from different mobile stations at the same time and the same frequency block (RB1, RB2). Therefore, the transmission symbol of the mobile station A interferes with the transmission symbol of the mobile station B, and the base station cannot normally decode the mobile station B packet that should be received. To do.

  The present invention has been made in view of the above, and can reduce the occurrence of erroneous determination of a signal notified from a base station to a mobile station and can reduce the frequency of retransmission. It is an object to provide a mobile station, a base station, and a communication control method.

  In order to solve the above-described problems and achieve the object, the present invention configures a communication system together with a base station, and wirelessly transmits to the base station using a frequency block assigned by a transmission instruction notified from the base station. A mobile station that transmits a transfer block and performs retransmission of the radio transfer block according to the instruction content of the retransmission control signal notified from the base station, and each time the retransmission control signal is received, the retransmission control signal Based on the magnitude relationship between the soft decision value and a predetermined threshold, it is determined whether the retransmission control signal indicates retransmission of the wireless transfer block, based on a magnitude relationship between the soft decision value and a predetermined threshold value The first determination means, the second determination means for determining whether or not the transmission instruction is received together with the retransmission control signal, the determination result by the first determination means, and the second determination means. Depending on the determination result, characterized by comprising a transmission control means for controlling a retransmission of the wireless transfer blocks.

  According to the present invention, it is possible to reduce the occurrence of erroneous determination of a signal notified from a base station to a mobile station and reduce the frequency of retransmission.

  Embodiments of a communication system and a communication method according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this embodiment.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a communication system according to a first embodiment of the present invention. This communication system includes a base station 100 and a plurality of mobile stations 200, and each base station 100 and the mobile station 200 can transmit and receive packets to and from each other. Although FIG. 1 shows the case where there are two mobile stations 200, the number of mobile stations 200 is not limited to this.

  FIG. 2 is a block diagram showing a configuration related to uplink communication of base station 100 shown in FIG. As shown in the figure, the base station 100 includes a radio signal receiving unit 101 that receives a signal from each mobile station 200, and a demodulation / decoding unit 102 that demodulates and decodes a signal received by the radio signal receiving unit 101. A transmission request receiving unit 103 that receives a transmission request signal received from each mobile station 200, a channel quality measuring unit 104 that measures radio channel quality between each mobile station and the base station, and a wireless transfer transmitted by each mobile station The wireless transfer block receiving unit 105 that receives the block, the retransmission control unit 106 that determines whether or not to instruct the mobile station to perform retransmission from the decoding result of the wireless transfer block, and the wireless transfer block was successfully decoded A packet reproduction unit 107 that reproduces packets from the radio transfer block, a scheduler unit 108 that controls the allocation of radio resources to each mobile station, and a re-transmission unit for each mobile station. A retransmission control signal transmitting unit 109 for transmitting a retransmission control signal indicating the presence or absence of transmission, a transmission instruction transmitting unit 110 for instructing each mobile station to allocate radio resources, and encoding a retransmission control signal and a transmission instruction. An encoder / modulator 111 for modulating, and a radio signal transmitter 112 for transmitting the encoded / modulated signal to each mobile station.

  FIG. 3 is a block diagram showing a configuration related to uplink communication of mobile station 200 shown in FIG. As shown in the figure, the mobile station 200 includes a packet generation unit 201 that generates a packet when data to be transmitted occurs, a packet buffer 202 that temporarily stores the packet, and a packet to the base station. A control unit 203 for instructing a transmission method at the time of transmission, a wireless transfer block generation unit 204 for dividing or combining packets into wireless transfer blocks according to information notified from the control unit, and A transmission request transmission unit 205 that requests a packet transmission opportunity, a retransmission control unit 206 that controls retransmission of the wireless transfer block based on a retransmission control signal notified from the base station 100, and controls the transmission request and the wireless transfer block. An encoding / modulation unit 207 that encodes and modulates the data transmission method specified by the unit, and the encoded / modulated signal to the base station Wireless signal transmitting section 208 for transmitting, radio signal receiving section 209 for receiving signals transmitted from the base station (hereinafter referred to as base station signals), and demodulating and decoding signals received by wireless signal receiving section 209 Demodulation / decoding section 210, retransmission control signal receiving section 211 for extracting a retransmission control signal from a base station signal, transmission instruction receiving section 212 for extracting transmission instruction information indicating a method for transmitting a radio transfer block from a base station signal, A signal determining unit 213 that estimates the reliability of the base station signal from the decoding result of the retransmission control signal and determines the retransmission control signal.

  Hereinafter, operations of the base station 100 and the mobile station 200 will be described with reference to FIG. 2 and FIG. First, when data to be transmitted is generated in the mobile station 200, the packet generation unit 201 generates a packet of the data, and stores the packet in the packet buffer 202 until a transmission opportunity of the packet is given from the base station 100. Further, the packet generation unit 201 notifies the control unit 203 that a new packet has been generated.

  Upon receiving a new packet generation notification from the packet generation unit 201, the control unit 203 generates a transmission request for requesting the base station 100 for a transmission opportunity of the packet, and transmits the transmission request to the transmission request transmission unit 205. .

  Here, it is assumed that the transmission request generated by the control unit 203 includes at least information instructing a transmission opportunity request. However, the present invention is not limited to this, for example, the packet size of a packet to be transmitted, The packet generation unit 201 may include the residence time from when the packet is stored in the packet buffer 202 to the present time, all the packet sizes stored in the packet buffer 202, and the like. Further, the packet size and the residence time may be used as they are, or the residence time may be represented by this index using a table registered in advance in association with each index as an index. Furthermore, information such as an ID unique to the mobile station may be included. The control unit 203 may continuously notify the transmission request transmission unit 205 of transmission requests until receiving a packet transmission instruction from the transmission instruction reception unit 212. In addition, although it is assumed that arbitrary information can be used as the ID unique to the mobile station, for example, the manufacturing number or the MAC address of the mobile station 200 can be used.

  The transmission request transmission unit 205 transmits the transmission request received from the control unit 203 to the encoding / modulation unit 207 at a predetermined timing. Here, the timing at which the transmission request is transmitted to the encoding / modulation unit 207 can be set to an arbitrary value. For example, information indicating the timing is received from a control unit (not shown) of the base station 100. It is good also as a mode notified. In addition, a rule for determining the timing for each mobile station 200 may be provided in advance. In this case, a modulo between an ID unique to each mobile station and a specific natural number is taken, and the value is an offset value from the reference timing. Each mobile station may transmit a transmission request at a timing shifted by an offset value from the reference timing.

  The encoding / modulating unit 207 encodes / modulates the transmission request received from the transmission request transmitting unit 205 based on a predetermined encoding method and modulation method, and transmits the base station 100 via the radio signal transmitting unit 208. Send to.

  On the other hand, in base station 100, when radio signal receiving section 101 receives a signal transmitted from mobile station 200, demodulation / decoding section 102 demodulates and decodes this signal using a predetermined demodulation method and decoding method. The transmission request receiving unit 103 detects the presence / absence of a transmission request from the signal decoded by the demodulation / decoding unit 102 and transmits the result to the scheduler unit 108. Here, the transmission request receiving unit 103 measures the time when the transmission request is received, and estimates from which mobile station the transmission request is transmitted at the time. Further, when the transmission request includes information such as the packet size and the residence time, the transmission request receiving unit 103 also extracts the information, and includes the scheduler unit together with the presence / absence of the transmission request and information on the mobile station 200. To 108.

  The channel quality measurement unit 104, based on a predetermined known signal transmitted from each mobile station 200, based on the result (reception state) of receiving these known signals by the radio signal receiving unit 101, the channel quality measurement unit 104 The uplink channel quality is measured and notified to the scheduler unit 108. Thus, by measuring the channel quality for each frequency block that is a basic unit of scheduling, it becomes possible to grasp the channel quality in a detailed manner with respect to a specific mobile station 200.

  Each mobile station 200 transmits a known signal according to a predetermined rule. For example, a period for transmitting a known signal to each mobile station from a control unit of the base station 100 (not shown) and a frequency for transmitting the known signal may be notified. Alternatively, a known signal may be transmitted according to a rule determined in advance using an ID unique to each mobile station, in the same manner as when the mobile station 200 determines the timing for transmitting a transmission request. Thereby, the base station 100 can identify a signal received at a predetermined time and frequency as a signal transmitted from a specific mobile station 200.

  The scheduler unit 108 holds, for each mobile station 200, the transmission request received from the transmission request receiving unit 103, the channel quality received from the channel quality measurement unit 104, and a retransmission control signal (described later) received from the retransmission control unit 106. For the mobile station 200 that has made a transmission request, a transmission method such as a radio resource (frequency block), a modulation scheme, and a coding scheme when the mobile station 200 transmits a radio transfer block is determined. Specifically, the scheduler unit 108 refers to the channel quality of each mobile station 200 held in units of one or a plurality of frequency blocks, and allocates a frequency block having good channel quality for the mobile station 200 that has requested transmission. . Also, the modulation scheme and coding rate are determined so that the wireless transfer block transmitted by the mobile station satisfies the target error rate.

  Here, a value that is uniquely determined in advance (for example, an error rate of 10%) may be used as the target error rate, and if the base station 100 can recognize the packet type that the mobile station 200 intends to transmit. Different target error rates may be used depending on the packet type. For example, if the mobile station 200 can recognize whether a packet to be transmitted is a real-time service such as VoIP or streaming or a non-real-time service such as HTTP or FTP, the target error rate of the real-time packet is set to a non-real-time packet. Lower than the target error rate. Therefore, retransmission delay due to packet errors can be reduced, and high-quality services can be provided.

  Further, scheduler section 108 transmits a transmission instruction including a transmission method such as a frequency block, a modulation scheme, and a coding rate assigned to mobile station 200 to transmission instruction transmission section 110.

  The transmission instruction transmission unit 110 transmits the transmission instruction received from the scheduler unit 108 to the encoding / modulation unit 111 at a predetermined transmission timing. Here, it is assumed that an arbitrary value can be set as the timing at which the transmission instruction is transmitted. For example, in Evolved UTRA, a fixed period defined as TTI (Transmission Time Interval) is used. Also good. If Evolved UTRA is referred to, the transmission timing is 1 ms.

  The encoding / modulation unit 111 encodes / modulates a transmission instruction based on a predetermined encoding method and modulation method, and transmits the transmission instruction to the mobile station 200 via the radio signal transmission unit 112. When encoding the transmission instruction, the encoding / modulating unit 111 may multiply the CRC given to the transmission instruction by the ID unique to the mobile station to be transmitted, thereby transmitting the mobile station. 200 can be identified as a transmission instruction addressed to itself by multiplying the result of decoding the transmission instruction with its own ID. Further, as another method for identifying whether the mobile station 200 is transmitting to its own station, radio resources predetermined for each mobile station are defined in the same way as the transmission request and the known signal transmission method. A transmission instruction may be transmitted.

  On the other hand, when the mobile station 200 receives a transmission instruction transmitted from the base station 100 via the radio signal receiving unit 209 and the demodulation / decoding unit 210, the transmission instruction receiving unit 212 receives the transmission instruction from its own mobile station 200. It is determined whether or not it is sent to the destination. As described above, when the base station 100 multiplies the transmission instruction by the ID unique to the mobile station, the transmission instruction reception unit 212 determines the composite result (transmission instruction) in the demodulation / decoding unit 210 as follows: It is determined whether or not a transmission instruction addressed to the own station is made by multiplying the ID of the own mobile station 200. As another method, if the base station 100 transmits a transmission instruction using a predetermined radio resource, the transmission instruction receiving unit 212 transmits a transmission instruction addressed to itself from the reception result of the radio resource. It is determined whether or not. When the transmission instruction receiving unit 212 determines that the transmission instruction transmitted from the base station 100 is a transmission instruction addressed to its own mobile station 200, the transmission instruction receiving unit 212 transmits this transmission instruction to the control unit 203 and the signal determination unit 213.

  When receiving a transmission instruction corresponding to the transmission request transmitted to the base station 100 from the transmission instruction receiving unit 212, the control unit 203 uses information such as a frequency block, a modulation scheme, and a coding rate included in the transmission instruction. The transmittable wireless transfer block size is calculated and notified to the wireless transfer block generation unit 204.

  The wireless transfer block generation unit 204 calls a packet stored at the head of the packet buffer 202 and generates a wireless transfer block according to the wireless transfer block size notified from the control unit 203. Here, when the wireless transfer block size is smaller than the packet size, a part of the packet may be cut out by the wireless transfer block size. On the contrary, when the wireless transfer block size is larger than the packet size, a plurality of packets may be called and combined into one wireless transfer block. Further, the wireless transfer block generation unit 204 may add packet information staying in the packet buffer 202 as control information to the generated wireless transfer block, or may add other control information together.

  The retransmission control unit 206 transmits the radio transfer block generated by the radio transfer block generation unit 204 to the encoding / modulation unit 207. The retransmission control unit 206 holds the transmitted radio transfer block until the control unit 203 receives a retransmission control signal to be described later. When retransmission is requested from the control unit 203, the retransmission control unit 206 encodes the radio transfer block to be retransmitted. The data is transmitted to the conversion / modulation unit 207. The encoding / modulation unit 207 encodes / modulates the radio transfer block using the encoding method and modulation method according to the transmission instruction notified by the control unit 203, and transmits to the base station 100 via the radio signal transmission unit 208. Send.

  On the other hand, in the base station 100, the wireless transfer block receiving unit 105 extracts a wireless transfer block from the signals received via the wireless signal receiving unit 101 and the demodulation / decoding unit 102 and transmits them to the retransmission control unit 106. Note that the wireless transfer block receiving unit 105 knows in advance the transmission method (frequency block, modulation scheme, coding rate, etc.) included in the transmission instruction determined by the scheduler unit 108 for each mobile station 200. To do.

  The retransmission control unit 106 determines a CRC (Cyclic Redundancy Check) of the wireless transfer block received from the wireless transfer block reception unit 105, and transmits the wireless transfer block to the packet reproduction unit 107 if this CRC is normal. At the same time, ACK indicating successful reception is notified to the scheduler unit 108 as a retransmission control signal. On the other hand, if the retransmission control unit 106 determines that the CRC is abnormal, the retransmission control unit 106 does not transmit the wireless transfer block to the packet reproduction unit 107 and notifies the packet reproduction unit 107 and the scheduler unit 108 of NACK indicating reception failure as a retransmission control signal. .

  The packet reproducing unit 107 assembles a packet from the normally received wireless transfer block, and transfers the assembled packet to the network. Further, when the packet reproducing unit 107 determines that reception of the wireless transfer block has failed due to NACK notified from the retransmission control unit 106, the packet reproducing unit 107 holds the remaining packets until the wireless transfer block is retransmitted.

  The scheduler unit 108 stores the retransmission control signal received from the retransmission control unit 106 for each mobile station 200 in addition to the above-described channel quality and transmission request. Here, when the retransmission control signal is NACK, it is necessary to receive the corresponding wireless transfer block again. Therefore, the NACK is transmitted to the retransmission control signal transmission unit 109, and the above-mentioned is described with reference to the line quality. In this way, a transmission instruction including an appropriate frequency block, modulation scheme, and coding rate is transmitted to the transmission instruction transmission unit 110. As described in the background art, when there is no need to change the frequency used by the mobile station 200 for the initial transmission or the frequency used for the previous retransmission, the transmission instruction is transmitted to the transmission instruction transmission unit 110. Shall not.

  On the other hand, scheduler section 108 transmits ACK to retransmission control signal transmission section 109 when the retransmission control signal is ACK. Further, scheduler section 108 determines whether or not to continuously transmit a transmission instruction according to the buffer state of the mobile station. If there is a transmission request corresponding to the mobile station or if packet information related to the packet buffer 202 of the mobile station 200 is received, a transmission instruction for the mobile station 200 is generated, and a transmission request transmission unit 205 Send to. Conversely, if it is not necessary to transmit a transmission instruction to the mobile station 200, nothing is done.

  Here, the scheduler unit 108 may include information indicating the number of retransmissions in the transmission instruction, and the information may include information indicating initial transmission. For example, the information indicating the number of retransmissions may be expressed by 2 bits. In this case, “00” indicates the first transmission, “01” indicates the first retransmission, “10” indicates the second retransmission, and “11 "May indicate the third retransmission. Or it is good also as expressing whether it is initial transmission or retransmission by the information for 1 bit. The retransmission control signal and the transmission instruction are transmitted to the mobile station 200 via the encoder / modulator 111 and the radio signal transmitter 112.

  On the other hand, in the mobile station 200, when the retransmission control signal receiving unit 211 receives a signal from the base station 100 via the radio signal receiving unit 209 and the demodulation / decoding unit 210, the retransmission control signal is extracted from this signal, and signal determination is performed. To the unit 213. Here, in order for retransmission control signal receiving section 211 to extract a retransmission control signal, information (frequency unit, time) of radio resources used when transmitting this retransmission control signal is required. Therefore, for example, any one of radio resource information and a transmission method (frequency block, modulation scheme, coding rate) included in a transmission instruction notified by the base station 100 to the mobile station 200 to transmit a radio transfer block By defining a rule that has a one-to-one correspondence with the above information), it is possible to extract a retransmission control signal corresponding to the transmission method. In addition, although described as “frequency unit” as the information of the radio resource used for transmitting the retransmission control signal, this is defined as the basic unit of the radio resource used by the mobile station 200 to transmit the radio transfer block. It is defined as different from “frequency block”. That is, one frequency block and one frequency unit may have different bandwidths or different bands.

  When the signal determination unit 213 calculates the soft decision value of the retransmission control signal received from the retransmission control signal reception unit 211, the retransmission control signal indicates ACK by comparing the soft decision value with a predetermined threshold value. Or NACK is transmitted, and the determination result (ACK or NACK) is transmitted to the control unit 203. It is assumed that a known technique can be used as a method for calculating the soft decision value. Further, although there is no particular mention about how to determine a threshold value that is a criterion for determining ACK or NACK, for example, the channel quality is measured using a known signal transmitted from the base station 100, and the threshold value is uniquely determined from the channel quality. Also good.

  Here, the operation of the signal determination unit 213 will be described with reference to FIG. Note that the signal determination unit 213 has a first threshold value and a second threshold value for determining ACK or NACK from the soft decision value (denoted as P in FIG. 4) of the retransmission control signal received from the retransmission control signal reception unit 211. Are previously stored in a storage medium (not shown). Here, in FIG. 4, the first threshold value is indicated as Th1 and the second threshold value is indicated as Th2, and the first threshold value Th1 is greater than the second threshold value Th2 (Th1> Th2).

  When the signal determination unit 213 receives a transmission instruction addressed to its own mobile station 200 from the transmission instruction reception unit 212, the signal determination unit 213 compares the soft decision value P of the retransmission control signal with the first threshold Th1, and determines the soft decision of the retransmission control signal. When it is determined that the value P is equal to or greater than the first threshold Th1 (P ≧ Th1), the retransmission control signal is determined to be ACK. Conversely, when the signal determination unit 213 determines that the soft decision value P of the retransmission control signal is smaller than the first threshold Th1 (P <Th1), the signal determination unit 213 determines the retransmission control signal as NACK.

  On the other hand, if the signal determination unit 213 does not receive a transmission instruction addressed to its own mobile station 200 from the transmission instruction reception unit 212, the signal determination unit 213 compares the soft decision value P of the retransmission control signal with the second threshold Th2, and transmits the retransmission control signal. When it is determined that the soft decision value P is equal to or greater than the second threshold Th2 (P ≧ Th2), the retransmission control signal is determined to be ACK. Conversely, if the signal determination unit 213 determines that the soft decision value P of the retransmission control signal is smaller than the second threshold Th2 (P <Th2), the signal determination unit 213 determines that the retransmission control signal is NACK.

  As described above, the retransmission control signal can be accurately determined by comparing the threshold determined in advance according to the transmission instruction addressed to itself and the other mobile station 200 and the soft decision value P of the retransmission control signal. This makes it possible to reduce the probability of erroneous determination of retransmission control signals.

  Note that the method of determining the threshold value between the first threshold value Th1 and the second threshold value Th2 is not particularly limited. For example, the first threshold value Th1 is a value that NACK is set as ACK with respect to the probability that ACK is mistaken as NACK. What is necessary is just to set to the value which can reduce the probability of misidentification about 10%. Conversely, the second threshold value Th2 may be set to a value that can reduce the probability of misidentifying ACK as NACK by about 10% with respect to the probability of misidentifying NACK as ACK. Here, “10%” is merely an example, and other values may be used. For example, a method may be used in which the threshold is updated as needed using the throughput as a cost function.

  The control unit 203 performs the following four types of operations according to the determination result (ACK or NACK) received from the signal determination unit 213 and the content of the transmission instruction received from the transmission instruction reception unit 212.

  When the control unit 203 receives an ACK from the signal determination unit 213 and does not receive a transmission instruction from the transmission instruction reception unit 212, the control unit 203 determines that a transmission opportunity has not been given and does nothing. In addition, when a packet stays in the packet buffer 202, a transmission request may be transmitted as necessary.

  In addition, when the control unit 203 receives an ACK from the signal determination unit 213 and receives a transmission instruction from the transmission instruction reception unit 212, the control unit 203 newly calls a packet from the packet buffer 202 and transmits a wireless transfer block.

  Further, when receiving a NACK from the signal determining unit 213 and not receiving a transmission instruction from the transmission instruction receiving unit 212, the control unit 203 determines Non-adaptive HARQ and uses it for the previous transmission. The wireless transfer block is retransmitted in the same manner as the transmission instruction.

  Further, when receiving a NACK from the signal determining unit 213 and receiving a transmission instruction from the transmission instruction receiving unit 212, the control unit 203 determines that the HARQ is Adaptive HARQ and retransmits the radio transfer block according to the transmission instruction.

  As described above, when the transmission instruction includes information indicating initial transmission and retransmission, a new wireless transfer block has been transmitted or transmitted according to the transmission instruction regardless of the determination result of the retransmission control signal. The wireless transfer block may be retransmitted.

  As described above, according to the present embodiment, it is a case where the mobile station 200 erroneously determines ACK as NACK even though the base station 100 notifies only ACK and does not notify the transmission instruction. However, the mobile station 200 can reduce the probability that another mobile station 200 interferes with the wireless transfer block transmitted to the base station 100 by retransmitting the wireless transfer block by non-adaptive HARQ. As a result, it is possible to reduce the frequency of occurrence of retransmissions, thereby increasing the throughput.

  Further, according to the present embodiment, since the probability that mobile station 200 erroneously determines ACK as NACK can be reduced, it is possible to reduce the probability that unnecessary retransmission occurs, and the power consumption of mobile station 200 Can be saved.

  If this embodiment is applied to Evolved UTRA, in addition to NACK determined by the conventional retransmission control signal determination method, mobile station 200 erroneously determines ACK as described in this embodiment as NACK. The NACK determined by the retransmission control signal determination method having a low probability of being performed may be defined as a reliable NACK (Reliable NACK). This makes it possible to perform more flexible control by properly using the conventional NACK and the highly reliable NACK.

Embodiment 2. FIG.
In Embodiment 1 described above, the first threshold Th1 and the second threshold Th2 are used, and the probability that ACK is erroneously determined as NACK is determined depending on whether or not the transmission instruction is directed to the mobile station 200 itself. The configuration to be reduced has been described. In the present embodiment, another configuration different from that in Embodiment 1 that can reduce the probability that a mobile station erroneously determines ACK or NACK will be described.

  FIG. 5 is a block diagram showing a configuration related to uplink communication of mobile station 300 according to the present embodiment. As illustrated in FIG. 5, the mobile station 300 has a configuration in which the signal determination unit 213 and the control unit 203 are replaced with the signal determination unit 301 and the control unit 302 among the functional units of the mobile station 200 described above. Yes.

  FIG. 6 is a block diagram showing a configuration related to uplink communication of the base station 400 according to the present embodiment. As illustrated in FIG. 6, the base station 400 has a configuration in which the scheduler unit 108 is replaced with the scheduler unit 401 among the functional units of the base station 100 described above. The relationship between base station 400 and mobile station 300 is the same as that shown in FIG. Hereinafter, the signal determination unit 301, the control unit 304, and the scheduler unit 401 will be described with reference to FIGS.

  In mobile station 300, signal determination section 301 has the same function as signal determination section 213, and generates a soft decision value for the retransmission control signal received from retransmission control signal reception section 211, and determines this soft decision value in advance. By comparing the first threshold Th3 and the second threshold Th4, it is determined whether the retransmission control signal indicates ACK or NACK.

  In addition, the signal determination unit 301 classifies the retransmission control signal into three states of “ACK”, “NACK”, and “undecided” based on the magnitude relationship of the first threshold Th3 and the second threshold Th4 with respect to the soft decision value. The determination result is transmitted to the control unit 302.

  Control unit 302 has the same function as control unit 203 and, based on the determination result of the retransmission control signal received from signal determination unit 301, when this determination result is ACK or NACK, is the same as in the first embodiment. Perform the process. In addition, when the determination result of the retransmission control signal is not determined, the control unit 302 requests the retransmission control signal to be retransmitted via the encoding / modulation unit 207 and the wireless signal transmission unit 208 (retransmission control signal retransmission request). ) To the base station 400.

  In base station 400, scheduler section 401 has the same function as scheduler section 108, and upon receiving a retransmission control signal retransmission request for requesting retransmission of a retransmission control signal from mobile station 300, for mobile station 300, Retransmit the retransmission control signal.

  Hereinafter, operations of the signal determination unit 301 and the control unit 302 will be described. When receiving the retransmission control signal from the retransmission control signal receiving unit 211, the signal determination unit 301 compares the soft decision value of the retransmission control signal with the first threshold Th3 and the second threshold Th4, respectively. The definitions of the threshold values Th3 and Th4 are the same as the threshold values Th1 and Th2 described in the first embodiment.

  When determining that the soft decision value is larger than the first threshold Th3 (soft decision value> Th3), the signal determination unit 301 determines that the retransmission control signal is ACK. In addition, when the signal determination unit 301 determines that the soft decision value is smaller than the second threshold Th4 (soft decision value <Th4), the signal determination unit 301 determines the retransmission control signal as NACK. Further, when the signal determination unit 301 determines that the soft decision value is equal to or less than the first threshold Th3 and equal to or greater than the second threshold Th4 (Th4 ≦ soft decision value ≦ Th3), the signal determination unit 301 determines that the retransmission control signal is not yet determined. To do. That is, the signal determination unit 301 sets the soft decision value of the retransmission control signal to “ACK”, “NACK”, “undecided” based on the magnitude relationship between the first threshold value Th3 and the second threshold value Th4 with respect to the soft decision value. The control unit 302 is notified of the determination result.

  Based on the determination result of the retransmission control signal notified from signal determination section 301, control section 302 performs the same processing as in Embodiment 1 when this determination result is ACK or NACK. In addition, when the determination result of the retransmission control signal notified from the signal determination unit 301 is not determined, the control unit 302 requests retransmission of the retransmission control signal through the encoding / modulation unit 207 and the radio signal transmission unit 208. A signal to be transmitted (retransmission control signal retransmission request) is transmitted to base station 400.

  Here, the retransmission control signal retransmission request may use a transmission request. For example, information indicating a normal transmission request may be distinguished from information indicating a retransmission control signal retransmission request using 1-bit information. . As another method, one state of channel quality information transmitted from a channel quality information transmitting unit that notifies a downlink channel quality (not shown) to the base station 400 may be used, and the channel quality information is 5 bits. If represented, “11111” may represent a retransmission control signal retransmission request. The number of bits and “11111” described above are examples, and the present invention is not limited to these.

  On the other hand, in base station 400, when scheduler section 401 receives a retransmission control signal retransmission request from mobile station 300, it retransmits a retransmission control signal to mobile station 300. Here, as in the first embodiment, a transmission instruction may be transmitted in addition to the retransmission control signal.

  As described above, according to the present embodiment, signal determination section 301 of mobile station 300 determines the retransmission control signal as one of three states of “ACK”, “NACK”, and “undecided”. When the retransmission control signal has not been determined, the control unit 302 requests the base station 400 to retransmit the retransmission control signal, thereby acquiring the retransmission control signal again.

  As a result, it is possible to reduce the erroneous determination probability of the retransmission control signal received by the mobile station 300, so that an unsteady operation such that the wireless transfer block is retransmitted wastefully or the wireless transfer block is not retransmitted. Can be prevented.

Embodiment 3 FIG.
In the first and second embodiments described above, the configuration for solving the problem caused when the mobile station erroneously determines ACK as NACK has been described. In the present embodiment, a configuration that can solve a problem that occurs when a mobile station fails to receive a transmission instruction even though the base station transmits a transmission instruction will be described.

  FIG. 7 is a diagram for explaining a problem to be solved by the present embodiment. Here, FIG. 7 shows a communication state with mobile station A and mobile station B with respect to the base station in the conventional mobile communication system shown in FIG.

  First, the base station notifies the mobile station A of a first transmission instruction including frequency block information (RB1, RB2) (see (1) in the figure). In accordance with the first transmission instruction notified from the base station, the mobile station A transmits (initial transmission) a wireless transfer block using RB1 and RB2 (see (2) in the figure). The base station decodes the radio transfer block received from the mobile station A, and notifies the mobile station A of ACK if the CRC is normal, and notifies the mobile station A of NACK if the CRC is abnormal. FIG. 7 shows a case where the base station determines that the CRC is abnormal and notifies NACK to mobile station A (see (3) in the figure).

  In addition, the base station measures the uplink channel quality between the mobile station A and the base station, and the channel quality of the frequency blocks (RB1, RB2) that have received the radio transfer block deteriorates due to the influence of frequency selective fading. If it is determined, the mobile station A is notified of the second transmission instruction so as to retransmit the wireless transfer block using a frequency block different from the frequency blocks (RB1, RB2). FIG. 7 shows a case where frequency block information (RB3, RB4) is notified as the second transmission instruction (see (4) in the figure). In addition, the base station notifies the mobile station B of the first transmission instruction including the frequency block information (RB1, RB2) at the same time as the notification of the second transmission instruction to the mobile station A (in the figure). (See (5)).

  On the other hand, the mobile station A decodes the retransmission control signal transmitted from the base station and determines whether it is ACK or NACK. In addition, the mobile station A extracts the second transmission instruction addressed to the mobile station A transmitted from the base station. Here, when the mobile station A cannot extract the second transmission instruction addressed to its own mobile station A even though the mobile station A determines that the retransmission control signal is NACK, the mobile station A determines RB1 and non-adaptive HARQ. The wireless transfer block is retransmitted using RB2 (see (6) in the figure).

  In addition, the mobile station B transmits a wireless transfer block using RB1 and RB2 in accordance with the first transmission instruction notified from the base station (see (7) in the figure). At this time, if the base station receives radio transfer blocks from the mobile stations A and B at the same time, the base station receives radio transmissions from the plurality of mobile stations A and B at the same time and the same frequency block (RB1, RB2). Since the transfer block is received, the transmission symbol of the mobile station A interferes with the transmission symbol of the mobile station B. This causes a first problem that the wireless transfer block of the mobile station B that should be received cannot be normally decoded.

  Further, the first problem causes the second problem described below. Since the base station notifies the mobile station A of the second transmission instruction including the frequency block (RB3, RB4), wireless transfer transmitted from the mobile station A using the frequency block (RB3, RB4). Decrypt the block. However, since the mobile station A transmits the radio transfer block using the frequency blocks (RB1, RB2), the base station cannot decode the radio transfer block transmitted from the mobile station A. Therefore, the base station notifies NACK to the mobile station A again (see (8) in the figure).

  Further, since the base station notifies the mobile station B of the first transmission instruction including the frequency blocks (RB1, RB2), it is transmitted from the mobile station A using the frequency blocks (RB1, RB2). However, as described above, since the transmission symbol of mobile station A interferes with the transmission symbol of mobile station B, the base station decodes the wireless transfer block transmitted from mobile station B. I can't. Therefore, the base station notifies the mobile station B of the NACK at the same time as the notification of the NACK to the mobile station A (see (9) in the figure). Note that, as described in the background art, the base station can select whether to notify the mobile station of only NACK or to notify the mobile station together with the transmission instruction. In the example of FIG. This shows the case of notification.

  Since each mobile station extracts the retransmission control signal transmitted by the base station, information on the radio resources (frequency unit, time) used for transmitting the retransmission control signal is required. Here, since each mobile station transmits a wireless transfer block corresponding to the retransmission control signal, any one of information (frequency block, modulation scheme, coding rate) included in the transmission instruction notified from the base station As described above, a rule that associates the above information) with the information (frequency unit, time) of the radio resource used to transmit the retransmission control signal is defined in advance. In this case, the base station transmits a NACK for the radio transfer block (retransmission) received from the mobile station A using radio resources corresponding to the second transmission instruction (RB3, RB4) notified to the mobile station A. To do. On the other hand, NACK for the wireless transfer block (initial transmission) received from mobile station B is transmitted using the radio resource corresponding to the first transmission instruction (RB1, RB2) notified to mobile station B.

  Since the mobile station B has normally received the first transmission instruction, the mobile station B receives and decodes the retransmission control signal using the radio resource corresponding to the first transmission instruction. On the other hand, since the mobile station A has not received the second transmission instruction normally, it receives and decodes the retransmission control signal using the radio resource corresponding to the first transmission instruction. In other words, the retransmission control signal transmitted from the base station to the mobile station A cannot be normally received, but the retransmission control signal transmitted from the base station to the mobile station B is erroneously received and decoded. As a result, as shown in FIG. 7, mobile station A and mobile station B use the same frequency block (RB1, RB2) again and transmit the radio transfer block to the base station at the same timing. (Refer to (10) and (11) in the figure) A second problem occurs in which the transmission symbol of mobile station A interferes with the transmission symbol of mobile station B. This problem occurs continuously unless the base station notifies the mobile station A of a transmission instruction again.

  Therefore, the present embodiment aims to solve the second problem described above. Note that this embodiment is not limited to the communication state and configuration shown in FIG. 7 but can be applied to communication states and configurations other than those shown in FIG.

  FIG. 8 is a block diagram showing a configuration related to uplink communication of the base station 500 according to the present embodiment. As illustrated in FIG. 8, the base station 500 has a configuration in which the retransmission control unit 106 and the scheduler unit 108 are replaced with the retransmission control unit 501 and the scheduler unit 502 among the functional units of the base station 100 described above. Yes. The relationship between base station 500 and mobile station 200 is the same as that shown in FIG. The configuration of the mobile station 200 is the same as the configuration of FIG.

  The retransmission control unit 501 has the same function as the retransmission control unit 106, and whether or not radio transfer blocks transmitted from each mobile station 200 collide, that is, radio transfer blocks transmitted from a plurality of mobile stations 200. Is determined to be in the interference state, and the determination result is notified to the scheduler unit 502 as the reception state of the wireless transfer block.

  The scheduler unit 502 has the same function as the scheduler unit 108 and transmits a transmission instruction to the mobile station 200 according to the reception state of the radio transfer block notified from the retransmission control unit 501.

  Hereinafter, the operations of base station 500 and mobile station 200 according to the present embodiment will be described using FIG. 8 and FIG. 3. First, when data to be transmitted is generated in the mobile station 200, the packet generation unit 201 generates a packet and stores it in the packet buffer 202 until a transmission opportunity of the packet is given. Further, the packet generation unit 201 notifies the control unit 203 that a new packet has been generated.

  When receiving a new packet generation notification from the packet generation unit 201, the control unit 203 generates a transmission request for requesting the base station 500 to transmit the packet, and transmits the transmission request to the transmission request transmission unit 205. Send to.

  The transmission request transmission unit 205 transmits the transmission request received from the control unit 203 to the encoding / modulation unit 207 at a predetermined timing. Encoding / modulating section 207 encodes and modulates a transmission request based on a predetermined encoding method and modulation method, and transmits the request to base station 500 via radio signal transmitting section 208.

  On the other hand, in base station 500, when radio signal receiving section 101 receives a signal transmitted from mobile station 200, demodulation / decoding section 102 demodulates and decodes this signal using a predetermined demodulation method and decoding method. . Subsequently, the transmission request receiving unit 103 detects the presence / absence of a transmission request from the signal decoded by the demodulation / decoding unit 102 and transmits the result to the scheduler unit 502. Further, when information such as a packet size and a residence time is added to the transmission request, the information is also extracted and transmitted to the scheduler unit 502 together with the presence / absence of the transmission request and the mobile station information.

  The channel quality measuring unit 104 measures the uplink channel quality from the mobile station 200 to the base station 500 using the result of receiving the known signal transmitted from each mobile station by the radio signal receiving unit 101, The measurement result is notified to the scheduler unit 502.

  The scheduler unit 502 holds, for each mobile station, the transmission request received from the transmission request receiving unit 103, the channel quality received from the channel quality measurement unit 104, and the retransmission control signal received from the retransmission control unit 501, for each mobile station. A radio resource and a transmission method for transmitting a radio transfer block to a certain mobile station are determined.

  The scheduler unit 502 transmits a transmission instruction including information such as the frequency block, modulation scheme, and coding rate assigned to the mobile station 200 to the transmission instruction transmission unit 110. The transmission instruction transmission unit 110 transmits the transmission instruction received from the scheduler unit 502 to the encoding / modulation unit 111 at a predetermined transmission timing. Subsequently, the encoding / modulation unit 111 encodes / modulates a transmission request based on a predetermined encoding method and modulation method, and transmits the request to the mobile station 200 via the radio signal transmission unit 112.

  On the other hand, in the mobile station 200, when the transmission instruction receiving unit 212 receives the transmission instruction transmitted from the base station 500 via the radio signal receiving unit 209 and the demodulation / decoding unit 210, the transmission instruction addressed to its own mobile station 200. It is determined whether or not. Here, when the transmission instruction receiving unit 212 determines that the transmission signal is a transmission instruction addressed to its own mobile station 200, the transmission instruction receiving unit 212 transmits this transmission instruction to the control unit 203 and the signal determination unit 213.

  When the control unit 203 receives a transmission instruction corresponding to the transmission request transmitted to the base station 500 from the transmission instruction receiving unit 212, the control unit 203 can transmit from information such as a frequency block, a modulation scheme, and a coding rate included in the transmission instruction. The wireless transfer block size is calculated and notified to the wireless transfer block generation unit 204. The wireless transfer block generation unit 204 calls a packet stored at the head of the packet buffer 202 and generates a wireless transfer block according to the wireless transfer block size notified from the control unit 203.

  The retransmission control unit 206 transmits the wireless transfer block to the encoding / modulation unit 207. The retransmission control unit 206 holds the wireless transfer block until the control unit 203 receives a retransmission control signal. When retransmission is requested from the control unit 203, the retransmission control unit 206 sends the retransmission target wireless transfer block to the encoding / modulation unit 207. Send. The encoding / modulation unit 207 performs encoding / modulation using the encoding method and modulation method according to the transmission instruction notified by the control unit 203, and transmits the result to the base station 100 via the radio signal transmission unit 208.

  On the other hand, in base station 500, radio transfer block receiving section 105 extracts radio transfer blocks from signals received via radio signal receiving section 101 and demodulation / decoding section 102, and transmits them to retransmission control section 501.

  Subsequently, the retransmission control unit 501 determines the CRC of the wireless transfer block received from the wireless transfer block receiving unit 105. If this CRC is normal, the retransmission control unit 501 transmits the wireless transfer block to the packet reproducing unit 107 and receives it to the scheduler unit 108. An ACK indicating success is notified as a retransmission control signal. On the other hand, if the retransmission control unit 106 determines that the CRC is abnormal, the retransmission control unit 106 does not transmit the wireless transfer block to the packet reproduction unit 107 and notifies the packet reproduction unit 107 and the scheduler unit 108 of NACK indicating reception failure as a retransmission control signal. .

  In addition, the retransmission control unit 501 transmits the first wireless transfer block received from the wireless transfer block receiving unit 105 from the valid mobile station 200 or the other wireless station 200 receives the first wireless transfer block. It is estimated whether or not there is a collision with the transmitted second wireless transfer block, and notifies the scheduler unit 502 of the reception state of the wireless transfer block.

  Here, the retransmission control unit 501 receives, as the reception state of the wireless transfer block, “not received” indicating that the wireless transfer block could not be received, and “collision” indicating that the wireless transfer block is in an interference state, Information that can be identified as “normal” indicating that the wireless transfer block has been successfully received is notified to the scheduler unit 502. In addition, as a method for the retransmission control unit 501 to estimate the reception state of the wireless transfer block, for example, a method of measuring received power in a frequency block that has received the wireless transfer block can be cited.

  Here, the method for measuring the received power described above will be described with reference to the example of FIG. When the base station 500 notifies the mobile station 200 (mobile station A) of the transmission instruction at the timing (4), the base station 500 converts the received power of the frequency blocks (RB3, RB4) included in the transmission instruction at the timing (6). Will be measured. At this time, if the received power for the frequency block (RB3, RB4) is below a predetermined threshold, the mobile station 200 (mobile station A) is transmitting the radio transfer block using the frequency block (RB3, RB4). It can be estimated that there is not.

  In addition to the above method, it is possible to estimate whether or not the wireless transfer blocks collide by performing a CRC check on the wireless transfer blocks. Specifically, when the base station 500 notifies the mobile station 200 (mobile station B) of a transmission instruction at the timing (5) shown in FIG. 7, reception of the frequency blocks (RB1, RB2) included in the transmission instruction is received. The power is measured at the timing (7). At this time, the CRC is abnormal as a result of decoding the wireless transfer block received from the mobile station 200 (mobile station B) at approximately the same time, even though the received power for the frequency blocks (RB1, RB2) is equal to or greater than the threshold. If so, it is estimated that the radio transfer block transmitted by the other mobile station 200 (mobile station A) interferes with the radio transfer block transmitted by the mobile station B (the radio transfer block collides). To do.

  In addition, if the reception power is equal to or greater than the threshold and the CRC is determined to be normal as a result of decoding the wireless transfer block by the above two steps, it can be estimated that the wireless transfer block has been received normally. . The means for estimating the reception state of the wireless transfer block is not limited to the method of measuring the reception power as described above, and other methods may be used.

  As described above, when the mobile station 200 erroneously determines the transmission instruction and retransmission control signal transmitted from the base station 500 to the mobile station 200 by determining the reception state of the radio transfer block transmitted from the mobile station 200. However, an erroneous determination can be detected early on the base station 500 side.

  The packet reproducing unit 107 assembles a packet from the normally received wireless transfer block, and transfers the assembled packet to the network. Further, when the packet reproducing unit 107 determines that reception of the wireless transfer block has failed due to NACK notified from the retransmission control unit 106, the packet reproducing unit 107 holds the remaining packets until the wireless transfer block is retransmitted.

  The scheduler unit 502 stores the retransmission control signal received from the retransmission control unit 106 and the radio transfer block reception status for each mobile station 200 in addition to the above-described channel quality and transmission request. Here, when the retransmission control signal is NACK, it is necessary to receive the corresponding wireless transfer block again, and therefore NACK is transmitted to retransmission control signal transmission section 109. On the other hand, when the retransmission control signal is ACK, ACK is transmitted to retransmission control signal transmission section 109.

  Furthermore, when the reception state of the wireless transfer block indicates “collision” or “not received”, the scheduler unit 502 transmits a transmission instruction again to the mobile station 200 that should transmit a NACK. Here, the frequency block instructed by the transmission instruction may be different from or the same as the frequency block used for the initial transmission or the frequency block used for the previous retransmission.

  In addition, when the wireless transfer block reception state indicates “normal”, the scheduler unit 502 gives a transmission instruction including an appropriate frequency block, modulation scheme, and coding rate as described above with reference to the line quality. Transmit to the transmission instruction transmission unit 110. However, as described in the background art, when there is no need to change the frequency block, the transmission instruction is not transmitted to the transmission instruction transmission unit 110.

  Also, scheduler section 502 determines whether or not to continuously transmit a transmission instruction according to the buffer state of mobile station 200. Here, the scheduler unit 502 generates a transmission instruction for the mobile station 200 when there is a transmission request corresponding to the mobile station 200 or when packet information related to the packet buffer 202 of the mobile station 200 is received. To the transmission instruction transmission unit 110. Conversely, the scheduler unit 502 does nothing if it is not necessary to transmit a transmission instruction to the mobile station 200. The retransmission control signal and the transmission instruction are transmitted to the mobile station 200 via the encoder / modulator 111 and the radio signal transmitter 112.

  On the other hand, in the mobile station 200, when the retransmission control signal receiving unit 211 receives a signal from the base station 500 via the radio signal receiving unit 209 and the demodulation / decoding unit 210, the retransmission control signal is extracted from this signal and signal determination is performed. To the unit 213.

  When the signal determination unit 213 generates a soft decision value of the retransmission control signal received from the retransmission control signal reception unit 211, the retransmission control signal indicates ACK by comparing the soft decision value with a predetermined threshold value. Or NACK is transmitted, and the determination result (ACK or NACK) is transmitted to the control unit 203. In the present embodiment, as in the first embodiment described above, the first threshold value and the second threshold value are provided in advance depending on whether there is a transmission instruction addressed to the mobile station 200 itself. However, the present invention is not limited to this mode. For example, it may be determined as ACK or NACK based on one threshold value.

  The control unit 203 performs the same operation as that of the above-described first embodiment according to the determination result (ACK or NACK) received from the signal determination unit 213 and the content of the transmission instruction received from the transmission instruction reception unit 212. . As described above, when the transmission instruction includes information indicating initial transmission and retransmission, the wireless transfer block may be newly transmitted or retransmitted according to the transmission instruction regardless of the determination result of the retransmission control signal. Good.

  As described above, according to the present embodiment, retransmission control section 501 of base station 500 determines the radio transfer block reception status, and the radio transfer block reception status indicates “not received” or “collision”. Regardless of whether or not to change the transmission instruction transmitted in the past, the scheduler unit 502 always notifies the mobile station 200 of the transmission instruction together with NACK. In addition, when the wireless transfer block reception state indicates “normal”, the scheduler unit 502 notifies the mobile station 200 of the transmission instruction together with NACK only when the transmission instruction transmitted in the past is changed, and transmitted in the past. When there is no need to change the transmission instruction, only NACK is notified to the mobile station 200.

  As a result, even when the base station 500 notifies the mobile station 200 of the NACK and the transmission instruction, even if the mobile station 200 cannot receive the transmission instruction, the mobile station 200 receives a non- By retransmitting the radio transfer block by adaptive HARQ, it is possible to reduce the probability of causing interference to the radio transfer block of another mobile station 200 received at the base station 500, and as a result, the frequency of retransmission can be reduced. Throughput can be increased.

  When the reception state of the wireless transfer block determined by the retransmission control unit 501 is “not received” or “collision”, the scheduler unit 502 notifies the mobile station 200 of a transmission instruction. Further, when the reception state is “normal”, and when it is necessary to change the content of the transmission instruction transmitted in the past, the mobile station 200 is notified of the transmission instruction, and the transmission transmitted in the past is transmitted. When there is no need to change the content of the instruction, the mobile station 200 is notified of the transmission instruction. As a result, the amount of downlink control information can be reduced as compared with the case where a transmission instruction is always notified.

  In the present embodiment, the index indicating whether or not to transmit a transmission instruction is changed according to the wireless transfer block reception state, but this is not restrictive. For example, as another method, when it is necessary to change the content of the transmission instruction transmitted from the base station 500 to the mobile station 200 in the past, the transmission instruction may be notified after that. Referring to FIG. 7, since the content of the transmission instruction is changed in (4), the transmission instruction is always sent from the base station 500 to the mobile station 200 regardless of the wireless transfer block reception state after (8). Can be notified.

Embodiment 4 FIG.
In this embodiment, a method for applying the method described in Embodiment 3 to Evolved UTRA will be described.

  FIG. 9 is a block diagram showing a configuration related to uplink communication of base station 600 according to the present embodiment. As illustrated in FIG. 9, the base station 600 has a configuration in which the scheduler unit 502 is replaced with the scheduler unit 601 among the functional units of the base station 500 described above. The relationship between the base station 600 and the mobile station 200 is the same as that shown in FIG. The configuration of the mobile station 200 is the same as the configuration of FIG.

  The scheduler unit 601 has the same function as the scheduler unit 502, and the channel quality received from the channel quality measuring unit 104, the retransmission control signal received from the retransmission control unit 106, and the transmission request received from the transmission request receiving unit 103 In response to this, a first transmission instruction or a second transmission instruction in which a specific component is removed from the first transmission instruction is generated and transmitted to the transmission instruction transmission unit 110 as a transmission instruction.

  Specifically, the scheduler unit 601 holds information indicating whether or not a transmission instruction is generated (transmitted) for each mobile station 200 and manages whether or not the transmission instruction is transmitted to each mobile station 200. When the scheduler unit 601 newly transmits a transmission instruction to the mobile station 200, the scheduler unit 601 generates a first transmission instruction and transmits the first transmission instruction to the transmission instruction transmission unit 110 as a transmission instruction.

  In addition, when the scheduler unit 601 has already transmitted a transmission instruction to the mobile station 200, the setting of a specific component among the components configuring the transmission instruction transmitted in the past may be changed. Then, a second transmission instruction instructing to change the setting of these specific components is generated and transmitted to the transmission instruction transmitting unit 110 as a transmission instruction. As in the second embodiment, when there is no need to change the contents of the transmission instruction transmitted in the past, only the retransmission control signal is transmitted, and both the first transmission instruction and the second transmission instruction are transmitted. It is not necessary to transmit.

  Hereinafter, specific examples of the first transmission instruction and the second transmission instruction will be described with reference to FIGS. Here, in a storage medium (not shown) provided in base station 600, there are a first transmission instruction and a second transmission instruction excluding static components that are fixed values from the first transmission instruction. Pre-stored.

  FIG. 10 is a diagram illustrating a storage destination table that defines the storage destinations of the first transmission instruction and the second transmission instruction. As shown in the figure, in the storage destination table, a “category” indicating the type of transmission instruction and a “parameter” indicating the storage destination of the transmission instruction corresponding to the category are registered in association with each other. It is assumed that the storage destination table is stored in advance in a storage medium (not shown) provided in the base station 600.

  As shown in FIG. 10, when there are two types of categories, two types of categories can be represented if there is 1-bit information. Further, the category type is not limited to the example of FIG. 10, and may be 3 or more. In this case, the information indicating the category may be 1 bit or more.

  FIG. 11 is a diagram showing components included in the first transmission instruction. Here, each component shown in the figure corresponds to each component defined in 3GPP R1-073870. Note that each component of the first transmission instruction is stored in the storage location indicated by the parameter associated with category 1 in the storage location table.

  When the scheduler unit 601 does not transmit a transmission instruction to the mobile station 200 and newly transmits a transmission instruction, the scheduler unit 601 stores the storage destination indicated by the parameter associated with the category 1 of the storage destination table, that is, FIG. The first transmission instruction is generated based on each component of the first transmission instruction shown in FIG. Note that FIG. 11 is an example, and not all the components shown in FIG. 11 are necessary. Moreover, it is good also as adding a new element with respect to the component of FIG.

  FIG. 12 is a diagram showing components included in the second transmission instruction. As shown in the figure, the components included in the second transmission instruction are “Transport format”, “TPC”, “Cyclic shift for DMRS”, “UL index” from the first transmission instruction shown in FIG. (TDD), “Frequency hopping information”, “Duration” and “Tx antenna selection” elements are excluded. Note that each component of the second transmission instruction is stored in the storage destination indicated by the parameter associated with category 2 in the storage destination table.

  When the scheduler unit 601 has already transmitted a transmission instruction to the mobile station 200 and the setting of a specific component among the components configuring the transmission instruction transmitted in the past may be changed, The storage destination indicated by the parameter associated with category 2 of the storage destination table, that is, each component of the second transmission instruction shown in FIG. 12 is referred to, and a second transmission instruction is generated based on each component To do.

  Note that the components shown in FIG. 12 are examples, and new elements may be added. However, the number of components included in the second transmission instruction is less than the number of components included in the first transmission instruction.

  As described above, according to the present embodiment, the first transmission instruction and the first transmission instruction are specified according to the presence / absence of the transmission instruction to mobile station 200 and the change contents of the transmission instruction. The transmission is switched to the second transmission instruction from which the component is removed. As a result, the base station 600 can reduce the frequency of transmitting a transmission instruction including unnecessary components, and thus can reduce the amount of downlink control information.

  In the present embodiment, the second transmission instruction component is held in a predefined state. However, the present invention is not limited to this, and the second transmission instruction is dynamically changed from the component included in the first transmission instruction. It is good also as an aspect which produces | generates a transmission signal.

Embodiment 5 FIG.
In the first embodiment, the configuration for solving the problem caused when the mobile station 200 erroneously determines ACK as NACK has been described. In the present embodiment, a configuration for solving a problem caused when mobile station 200 erroneously determines NACK as ACK will be described.

  First, the problem targeted by the present embodiment will be described with reference to FIG. FIG. 13 is a diagram for explaining a problem to be solved by the present embodiment. Here, FIG. 13 shows a communication state between the base station and mobile station A in the conventional mobile communication system shown in FIG.

  First, the base station notifies the mobile station A of a transmission instruction including frequency block information (RB1, RB2) (see (1) in the figure). In accordance with the transmission instruction notified from the base station, the mobile station A transmits (initially transmits) the wireless transfer block using RB1 and RB2 (see (2) in the figure). Subsequently, the base station decodes the radio transfer block received from mobile station A, and notifies ACK to mobile station A if the CRC is normal, and notifies NACK to mobile station A if the CRC is abnormal. To do. FIG. 13 shows the communication state when the CRC is determined to be abnormal, and the base station notifies the mobile station of NACK (see (3) in the figure). At this time, the base station measures the uplink channel quality from the mobile station A, and determines that the channel quality has not changed significantly from the time when the transmission instruction was transmitted in the past. The transmission instruction is not notified.

  On the other hand, when the retransmission control signal transmitted from the base station is decoded, the mobile station A determines whether this retransmission control signal is ACK or NACK. In addition, the mobile station A extracts a transmission instruction addressed to its own mobile station transmitted from the base station. Here, when the base station notifies NACK, but mobile station A erroneously determines the retransmission control signal as ACK, and further fails to extract a transmission instruction addressed to its own mobile station, mobile station A Therefore, the wireless transfer block is not retransmitted to the base station (see (4) in the figure). As a result, the first problem that the base station cannot receive the radio transfer block to be retransmitted from the mobile station A occurs.

  The first problem described above causes the following second problem. Since the base station could not receive the wireless transfer block from the mobile station A, the base station transmits a NACK instructing the mobile station A to perform retransmission again in the retransmission control signal (see (5) in the figure). Here, the base station can select the case of transmitting a transmission instruction together with NACK to the mobile station A and the case of transmitting only NACK, but if the channel quality does not vary greatly, Since there is no need to change the content of the instruction, it is possible to transmit only NACK.

  In the case of FIG. 13, in the case where re-transmission is instructed, no transmission instruction is transmitted, and only NACK is transmitted. In this case, since the mobile station A has not retransmitted the wireless transfer block in (4), the mobile station A does not attempt to receive a retransmission control signal corresponding to the wireless transfer block. Therefore, since the mobile station A does not retransmit the wireless transfer block (see (6) in the figure), a second problem occurs that the base station cannot receive the wireless transfer block. This problem occurs continuously unless the base station notifies the mobile station 200 of a transmission instruction again. As a result, since the base station cannot receive the wireless transfer block to be received from the mobile station A, data dropout occurs and the packet cannot be transferred to the upper level. Therefore, the throughput is reduced.

  Therefore, the present embodiment aims to solve the first and second problems. The present embodiment is not limited to the communication state and configuration shown in FIG. 13, but can be applied to communication states and configurations other than those shown in FIG.

  FIG. 14 is a block diagram showing a configuration related to uplink communication of the base station 700 according to the present embodiment. As shown in FIG. 14, base station 700 replaces scheduler section 108 and retransmission control signal transmission section 109 with scheduler section 701 and retransmission control signal transmission section 702 among the functional sections of base station 100 described above. It has a configuration. The relationship between the base station 700 and the mobile station 200 is the same as that shown in FIG. The configuration of the mobile station 200 is the same as the configuration of FIG.

  The scheduler unit 701 has the same function as the scheduler unit 108, and sets the target error rate of the retransmission control signal to the first target error rate or the second target error rate depending on whether or not a transmission instruction is generated. The first target error rate is notified to the retransmission control signal transmission unit 702. The first target error rate is higher than the second target error rate.

  Specifically, the scheduler unit 701 notifies the retransmission control signal transmission unit 109 to transmit a retransmission control signal using the first target error rate when generating a transmission instruction. In addition, the scheduler unit 701 notifies the retransmission control signal transmission unit 109 to transmit the retransmission control signal using the second target error rate when the transmission signal is not generated.

  Retransmission control signal transmission section 702 has the same function as retransmission control signal transmission section 109 and transmits a retransmission control signal according to the target error rate received from scheduler section 701. Here, as a transmission method of the retransmission control signal satisfying the second target error rate, for example, the retransmission control signal may be transmitted with a transmission power higher than the transmission power determined by the first target error rate. According to another method, if the retransmission control signal is transmitted with k bits at the first target error rate, the k-bit retransmission control signal may be transmitted n times repeatedly (k and n are integer).

  Note that in order to repeat the k-bit retransmission control signal n times, radio resources (frequency units, time) used for transmission of the retransmission control signal are required n times. As described above, the information included in the transmission instruction notified by the base station 700 for the mobile station 200 to transmit the wireless transfer block and the information on the radio resource used for transmitting the retransmission control signal are a pair. When a rule corresponding to 1 is defined in advance, if there are p frequency blocks included in the transmission instruction (n ≦ p), p is used to transmit the retransmission control signal at the first target error rate. K bits are transmitted using one of the radio resources, and k × n bits are transmitted using n of the p radio resources when the retransmission control signal is transmitted with the second target error rate. do it.

  As described above, in the present embodiment, the target error rate of the retransmission control signal is changed according to whether scheduler section 701 transmits the retransmission control signal and the transmission instruction at the same time. Thereby, in the case where the mobile station 200 cannot extract the transmission instruction addressed to itself, the base station 700 notifies the NACK, whereas the probability that the mobile station 200 erroneously determines the retransmission control signal as ACK is reduced. Therefore, the mobile station 200 determines that there is no transmission instruction addressed to itself, and can reduce the probability that the wireless transfer block will not be retransmitted to the base station 100. The base station 100 retransmits from the mobile station 200. Since it is possible to solve the problem that the packet cannot be transferred to the upper level because the wireless transfer block to be received cannot be received, the throughput can be improved as a result.

  Although the embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications, substitutions, additions, and the like can be made without departing from the spirit of the present invention. For example, a configuration in which any of the above embodiments is combined may be employed.

  As described above, the mobile station, the base station, and the communication control method according to the present invention are useful for a communication system in which a mobile station transmits a radio transfer block to a base station using a frequency block allocated from the base station. It is suitable for a communication system using frequency division multiplexing such as Evolved UTRA.

It is the figure which showed the structure of the communication system. 1 is a block diagram showing a configuration of a base station according to a first exemplary embodiment. 1 is a block diagram showing a configuration of a mobile station according to a first exemplary embodiment. It is a figure for demonstrating operation | movement of the signal determination part shown in FIG. FIG. 4 is a block diagram showing a configuration of a mobile station according to a second exemplary embodiment. FIG. 3 is a block diagram showing a configuration of a base station according to a second exemplary embodiment. FIG. 10 is a diagram for explaining a problem to be solved in a third embodiment. FIG. 6 is a block diagram showing a configuration of a base station according to a third exemplary embodiment. FIG. 6 is a block diagram showing a configuration of a base station according to a fourth exemplary embodiment. It is the figure which showed an example of the storage location table which defined the storage location of the 1st transmission instruction and the 2nd transmission instruction. It is the figure which showed an example of the component contained in a 1st transmission instruction | indication. It is the figure which showed an example of the component contained in a 2nd transmission instruction | indication. FIG. 10 is a diagram for explaining a problem to be solved in a fifth embodiment. FIG. 10 is a block diagram showing a configuration of a base station according to a fifth exemplary embodiment. It is the figure which showed the structure of the conventional communication system. It is a figure for demonstrating Non-adaptive HARQ. It is a figure for demonstrating Adaptive HARQ. It is the figure which showed the state of communication in the conventional mobile communication system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Base station 101 Radio signal receiving part 102 Demodulation / decoding part 103 Transmission request receiving part 104 Channel quality measurement part 105 Wireless transfer block receiving part 106 Retransmission control part 107 Packet reproduction part 108 Scheduler part 109 Retransmission control signal transmission part 110 Transmission instruction | indication transmission Unit 111 encoding / modulating unit 112 wireless signal transmitting unit 200 mobile station 201 packet generating unit 202 packet buffer 203 control unit 204 wireless transfer block generating unit 205 transmission request transmitting unit 206 retransmission control unit 207 encoding / modulating unit 208 wireless signal transmission Unit 209 wireless signal reception unit 210 demodulation / decoding unit 211 retransmission control signal reception unit 212 transmission instruction reception unit 213 signal determination unit 300 mobile station 301 signal determination unit 302 control unit 400 base station 401 scheduler unit 500 base station 501 retransmission control Control unit 502 Scheduler unit 600 Base station 601 Scheduler unit 700 Base station 701 Scheduler unit 702 Retransmission control signal transmission unit

Claims (8)

Configure a communication system with the base station, transmit a radio transfer block to the base station using a frequency block assigned by a transmission instruction notified from the base station, and send a retransmission control signal instruction notified from the base station A mobile station that retransmits the wireless transfer block according to content,
Soft decision value calculating means for calculating a soft decision value of the retransmission control signal each time the retransmission control signal is received;
First determination means for determining whether the retransmission control signal indicates retransmission of the wireless transfer block based on a magnitude relationship between the soft decision value and a predetermined threshold;
Second determination means for determining whether the transmission instruction is received together with the retransmission control signal;
Transmission control means for controlling retransmission of the wireless transfer block according to the determination result by the first determination means and the determination result by the second determination means;
Third determination means for determining whether or not the transmission instruction is transmitted to the mobile station;
Equipped with a,
The first determination means is based on the determination result of the third determination means, the first threshold corresponding to the case where the determination result is addressed to its own mobile station, or the determination result is addressed to another mobile station. A mobile station characterized in that a second threshold value corresponding to a case is compared with the soft decision value . The mobile station according to claim 1 , wherein the first threshold value is larger than the second threshold value. The first determination unit determines that the retransmission control signal is NACK instructing retransmission of the radio transfer block when the soft decision value is lower than the first threshold or the second threshold, and the soft decision If the value is not less than the first threshold or the second threshold value, according to claim 1 or 2, wherein the retransmission control signal and judging an ACK instructing the transmission of a new radio transfer blocks Mobile stations.   The first determination means compares the soft decision value with a first threshold value and a second threshold value that is smaller than the first threshold value, and the retransmission control signal is transmitted from the wireless transfer block according to the magnitude relationship between the values. 2. The mobile station according to claim 1, wherein the mobile station determines whether or not to instruct retransmission of the mobile station. The first determination unit determines that the retransmission control signal is NACK instructing retransmission of the radio transfer block when the soft decision value is less than the second threshold, and the soft decision value is the first decision value. The retransmission control signal is determined to be ACK instructing transmission of a new wireless transfer block when the threshold is exceeded, and the soft decision value is greater than or equal to the second threshold and less than or equal to the first threshold The mobile station according to claim 4 , wherein the instruction content of the retransmission control signal is not determined yet. When the determination result by the first determination unit is ACK and the second determination unit determines that the transmission instruction is received, the transmission control unit uses the frequency block assigned by the transmission instruction. When a new wireless transfer block is transmitted, the determination result by the first determination unit is NACK, and the second determination unit determines that the transmission instruction has not been received, the same frequency block as the previous transmission When the wireless transfer block is retransmitted using N, the determination result by the first determination unit is NACK, and the second determination unit determines that the transmission instruction has been received, the allocation is performed according to the transmission instruction. The mobile station according to claim 3 or 5 , wherein the radio transfer block is retransmitted using a frequency block. The mobile station according to claim 6 , further comprising retransmission requesting means for requesting the base station to retransmit the retransmission control signal when the determination result by the first determining means is not determined. Configure a communication system with the base station, transmit a radio transfer block to the base station using a frequency block assigned by a transmission instruction notified from the base station, and send a retransmission control signal instruction notified from the base station A communication control method in a mobile station that retransmits the wireless transfer block according to contents,
A soft decision value calculating step for calculating a soft decision value of the retransmission control signal every time the soft decision value calculating means receives the retransmission control signal;
A first determination step of determining whether or not the retransmission control signal indicates retransmission of the wireless transfer block based on a magnitude relationship between the soft decision value and a predetermined threshold;
A second determination step of determining whether the second determination means has received the transmission instruction together with the retransmission control signal;
A control unit that controls retransmission of the wireless transfer block according to a determination result in the first determination step and a determination result in the second determination step;
Only including,
In the first determination step, it is determined whether or not the transmission instruction is transmitted to the own mobile station, and based on the determination result, the determination result corresponds to the case where the determination result is addressed to the own mobile station. A communication control method characterized by comparing a threshold value of 1 or a second threshold value corresponding to a case where the determination result is addressed to another mobile station with the soft decision value .

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