JP5121343B2 - Base station, terminal device and communication method - Google Patents

Description

  The present invention relates to a base station, a terminal device, and a communication method, and more particularly to a channel selection method and a retransmission method, for example.

  For example, Patent Document 1 discloses a technique for improving communication quality when receiving data over a plurality of slots. In this Patent Document 1, in downlink communication, a mobile station (terminal device) measures the C / I value of each slot to which received data is assigned in slot units, and receives the slot number and the corresponding C / I. A CIR table representing (Carrier / Interference) values is created. The mobile station transmits a NACK and a CIR table to the base station if the reception quality of the received data is less than a predetermined standard. Upon receiving the NACK and CIR table, the base station transmits each retransmission data block obtained by dividing the retransmission data by changing the transmission slot in accordance with a rule determined in advance with the mobile station. When the mobile station receives each retransmission data block, the mobile station restores the retransmission data from each retransmission data block according to the rules agreed with the base station. In uplink communication, the transmission side is the mobile station and the reception side is the base station, and the same operation is performed.

In Patent Document 2, a data frame is divided into a plurality of data series, an error detection code is added to each of the data frames, and transmission is performed using a plurality of physical resources (frequency channels). Retransmission control and transmission rate control are performed in units of physical resources by notifying the transmission side of ACK / NACK and CQI (Channel Quality Information) for each physical resource.
JP 2003-163960 A JP 2005-333345 A

  However, in Patent Document 1, when it is determined that a transmission error is included in the received data in the mobile station, all the data is retransmitted, and is therefore mapped to a slot in which the channel condition is good and the need for retransmission is low. The data that has been sent will also be retransmitted. For this reason, there is a problem that a great effect cannot be obtained in quality improvement and the frame efficiency is lowered. Further, the above-mentioned Patent Document 2 has a problem that the overhead due to the error detection code is large, and the frame efficiency is lowered particularly when the number of data frame division is large.

  Further, in common with the above-mentioned Patent Document 1 and Patent Document 2, there is a problem that throughput is lowered because data transmission using the channel is performed even when the channel condition continues to be bad due to inter-cell interference or the like. there were.

  The present invention provides a base station and a communication method capable of performing channel selection control so as to prevent a decrease in data transmission throughput as much as possible. The present invention also provides a base station, a terminal device, and a communication method capable of performing retransmission control so as to prevent a decrease in frame efficiency as much as possible.

The base station as one aspect of the present invention is:
The uplink frame for uplink communication and the downlink frame for downlink communication, which are each divided into a plurality of subchannels, are alternately switched in time, and the subchannels at the same position in the uplink frame and the downlink frame are switched to the terminal device. A base station that performs communication by assignment,
Mapping for mapping one or more segments obtained by dividing the first data frame to be transmitted to the terminal apparatus to one or more subchannels of subchannels allocated in advance to the terminal apparatus in the downlink frame Means,
Transmitting means for transmitting each mapped segment to the terminal device in the downlink frame;
Notification receiving means for receiving an error detection notification from the terminal device for notifying that an error has been detected in the first data frame restored by concatenating the mapped segments;
First channel quality information indicating the quality of the one or more subchannels to which the first data frame in which the error is detected is mapped in the downlink frame in which the first data frame in which the error is detected is transmitted. First information acquisition means for acquiring from the terminal device;
First evaluation value calculation means for calculating, for each subchannel, a first quality evaluation value for evaluating the quality of the subchannel in the downlink frame allocated to the terminal device from the acquisition history of the first channel quality information;
Availability determination means for determining, for the uplink frame and the downlink frame, suspension of use of the subchannel in which the first quality evaluation value that does not satisfy a first evaluation threshold given in advance is calculated;
Is provided.

The terminal device as one aspect of the present invention is:
From a base station that performs communication by alternately switching an uplink frame for uplink communication and a downlink frame for downlink communication that are divided into a plurality of subchannels in time, subframes at the same position in the uplink frame and the downlink frame A terminal device that is assigned a channel,
One or more segments obtained by dividing a third data frame to be transmitted to the base station are mapped to one or more subchannels of subchannels allocated in advance from the base station in the uplink frame. Mapping means;
Transmitting means for transmitting each mapped segment to the base station in the uplink frame;
Notification receiving means for receiving an error detection notification from the base station for notifying that an error has been detected in the third data frame restored by concatenating the mapped segments;
Third line quality representing the quality of each of the one or more subchannels to which the third data frame in which the error is detected is mapped in the uplink frame in which the third data frame in which the error is detected is transmitted Information acquisition means for acquiring information from the base station;
Retransmission segment determination for determining a segment to be retransmitted from among the segments obtained by dividing the third data frame based on the third channel quality information of the one or more subchannels acquired by the information acquisition means Means,
Retransmission subchannel determination means for determining, from among the subchannels allocated by the base station in the uplink frame, a subchannel to which the segment to be retransmitted determined by the retransmission segment determination means is mapped;
Using the mapping means, the segment to be retransmitted determined by the retransmission segment determining means is mapped to the subchannel determined by the retransmission subchannel determining means, and each mapped segment to be retransmitted is transmitted Retransmitting means for transmitting to the base station in the uplink frame using means;
Is provided.

A communication method as one aspect of the present invention includes:
A base station that performs communication by alternately switching an uplink frame for uplink communication and a downlink frame for downlink communication that are each divided into a plurality of subchannels, and the uplink frame and the downlink frame from the base station A communication method performed with a terminal apparatus that is assigned subchannels at the same position,
One or more segments obtained by dividing the first data frame to be transmitted to the terminal device are mapped to one or more subchannels of subchannels allocated in advance to the terminal device in the downlink frame. ,
Transmitting each mapped segment to the terminal device in the downlink frame;
Concatenating each mapped segment to restore the first data frame;
When an error is detected in the restored first data frame, an error detection notification indicating that an error has been detected, and the error in the downlink frame that has transmitted the first data frame in which the error has been detected. Transmitting the first channel quality information indicating the quality of the one or more subchannels to which the detected first data frame is mapped to the base station;
A first quality evaluation value for evaluating the quality of the subchannel in the downlink frame allocated to the terminal device from the acquisition history of the first channel quality information is calculated for each subchannel,
Determining whether to stop using the subchannel for which the first quality evaluation value that does not satisfy the first evaluation threshold given in advance is calculated for the uplink frame and the downlink frame;
It is characterized by that.

  According to the present invention, channel selection control can be performed so as to prevent a decrease in data transmission throughput as much as possible, and retransmission control can be performed so as to prevent a decrease in frame efficiency as much as possible.

  Hereinafter, this embodiment will be described in detail with reference to the drawings.

  FIG. 3 shows a frame configuration example used in the radio communication system according to the present embodiment.

  In this system, TDD (Time Division Duplex) is used as a duplex method in the time domain, and one frame is an uplink frame that is a TDD uplink (uplink) section and a downlink frame that is a TDD downlink (downlink) section. It is divided into and. Each of the upstream frame and the downstream frame is divided into a plurality of TDMA slots (time slots) in accordance with TDMA (Time Division Multiple Access) in the time domain, and FDMA (Frequency Division Multiple Access) or OFDMA (Orthogonal Frequency) which is one form thereof in the frequency domain. Division into multiple FDMA channels according to (Division Multiple Access). A physical resource having one TDMA slot as a time width and one FDMA channel as a frequency width is called a subchannel.

  FIG. 4 shows an example of subchannel usage according to the present embodiment.

  As shown in FIG. 4A, the base station 100 according to the present embodiment uses the subchannel of the TDD downlink section (downlink frame) toward the terminal device (mobile station) 200 according to the present embodiment. Perform data transmission. Further, as shown in FIG. 4B, the terminal device 200 uses a subchannel located at the same position as that used for transmission in the TDD downlink section (downlink frame) in the TDD uplink section (uplink frame). Data transmission to the base station 100. The base station 100 determines a subchannel used for data transmission between the base station 100 and the terminal device 200, and the base station 100 notifies the terminal device 200 of the determined subchannel. The notification method includes a method of transmitting a bit string (hereinafter referred to as MAP (map)) indicating the position of a subchannel to be used by the terminal device 200, and a terminal device to the subchannel to be used by the terminal device 200. There are ways to include 200 identification numbers. The following description will be made assuming a notification method using MAP, but the present invention is not limited to this.

  FIG. 1 is a block diagram showing a configuration of a base station 100 as an embodiment of the present invention.

  At the time of data transmission from the base station, the error detection code adding unit 116 reads data from the transmission buffer 115 that stores data to be transmitted, adds an error detection code (EDC) to the read data, and performs data transmission. A frame is generated, and the generated data frame is input to the error correction encoding unit 117. As the error detection code, for example, there is a CRC (Cyclic Redundancy Check) code. The base station can also simultaneously transmit two or more data frames for one terminal device in one TDD downlink section (downlink frame). In that case, data for generating two or more data frames is read from the transmission buffer 115.

  The error correction encoding unit 117 encodes the data sequence of the data frame by a predetermined encoding method, and inputs the encoded data sequence to the data frame dividing unit 118.

  The data frame dividing unit 118 divides the encoded data series input from the error correction encoding unit 117 into one or more segments, and inputs each segment obtained by the division to the subchannel mapping unit 119. The data frame dividing unit 118 also inputs each segment obtained by the division to the transmission signal buffer 122 in preparation for retransmission.

  The sub-channel mapping unit (mapping unit) 119 maps (arranges) each segment input from the data frame dividing unit 118 to a usable sub-channel among sub-channels allocated in advance to the terminal device. 120. The information on usable subchannels is obtained from, for example, a MAP (see FIG. 10) describing usable subchannels generated by the MAP generation unit 111 described later. Here, when the base station assigns subchannels to the terminal device in advance, it performs carrier sense using subchannels that are not used for transmission, and the measured received power is lower than the preset received power threshold. Assume that a low subchannel is allocated to a terminal device. However, in the present invention, the subchannel allocation method is not limited, and any known method as the subchannel allocation method for the terminal apparatus can be used. As a method of mapping each segment, for example, when the number of segments is fixed, a subchannel number among usable subchannels (a number is assigned to each subchannel in an uplink frame or a downlink frame as shown in FIG. 10 described later). May be sequentially mapped to a predetermined number of segments in ascending order. Alternatively, mapping data indicating in which order each segment is mapped from the base station to which subchannel is included in the control information and notified to the terminal device, and mapping may be performed in the same manner as this notification content. . Or the said mapping data shall be notified by a specific subchannel, and you may map like this notification content.

  FIG. 5 shows the correspondence between the data frame, the error correction encoded data frame, the segment, and the subchannel. Here, a state is shown in which a data frame subjected to error correction coding is divided into K segments and K segments are mapped to K subchannels. Note that, referring to FIG. 10 described later, when numbers are assigned to the subchannels in the frame, the channels assigned to the terminal devices may not be consecutively numbered channels.

  The modulation processing unit 120 modulates the data input from the subchannel mapping unit 119 to generate a baseband modulation signal, and inputs the generated baseband modulation signal to the radio processing unit 121.

  The radio processing unit 121 converts the baseband modulated signal input from the modulation processing unit 120 into a radio frequency (RF) signal and transmits the RF signal via the antenna 101.

  A set of the modulation processing unit 120, the wireless processing unit 121, and the antenna 101 corresponds to, for example, a transmission unit.

  At the time of data reception at the base station, the wireless processing unit 102 performs predetermined wireless processing such as amplification and band limitation on the RF signal received by the antenna 101 to acquire a baseband signal, and acquires the acquired baseband The signal is input to the demodulation processing unit 103. A set of the antenna 101, the wireless processing unit 102, and the demodulation processing unit 103 corresponds to a receiving unit, for example.

  Demodulation processing section 103 demodulates the input baseband signal and inputs the demodulated signal to data frame signal reconstruction section 104 and reception quality measurement section 108.

  The data frame signal reconstructing unit 104 concatenates the segments transmitted on the plurality of subchannels to reconstruct the data frame, and inputs the data frame signal to the decoding processing unit 105.

  Decoding processing section 105 performs error correction decoding processing on the data frame signal input from data frame signal reconstruction section 104 and inputs the decoded data sequence to error detection processing section 106.

  An error detection processing unit (error detection means) 106 detects whether an error is included in the data frame by using an error detection code (EDC) included in the data series (data frame) input from the decoding processing unit 105, An error detection signal indicating the presence or absence of an error is input to a UL (Up link) quality monitoring unit 109. For a data frame in which no error is detected, error detection processing section 106 inputs a data sequence obtained by removing the error detection code from the data frame to reception buffer 107. For a data frame in which an error is detected, the base station may request the terminal device to retransmit the data frame, or the cause of the error among the segments transmitted in a plurality of subchannels according to the second embodiment to be described later. Only the highly likely segment may be retransmitted from the terminal device.

  Reception quality measurement section (quality measurement means) 108 estimates the reception quality (for example, reception SINR) of each subchannel in the uplink from the demodulated signal input from demodulation processing section 103, and subtracts from the estimated reception quality of each subchannel. An uplink CQI (second channel quality information) representing the quality of each channel is generated and input to the UL quality monitoring unit 109.

  When the error detection processing unit 106 detects an error in the data frame, the UL quality monitoring unit (second information acquisition unit, second evaluation value calculation unit) 109 detects each subchannel to which the data frame is mapped. Based on the uplink CQI, the quality of each subchannel in the uplink is inspected. A detailed operation flow of the UL quality monitoring unit 109 is shown in FIG.

The UL quality monitoring unit 109 refers to the error detection signal input from the error detection processing unit 106, determines whether there is a transmission error in the data frame transmitted on the uplink (step S11), and there is a transmission error. In the case, the uplink CQI of each subchannel to which the data frame is mapped (referred to here as reception SINR) is referred to (step S12). Next, the received SINR of each subchannel is compared with a preset SINR threshold γ _Uth (step S13). As a result of the comparison, if reception SINR <SINR threshold γ _Uth , the uplink error counter n _U (second counter) of the subchannel is incremented by 1 (n _U = n _U +1) (step S14). The value of the uplink error counter n _U corresponds to, for example, a second quality evaluation value, the SINR threshold value γ _Uth corresponds to, for example, a second quality threshold value, and the second quality evaluation value is an uplink CQI (second channel quality information) value. It depends on the acquisition history. Further, UL quality monitoring unit 109 inputs the uplink error counter _{n U} to the channel selection control section 110. Through the above operation, the UL quality monitoring unit 109 performs transmission / reception on each sub-channel in the uplink based on the presence / absence of transmission error of the data frame transmitted on the uplink and the uplink CQI of each sub-channel to which the data frame is mapped. The channel quality is monitored, and the quality value (that is, the second quality evaluation value) of each subchannel obtained by the monitoring is used for channel selection control in a channel selection control unit (usability determination unit) 110 described later.

  The control information reference unit (notification receiving unit, first information acquisition unit) 113 acquires various control information transmitted from the terminal device from the demodulated signal output from the demodulation processing unit 103. The various control information includes, for example, ACK / NACK indicating whether or not the data frame transmitted from the base station has been correctly received (without error) at the terminal device, and each subchannel (for example, the terminal) in the downlink frame measured at the terminal device There is a downlink CQI representing the quality of the subchannel assigned to the device. NACK corresponds to, for example, error detection notification, and downlink CQI corresponds to, for example, first line quality information. When there are a plurality of data frames transmitted from the base station, a plurality of ACK / NACKs are included in the control information. Control information reference section 113 passes control information (here, ACK / NACK and downlink CQI) to retransmission control section 114 and DL (Down Link) quality monitoring section 112. Details of the downlink CQI will be described in the operation description of the terminal device to be described later.

  The DL quality monitoring unit (first evaluation value calculation means) 112, when a data frame error is detected in the terminal device, is based on the downlink CQI of each subchannel to which the data frame is mapped. Inspect the quality of each subchannel. A detailed operation flow of the DL quality monitoring unit 112 is shown in FIG.

The DL quality monitoring unit 112 refers to the ACK / NACK input from the control information reference unit 113, determines whether or not there is a transmission error in the data frame transmitted on the downlink (step S21), and if there is a transmission error Refers to the downlink CQI (received SINR) of the subchannel to which the data frame is mapped (step S22). Next, the received SINR of each subchannel is compared with a preset SINR threshold value γ _Dth (step S23). As a result of the comparison, if reception SINR <SINR threshold γ _Dth , the downlink error counter n _D (first counter) of the subchannel is incremented by 1 (n _D = n _D +1) (step S24). The value of the downlink error counter n _D corresponds to, for example, a first quality evaluation value, the SINR threshold value γ _Dth corresponds to a first quality threshold value, and the first quality evaluation value is obtained as a downlink CQI (first channel quality information). It depends on the history. Also, DL quality monitoring unit 112 inputs the downlink error counter _{n D} to the channel selection control section 110. With the above operation, the DL quality monitoring unit detects whether there is a transmission error in the data frame transmitted on the downlink and the downlink CQI of each subchannel to which the data frame is mapped. The quality is monitored, and the quality value (that is, the first quality evaluation value) of each subchannel obtained by the monitoring is used for channel selection control in the channel selection control unit 110 described later.

  The channel selection control unit (usability determination unit) 110 determines whether to continue or stop using each subchannel assigned to the terminal device. A detailed operation flow of the channel selection control unit 110 is shown in FIG.

The channel selection control unit 110 refers to the uplink error counter n _U value input from the UL quality monitoring unit 109 and the downlink error counter n _D value input from the DL quality monitoring unit 112, and these values are Conditions for stopping channel use (sub-channel use stop conditions): n _U ≧ N _U or n _D ≧ N _D (where N _U <N _D and N _U and N _D are integers of 1 or more) It is determined whether or not the condition is satisfied (step S31). N _D corresponds to, for example, the first evaluation threshold value, N _U corresponds to, for example, the second evaluation threshold. Therefore, the first evaluation threshold is larger than the second evaluation threshold.

When the subchannel use stop condition is satisfied, the use of the subchannel is stopped (step S32), and the uplink error counter n _U and the downlink error counter n _D related to the subchannel are reset to 0 (step S33). .

  Then, the channel selection control unit 110 inputs, to the MAP generation unit 111, information indicating availability of each subchannel assigned to the terminal device.

  The base station that performs channel selection control by the above operation uses based on the presence / absence of transmission error of the data frame in the uplink and the uplink CQI, and the presence / absence of the transmission error of the data frame in the downlink and the downlink CQI. The selection of the subchannel to be controlled can be controlled independently of other base stations.

When such autonomous distributed channel selection control is performed, there is a possibility that the usage efficiency of the subchannel may be reduced due to the presence of the so-called hidden terminal problem. However, as shown in step S31, by the N U _{<N D} can be avoided this problem. This will be described in more detail as follows.

  It is assumed that base stations CS1 and CS2 are communicating with terminals PS1 and PS2 respectively in adjacent cells, and the links are referred to as L1 and L2, respectively. The link L1 has poor downlink quality and good uplink quality, but the link L2 may have good downlink quality and poor uplink quality (for example, the terminal PS1 crosses adjacent cells). If the terminal PS2 is in a region and is in a region different from the intersection region in the cell of the base station CS2, in this case, the terminal PS2 becomes a hidden terminal for the base station CS1). At this time, if the link L2 having poor uplink quality stops using the subchannel prior to the link L1, the adjacent cell interference is eliminated, and the terminal PS1 uses the subchannel for both the uplink and the downlink with high quality. Can be used. Since the signal from the terminal PS1 can be monitored by the base station CS2, the base station CS2 monitors the transmission signal of the terminal PS1, and as soon as the end of transmission is detected by carrier sense, the base station CS2 uses the subchannel for the terminal PS2. It is possible to resume.

The MAP generation unit 111 generates a MAP from information indicating availability of each subchannel input from the channel selection control unit 110 and outputs the MAP to the transmission buffer 115 and the retransmission control unit 114. FIG. 10 shows the usage status of the subchannel of the terminal apparatus in the uplink frame or the downlink frame, and the subchannel i (i = 1,..., N _SC ) corresponds to the bit b _i of the MAP. In the MAP, among the subchannels assigned to the terminal device, 1 is set for the usable subchannel, and 0 is set for the subchannel that is not usable and the subchannel that is not originally assigned to the terminal device. That is, b _i = 1 is set when the subchannel i is usable, and b _i = 0 is set when the sub channel i is not usable. This MAP is input to the transmission buffer 115 and notified to the terminal device as part of the control information.

  Retransmission control unit (retransmission segment determination unit, retransmission subchannel determination unit, retransmission unit) 114 receives ACK / NACK from control information reference unit 113 and the downlink of each subchannel (for example, a subchannel assigned to a terminal device). CQI is input, and MAP is input from the MAP generation unit 111. When NACK is input, retransmission control section 114 determines a segment to be retransmitted (retransmission segment) and a subchannel to be used for retransmission (retransmission subchannel), and controls transmission of the retransmission segment through the retransmission subchannel. A detailed operation flow of the retransmission control unit 114 is shown in FIG.

  Based on the ACK / NACK input from control information reference section 113, retransmission control section 114 determines the presence / absence of a transmission error in the data frame transmitted on the downlink (step S41). Here, the ACK / NACK (and the downlink CQI) from the terminal device is sent from the terminal device in the TDMA frame next to the TDMA frame that transmitted the data frame or the TDMA frame at a predetermined relative frame position, for example. Therefore, the retransmission control unit 114 can grasp which TDMA frame the ACK / NACK input from the control information reference unit 113 is for the transmitted data frame. Also, when a plurality of data frames are sent to the terminal device in one TDMA frame, a plurality of ACK / NACKs returned from the terminal device are arranged in a prescribed order, for example, arranged in ascending order of the sequence number of the data frame. By doing so, it is possible to grasp which data frame each ACK / NACK corresponds to.

  If there is a transmission error in step S41, referring to the downlink CQI of the subchannel to which the data frame is mapped (step S42), there is a high possibility that the channel quality is poor and a transmission error is caused. A subchannel is determined, and it is determined to retransmit a segment (retransmission segment) mapped to such a subchannel (retransmission segment determination process) (step S43). Then, the transmission signal buffer 122 is notified of the transmission instruction of the retransmission segment. In addition, retransmission control section 114 determines a subchannel (retransmission subchannel) used for retransmission segment transmission (retransmission subchannel determination processing) (step S44). The retransmission control unit 114 notifies the subchannel mapping unit 119 of the determined subchannel. The subchannel mapping unit 119 receives the retransmission segment from the transmission signal buffer 122, arranges the received retransmission segment in the subchannel determined by the retransmission control unit 114, and outputs it to the modulation processing unit 120. If a transmission error occurs in step S41, the process ends. When there is no transmission error, a data frame without an error may be deleted from the transmission signal buffer 122.

  Hereinafter, the retransmission segment determination process performed in step S43 and the retransmission subchannel determination process performed in step S44 will be described in more detail.

  First, the retransmission segment determination process performed in step S43 will be described.

In the first scheme of the retransmission segment determination process, the retransmission control unit 114 refers to the downlink CQI, and _selects a segment mapped to a subchannel that satisfies downlink reception SINR <SINR threshold γ _Dth (first quality standard). Decide to resend. When there is no corresponding subchannel, it is determined to retransmit a total of m segments mapped to the subchannels from the subchannel with the lowest received SINR to the mth subchannel (1 ≦ m ≦ the maximum number of divisions of the data frame).

  In the second scheme of retransmission segment determination processing, the retransmission control unit 114 refers to the downlink CQI, and segments mapped to those subchannels from the subchannel with the lowest received SINR to the subchannel with the mth lowest. Are determined to be retransmitted in total (1 ≦ m ≦ maximum number of data frame divisions).

  Which of the first and second methods is used is matched in advance by both the base station and the terminal device. Both the first method and the second method preferentially retransmit a segment that is highly likely to cause a transmission error, and improve the frame efficiency by retransmitting one of these methods. Can be expected.

  Next, the retransmission subchannel determination process performed in step S44 will be described.

  In the first method of retransmission subchannel determination processing, a required number of subchannels are determined as retransmission subchannels in order from the top of usable subchannels based on the MAP given from the MAP generation unit 111. That is, the required number of subchannels (for example, the number of retransmission segments when one segment is transmitted on one subchannel) is determined as the retransmission subchannel in ascending order of usable subchannel numbers.

In the second method of retransmission subchannel determination processing, a data frame in which an error is detected is mapped out of usable subchannels based on the MAP given from the MAP generation unit 111, and the downlink A required number of subchannels satisfying the received SINR> SINR threshold γ _Dth (second quality criterion) are selected, for example, in ascending or descending order of the subchannel numbers, and the selected subchannels are determined as retransmission subchannels.

  Which of the first and second methods is used is matched in advance by both the base station and the terminal device. In either case, if the number of retransmission subchannels is small relative to the number of retransmission segments and all retransmission segments cannot be transmitted in one TDMA frame, all retransmission subchannels are transmitted. After mapping the retransmission segments, the remaining retransmission segments are transmitted in the next and subsequent TDMA frames.

  As will be described later, the terminal apparatus receives the retransmission segment mapped to the retransmission subchannel, and concatenates the received retransmission segment and the segment determined to have been normally received in the first transmission to generate a data frame. Build and error detection. If an error is detected as a result of error detection, control information including NACK or the like is returned to the base station again. In this case, the retransmission control unit 114 in the base station basically performs the same as described above. The retransmission segment determination process of the first or second scheme and the retransmission subchannel determination process of the first or second scheme may be performed. However, in the retransmission segment determination process, a retransmission segment is selected from the previously retransmitted segments.

  FIG. 2 is a block diagram showing a configuration of the terminal device 200 as an embodiment of the present invention.

  At the time of data reception, the radio processing unit 202 performs predetermined radio processing such as amplification and band limitation on the RF signal received by the antenna 201 to generate a baseband signal, and the generated baseband signal is demodulated 203.

  Demodulation processing section 203 demodulates the baseband signal input from radio processing section 202 and inputs the demodulated signal to data frame signal reconstruction section 204 and reception quality measurement section 211.

  The data frame signal reconstruction unit 204 reconstructs a data frame by concatenating segments mapped to a plurality of subchannels, and inputs the data frame to the decoding processing unit 205. The subchannel to which the segment is mapped can be identified from the MAP acquired by the control information reference unit 209 described later, for example. The segment connection method may be notified by including it in the control information from the base station, for example, by a subchannel at a specific location, or may be determined in advance (for example, a predetermined number in ascending order of numbers). Concatenate segments in this order). In addition, when a transmission error is detected in the data frame by the error detection processing unit 206, the data frame signal reconstructing unit 204 sends the data frame in which this error is detected according to an instruction from the retransmission data decoding control unit 210 described later. And stored in the received signal buffer 208. For this reason, the data frame signal reconstruction unit 204 may include holding means for holding the data frame for a certain period.

  Decoding processing section 205 performs error correction decoding processing on the data frame signal input from data frame signal reconstruction section 204, and inputs the decoded data frame data sequence to error detection processing section 206.

  The error detection processing unit 206 detects whether or not there is an error in the data frame using an error detection code included in the data series (data frame) input from the decoding processing unit 205, and an error detection signal indicating the presence or absence of an error Is input to the ACK / NACK generation unit 212 and the CQI generation unit 213. The error detection processing unit 206 inputs the data series excluding the error detection code to the reception buffer 207 for the data frame in which no error is detected. The data series input to the reception buffer 207 is passed to an upper layer application, for example.

  The ACK / NACK generation unit 212 sets ACK or NACK according to an error detection signal indicating the presence or absence of an error in the data frame, and outputs the set ACK / NACK to the transmission buffer 214 and the retransmission data decoding control unit 210. The ACK / NACK input to the transmission buffer 214 is transmitted (notified) to the base station as part of the control information.

  The control information reference unit 209 acquires various control information (here, MAP) notified from the base station from the demodulated signal, and passes the acquired control information (MAP) to the retransmission data decoding control unit 210.

  Reception quality measurement section 211 measures the reception quality (for example, reception SINR) of each subchannel (for example, all subchannels) in the downlink from the demodulated signal input from demodulation processing section 203, and receives CQI generation section 213 and retransmission data. Input to the decoding control unit 210.

  The CQI generation unit 213 generates a downlink CQI (for example, reception SINR itself or other index value described later) of each subchannel from the reception quality of each subchannel input from the reception quality measurement unit 211 and inputs it to the transmission buffer 214. To do. The downlink CQI of each subchannel input to the transmission buffer 214 is transmitted (notified) to the base station as part of the control information. At this time, a method of transmitting downlink CQIs of all subchannels as shown in FIG. 15 (a), or a downlink CQI of subchannels to which each data frame is mapped as shown in FIG. 15 (b). A transmission method or a method of transmitting a downlink CQI of a subchannel to which a data frame in which an error is detected is mapped as shown in FIG.

As an example of the downlink CQI, for example, there is a value of the reception SINR itself of the subchannel. As another example of the downlink CQI, there is a value obtained by quantizing the reception SINR of the subchannel into a finite number of discrete values of 2 or more. Further, as a special case of this example, preset based on a result of comparison between the SINR threshold gamma _Dth that has been, if the reception SINR ≧ SINR threshold gamma _Dth downlink CQI = 1, the reception SINR <SINR threshold gamma If it is _Dth , there is a binary CQI that is set as downlink CQI = 0.

  Hereinafter, the processes of the CQI generation unit 213 and the ACK / NACK generation unit 212 will be described in more detail.

  FIG. 11 is a flowchart showing a processing flow of the CQI generating unit 213 and the ACK / NACK generating unit 212 corresponding to the format of FIG.

  CQI generating section 213 creates a downlink CQI (for example, received SINR itself) from the reception quality of the subchannel (step S51). When no error is detected in the data frame in the error detection processing unit 206 (NO in step S52), the ACK / NACK generation unit 212 inputs an ACK notifying the successful transmission of the data frame to the transmission buffer 214. The ACK is transmitted to the base station, and the CQI generation unit 213 inputs the downlink CQI of each subchannel to which the data frame has been mapped to the transmission buffer 214, thereby transmitting the downlink CQI of each subchannel to the base station. Transmit (step S53). On the other hand, if an error is detected in the data frame (YES in step S52), the ACK / NACK generation unit 212 inputs a NACK notifying the transmission failure of the data frame to the transmission buffer 214, and sends a NACK to the base station. The CQI generation unit 213 transmits the downlink CQI of each subchannel to which the data frame has been mapped to the transmission buffer 214, thereby transmitting the downlink CQI of each subchannel to the base station (step S54). ).

  FIG. 12 is a flowchart showing a processing flow of the CQI generating unit 213 and the ACK / NACK generating unit 212 corresponding to the format of FIG.

  If no error in the data frame is detected in the error detection processing unit 206 (NO in step S61), the ACK / NACK generation unit 212 inputs an ACK notifying the successful transmission of the data frame to the transmission buffer 214. ACK is transmitted to the base station (step S62). On the other hand, if an error is detected in the data frame (YES in step S61), a downlink CQI (for example, reception SINR itself) is created from the reception quality of each subchannel to which the data frame is mapped (step S63). Then, the ACK / NACK generation unit 212 transmits the NACK to the base station by inputting the NACK notifying the transmission failure of the data frame to the transmission buffer 214, and the CQI generation unit 213 transmits each subframe to which the data frame is mapped. By inputting the downlink CQI of the channel to the transmission buffer 214, the downlink CQI of each subchannel is transmitted to the base station (step S64). Thus, in the method of FIG. 12, the downlink CQI is transmitted only for the data frame in which an error is detected. That is, only the minimum information necessary for channel selection control and retransmission control is notified to the base station. Therefore, it is possible to reduce the amount of information to be transmitted and to use the uplink more efficiently than the method of FIG. 11 that transmits the downlink CQI regardless of whether there is an error.

  When the ACK / NACK information input from ACK / NACK generation unit 212 indicates NACK, retransmission data decoding control unit 210 maps the data frame in which an error is detected input from reception quality measurement unit 211. Based on the reception quality of each subchannel, the segment (retransmission segment) retransmitted from the base station is specified (retransmission segment specifying process). Also, retransmission data decoding control section 210 refers to the MAP passed from control information reference section 209 and identifies the subchannel (retransmission subchannel) in which the retransmission segment is arranged (retransmission subchannel identification processing). Information regarding the specified retransmission segment and the specified retransmission subchannel is passed to the data frame signal reconstruction unit 204 via the reception signal buffer 208.

  Hereinafter, retransmission segment identification processing and retransmission subchannel identification processing performed in retransmission data decoding control section 210 will be described in detail.

  First, the retransmission segment specifying process in the retransmission data decoding control unit 210 will be described.

The retransmission segment specifying process in the retransmission data decoding control unit 210 is paired with the retransmission segment determining process in the retransmission control unit 114 of the base station. Therefore, when the retransmission segment determination process of scheme 1 is performed in the base station, retransmission data decoding control section 210 receives downlink received SINR <SINR threshold among subchannels mapped with data frames in which errors are detected. It is determined that the segment mapped to the subchannel satisfying γ _Dth is retransmitted from the base station. If there is no corresponding subchannel, it is determined that a total of m segments mapped to these subchannels are retransmitted from the subchannel with the lowest received SINR to the subchannel with the mth received SINR ( 1 ≦ m ≦ the maximum number of divisions of the data frame). On the other hand, when the retransmission segment determination process of scheme 2 is performed in the base station, retransmission data decoding control section 210 refers to the received SINR of the downlink, and the received SINR is the mth lowest from the subchannel with the lowest received SINR. It is determined that a total of m segments mapped to these subchannels are retransmitted up to the subchannel (1 ≦ m ≦ maximum number of divisions of data frame). Which of the above method 1 and method 2 is used is matched in advance in both the base station and the terminal device.

  Next, retransmission subchannel specifying processing in retransmission data decoding control section 210 will be described.

The retransmission subchannel specifying process in retransmission data decoding control section 210 is paired with the retransmission subchannel determination process in retransmission control section 114 of the base station. The retransmission data decoding control unit 210 refers to the MAP passed from the control information reference unit 209 and identifies the position of the subchannel used for retransmission by the base station. More specifically, when the retransmission subchannel determination process of scheme 1 is performed in the base station, the necessary number of retransmission subchannels (for example, the number of retransmission segments) are sequentially provided from the top of the usable subchannels designated by the MAP. Judge that it is specified. On the other hand, when performing retransmission subchannel determination processing of scheme 2 in the base station, it is designated as a subchannel that can be used by the MAP among subchannels in which a data frame in which an error is detected is transmitted, and the downlink It is determined that the necessary number of subchannels satisfying the received SINR> SINR threshold γ _Dth are determined as retransmission subchannels, for example, in ascending or descending order of the subchannel numbers. Which of the above method 1 and method 2 is used is matched in advance in both the base station and the terminal device. Also, in either case, it is determined that not all retransmission segments can be transmitted in one TDMA frame because the number of specified retransmission subchannels is smaller than the specified number of retransmission segments. Determines that the remaining retransmission segments that could not be mapped in one TDMA frame are transmitted by the base station in the next and subsequent TDMA frames.

  The data frame signal reconstruction unit 204 receives information on the retransmission segment and retransmission subchannel specified by the retransmission data decoding control unit 210. The data frame signal reconstruction unit 204 determines that the retransmission segment transmitted on the specified retransmission subchannel and the segments included in the data frame held in the reception signal buffer 208 have been normally received. The segment is connected to form a data frame signal, and the data frame signal is input to the decoding processing unit 205. The timing at which the retransmission segment is retransmitted is, for example, the TDMA frame next to the TDMA frame from which the data frame in which the previous error was detected was transmitted, or the relative frame position determined in advance by negotiation between the terminal device and the base station. A TDMA frame. The processing after the decryption processing unit 205 is as described above.

  At the time of data transmission from the terminal device, the error detection code adding unit 215 reads data from the transmission buffer 214, adds an error detection code (EDC) to the read data, generates a data frame, and corrects the error. The data is input to the encoding unit 216. As the error detection code, for example, there is a CRC (Cyclic Redundancy Check) code. The terminal device can also simultaneously transmit two or more data frames in one TDD uplink section (uplink frame). In this case, the transmission buffer 115 transmits data for generating two or more data frames. Read from. The data frame to be generated also includes a control data frame including control information such as ACK / NACK and CQI as shown in FIG.

  The error correction encoding unit 216 encodes the data sequence of the data frame input from the error detection code adding unit 215 using a predetermined encoding method, and inputs the encoded data sequence to the data frame dividing unit 217.

  The data frame division unit 217 divides the data series input from the error correction encoding unit 216 into one or more segments and inputs the data series to the subchannel mapping unit 218.

  The subchannel mapping unit (mapping unit) 218 arranges each segment in an available subchannel specified by the MAP acquired by the control information reference unit 209 and inputs the segment to the modulation processing unit 219.

  FIG. 13 shows the correspondence between data frames, error correction encoded data frames, segments, and subchannels. Here, a state in which a data frame subjected to error correction coding is divided into K segments and mapped to K subchannels is shown. Note that subchannels assigned to terminal devices are not necessarily consecutively numbered subchannels.

  The modulation processing unit 219 modulates the data input from the subchannel mapping unit 218 to generate a baseband modulation signal, and inputs the generated baseband modulation signal to the radio processing unit 219.

  The radio processing unit 220 converts the baseband modulated signal input from the modulation processing unit 219 into a radio frequency (RF) signal, and transmits the RF signal to the base station via the antenna 201. A set of the modulation processing unit 219, the radio processing unit 220, and the antenna 201 corresponds to, for example, a transmission unit.

  As described above, according to the embodiment of the present invention, when an error is detected in a data frame in a system in which each segment obtained by dividing a data frame is transmitted through a plurality of subchannels, the segment is partially By retransmitting, the frame efficiency can be improved. Further, by performing channel selection based on independent determination of each base station, the inter-cell interference problem can be solved in an autonomous and distributed manner.

(Second Embodiment)
In the first embodiment, when the data frame transmitted from the base station to the terminal device has an error, the base station and the terminal device each perform control related to retransmission. In the case where there is an error in a data frame transmitted to a station, an example in which control related to retransmission is performed in the base station and the terminal device in the same manner as described above. In this case, the processes performed at the base station and the terminal device are interchanged. For this reason, the base station according to the second embodiment includes a CQI generation unit 213, an ACK / NACK generation unit 212, a retransmission data decoding control unit 210, a reception signal buffer 208, and a data frame signal of the terminal device according to the first embodiment. On the other hand, the terminal apparatus includes a block having a function corresponding to a block such as the reconfiguration unit 204, while the terminal apparatus performs retransmission control units (retransmission segment determination unit, retransmission subchannel determination unit, retransmission unit) in the first embodiment 114, a transmission signal buffer 115, a sub-channel mapping unit 119, a control information reference unit (notification reception unit, information acquisition unit) 113, and the like.

  For example, a block having a function corresponding to the CQI generation unit of the terminal device in the base station is based on the reception quality of each subchannel in the uplink frame measured by the reception quality measurement unit of the base station. It has a function of generating an uplink CQI (for example, reception SINR itself) and transmitting it to a terminal device via a transmission buffer. The block having a function corresponding to the ACK / NACK generation unit of the terminal device in the base station generates ACK / NACK indicating whether or not an error is detected in the data frame received from the terminal device, and generates the generated ACK. / NACK is transmitted to the terminal device via the transmission buffer. In addition, the function corresponding to the retransmission data decoding control unit of the terminal device in the base station has a function of performing retransmission segment identification processing and retransmission channel identification processing.

  Further, the block having a function corresponding to the control information reference unit of the base station in the terminal apparatus has a function of acquiring the uplink CQI of each subchannel in the uplink frame and the ACK / NACK from the base station. A block having a function corresponding to the retransmission control unit of the base station in the terminal device has a function of performing a retransmission segment determination process and a retransmission subchannel determination process when a NACK is received from the base station.

  Hereinafter, in particular, retransmission segment determination processing and retransmission subchannel determination processing performed in the terminal device, and retransmission segment identification processing and retransmission subchannel identification processing performed in the base station will be described.

  In the terminal device, when an error is detected in the data frame received from the base station, the retransmission segment determination process and the retransmission subchannel determination process are performed, the retransmission segment and the retransmission subchannel are determined, and the determined retransmission segment is determined. Transmit on retransmission subchannel.

More specifically, in the retransmission segment determination process in the terminal device, it is possible to refer to the uplink CQI of the subchannel to which the data frame in which the error is detected is mapped, which causes a transmission error due to poor channel quality A subchannel having a high probability is determined, and a segment mapped to such a subchannel is determined as a retransmission segment. That is, in the first scheme of retransmission segment determination processing, it is determined to retransmit a segment mapped to a subchannel satisfying uplink reception SINR <SINR threshold γ _Uth with reference to uplink CQI. When there is no corresponding subchannel, it is determined to retransmit a total of m segments mapped to the subchannels from the subchannel with the lowest received SINR to the mth subchannel (1 ≦ m ≦ the maximum number of divisions of the data frame). In the second method of retransmission segment determination processing, a total of m segments mapped to subchannels from the subchannel with the lowest received SINR to the mth lowest subchannel are retransmitted with reference to the uplink CQI (1 ≦ m ≦ maximum number of divisions of data frame).

In the retransmission subchannel determination process, a retransmission subchannel is selected from usable subchannels notified as MAP from the base station. That is, in the case of the first scheme of retransmission subchannel determination processing, the necessary number (for example, the number of retransmission segments determined in the terminal device), retransmission, in order from the top of the usable subchannel notified from the base station as MAP. Determine as subchannel. In the case of the second scheme of retransmission subchannel determination processing, among usable subchannels notified from the base station as MAP, a data frame in which an error is detected is mapped, and uplink reception SINR> A required number of subchannels satisfying the SINR threshold γ _Uth are selected, for example, in ascending or descending order of subchannel numbers, and the selected subchannels are determined as retransmission subchannels.

  On the other hand, the base station performs retransmission segment identification processing and retransmission subchannel identification processing to identify the retransmission segment to be retransmitted from the terminal device and the retransmission subchannel in which the retransmission segment is arranged. The data frame is reconstructed by concatenating the retransmitted retransmitted segment and the segment determined to be normally received among the segments included in the data frame in which the error is detected.

More specifically, when the base station performs the retransmission segment determination process of scheme 1 in the terminal device, the uplink received SINR <SINR threshold γ among the subchannels to which the data frame in which the error is detected is mapped. It is determined that the segment mapped to the subchannel satisfying _Uth is retransmitted from the terminal device. If there is no corresponding subchannel, it is determined that a total of m segments mapped to these subchannels are retransmitted from the subchannel with the lowest received SINR to the subchannel with the mth received SINR ( 1 ≦ m ≦ the maximum number of divisions of the data frame). On the other hand, when performing the retransmission segment determination process of scheme 2 in the terminal device, the base station refers to the received SINR of the uplink, from the subchannel having the lowest received SINR to the subchannel having the lowest received SINR, It is determined that a total of m segments mapped to these subchannels are retransmitted (1 ≦ m ≦ maximum number of data frame divisions). Which of the above method 1 and method 2 is used is matched in advance in both the base station and the terminal device.

In the retransmission subchannel specifying process, it is determined that the retransmission subchannel is determined by the terminal apparatus from the usable subchannels notified to the terminal apparatus by the base station as the MAP. That is, when the retransmission subchannel determination process of scheme 1 is performed in the terminal apparatus, it is determined that the necessary number of retransmission subchannels are determined in order from the top of the usable subchannels notified by the base station as MAP. When the retransmission subchannel determination process of scheme 2 is performed in the terminal device, the base station is the one in which the data frame in which the error is detected is mapped among the usable subchannels notified as the MAP, and the uplink It is determined that the necessary number of subchannels satisfying the line reception SINR> SINR threshold value γ _Uth are determined as retransmission subchannels, for example, in ascending or descending order of the subchannel numbers.

The block diagram which shows the structure of the base station as one Embodiment of this invention. The block diagram which shows the structure of the terminal device as one Embodiment of this invention. The figure which shows the example of a flame | frame structure used with the radio | wireless communications system concerning one Embodiment of this invention. The figure which shows the usage example of a subchannel concerning one Embodiment of this invention. The figure which shows the correspondence of a data frame, the data frame by which error correction coding was carried out, a segment, and a subchannel. The figure which shows the detailed operation | movement flow of a UL quality monitoring part. The figure which shows the detailed operation | movement flow of a DL quality monitoring part. The figure which shows the detailed operation | movement flow of a channel selection control part. The figure which shows the detailed operation | movement flow of a resending control part. The figure which shows the example of MAP. The flowchart which shows an example of the processing flow of a CQI production | generation part and an ACK / NACK production | generation part. The flowchart which shows the other example of the processing flow of a CQI production | generation part and an ACK / NACK production | generation part. The figure which shows the correspondence of a data frame, the data frame by which error correction coding was carried out, a segment, and a subchannel. The figure which shows an example of the control data frame containing control information. The figure explaining the example of the subchannel used as the object which transmits downlink CQI.

Explanation of symbols

100: base station 101: antenna 102: wireless processing unit 103: demodulation processing unit 104: data frame signal reconstruction unit 105: decoding processing unit 106: error detection processing unit 107: reception buffer 108: reception quality measurement unit 109: UL quality Monitoring unit 110: Channel selection control unit 111: MAP generation unit 112: DL quality monitoring unit 113: Control information reference unit 114: Retransmission control unit 115: Transmission buffer 116: Error detection code addition unit 117: Error correction coding unit 118: Data frame division unit 119: subchannel mapping unit 120: modulation processing unit 121: radio processing unit 200: terminal device 201: antenna 202: radio processing unit 203: demodulation processing unit 204: data frame signal reconstruction unit 205: decoding processing unit 206: Error detection processing unit 207: Reception buffer 208: Reception signal buffer 2 9: Control information reference unit 210: Retransmission decoding control unit 211: Reception quality measurement unit 212: ACK / NACK generation unit 213: CQI generation unit 214: Transmission buffer 215: Error detection code addition unit 216: Error correction coding unit 217: Data frame division unit 218: subchannel mapping unit 219: modulation processing unit 220: radio processing unit

Claims (14)

The uplink frame for uplink communication and the downlink frame for downlink communication, which are each divided into a plurality of subchannels, are alternately switched in time, and the subchannels at the same position in the uplink frame and the downlink frame are switched to the terminal device. A base station that performs communication by assignment,
Mapping for mapping one or more segments obtained by dividing the first data frame to be transmitted to the terminal apparatus to one or more subchannels of subchannels allocated in advance to the terminal apparatus in the downlink frame Means,
Transmitting means for transmitting each mapped segment to the terminal device in the downlink frame;
Notification receiving means for receiving an error detection notification from the terminal device for notifying that an error has been detected in the first data frame restored by concatenating the mapped segments;
First channel quality information indicating the quality of the one or more subchannels to which the first data frame in which the error is detected is mapped in the downlink frame in which the first data frame in which the error is detected is transmitted. First information acquisition means for acquiring from the terminal device;
First evaluation value calculation means for calculating, for each subchannel, a first quality evaluation value for evaluating the quality of the subchannel in the downlink frame allocated to the terminal device from the acquisition history of the first channel quality information;
Availability determination means for determining, for the uplink frame and the downlink frame, suspension of use of the subchannel in which the first quality evaluation value that does not satisfy a first evaluation threshold given in advance is calculated;
Base station equipped with.   The first evaluation value calculating means obtains the first channel quality information for each subchannel every time the first channel quality information that does not satisfy a first quality threshold given in advance is acquired for each subchannel assigned to the terminal device. The base station according to claim 1, wherein the first quality evaluation value of each of the subchannels assigned to the terminal device is calculated by incrementing a first counter. Receiving means for receiving, from the terminal device, one or more segments obtained by dividing the second data frame, which are mapped to one or more subchannels of subchannels assigned in advance to the terminal device in the uplink frame When,
Data frame restoring means for restoring the second data frame by concatenating each segment received by the receiving means;
Error detection means for detecting errors in the restored second data frame;
Quality measuring means for measuring the quality of each of the subchannels assigned to the terminal apparatus in the uplink frame;
Second line quality information indicating the quality of each of the one or more subchannels to which the second data frame in which the error is detected is mapped in the uplink frame in which the second data frame in which the error is detected is transmitted. Second information acquisition means for acquiring the information based on the quality measurement means;
Second evaluation value calculation means for calculating, for each subchannel, a second quality evaluation value for evaluating the quality of the subchannel in the uplink frame allocated to the terminal device from the acquisition history of the second channel quality information; Prepared,
The usability determining unit is configured to calculate at least one of the first quality evaluation value not satisfying the first evaluation threshold and the second quality evaluation value not satisfying a second evaluation threshold given in advance. Determining channel suspension for the upstream and downstream frames;
The base station according to claim 1.   The second evaluation value calculation means, for each subchannel assigned to the terminal device, every time the second channel quality information that does not satisfy a second quality threshold value given in advance is acquired for each subchannel. The base station according to claim 3, wherein the second quality evaluation value of each of the subchannels assigned to the terminal device is calculated by incrementing a second counter. The first evaluation value calculating means obtains the first channel quality information that does not satisfy a first quality threshold given in advance for each of the subchannels assigned to the terminal device in the downlink frame. Calculating the first quality evaluation value of each subchannel allocated to the terminal device by incrementing a first counter for each subchannel;
The second evaluation value calculation means, whenever the second channel quality information that does not satisfy a second quality threshold given in advance is acquired for each of the subchannels assigned to the terminal device in the uplink frame, Calculating the second quality evaluation value of each of the subchannels assigned to the terminal device by incrementing a second counter for each subchannel;
The availability determination unit stops using a subchannel from which at least one of the first quality evaluation value that is equal to or higher than the first evaluation threshold and the second quality evaluation value that is equal to or higher than the second evaluation threshold is obtained. For the upstream frame and the downstream frame,
The first evaluation threshold is greater than the second evaluation threshold;
The base station according to claim 3. When the error detection notification is received by the notification receiving unit, a segment to be retransmitted among the segments into which the first data frame has been divided is detected when the error acquired by the information acquiring unit is detected. Retransmission segment determining means for determining based on the first channel quality information of the one or more subchannels to which one data frame has been mapped;
A subchannel that maps the segment to be retransmitted determined by the retransmission segment determining means is usable in the downlink frame that has not been suspended by the availability determining means among the subchannels assigned to the terminal apparatus. Retransmission subchannel determination means for determining from among subchannels;
Using the mapping means, the segment to be retransmitted determined by the retransmission segment determining means is mapped to the subchannel determined by the retransmission subchannel determining means, and each mapped segment to be retransmitted is transmitted Retransmitting means for transmitting to the terminal device in the downlink frame using means;
The base station according to claim 1, further comprising:   The retransmission segment determining means is mapped to a subchannel having a quality lower than a preset first quality standard among the one or more subchannels to which the first data frame in which the error is detected is mapped. 7. The base station according to claim 6, wherein a segment that has been determined is determined as the segment to be retransmitted.   The retransmission segment determination means retransmits segments mapped to a certain number of subchannels in order of poor quality among the one or more subchannels to which the first data frame in which the error is detected is mapped. The base station according to claim 6, wherein the base station is determined as a segment to be performed.   The retransmission subchannel determination means has a quality higher than a preset second quality standard among the usable subchannels that have not been suspended by the availability determination means, and the first error is detected. The base station according to any one of claims 6 to 8, wherein a subchannel to which a data frame is mapped is determined as the retransmission subchannel. From a base station that performs communication by alternately switching an uplink frame for uplink communication and a downlink frame for downlink communication that are divided into a plurality of subchannels in time, subframes at the same position in the uplink frame and the downlink frame A terminal device that is assigned a channel,
One or more segments obtained by dividing a third data frame to be transmitted to the base station are mapped to one or more subchannels of subchannels allocated in advance from the base station in the uplink frame. Mapping means;
Transmitting means for transmitting each mapped segment to the base station in the uplink frame;
Notification receiving means for receiving an error detection notification from the base station for notifying that an error has been detected in the third data frame restored by concatenating the mapped segments;
Third line quality representing the quality of each of the one or more subchannels to which the third data frame in which the error is detected is mapped in the uplink frame in which the third data frame in which the error is detected is transmitted Information acquisition means for acquiring information from the base station;
Retransmission segment determination for determining a segment to be retransmitted from among the segments obtained by dividing the third data frame based on the third channel quality information of the one or more subchannels acquired by the information acquisition means Means,
Retransmission subchannel determination means for determining, from among the subchannels allocated by the base station in the uplink frame, a subchannel to which the segment to be retransmitted determined by the retransmission segment determination means is mapped;
Using the mapping means, the segment to be retransmitted determined by the retransmission segment determining means is mapped to the subchannel determined by the retransmission subchannel determining means, and each mapped segment to be retransmitted is transmitted Retransmitting means for transmitting to the base station in the uplink frame using means;
A terminal device comprising:   The retransmission segment determination means is mapped to a sub-channel having a quality lower than a preset third quality standard among the one or more sub-channels to which the third data frame in which the error is detected is mapped. The terminal apparatus according to claim 10, wherein the segment is determined as the segment to be retransmitted.   The retransmission segment determination means retransmits the segments mapped to a certain number of subchannels in order of poor quality among the one or more subchannels mapped with the third data frame in which the error is detected. The terminal device according to claim 10, wherein the terminal device is determined as a power segment.   The retransmission subchannel determining means determines, as the retransmission subchannel, a subchannel having a quality higher than a preset fourth quality criterion and mapped with the third data frame in which the error is detected. The terminal device according to claim 10, wherein the terminal device is characterized in that A base station that performs communication by alternately switching an uplink frame for uplink communication and a downlink frame for downlink communication that are each divided into a plurality of subchannels, and the uplink frame and the downlink frame from the base station A communication method performed with a terminal apparatus that is assigned subchannels at the same position,
One or more segments obtained by dividing the first data frame to be transmitted to the terminal device are mapped to one or more subchannels of subchannels allocated in advance to the terminal device in the downlink frame. ,
Transmitting each mapped segment to the terminal device in the downlink frame;
Concatenating each mapped segment to restore the first data frame;
When an error is detected in the restored first data frame, an error detection notification indicating that an error has been detected, and the error in the downlink frame that has transmitted the first data frame in which the error has been detected. Transmitting the first channel quality information indicating the quality of the one or more subchannels to which the detected first data frame is mapped to the base station;
A first quality evaluation value for evaluating the quality of the subchannel in the downlink frame allocated to the terminal device from the acquisition history of the first channel quality information is calculated for each subchannel,
Determining whether to stop using the subchannel for which the first quality evaluation value that does not satisfy the first evaluation threshold given in advance is calculated for the uplink frame and the downlink frame;
A communication method characterized by the above.

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