JP2010035207A - Transmission equipment, receiving equipment, and retransmission equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress excessive quality in a receiving apparatus capable of obtaining a combined gain by distinguishing and controlling retransmission for initial transmission.
In the present invention, for example, when performing re-transmission in a transmitting apparatus that transmits data to a receiving apparatus that reproduces data using received data and re-transmitted data. For the first transmission, there is used a transmission apparatus comprising a control means for controlling a transmission parameter for performing retransmission in a direction that saves radio resources.
[Selection] Figure 4

Description

  The present invention relates to a transmission apparatus, a reception apparatus, and a retransmission control method, for example, a radio base station and a mobile station in a mobile radio communication system adopting a W-CDMA communication system.

Currently, standardization of the W-CDMA system, which is one system of the third generation mobile communication system, is being promoted by 3GPP (3rd Generation Partnership Project). As one of the themes of standardization, HSDPA (High Speed Downlink Packet Access) that provides a maximum transmission speed of about 14 Mbps in the downlink is defined.
HSDPA employs an adaptive coded modulation system, and is characterized by, for example, adaptively switching between a QPSK modulation system and a 16-value QAM system according to the radio environment between a base station and a mobile station.
HSDPA adopts an H-ARQ (Hybrid Automatic Repeat reQuest) system. In HSDPA, when the mobile station detects an error in the received data from the base station, data is retransmitted from the base station in response to a request from the mobile station, and the mobile station is retransmitted with already received data. It is characterized by performing error correction decoding using both received data. As described above, in H-ARQ, even if there is an error, the already received data is effectively used to increase the error correction decoding gain and to reduce the number of retransmissions.

  Main wireless channels used for HSDPA include HS-SCCH (High Speed-Shared Control Channel), HS-PDSCH (High Speed-Physical Downlink Shared Channel), and HS-DPCCH (High Speed-Dedicated Physical Control Channel).

  HS-SCCH and HS-PDSCH are both common channels in the downlink direction (that is, the direction from the base station to the mobile station), and HS-SCCH transmits various parameters related to data to be transmitted on HS-PDSCH. Control channel. The various parameters include, for example, modulation type information indicating which modulation method is used to transmit data by HS-PDSCH, the number of assigned spreading codes (number of codes), a pattern of rate matching performed on transmission data, etc. Information.

On the other hand, the HS-DPCCH is an individual control channel in the uplink direction (that is, the direction from the mobile station to the base station), and an ACK signal can be received depending on whether data received via the HS-PDSCH is receivable This is used when the mobile station transmits a NACK signal to the base station. When the mobile station fails to receive data (when the received data is a CRC error, etc.), the base station executes retransmission control because a NACK signal is transmitted from the mobile station.
In addition, the HS-DPCCH is also used by a mobile station that measures the reception quality (for example, SIR) of a received signal from a base station and transmits the result as a CQI (Channel Quality Indicator) to the base station. Based on the received CQI, the base station determines whether the downlink radio environment is good or not. If it is good, the base station switches to a modulation method capable of transmitting data at a higher speed. Switch to the modulation method to be transmitted (that is, perform adaptive modulation).
・ "Channel structure"
Next, a channel configuration in HSDPA will be described.
FIG. 1 is a diagram for illustrating a channel configuration in HSDPA. Since W-CDMA employs a code division multiplexing system, each channel is separated by a code.

First, the channels not described will be briefly described.
CPICH (Common Pilot Channel) and P-CCPCH (Primary Common Control Channel) are downlink common channels, respectively.

  The CPICH is a channel used for channel estimation, cell search, and a timing reference for other downlink physical channels in the same cell in a mobile station, and is a channel for transmitting a so-called pilot signal. P-CCPCH is a channel for transmitting broadcast information.

Next, channel timing relationships will be described with reference to FIG.
As shown in the figure, each channel constitutes one frame (10 ms) by 15 slots. As described above, since CPICH is used as a reference for other channels, the heads of P-CCPCH and HS-SCCH frames coincide with the heads of CPICH frames. Here, the head of the HS-PDSCH frame is delayed by 2 slots with respect to HS-SCCH or the like. However, after the mobile station receives the modulation type information via HS-SCCH, the received modulation type is changed to the received modulation type. This is because HS-PDSCH can be demodulated by a corresponding demodulation method. HS-SCCH and HS-PDSCH constitute one subframe with three slots.
This is because HS-DPCCH is not synchronized with CPICH, but is an uplink channel and is based on timing generated in the mobile station.

The above is a simple description of the channel configuration of HSDPA. Next, a process until transmission data is transmitted via HS-PDSCH will be described with reference to a block diagram.
・ Base station configuration
FIG. 2 shows the configuration of a base station that supports HSDPA.

In the figure, 1 is a CRC adding unit, 2 is a code block dividing unit, 3 is a channel coding unit, 4 is a bit separating unit, 5 is a rate matching unit, 6 is a bit collecting unit, and 7 is a modulating unit.
Next, the operation of each block will be described.
Transmission data transmitted via HS-PDSCH (data stored in one subframe of HS-PDSCH in FIG. 1) is first subjected to CRC calculation processing in one CRC adding unit, and the calculation result is the transmission data. Added to the end. The transmission data to which the CRC calculation result is added is input to the code block dividing unit 2 and divided into a plurality of blocks. This is for shortening the data length of the unit for performing error correction coding in consideration of the decoding processing load on the receiving side. When the data length exceeds a predetermined length, it is equally divided into a plurality of blocks. The number of divisions can be an integer greater than or equal to 2, but the case where the number of divisions is 2 will be described below for the sake of simplicity. Of course, when the data length is short, division is not necessary.

Each of the divided transmission data is handled as data to be subjected to separate error correction coding in the channel coding unit 3. That is, error correction coding processing is performed on each of the divided first block and second block. An example of channel coding is turbo coding.
Here, the turbo coding will be briefly described. In turbo coding, if the data to be coded is U, based on U, U itself, U ′ obtained by convolutional coding of U, and U are interleaved (rearrangement processing). Similarly, U ″ obtained by convolutional coding is output. Here, U is referred to as a systematic bit, and is data used in both of the two element decoders in turbo decoding. Since U is frequently used, it can be understood that U is highly important data. On the other hand, U ′ and U ″ are redundant bits, each of which is data used by one of the two element decoders. Since the usage frequency is low, it can be understood that the importance is lower than U.
That is, the systematic bits are more important than the redundant bits, and it can be said that a correct decoding result can be obtained by the turbo decoder when the systematic bits are received more correctly.

The systematic bits and the redundant bits generated in this way are input to the bit separation unit 4 as serial data, and the bit separation unit 4 converts the input serial data into U, U ′, U ″. The data is separated into three systems and output as parallel data.
The rate matching unit 5 performs a puncturing process for deleting bits by a predetermined algorithm or a repetition process by repeating the bits so as to be within a subframe composed of 3 slots of HS-PDSCH.

  In this way, the bits subjected to the bit adaptation processing for the subframe in the rate matching unit 5 are input in parallel to the bit collection unit 6.

For example, the bit collection unit 6 generates and outputs a 4-bit bit string indicating each signal point of 16-level QAM modulation based on the input data. When generating a bit string, the systematic bits are preferentially arranged on the higher-order bit side that is not prone to error during the initial transmission.
The modulation unit 7 outputs a 16-value QAM modulated signal having an amplitude and phase corresponding to the signal point indicated by the input bit string, converts the signal to a radio frequency by frequency conversion, and then an antenna (not shown) Send to the side.

The matters relating to HSDPA described above are disclosed in, for example, the following Patent Documents 1 and 2 and Non-Patent Document 1.
JP 2002-9741 A JP 2002-281003 A 3G TS 25.212 (3rd Generation Partnership Project: Technical Specification Group Radio Access Network; Multiplexing and channel coding (FDD))

According to the background art described above, when the base station receives a NACK signal from the mobile station, the base station performs retransmission, and at that time, special control such as making the transmission power different from that of the initial transmission. Therefore, at the time of retransmission, transmission is performed with the same transmission power as the first transmission.
However, as described above, when the received data is reproduced (decoded) by combining both the first received signal and the signal received by retransmission, the received signal is used alone. In the first place, a combined gain is obtained.
Therefore, the data can be reproduced (decoded) in a little more by the first transmission, but even if the data cannot be reproduced (decoded) due to an error of several bits, re-transmission is performed with the same transmission power, etc. It may become quality.
Therefore, one of the objects of the present invention is to suppress excessive quality in a receiving apparatus that can obtain a combined gain by distinguishing and controlling retransmission for initial transmission.

  It is to be noted that the present invention is not limited to the above-described object, and is an effect derived from each configuration shown in the best mode for carrying out the invention described later, and has an effect that cannot be obtained by the conventional technique. Can be positioned as one.

(1) In the present invention, in a transmitting apparatus that transmits data to a receiving apparatus that reproduces data using received data and retransmitted data, retransmission is performed for the first transmission. A transmission apparatus characterized by comprising control means for controlling transmission parameters when performing in a direction to save radio resources is used.
(2) Also, in the present invention, in a transmission apparatus that transmits data to a reception apparatus that reproduces data using received data and retransmitted data, a transmission parameter at the time of transmission is changed. A transmission apparatus comprising: control means for performing control; and suppression means for controlling the control in a direction to suppress consumption of radio resources when retransmitting the first transmission. Use.
(3) Further, in the present invention, in the receiving apparatus that reproduces data using the received data and the retransmitted data, the received data is transmitted to the transmitting apparatus that can control the transmission parameter at the time of retransmission. And a feedback unit that feeds back the information calculated from the likelihood information or the information calculated from the likelihood information to the transmission device.
(4) Moreover, in this invention, the information calculated from the said likelihood information contains the information which specifies the transmission parameter which should be changed, The receiver of Claim 3 characterized by the above-mentioned is used.
(5) Further, in the present invention, in the transmitting apparatus that transmits data to the receiving apparatus that reproduces the data using the received data and the retransmitted data, the likelihood information of the received data or the data A receiving means for receiving information calculated from the likelihood information from the receiving device, and a control for determining a transmission parameter at the time of retransmission based on the information obtained by the reception and executing retransmission with the determined parameter And a control unit for performing transmission.
(6) In the present invention, in a CDMA mobile communication system that performs transmission employing a hybrid ARQ scheme between a base station and a mobile station, when the base station performs retransmission, the first transmission is performed. On the other hand, a CDMA mobile communication system is used, which includes a control unit that controls transmission by reducing transmission power, reducing the number of spreading codes to be used, or increasing the spreading factor.
(7) Also, in the present invention, in a CDMA mobile communication system including a base station that performs adaptive modulation based on CQI information from a mobile station and performs transmission using a hybrid ARQ scheme with the mobile station, When the base station performs re-transmission, in order to perform adaptive modulation based on the CQI information, transmit at a lower transmission power, reduce the number of spreading codes to be used, or increase the spreading factor. A CDMA mobile communication system including a control unit for controlling is used.

  According to the transmission device of the present invention, when performing retransmission, radio resources are conserved and transmitted, so that excessive quality in the reception device can be suppressed or the saved radio resources can be allocated to other reception devices. it can.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[A] Description of First Embodiment FIG. 3 is a diagram illustrating a transmission apparatus according to the present invention.

  As an example of the transmission apparatus, a transmission apparatus (radio base station) of the W-CDMA communication system corresponding to the HSDPA described above will be described. It is also possible to apply to a transmission device in another communication system.

In the figure, reference numeral 10 denotes a control unit that sequentially outputs transmission data (data to be transmitted within one subframe) transmitted via the HS-PDSCH and controls each unit (11 to 26, etc.). The main control of the control unit 10 includes the following items.
(1) Retransmission is controlled based on a NACK signal received by the receiving unit 26 described later.
(2) Distinguish between the first transmission and the retransmission, and control the transmission parameters for performing the retransmission in the direction of saving radio resources with respect to the first transmission.

Here, examples of radio resources include transmission power, the number of transmission antennas, the number of spreading codes, the number of carriers, and the like.
Since HS-PDSCH is a common channel, transmission data that are sequentially output are allowed to be addressed to different mobile stations.
11 is a CRC attachment unit for performing CRC calculation on sequentially input transmission data (data to be transmitted in the same radio frame) and adding a CRC calculation result to the end of the transmission data; A bit scrambling unit that gives transmission data randomness by scrambling transmission data to which the CRC calculation result is added in units of bits is shown.
13 is a bit input for the purpose of preventing an increase in the amount of calculation of the decoder on the receiving side due to the data length to be encoded becoming too long in the next channel encoding. A code block segmentation unit that divides (for example, bisects) when scrambled transmission data exceeds a predetermined data length. In the figure, the output when the input data length exceeds a predetermined data length and is divided into two equal parts (divided into a first data block and a second data block) is shown. Of course, an example in which the number of divisions is other than 2 is also conceivable, and an example in which the data is not divided equally but divided into different data lengths is also conceivable.
Reference numeral 14 denotes a channel coding unit that performs error correction coding processing on each divided data separately. Note that the above-described turbo encoder is preferably used as the channel encoding unit 14, and a turbo encoder is also used here.
Therefore, as described above, the first output is obtained by convolutionally encoding the systematic bits (U) and the systematic bits (U), which are the same data as the data to be encoded, for the first block. The obtained first redundant bit (U ′) and the second redundant bit (U ″) obtained by interleaving the systematic bit and then performing convolutional coding in the same manner are included. Similarly, the second output includes a systematic bit (U), a first redundant bit (U ′), and a second redundant bit (U ″) for the second block. The coding rate is included in one of the transmission parameters.
When the coding rate is increased, the number of redundant bits is reduced, so that the spreading factor as a transmission parameter can be increased (the number of spreading code chips allocated to one symbol can be increased) and can be used for other communications. You can increase the number. If the chip rate is fixed, the spreading factor can be increased by widening the data width.
In addition, since the amount of data is large, when transmitting using a plurality of spreading codes, since the number of redundant bits is reduced, the number of spreading codes to be used can be reduced, and the number of spreading codes as a transmission parameter can be reduced. Can be saved.
15 is a systematic bit (U), a first redundant bit (U ′), and a second redundant bit (U ″) of the first block and the second block serially input from the channel encoding unit 14 (turbo encoder). ) Shows a bit separation part for separating and outputting each. Since the same applies to the second block, only the output corresponding to the first block is shown.
16 is input so that the input data (all of the data of the divided blocks in the case of dividing into a plurality of blocks) has a data amount that fits in a predetermined area of the virtual buffer unit 17 at the subsequent stage. a first rate matching (1 ^st rate matching) unit for performing rate matching processing such as puncturing processing (thinning) for data.
17 is a virtual buffer (set by the control unit 10 in accordance with the reception processing capability of the mobile station to be transmitted, and in which data subjected to rate matching processing by the first rate matching unit 16 is stored. Buffer) part. At the time of retransmission, by outputting the stored data, the processing from the CRC adding unit 11 to the first rate matching unit 16 can be omitted. However, if the coding rate is to be changed at the time of retransmission, the stored data is stored. It is desirable to output the transmission data stored in the control unit 10 again without using the processed data. Note that a buffer is not provided as the virtual buffer unit 17, and it can be made through as it is. In this case, the retransmission data is output again from the control unit 10.
18, the control unit 10, shows a second rate matching (2 ^nd rate matching) unit for adjusting the data length that can be accommodated in one subframe specified, puncturing (thinning), repetition processing (repetition ) To adjust the data length of the input data so that the specified data length is obtained.
Note that the symbol rate can be lowered by increasing the number of bits to be deleted as a result of puncture processing or the like in the first rate matching unit 16 or the second rate matching unit 18. The rate matching pattern is one of the transmission parameters. By changing the rate matching pattern to a pattern that reduces the amount of data, the spreading factor as the transmission parameter is increased (the spreading code assigned to one symbol). The number of chips can be increased), and the number of spreading codes available for other communications can be increased. If the chip rate is fixed, the spreading factor can be increased by widening the data width.
In addition, since the amount of data is large, when transmitting using a plurality of spreading codes, the amount of transmission data decreases, so the number of spreading codes to be used can be reduced, and the number of spreading codes as a transmission parameter can be reduced. Can be saved.
Reference numeral 19 denotes a bit collection unit that arranges data from the second rate matching unit 19 in a plurality of bit strings. That is, by arranging the data of the first block and the data of the second block by a predetermined bit arrangement method, a plurality of bit strings for indicating signal points on the phase plane are output. In this embodiment, since the 16-value QAM modulation method is used, the bit string is composed of 4 bits. However, when the 64-value QAM modulation method is used, the bit string is 6 bits, and when the QPSK modulation method is used, the bit string is 2 bits. Make a bit.
Here, the number of bits of the bit string (the value of N when performing N-value modulation) is considered as one of the transmission parameters. By increasing the number of bits in the bit string, the rate of symbols composed of the bit string can be lowered, and the spreading factor as a transmission parameter can be increased (the number of spreading code chips allocated to one symbol can be increased). The number of spreading codes that can be used for other communications can be increased.
In addition, since the amount of data is large, when transmitting using a plurality of spreading codes, the amount of data that can be allocated to one signal point increases, so the number of spreading codes to be used can be reduced, and transmission parameters can be reduced. As a result, the number of spreading codes can be saved.

  20 divides and outputs the bit string to the same number of systems as the number of spreading codes (number of codes) notified by the control unit 10. That is, when the number of codes in the transmission parameter notified by the control unit 10 is N, a physical channel segmentation unit that divides an input bit string into 1 to N systems in order and outputs the system.

  Reference numeral 21 denotes an interleaving unit that performs interleaving processing on each of the N bit strings and outputs the result.

  Reference numeral 22 denotes a constellation re-arrangement for 16 QAM unit that can re-arrange bits in each bit string for each input bit string. For example, at the time of the first transmission, each input bit string can be output as it is, and the bits can be rearranged at the time of retransmission in H-ARQ described above. The bit rearrangement is, for example, processing such as switching the upper bit and the lower bit, and it is preferable to perform bit replacement according to the same rule for a plurality of bit strings. In addition, it is possible to pass through as it is at the time of retransmission.

  Reference numeral 23 denotes a physical channel mapping unit that distributes the N-system bit string in the subsequent stage to the corresponding spreading unit of the spreading processing unit 24 in the subsequent stage.

  24 includes a plurality of spreading sections, each of which outputs a corresponding I and Q voltage value based on each of N systems of bit strings, and performs a spreading process using different spreading codes, and outputs a spreading process (Spreading) section. Show. As described above, in order to increase the spreading factor when the symbol rate can be lowered by changing the coding rate as a transmission parameter, the rate matching pattern, and the value N at the time of N-value modulation. More spread code chips are assigned to one symbol, and the number of spread codes that can be used for other communications increases. Further, when the number of spreading codes to be used is reduced, the number of spreading units to be used is reduced and can be assigned to other transmissions.

  25 synthesizes each signal spread by the spread processing unit 24, performs amplitude phase modulation such as a 16-value QAM modulation system based on this, amplifies it by a variable gain amplifier, and further converts the frequency into a radio signal Then, a modulation unit that enables output to the antenna side and transmission as a radio signal is shown. Here, the distance between signal points at the time of modulation is considered as one of transmission parameters. This is because by reducing the distance between signal points, errors are likely to occur, but transmission power as a radio resource can be suppressed.

  In HSDPA, signals destined for other mobile stations can be multiplexed by spreading codes even in subframes of the same timing, so a set of 10 to 25 and a variable gain amplifier (referred to as a transmission set) Preferably, the output signals of the variable gain amplifiers are combined and then frequency-converted in common before being transmitted to the antenna side. Of course, since the codes need to be separated, the spread codes used in the spread processing unit 24 in each transmission set are different spread codes so that they can be separated.

  Here, the gain in the variable gain amplifier can be considered as one of the transmission parameters. That is, if the maximum transmission power after combining with other transmission sets is limited by simply lowering the gain, transmission power can be allocated to other transmission sets, and interference with other signals can be achieved. As a result, it is possible to save radio resources.

  Reference numeral 26 denotes a reception unit, which receives a signal from a mobile station received via HS-DPCCH or the like, and gives an ACK, NACK signal, CQI, or the like to the control unit 10.

The above is the description of each part name and its operation.
When the base station supports MIMO (multi input multi output), the base station includes a plurality of antennas and can transmit signals separately. That is, the signal given from the physical channel mapping unit 23 to the first spreading processing unit 24 is sent from the first antenna, and the signal given to the second despreading processing unit 24 is sent from the second antenna. Thereby, different data can be transmitted from different antennas to the same mobile station. The spreading codes in the first despreading unit and the second despreading unit are different spreading codes when transmitted from the same antenna. Thus, when MIMO is applied, the same spreading code is used. A code can be used. Therefore, if there are N sequences to be transmitted to the same mobile station and there are M MIMO antennas, it is sufficient to use [N / M] spreading codes for this mobile station. (Here, [n] is a minimum integer equal to or greater than n.) Preferably, a spreading code used for spreading signals transmitted from the first antenna and the second antenna is a common spreading code generation. Use the output from the instrument. This is because the spreading code generator can be shared.
Therefore, in such a case, the amount of data that can be transmitted can be controlled by changing the number of antennas that transmit to the mobile station of the transmission partner. That is, if there are M antennas, assigning L channels (L ≦ M) for transmission of signals to one mobile station allows L channels to be assigned in the same way as assigning L spreading codes. Can be assigned. As described above, the number of antennas to be allocated when adopting MIMO is given as one of the transmission parameters, and belongs to one of the transmission parameters that can be controlled by the control unit 10. MIMO can transmit individual data with each antenna. However, in order to reduce the number of antennas, increase the code rate or increase N of N-value modulation as the transmission parameter described above. This can be achieved by taking measures such as changing the rate matching pattern and increasing the number of bits not transmitted as a result.

When the base station supports the OFDM scheme, the number of subcarriers used when transmitting to one mobile station is listed as one of the transmission parameters, and this can be controlled by the control unit 10 as well. Belongs to one of the parameters. In order to reduce the number of subcarriers, the number of bits not transmitted as a result of increasing the code rate, increasing N of N-value modulation, or changing the rate matching pattern as the transmission parameter described above It is possible by taking measures such as increasing
・ "Processing of control unit 10"
Next, processing of the control unit 10 regarding retransmission control will be described in detail with reference to FIG.
FIG. 4 is a flowchart showing the process 1 of the control unit 10.
First, the control unit 10 prepares transmission data i that is data to be transmitted (step 1). The transmission data may be received as data addressed to the mobile station from the base station controller side, for example.
Then, the transmission parameter is set as X (step 2), and transmission is performed (step 3). Transmission parameters include, for example, the coding rate in the channel coding unit 14, the rate matching pattern in the first and second rate matching units 16 and 17, the number of separations according to the number of spreading codes in the physical channel separation unit, and the spreading processing unit 24, a modulation method (1 to N in total, 1 to N) in the modulation unit 25, and a variable gain (not shown) for amplifying the output of the modulation unit 25 before combining with a signal addressed to another mobile station The gain of the amplifier, the number of transmission antennas (not shown) when the MIMO system is employed, and the like are mentioned, and these values are set as corresponding portions as X1, X2,. X indicates a combination of these transmission parameters (xi).

  After the transmission, the mobile station as a receiving apparatus, which will be described later, waits for the reception of the ACK and NACK signals transmitted according to the error detection result (CRC check result) for the received data, and receives the ACK signal within a predetermined time. Is determined (step 4). Here, when the ACK signal is received, the next transmission data i + 1 is prepared as the transmission data (step 5), and the process returns to step 2.

  On the other hand, if a NACK signal is received from the mobile station or no ACK signal is received within a predetermined time, the process proceeds to a retransmission control process (step 6). That is, the data i that failed to be transmitted is output and retransmitted. Note that the control unit 10 includes a storage unit that stores the transmission data i until the ACK is received, and it is desirable to perform transmission again by reading from the storage unit.

  When the process proceeds to the retransmission control process, the transmission parameter is set to Y this time (step 7), and transmission is performed again. Here, the reason why the transmission parameter is set to Y with respect to X is to mean that at least one of the parameters of Xi is different. Furthermore, the setting value Y is characterized in that it is a value that saves radio resources with respect to X.

For example, (i) increase the encoding rate in the channel encoding unit 14, or (ii) change the rate matching pattern in the first and second rate matching units 16 and 17 to reduce the data amount, or (iii) bits The collection unit 19 increases the number of bits of the bit string, and the modulation unit 25 either increases N when performing N-value modulation (any of (i) to (iii)), and further spreads. Increasing the rate or reducing the number of spreading codes used results in an increase in the number of codes available for other communications.
In addition, the modulation method in the modulation unit 25 is changed to a method in which the distance between signal points is narrower, and as a result, transmission power is suppressed.
Further, the gain of a variable gain amplifier (not shown) for amplifying the output of the modulation unit 25 before combining with the signal addressed to another mobile station is lowered to simply reduce the transmission power. Increase the encoding rate in the encoding unit 14, (ii) increase the number of bits to be punctured in the rate matching pattern in the first and second rate matching units 16 and 17, or (iii) N when N-value modulation is performed To reduce the number of transmission antennas (not shown) when the MIMO scheme is employed.

In this way, the control unit 10 changes the transmission parameter to a direction that saves radio resources at the time of retransmission, and therefore, with respect to a receiving apparatus (mobile station) that can obtain a combined gain, such as H-ARQ, excessive quality is achieved. It is possible to suppress the transmission with The saved radio resource is preferably used by the control unit 10 for communication with other mobile stations.
・ "Another process of the control unit 10"
FIG. 5 shows another process as the process of the control unit 10.

  Since the characteristic is about the added step 8, this part will be described in particular. Refer to the previous description for other steps.

  When the process proceeds to the retransmission control process in step 6, it is determined whether or not the retransmission is the Nth time. Here, if it is the Nth time, the transmission parameter is set to Y, but if it is not the Nth time, the transmission parameter is set to X even if it is retransmission.

  Here, N may be set to any one of 1, 2, 3,..., And a plurality (two, etc.) of these may be set.

Since it is considered that the mobile station can obtain a larger combined gain as retransmission is performed, N can be set to a large value. However, in terms of suppressing excessive quality, the value is set as small as possible. This is also useful, for example, when the first retransmission (ie, N = 1) and the last retransmission (N = L (L is the maximum number of retransmissions)).
Next, the receiving apparatus according to the present invention will be described.
・ "Description of receiver (mobile station)"
FIG. 6 is a diagram showing a receiving apparatus according to the present invention.

  As an example of the receiving apparatus, a receiving apparatus (mobile station) of the W-CDMA communication system corresponding to the HSDPA described above will be described. Of course, by providing a plurality of antennas like a base station, it can be a mobile station compatible with MIMO or a mobile station compatible with OFDM.

  In the figure, reference numeral 27 denotes a receiving unit that outputs a received signal obtained by subjecting the received signal to quadrature detection, despreading processing, and the like. In the channel decoding 32 described later, since soft decision information is also used, the output of the receiving unit 27 includes soft decision information.

  Reference numeral 28 denotes a first puncture unit, which corresponds to the reverse process of the process of the second rate matching unit 18 and inserts information of likelihood 0 into the bit position deleted by the puncture process. By including information of likelihood 0, adverse effects on the error correction decoding process in the channel decoding unit 32 can be suppressed.

  Although the rate matching pattern in the second rate matching unit 18 is changed for each transmission, the control unit 10 can recognize the pattern in advance via the HS-SCCH. The first depuncture unit 28 is controlled so that the depuncture process corresponding to the pattern notified from the base station is performed for each reception.

  Reference numeral 29 denotes a synthesis unit, and 30 denotes a memory. Data relating to the first transmission is output to the second depuncture unit 31 as it is and stored in the memory 31. On the other hand, the second and subsequent transmission data that are not specific retransmission are combined with the data already stored in the memory 30 and output to the second depuncture unit 31, and the combined data is stored in the memory 30 again. Note that, when combining, for example, it is conceivable to average likelihood information. That is, the likelihood is high only for the first reception, but if the subsequent reception has a low likelihood, the likelihood is lowered with respect to the first likelihood by synthesis.

  Reference numeral 31 denotes a second depuncture unit, which corresponds to the reverse process of the process of the first rate matching unit 16 and inserts information of likelihood 0 at the bit position deleted by the puncture process.

  Reference numeral 32 denotes a channel decoding unit, which performs error correction decoding processing such as turbo decoding based on the output from the second depuncture unit 31 and outputs data after error correction.

Here, the configuration of a case where a turbo decoder is used as an example of the channel decoding unit 32 will be briefly described.
"Configuration of turbo decoder"
FIG. 7 is a diagram showing the configuration of the turbo decoder.

  In the figure, reference numeral 321 denotes a first element decoder, 323 denotes a second element decoder, 322 denotes an interleaver, and 324 denotes a deinterleaver.

It should be noted that U, U ′, U ″ are obtained by turbo coding on the transmission side (base station side), and information corresponding to these is obtained by converting the received information to Y, Y ′, Y ′, respectively. Shown as'. Next, the operation will be briefly described.
When turbo decoding is performed, first of all Y, Y ′, Y ″, Y, Y ′ is used for decoding by the first element decoder (DEC1) 321. The element decoder 321 is a soft output element decoder and outputs a likelihood to a decoding result. Next, similar decoding is performed by the second element decoder (DEC2) 323 using the likelihood and Y ″ output from the first element decoder. That is, the second element decoder 323 is also a soft output element decoder and outputs the likelihood of the decoding result. Since Y ″ is a received signal corresponding to U ″ obtained by (convolutional) encoding the information data U interleaved, the likelihood output from the first element decoder 321 is the second element. Before being input to the decoder 323, interleaving is performed by an interleaver (π) 322.

The likelihood output from the second element decoder 323 is deinterleaved by a deinterleaver (π ⁻¹ ) 324 and then fed back as an input to the first element decoder 321. After this feedback is made, the first element decoder performs decoding using the feedback likelihood information and a set of Y and Y ′, and the decoding result is delivered to the second element decoder 323. .
As described above, the first element decoder 321 and the second element decoder sequentially perform decoding N times in order, and the decoding result is output from the deinterleaver 324 as the turbo decoding result. Includes not only the determination data of “0” and “1” but also likelihood information, so that the probability of the determination data is known.

  This likelihood information is included in both the output of the element decoder 321 and the deinterleaver 324, but the more accurate likelihood information is obtained by performing more decoding, and has the highest accuracy. Likelihood information considered to be output from the deinterleaver 324 as a result of decoding with N repetitions.

  Reference numeral 33 denotes a CRC check unit, which performs error detection processing using the CRC bits added to the data after error correction, and notifies the control unit 34 of the result.

  The control unit 34 controls each unit and controls the transmission unit 35 according to the presence or absence of CRC error from the CRC check unit 33 to transmit ACK and NACK to the base station. If there is no CRC error, an ACK signal is transmitted, and if there is a CRC error, a NACK signal is transmitted. Therefore, the base station performs retransmission upon reception of the NACK signal.

  Also, the likelihood information from the channel decoding unit 32 is received, the average value A of the likelihood for the data transmitted in the subframe is obtained, and the ratio r (= A / T) with the reference value T is calculated. To do.

  Then, K = [(1-r) M] is obtained, and the transmission unit 35 (feedback unit) is controlled so as to transmit K to the base station together with NACK using K as feedback information. Here, M represents the number of spreading codes, and [n] represents the maximum natural number equal to or less than n. In this case, K may be transmitted when an NACK signal is transmitted, but K is not transmitted when an ACK signal is transmitted. The increase of the is suppressed.

  In this case, K is transmitted to the base station. However, the soft decision data obtained from the receiving unit 27, the likelihood information obtained from the channel decoder itself, or the like are obtained by converting them with a predetermined function. Information is preferably transmitted to the base station. Such information is referred to as received data reliability information. At that time, it is preferable to select a function that can reduce the amount of information, and the function used to calculate K described above is an example.

  Thus, the base station that has received the reliability information of the received data determines Y based on this reliability information. That is, retransmission is determined by receiving a NACK signal, but this reliability information is used when determining the transmission parameter Y.

  When the reliability information is K described above, the number of spreading codes as a transmission parameter can be simply set as K. However, when the reliability information is not information corresponding to Xi, The station preferably determines whether the transmission parameter should be Y or X based on the reliability information.

That is, when the base station receives reliability information transmitted when soft decision data, likelihood information obtained from the channel decoder, etc. indicate that there is a high degree of uncertainty regarding the determination of received data, If the base station receives the reliability information transmitted when soft decision data, likelihood information obtained from the channel decoder, etc. indicates that the uncertainty about the determination of received data is low, The transmission parameter is Y (value that saves radio resources with respect to X).
・ "Coexistence with CQI control"
It should be noted that separate control for changing the transmission parameter X based on CQI information from the mobile station is allowed.
That is, when a mobile station that measures SIR or the like as reception quality transmits a CQI to the base station as a report, the control unit 10 of the base station performs transmission parameter change control such as adaptive modulation according to the CQI. I do. For example, when it is recognized that the SIR is good by CQI, there is a case where the QPSK modulation is switched to 16-value QAM or the number of spreading codes is increased.
In this case, the transmission parameter X will fluctuate due to control by CQI, but the transmission parameter Y is a value that saves radio resources with respect to the transmission parameter X at the time of transmission of data that the mobile station failed to receive. In addition to the technique of performing, it is also possible to set a value that saves radio resources for the subsequent transmission parameter X ′ to be changed by CQI control. In this way, the control by CQI is originally changed to excessive quality, but control is performed in a direction to suppress the change, and the control unit 10 performs control based on CQI in a direction to suppress consumption of radio resources. It will operate as a restraining means to control to.
・ "Other"
Finally, the spreading process in the base station when adopting MIMO will be described in detail. FIG. 8 is a diagram showing a configuration around the spreading processing unit in the base station when MIMO is employed.

The figure shows a transmission system for one mobile station, in which 24 _{1 to} 24 ₃ are spreading processing units, 25 _{1 to} 25 ₃ are modulation units, 36 ₁ and 36 ₂ are spreading code generating units, Reference numerals 37 ₁ and 37 ₂ denote variable gain amplifiers, and 38 ₁ and 38 ₂ denote antennas.

The N-sequence (here, three-sequence) signals output from the physical channel mapping unit 23 in FIG. 3 are respectively input to the spreading processing units 24 _{1 to} 24 ₃ . Since the signals spread by the spread processing units 24 ₁ and 24 ₂ are transmitted from the separate antennas 38 ₁ and 38 ₂ , a common spread code can be used. Thus, as shown, it has given common spreading codes 24 _1, 24 ₂ from the spreading code generator 36 _1. However, since the signals spread by the spreading processing units 24 ₂ and 24 ₃ are transmitted from the common antenna 38 _2, since the spreading codes are used separately, the spreading code generating units 36 ₁ and 36 ₂ respectively. Spreading processing is performed using a given spreading code. The signals output from the respective spread processing units are modulated by the modulation units 25 _{1 to} 25 ₃ , the output of the modulation unit 251 is input to the variable gain amplifier 37 _1, and the outputs of the modulation units 25 ₂ and 25 ₃ are combined. It is given to the variable gain amplifier 37 _2.

The outputs of the variable gain amplifiers 37 ₁ and 37 ₂ are combined with signals destined for other mobile stations as necessary, and supplied to the antennas 38 ₁ and 38 ₂ , respectively. Although frequency conversion is performed as necessary, it is omitted in the figure.

It is a figure for showing the channel structure in HSDPA. It is a figure which shows the structure of the base station which supports HSDPA. 1 shows a transmission apparatus according to the present invention. It is a figure which shows the process 1 of the control part 10 which concerns on this invention. It is a figure which shows the process 2 of the control part 10 which concerns on this invention. It is a figure which shows the receiver which concerns on this invention. It is a figure which shows a channel decoder (turbo decoder). It is a figure which shows the spreading | diffusion process at the time of MIMO application.

DESCRIPTION OF SYMBOLS 1 CRC addition part 2 Code block division part 3 Channel encoding part 4 Bit separation part 5 Rate matching part 6 Bit collection part 7 Modulation part 10 Control part 11 CRC addition part 12 Bit scrambling part 13 Code division part 14 Channel encoding part 15 Bit separation unit 16 First rate matching unit 17 Virtual buffer unit 18 Second rate matching unit 19 Bit collection unit 20 Physical channel division unit 21 Interleave processing unit 22 Constellation rearrangement unit 23 Physical channel mapping unit 24 Spreading processing unit 25 Modulation unit 26 receiving unit 25 receiving unit 28 first depuncture unit 29 combining unit 30 memory 31 second depuncturing unit 32 channel decoding unit 33 CRC check unit 34 control unit 35 transmitting unit 36 Spreading code generator 37 Variable gain amplifier 38 Antenna 321 DEC1 (first element decoder)
322 π (interleaver)
323 DEC2 (second element decoder)
324 π ^-1 (deinterleaver)

Claims (5)

In a receiving apparatus that reproduces data using received data and retransmitted data,
A feedback unit that feeds back the likelihood information of the received data or information calculated from the likelihood information to the transmitter that can control the transmission parameters at the time of retransmission,
A receiving apparatus comprising: Information calculated from the likelihood information includes information for specifying a transmission parameter to be changed,
The receiving device according to claim 3. In a transmitting apparatus that transmits data to a receiving apparatus that reproduces data using received data and retransmitted data,
Receiving means for receiving likelihood information of received data or information calculated from the likelihood information from the receiving device;
Based on the information obtained by the reception, a control unit that determines a transmission parameter at the time of retransmission, and performs control to execute retransmission with the determined parameter;
A transmission device comprising: In a CDMA mobile communication system that performs transmission employing a hybrid ARQ scheme between a base station and a mobile station,
When the base station performs re-transmission, a control unit is provided that controls to reduce the transmission power, reduce the number of spreading codes to be used, or increase the spreading factor with respect to the first transmission. ,
A CDMA mobile communication system. In a CDMA mobile communication system including a base station that performs adaptive modulation based on CQI information from a mobile station and performs transmission using a hybrid ARQ scheme with the mobile station,
When the base station performs re-transmission, in order to perform adaptive modulation based on the CQI information, transmit at a lower transmission power, reduce the number of spreading codes to be used, or increase the spreading factor. With a control unit to control,
A CDMA mobile communication system.

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