JP2008252629A - Radio communication system, and encoding control method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication system capable of reducing the effect of frequency selective fading and enhancing the effect of error correction even when data without expecting accuracy are received, and to provide an encoding control method therefor. <P>SOLUTION: In a transmission/reception system 10, redundant encoding is applied by an encoder 16, data are deleted in accordance with a first rule by a puncture processing section 18, and the data are transmitted from a transmitter. The data are then received by a receiver 14, dummy data are embedded at a position of the deleted data by a depuncture processing section 60, and bit error of data 80 is inferred by a bit error observation function block 63. In accordance with the inference, the effect of frequency fading is then judged and while using a control frame in accordance with the presence of the effect, the deletion/modification of data according to a second rule is requested from the receiver 14 to the puncture processing section 18 of the transmitter 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a radio communication system and a coding control method in the communication, and particularly relates to the influence of frequency selective fading when frequency division multiplexing (FDM) is used in modulation / demodulation of a radio apparatus. It relates to the technology to reduce.

Conventionally, there is Patent Document 1 as a technique using FDM (Frequency Division Multiplexing). In the receiver shown in Patent Document 1, a received signal is converted into digital received data by an A / D conversion circuit, the received data is synchronized by a synchronizing circuit, and this synchronization is performed by an FFT (Fast Fourier Transfer) arithmetic circuit. Fast Fourier transform processing is performed on the received data at the timing of, and the demodulated data is demodulated by the demodulation circuit, and the demodulated data is deinterleaved by the data conversion circuit. The error of the data processed by the data conversion circuit is corrected by the error correction circuit. Further, there is Patent Document 2 as a technique using punctured coding. In the punctured circuit, the signal from the convolutional encoder is parallelized in block units by a serial / parallel converter and latched in a latch circuit. The parallel / serial converter reads only the bits of the data latched by the latch circuit, excluding the erase bit specified by the erase pattern, serializes it, and sends it out. Upon receiving this, the depunctured circuit converts the input serial data into parallel data for each block and latches it in the latch circuit. The latched data is read while adding dummy data to the erased bit positions, converted into serial data, and output. The punctured circuit and the depunctured circuit are configured in this way, and the circuit configuration is simple and high speed can be realized easily.
JP 2001-136145 A JP 2002-176364 A)

  However, in the case of broadband communication, the amount of phase rotation with respect to the propagation path length varies depending on the frequency. For this reason, in the band, a frequency in which multiple waves are synthesized in phase and a frequency in which inverse phases are synthesized are mixed. As a result, the reception level may decrease at a specific frequency within the band. This is called frequency selective fading.

  When transmission is performed using a plurality of subcarriers as in FDM, if frequency selective fading occurs, data transmitted using a specific subcarrier assigned to this frequency has a higher probability of error during reception. .

  On the other hand, for example, zero is inserted as dummy data at the time of reception at the position of data deleted by punctured encoding. For this reason, data having a high probability of obtaining an incorrect result is included.

  If these two data are input to the decoder at the same time, neither data can be expected to be accurate. For this reason, the influence on decoding is large, and the probability of obtaining an erroneous result is increased. As a countermeasure against errors caused by such a phenomenon, the existing method cannot be technically satisfactory.

  The present invention eliminates such drawbacks of the prior art, and can reduce the influence of frequency selective fading and improve the error correction effect even when receiving data whose accuracy cannot be expected, and a radio communication system thereof An object is to provide a coding control method in communication.

  In order to solve the above-described problem, the present invention uses a transmission device that transmits data using a plurality of subcarriers divided by frequency division multiplexing, and a plurality of subcarriers divided by frequency division multiplexing, In a wireless communication system comprising a receiving device for receiving transmitted data, and transmitting information between the transmitting device and the receiving device using a control frame, the transmitting device encodes data to be encoded And a deleting unit that deletes the encoded data according to the first rule. The receiving device receives the encoded data and is deleted by the deleting unit from the received encoded data. An inserting means for embedding dummy data in the data; and a decoding means for decoding the data supplied from the inserting means. The decoding means includes data supplied from the inserting means. And a guess function that estimates the bit error of the observed data, determines the influence of frequency fading according to the estimated bit error, and uses the control frame according to the presence of this influence, and this receiving device From the above, the deletion means of the transmitting apparatus is requested to change the data encoded by the second rule different from the first rule.

  In order to solve the above-described problem, the present invention transmits data using a plurality of subcarriers divided by frequency division multiplexing, and transmits using a plurality of subcarriers divided by frequency division multiplexing. In a coding control method in a wireless communication system that receives received data and transmits information using a control frame to each other, the method includes: a first step of coding data in transmission; A second step of deleting data in accordance with the first predetermined rule, receiving encoded data in reception, and dummy data for the deleted data among the received encoded data And a fourth step of decoding the supplied data, and the fourth step is a fifth step of estimating a bit error of the plurality of supplied data. And a sixth step of determining the influence of frequency fading according to the estimated bit error, and if there is an influence of this frequency fading, the control frame is used and the second step from the reception side to the transmission side is used. And a seventh step of requesting a change to delete data encoded according to a second rule different from the first rule.

  Here, as a method for estimating a bit error, for example, the magnitude of a metric at the time of Viterbi decoding may be used. Further, before transmitting actual data, bit data may be measured after first transmitting test data.

  According to the wireless communication system and the encoding control method in the communication of the present invention, the encoding unit encodes one data into a plurality of data, and the deleting unit deletes the encoded data according to the first rule. The obtained data is transmitted from the transmission device, the data encoded by the reception device is received, and the encoded data received by the insertion unit is embedded with dummy data in the data deleted by the deletion unit, The estimation function block of the decoding means estimates a bit error of a plurality of data supplied from the insertion means, determines the influence of frequency fading according to the estimated bit error, and uses the control frame according to the presence of this influence By requesting a change to delete the encoded data according to the second rule different from the first rule from the receiving device to the deleting means of the transmitting device. The duplication of the position of the data to be cut by the first rule and the position of the bit error due to the influence of frequency fading is avoided, and the error correction effect is enhanced by decoding into one data based on a plurality of supplied data. be able to.

  Next, an embodiment of a wireless communication system according to the present invention will be described in detail with reference to the accompanying drawings. Referring to FIG. 1, in the embodiment of the wireless communication system according to the present invention, the encoder 16 encodes data from one data into a plurality of data, and the puncture processing unit 18 encodes the data encoded according to the first rule. Data that is deleted, transmitted from the transmitter 12, received data encoded by the receiver 14, out of the encoded data received by the depuncture processing unit 60, the data deleted by the puncture processing unit 18 Dummy data is embedded in the bit error measurement function block 63 of the decoder 62, and a plurality of data 80 supplied from the depuncture processing unit 60 is used to estimate the bit error by the error correction processing function. The influence of frequency fading is determined in accordance with the presence of the influence, and a control frame is used in accordance with the presence of this influence, and the receiver 14 punctures the puncture processing unit 18 of the transmitter 12. By requesting a change to delete the encoded data according to the second rule different from that of the first rule, the position of the data to be deleted according to the first rule and the bit error position due to the influence of frequency fading are avoided and supplied. The effect of error correction can be enhanced by decoding into a single data based on a plurality of data.

  In this embodiment, the radio communication system of the present invention is applied to the transmission / reception system 10. The illustration and description of parts not directly related to the present invention are omitted. In the following description, the signal is indicated by the reference number of the connecting line in which it appears.

  The transmission / reception system 10 includes a transmitter 12 and a receiver 14 as shown in FIG. The transmitter includes an encoder 16, a puncture processing unit 18, a subcarrier modulation unit 20, a quadrature modulation unit 22, a frequency transmitter 24, an up converter 26, and a transmission antenna 28.

  The encoder 16 has a function of performing redundant encoding for error correction. The encoder 16 receives the data 30 and generates redundantly encoded data. The encoder 16 outputs the generated data 32 to the puncture processing unit 18.

  The puncture processing unit 18 has a function of deleting data at a predetermined position. The puncture processing unit 18 may provide a plurality of data deletion procedures at a predetermined position or supply a deletion procedure. In the former case, the puncture processing unit 18 uses the signal line 33 as a control signal, and selects a data deletion procedure by the control signal 33. In the latter case, the puncture processing unit 18 uses the signal line 33 as a data input signal, and supplies a data deletion procedure using the data input signal 33. The data deletion procedure may use one of an algorithm, sequential selection, and random change. The data deletion procedure is selected by using a control frame included in communication between the transmitter 12 and the receiver 14 and exchanging information with each other. The puncture processing unit 18 outputs data 34 from which data at a predetermined position has been deleted to the subcarrier modulation unit 20.

  The subcarrier modulation unit 20 has a function of dividing the data 34 supplied as primary modulation into a plurality of subcarriers for modulation. The subcarrier modulation unit 20 outputs a plurality of modulated data 36 to the orthogonal modulation unit 22. The orthogonal modulation unit 22 has a function of modulating the data 36 using, for example, orthogonal frequency division multiplexing (OFDM) as secondary modulation. The quadrature modulation unit 22 outputs the quadrature modulated signal 38 to the one end 40 side of the up-converter 26.

  The frequency transmitter 24 is a local transmitter and has a function of generating an intermediate frequency. The frequency transmitter 24 outputs an intermediate frequency signal 42 to the other end 44 of the upconverter 26. The up-converter 26 has a function of converting into a predetermined high-frequency signal based on the modulation signal 38 and the intermediate frequency supplied as a baseband signal. The up-converter 26 outputs the converted high-frequency signal 46 to the transmission antenna 28. The transmitting antenna 28 radiates as a radio signal 48.

  The receiver 14 includes a reception antenna 50, a down converter 52, a frequency transmitter 54, a quadrature detection unit 56, a subcarrier demodulation unit 58, a depuncture processing unit 60, and a decoder 62.

  The receiving antenna 50 receives the radiated radio signal 64 and supplies the received radio signal 64 to the one end 68 of the down converter 52 as a high frequency signal 66. The frequency transmitter 54 is a local transmitter and has a function of generating an intermediate frequency. The frequency transmitter 54 outputs the intermediate frequency signal 70 to the other end 72 of the down converter 52. The down converter 52 has a function of converting a demodulated signal as a baseband signal based on a predetermined high-frequency signal and intermediate frequency supplied. The down converter 52 outputs the converted demodulated signal 74 to the quadrature detection unit 56.

  The quadrature detection unit 56 has a function of detecting a demodulated signal 74 supplied as a baseband signal based on, for example, an OFDM scheme and demodulating it into a plurality of subcarriers. The quadrature detection unit 56 outputs a demodulated signal 76 including a plurality of detected subcarriers to the sub quadrature detection unit carrier demodulation unit 58.

  The subcarrier demodulator 58 has a function of demodulating the supplied demodulated signal 76 for each subcarrier. Subcarrier demodulation section 58 outputs data 78 demodulated for each subcarrier to depuncture processing section 60.

  The depuncture processing unit 60 has a function of inserting dummy data at a predetermined position in the supplied data 78. The depuncture processing unit 60 may provide a plurality of data insertion procedures at a predetermined position or supply an insertion procedure. In the former case, the depuncture processing unit 60 uses the signal line 79 as a control signal, and selects a data insertion procedure based on the control signal 79. In the latter case, the depuncture processing unit 60 uses the signal line 79 as a data input signal, and supplies a data insertion procedure using the data input signal 79. As the data insertion procedure, any one of an algorithm, sequential selection, and random change may be used corresponding to the data deletion procedure. The data insertion procedure is selected by using a control frame included in communication between the transmitter 12 and the receiver 14 and exchanging information with each other. The depuncture processing unit 60 outputs the data 80 with the dummy data inserted to the decoder 62. The decoder 62 has a function of measuring or estimating a bit error of the supplied data 80, a bit error measurement function block 63, and the bit error measurement function block 63 also has a function of performing error correction. The decoder 62 outputs error-corrected data 82.

Next, the operation of the transmitter 12 will be described. As shown in FIG. 2 (a), the encoder 16 inputs the input data _Xn as a transmission data string. The encoder 16 converts the input data _Xn into, for example, a convolutional code. As shown in FIG. 2 (b), the encoder 16 generates and outputs data _An columns and B _n columns as outputs.

Next, punctured encoding by the puncture processing unit 18 will be described. Here, for the sake of convenience, as shown in FIG. 3 (a), the coding rate by punctured coding is set to 7/8. That is, the puncture processing unit 18 performs a process of intentionally deleting one piece of data from eight pieces of data. As shown in FIG. 3 (a), data is divided by 8 pieces, and the second data B _n column is deleted as a predetermined position in the divided block. The deleted state is shown in FIG. Further, the puncture processing unit 18 rearranges the seven deleted data as shown in FIG. In this embodiment, the method of alternately arranging the data _An and _Bn is used, but the present invention is not limited to this, and other algorithms are used and rearranged by a special procedure such as an interleave technique. Also good.

  The subcarrier modulation unit 20 according to the present embodiment uses FDM to assign subcarriers to each data. As shown in FIG. 4, the subcarrier modulation unit 20 is a process of assigning a data string and a subcarrier. For convenience, the subcarrier modulation unit 20 sets that there are 14 subcarriers, and arranges the data strings supplied in order from the subcarriers with the lower frequencies. The subcarrier modulation unit 20 assigns one subcarrier to one piece of data, but a plurality of data sequences are used as primary modulation using a technique such as quadrature amplitude modulation (QAM). Alternatively, the bit string may be mapped and assigned to the subcarrier.

  The subcarrier modulation unit 20 outputs the data 36 to which the subcarrier is assigned to the orthogonal modulation unit 22. The quadrature modulation unit 22 outputs the quadrature modulated signal 38 to the up-converter 26. The up-converter 26 converts the modulation signal 38 into a high-frequency signal 46 and transmits a radio signal 48 via the transmission antenna 28.

Next, the operation of the receiver 14 will be described. The receiver 14 receives the radio signal 64 with the receiving antenna 50. It is assumed that the reception data of this embodiment receives a radio signal 48 including transmission data from the transmitter 12. Further, the transmission path may cause fading depending on the frequency in the radio signal. As will be described later, received data affected by this fading is represented by lowercase letters a _n and b _n .

  The received high frequency signal 66 becomes a baseband signal 74 in the down converter 52. The signal 74 becomes a demodulated signal 76 having a plurality of subcarriers by the quadrature detection unit 56. As for the demodulated signal 76, the subcarrier demodulator 58 generates data 78 and outputs it.

When greatly influenced by fading, the signal level at the positions of arrows 84 and 86 shown in FIG. The subcarrier demodulation unit 58 generates reception data 78. Further, FIG. 5 shows a situation in which the received data a ₂ and a ₆ are greatly affected by the signal level of the received data 78, as indicated by hatching. The received data 78 is supplied to the depuncture processing unit 60.

Next, a procedure for rearranging the received data 78 in the depuncture processing unit 60 and inserting dummy data will be described. The received data 78 is input to the depuncture processing unit 60 as shown in FIG. As shown in FIG. 6 (b), the depuncture processing unit 60 divides the input received data 78 into data _An columns and B _n columns and rearranges them. The portions where the data is intentionally deleted on the transmission side, that is, the received data b ₂ and b ₆ are blank. Depuncturing unit 60, as shown hatched in FIG. 6 (c), the position of the received data b ₂ and b _6, for example, inserting zeros as dummy data, outputted.

Next, the decoder 62 inputs the received data 80 shown in FIG. 7 (a) as input data _An columns and B _n columns. The decoder 62 decodes the input received data and outputs it as output data Y _n shown in FIG. 7 (b).

Here, the data a ₂ and a ₆ have a high error probability due to fading. Furthermore, the data b ₂ and b ₆ contain data that cannot be expected to be accurate as a dummy. Therefore, in the present embodiment, when the data a ₂ and b ₂ or the data a ₆ and b ₆ are simultaneously input to the decoder 62, neither of them can be expected to be accurate. For this reason, the receiver 14 is greatly affected by the decoding accuracy.

  Next, the decoding procedure in the receiver 14 will be described with reference to FIG. A bit error is measured by the decoder 62 (step S10). The decoder 62 of the receiver 14 has a bit error measurement function block 63 that measures a bit error. The decoder 62 may measure a bit error for each subcarrier. Thereby, it can be confirmed that there is a possibility that the data affected by fading and the data cut by the punctured encoding may be input to the decoder 62 at the same time. Further, it may be specified which subcarrier fading causes the error.

  Next, based on the confirmation result, it is determined whether or not to change the position of data to be deleted by punctured encoding (step S12). If the data affected by fading and the data cut by punctured encoding are input simultaneously (YES), the process proceeds to the position change process (to step S14). If the data affected by fading and the data cut by punctured encoding are not input simultaneously (NO), it is determined that there is little influence on the decoding accuracy, and the process proceeds to the decoding process (step S16). What).

  Next, the position change process requests the transmitter 12 to change the position of data to be deleted in the puncture process (step S14). In a general communication device, a transmitter and a receiver can exchange information with each other using a control frame. By using this, when the decoder 62 can confirm the input status of such received data, the decoder 62 changes the position of data to be deleted by punctured encoding to the transmitter 12. Request. The designation of the position may be changed by an algorithm, sequential selection or random. By this process, the transmitter 12 that has received a request (not shown) changes the position of data to be deleted by punctured encoding, and resumes communication.

Next, decryption processing is performed (step S16). In the decoding, data having less influence on accuracy is supplied, and the effect of error correction can be enhanced. After the decoding process, the operation of the decoder 62 is terminated. After receiving the position change process, the transmitter 12 transmits the punctured transmission data 34. That is, as shown in FIG. 9 (a), the deletion position in the puncturing process is changed from the second to the fourth in the data B _n column. Even if it is affected by fading in the transmission path, the received data 80 after rearrangement has the data position affected by fading and the data position by puncture processing as data A as shown in FIG. _n and B _n columns can be provided without being duplicated.

  As shown in FIG. 10, the operation procedure of the decoder 62 is not shown in the figure, but after measuring all received data, a bit error is measured (step S10), and it is determined whether or not to change the deletion position (step S12). ) If not changed, return to decoding of received data. On the other hand, if changed (YES), request transmitter 12 to change position of puncture (step S14), return to decoding received data, and supplied next time The result may be reflected from the received data.

  Since data that cannot be expected to be accurate is distributed and arranged in this way, the decoder 62 can enhance the effect of error correction by the decoder 62.

  When frequency selective fading occurs in this way, based on the fading information estimated by the receiver 14, by requesting the transmitter 12 to change the position of the data to be cut by the punctured code, by transmitting and receiving, The effect of error correction in received data can be enhanced.

  The present invention can be used in a radio communication system, and in particular, can be applied to a radio communication system that transmits by dividing a frequency into a plurality of subcarriers like OFDM.

It is a block diagram which shows schematic structure of the transmitter and receiver in the transmission / reception system to which the radio | wireless communications system which concerns on this invention is applied. It is a figure explaining the function of the encoder of FIG. It is a figure explaining the function of the puncture process part of FIG. It is a figure explaining the function of the subcarrier modulation part of FIG. It is a figure explaining the function of the subcarrier demodulation part of FIG. It is a figure explaining the function of the depuncture process part of FIG. It is a figure explaining the function of the decoder of FIG. It is a flowchart explaining the operation | movement procedure of the decoder in the Example to which the encoding control method in the radio | wireless communications system which concerns on this invention is applied. It is a figure which shows the transmission / reception data after the puncture position change accompanying generation | occurrence | production of frequency selective fading in the transmission / reception system of FIG. It is a flowchart explaining the operation | movement procedure of the decoder in the Example to which the encoding control method in the radio | wireless communications system which concerns on this invention is applied.

Explanation of symbols

10 Wireless communication system
12 Transmitter
14 Receiver
16 Encoder
18 Puncture processing unit
60 Depuncture processing unit
62 Decoder

Claims (6)

A transmitting apparatus that transmits data using a plurality of subcarriers divided by frequency division multiplexing, and a receiving apparatus that receives data transmitted using the plurality of subcarriers divided by frequency division multiplexing; With
In the wireless communication system in which the transmitting device and the receiving device transmit information to each other using a control frame,
The transmission device includes encoding means for encoding data;
Deleting means for deleting data encoded according to the first rule,
The receiving device receives the encoded data, and among the received encoded data, an inserting unit that embeds dummy data in the data deleted by the deleting unit;
Decoding means for decoding data based on a plurality of data supplied from the insertion means,
The decoding means includes an estimation function that observes data supplied from the insertion means and estimates a bit error of the observed data, determines an influence of frequency fading according to the estimated bit error, and A control frame is used in accordance with the existence, and the receiving device requests the deleting unit of the transmitting device to change the encoded data according to a second rule different from the first rule. A wireless communication system.   2. The wireless communication system according to claim 1, wherein the deleting unit is a punctured encoding process.   The wireless communication apparatus according to claim 1, wherein the second rule uses any one of an algorithm, a sequential selection, and a random change. Data is transmitted using a plurality of subcarriers divided by frequency division multiplexing, and the transmitted data is received using the plurality of subcarriers divided by frequency division multiplexing, and is used for mutual control. In a coding control method in a wireless communication system that transmits information using a frame, the method includes:
A first step of encoding data in transmission;
A second step of deleting data according to a first predetermined rule,
In reception, a third step of receiving the encoded data and embedding dummy data in the deleted data of the received encoded data;
A fourth step of decoding the supplied data,
The fourth step includes a fifth step of estimating a bit error of the plurality of supplied data,
A sixth step of determining the influence of frequency fading according to the estimated bit error;
When the influence of the frequency fading exists, a change is made to delete the encoded data by the second rule different from the first rule for the second process from the receiving side to the transmitting side using the control frame. A coding control method comprising: a seventh step that requests   5. The encoding control method according to claim 4, wherein the second step is a punctured encoding process.   5. The encoding control method according to claim 4, wherein the second rule uses one of an algorithm, sequential selection, and random change.

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