JP2011024258A - Interleaving method and communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an interleaving method which can reduce a circuit size and a processing delay while controlling deterioration in performance. <P>SOLUTION: The interleaving method interleaves an error-correction encoded sequence which has been subjected to error correction encoding, and includes a step of arranging elements of the error-correction encoded sequence in an arranging order corresponding to an error correction scheme applied in the error correction encoding in a plurality of error-correction schemes. In the step, the arranging order corresponding to the error correction scheme is an order which varies depending on whether the error correction scheme is a predetermined error correction scheme. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an interleaving method in a wireless communication system, and more particularly to a communication apparatus that performs interleaving on a sequence after encoding.

  The conventional interleaving method is described in Patent Document 1 below. For example, in a communication apparatus that transmits using OFDM (Orthogonal Frequency Division Multiplexing), when a concatenated code of an RS code and a convolutional code is used as an error correction code, the received signal is subjected to FFT, and further, frequency deinterleaving is performed. Time deinterleaving is performed on the performed signal. The information on the I axis and Q axis after time deinterleaving is demapped to information on the number of modulation points according to the modulation method. The modulation scheme is predetermined for each block composed of n carriers of one OFDM symbol, and is demapped for each segmented block.

  Further, the demapped information is divided into a plurality of layers, and bit deinterleaving is performed on each layer in order to increase error resistance against the convolutional code, and then convolutional decoding is performed. Next, the result of convolutional decoding is divided into a plurality of layers, and byte deinterleaving processing is performed on each layer in order to increase error resistance with respect to the RS code. Further, for the byte deinterleaved sequence, An RS decoding process is performed and a decoding result is output.

JP 2002-217860 A

  In the conventional interleaving method, four-stage interleaving processing is performed: frequency interleaving, time interleaving, bit interleaving, and byte interleaving. In general, when configuring an interleaver, there has been a problem that the capacity of storage means for rearranging the order increases, and the circuit scale increases accordingly. There is also a problem that processing delay increases due to the interleaving process.

  Further, when a concatenated code as shown in Patent Document 1 is used when transmitting control information or the like, many redundant bits are required. Therefore, it is necessary to transmit with a plurality of OFDM symbols, which causes a problem that transmission efficiency deteriorates. In addition, when interleaving is performed within an OFDM symbol, there is a problem that as the number of modulation points increases, the number of target interleaving bits increases and the memory capacity increases.

  The present invention has been made in view of the above, and an object of the present invention is to obtain an interleaving method capable of realizing a reduction in circuit scale and a reduction in processing delay while suppressing deterioration in performance.

  It is another object of the present invention to obtain an interleaving method capable of improving transmission efficiency while reducing the amount of memory.

  In order to solve the above-described problems and achieve the object, an interleaving method according to the present invention is an interleaving method for interleaving error-correction encoded error correction sequences. , Among the plurality of error correction schemes, having a step of arranging based on an arrangement order according to the error correction scheme applied in the error correction encoding, wherein the arrangement order according to the error correction scheme is The error correction methods are different in order depending on whether or not the error correction method is a predetermined error correction method.

  In the interleaving method according to the present invention, the memory amount can be reduced, that is, the circuit scale can be reduced, and further, the processing delay amount can be reduced by reducing the interleaving process.

FIG. 1 is a diagram illustrating a configuration example of a communication system (a communication device on a transmission side and a communication device on a reception side) that realizes an interleaving method according to the present invention. FIG. 2 is a diagram illustrating an example of reading a modulation scheme from the modulation scheme table. FIG. 3 is a diagram illustrating a signal point arrangement when the modulation method is 256QAM. FIG. 4 is a diagram illustrating an example of rearrangement.

  Hereinafter, embodiments of an interleaving method and a communication apparatus according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment.
FIG. 1 is a diagram illustrating a configuration example of a communication system (a communication device on a transmission side and a communication device on a reception side) that implements an interleaving method according to the present invention. The communication device on the transmission side includes a CRC addition unit (CRC Addition) 1, a scramble unit (Scramble) 2, an RS encoding unit (RS Encode) 3, a convolutional encoding unit (Conv. Encode) 4, an intra-carrier bit interleaver (Bit INT.) 5, an inter-carrier interleaver (Carrier INT.) 6, a modulation unit (MOD.) 7, and a modulation scheme table (MOD. Table) 8 for storing the modulation scheme for each carrier. Demodulator (DEM.) 9, inter-carrier deinterleaver (Carrier DINT.) 10, bit deinterleaver (Bit DINT.) 11, convolutional code decoder (Conv. Decode) 12, RS code decoder (RS Decode) 13, A descrambling part (De-Scramble), a CRC check part (CRC) 15 and a demodulation system table (DEM Table) 16 (same content as the modulation system table 8) for storing the modulation system for each carrier are included.

  Next, the operation of the communication system will be described. First, the CRC adding unit 1 adds a CRC check bit to the data sequence input from the MAC, and the scramble unit 2 scrambles the sequence after adding the CRC check bit by adding the PN sequence. I do.

  Next, the RS encoder 3 encodes the RS code by dividing the scrambled data series into predetermined information symbol lengths for the information of the channel on which RS encoding is performed. Then, the generated RS check bit is added to the scrambled information bit and output. When RS encoding is not performed, the scrambled data sequence is output as it is.

  Next, the convolutional encoding unit 4 encodes information on a channel on which convolutional encoding is performed at a predetermined encoding rate. When the convolutional encoding is not performed, the data output from the RS encoding unit 3 is output as it is.

  Next, the intercarrier interleaver 6 rearranges the order of the carrier numbers according to the error correction method, searches the modulation method table 8 for the modulation method in the rearranged order, and converts the encoded sequence to each modulation. A process is performed for each bit number corresponding to the method. Regarding the rearrangement of the order, for example, the encoded series is sequentially assigned to carriers at a constant interval.

  Next, the in-carrier bit interleaver 5 rearranges the order for each number of bits divided according to the modulation method. The rearrangement of the order is determined in advance. Finally, the modulation unit 7 converts each carrier into I-axis information and Q-axis information according to the modulation method specified in the modulation method table 8, and stores the carrier number as an address in an internal memory. Then, the result of the FFT operation is transmitted.

  Next, on the receiving side, first, the demodulator 9 performs IFFT calculation, calculates information on the I axis and the Q axis for each carrier, and stores the information in the internal memory.

  Next, in the inter-carrier deinterleaver 10, as in the inter-carrier interleaver 6, the carrier numbers are rearranged according to the error correction scheme, and the modulation scheme is searched from the demodulation scheme table 16 in the rearranged order. Soft decision information is generated for each number of bits corresponding to each modulation method.

  Next, the in-carrier bit deinterleaver 11 rearranges the order of the soft decision information for each number of bits corresponding to each modulation method according to the modulation method selected in the demodulation method table 16.

  Next, the convolutional decoding unit 12 decodes the convolutionally encoded sequence by Viterbi decoding or the like based on the input soft decision information. For sequences that are not convolutionally encoded, the input soft decision information is converted to hard decision information.

  Next, the RS decoding unit 13 performs RS decoding processing on the RS-encoded sequence, and outputs an information bit portion obtained as a decoding result. For a sequence that is not RS-encoded, the input sequence is output as it is.

  Next, the descramble unit 14 adds the PN sequence at the same timing as the scramble unit 2, and finally the CRC check unit 15 performs error detection and outputs the sequence after the CRC check bit is removed. To do.

  Thus, in this embodiment, the interleaving is configured in two stages, and the intra-carrier bit interleaver is configured only to change the order of bits within the carrier. Thereby, the amount of memory can be reduced, that is, the circuit scale can be reduced, and further, the amount of processing delay can be reduced by reducing the interleave processing.

  Next, an example of rearrangement of the order of the carrier numbers according to the error correction method by the intercarrier interleaver 6 will be described.

  In the above communication system, for example, when RS encoding is performed alone, the inter-carrier interleaver 6 generates data in the order of carrier numbers, and when other error correction methods are used, the order of carrier numbers is changed. Sort by a specific number.

  By configuring the inter-carrier interleaver 6 as described above, even if a burst error occurs in the communication channel, inter-carrier interleaving is not performed when RS encoding is performed alone. Will be input to the RS code decoding unit 13 as it is hardened, and the effect of RS decoding will increase.

  In the case where convolutional encoding is included in the encoding process, errors are dispersed by interleaving and deinterleaving between carriers, so that the effect of convolutional decoding is increased and performance is improved.

  Specifically, the intercarrier interleaver 6 reads the modulation scheme from the modulation scheme table 8 for every C carriers with respect to N = RC carriers, as shown in FIG. As a result, information on adjacent carriers is separated on the transmission line, so that even if the state of the transmission line in a specific band suddenly deteriorates and an error occurs, deinterleaving is performed. Since the error is close to a random error, the performance can be improved when performing convolutional decoding.

  Thus, in this embodiment, by switching the interleaving method according to the error correction method, it is possible to control the error correction so that it works effectively, so that the transmission efficiency can be greatly improved.

  Next, an example of bit rearrangement by the intercarrier interleaver 5 will be described.

  In the bit interleaver 5 in the carrier, when the modulation method is BPSK or QPSK, the error rate of each bit is the same, so there is no effect by bit interleaving. However, in the case of QAM modulation, the bit with high error and the error rate Since low bits are mixed, the effect of bit interleaving can be obtained. For example, when the modulation scheme is 256QAM and the signal point arrangement is as shown in FIG. 3, when the signals are arranged as i0, i1, i2, i3, q0, q1, q2, q3, the error rate from i0 to i3 is i0. <I1 <i2 <i3, and the error rate from q0 to q3 is q0 <q1 <q2 <q3. Therefore, there is a high possibility that errors will continue if transmitted as they are.

  Therefore, in the present embodiment, for example, as shown in FIG. 4, by rearranging the order as i0, i3, i1, i2, q0, q3, q1, q2, the convolution decoding is not performed. When performing the above, decoding performance is improved and transmission efficiency is improved.

  Also, in the error correction code, when the RS code is used alone without using the convolutional code, and when the modulation scheme is 256QAM and the signal point arrangement as shown in FIG. 3 is used, i0, i1, i2, When the signals i3, q0, q1, q2, and q3 are arranged, the error rate from i0 to i3 is i0 <i1 <i2 <i3, and the error rate from q0 to q3 is q0 <q1 <q2 <q3. Therefore, there is a high possibility that errors will continue if transmitted as they are.

  Therefore, in the present embodiment, for example, by rearranging the order as i0, q0, i1, q1, i2, q2, i3, and q3, bits having a high error rate are consolidated as much as possible, and bits having a low error rate are consolidated. As a result, errors can be fixed in bursts, improving performance.

  In the present embodiment, when the channel state in each carrier varies greatly, for example, a modulation scheme table may be provided for each carrier. In this case, the corresponding number of bits is extracted from the encoded sequence based on the modulation scheme obtained by searching the modulation scheme table for each carrier. Then, the rearranged order is performed between the extracted bits, and the rearranged sequence is assigned to the carrier after the rearranged order by inter-carrier interleaving. Thereby, even if the state of the communication path of a specific band is bad, communication can be performed efficiently.

  If the carrier number for interleaving between carriers is a band in which data cannot be transmitted, the corresponding number of bits is extracted from the encoded data based on the modulation scheme of the next carrier number obtained by searching the modulation scheme table. Then, the extracted encoded data is assigned to the corresponding carrier number in the same procedure as described above. As a result, the same performance can be obtained even when a certain band cannot be used because another communication device uses a specific band.

  As described above, the interleaving method according to the present invention is useful for, for example, a communication device that employs the OFDM scheme, and is particularly suitable for a communication device that uses a concatenated code of an RS code and a convolutional code as an error correction code.

1 CRC Addition (CRC Addition)
2 Scramble Club (Scramble)
3 RS Encoder (RS Encode)
4 Convolutional encoding unit (Conv. Encode)
5 Bit interleaver in carrier (Bit INT.)
6 Carrier interleaver (Carrier INT.)
7 Modulator (MOD.)
8 Modulation table (MOD. Table)
9 Demodulator (DEM.)
10 Carrier deinterleaver (Carrier DINT.)
11-bit deinterleaver (Bit DINT.)
12 Convolutional code decoder (Conv. Decode)
13 RS code decoding unit (RS Decode)
14 Descramble Club (De-Scramble)
15 CRC check part (CRC)
16 Demodulation method table (DEM Table)

Claims (7)

In an interleaving method for interleaving error correction coded error correction coded sequences,
Arranging each element of the error correction coding sequence based on an arrangement order according to an error correction method applied in the error correction coding among a plurality of error correction methods;
In the step, the interleaving method according to the error correction method is different from each other depending on whether or not the error correction method is a predetermined error correction method.   In the step, when the error correction scheme applied in the error correction coding is a predetermined error correction scheme, each element of the error correction coding sequence is arranged in the same order as the order of the elements in the error correction coding sequence. The interleaving method according to claim 1, wherein the interleaving method is arranged.   The interleaving method according to claim 1, wherein the predetermined error correction method is an RS (Read Solomon) encoding method alone. In an interleaving method for interleaving error correction coded error correction coded sequences,
Each element of the error correction coding sequence is arranged in a unit divided by a predetermined number of elements based on an arrangement order corresponding to the error correction method applied in the error correction coding among a plurality of error correction methods. An interleaving method comprising steps. In an interleaving method for interleaving error correction coded error correction coded sequences,
Among the plurality of error correction methods, the error correction coding is performed in a memory of C (C is an integer) × R (R is an integer) based on the arrangement order according to the error correction method applied in the error correction coding. An interleaving method comprising the steps of: writing each element of a series in a unit divided by a predetermined number of elements, and arranging the elements by reading in a unit different from the writing order in a unit divided by the predetermined number of elements . In the interleaving method,
An interleaving method, wherein elements of an error correction coded sequence that have been error correction coded by applying any one of a plurality of error correction methods are arranged in a predetermined order. Error correction coding means for applying an error correction method among a plurality of error correction methods and generating an error correction coded sequence by performing error correction coding on an error correction coding target data sequence;
Interleaving that arranges each element of the error correction coding sequence generated by the error correction coding means based on the order of arrangement of the plurality of error correction methods according to the error correction method applied in the error correction coding And a communication device.

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