JP2015226098A - Interleaving device, transmitter, receiver, and communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an interleaving device capable of increasing a probability that errors can be corrected better than conventional interleaving devices.SOLUTION: An interleaver 23 performs interleaving processing for transmission data in a transmitter that transmits the transmission data by OFDM transmission. The interleaver 23 comprises: a rearranging unit 230 that performs first interleaving processing for rearranging the transmission data in time and frequency directions; and a reading position calculating device 234 that groups the transmission data after the first interleaving processing per OFDM symbol time, and outputs a bit string in a group by cyclically shifting an output start position in the bit string per group.

Description

  The present invention relates to an interleave device, a transmission device, a reception device, and a communication system.

  OFDM (Orthogonal Frequency-Division Multiplexing) is used in various systems such as terrestrial digital broadcasting, wireless local area network (LAN), and long term evolution (LTE). OFDM is a transmission method in which subcarriers are orthogonally transmitted. As a result, a large amount of information can be transmitted simultaneously, and the transmission speed can be improved.

  However, due to reflection, scattering, and the like, when received by the receiving device, an error occurs in a continuous bit string, and error detection or error correction using an error correction code may not be possible. Therefore, a method for improving performance by performing frequency interleaving and time interleaving and distributing bits in the frequency direction and the time direction has been proposed.

  For example, in the technique described in Patent Document 1, interleaving in the time direction, the frequency direction, and the spatial direction is used to modulate and transmit a sequence after interleaving. Patent Document 1 discloses a digital modulation device, a digital demodulation device, and a method for reducing deterioration due to interference such as reflection and scattering as described above.

  Patent Document 2 discloses a technique for simplifying the interleaving process by using pseudo-random numbers with respect to the interleaving technique.

JP 2006-295756 A JP 2009-33622 A

In an apparatus used in an ISM (Industry Science Medical) band that does not require a license for wireless communication, a signal transmitted in a narrow band may interfere with a part of an OFDM subcarrier.
At this time, the conventional interleaving performed in a system using OFDM has a problem that the bit dispersion effect in the time and frequency directions is insufficient, the error cannot be corrected in error correction, and the transmission efficiency is lowered. There was.

  The present invention has been made in view of the above, and an object of the present invention is to obtain an interleave device, a transmission device, a reception device, and a communication system that can increase the probability of correcting an error as compared with the related art.

  In order to solve the above-described problems and achieve the object, the present invention is an interleaving apparatus that performs interleaving processing on the transmission data in a transmission apparatus that transmits transmission data by Orthogonal Frequency-Division Multiplexing transmission, A first interleaving unit that performs a first interleaving process for rearranging transmission data in time and frequency directions, and grouping the transmission data after the first interleaving process for each Orthogonal Frequency-Division Multiplexing symbol time, And a second interleave processing unit for performing a second interleave process for cyclically shifting and outputting the output start position in the bit string for each group.

  According to the present invention, it is possible to increase the probability that an error can be corrected as compared with the related art.

FIG. 1 is a diagram showing a configuration example of a communication system according to the present invention. FIG. 2 is a diagram illustrating a configuration example of a transmitter included in the transmission apparatus. FIG. 3 is a diagram illustrating a configuration example of a receiver included in the reception device. FIG. 4 is a diagram illustrating a configuration example of a radio station in which a part of a transmitter and a receiver are integrated. FIG. 5 is a diagram illustrating a configuration example of an interleaver. FIG. 6 is a diagram illustrating an example of data after convolutional coding. FIG. 7 is a diagram illustrating an example of a storage method in the first storage device. FIG. 8 is a diagram illustrating an example of the first interleaving process. FIG. 9 is a diagram illustrating an example of the reading position calculated by the reading position calculation device and the output direction from the second storage device. FIG. 10 is a diagram illustrating an example of data output when the interleaving process according to the embodiment is applied.

  Embodiments of an interleave device, a transmission device, a reception device, and a communication system according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment.
FIG. 1 is a diagram showing a configuration example of an embodiment of a communication system according to the present invention. In the configuration example shown in FIG. 1A, the communication system includes radio stations 1-1 and 1-2 that are a transmission device according to the present invention and a reception device according to the present invention. In the configuration example shown in FIG. 1B, the communication system includes a transmission device 2 according to the present invention and a reception device 3 according to the present invention.

  The radio stations 1-1 and 1-2 shown in FIG. 1A include transmission / reception antennas 10 that can transmit and receive radio waves, respectively. The transmission device 2 illustrated in FIG. 1B includes a transmission antenna 20 that can transmit radio waves, and the reception device 3 includes a reception antenna 30 that can receive radio waves.

  FIG. 2 is a diagram illustrating a configuration example of the transmitter 200 included in the transmission device 2 according to the present embodiment. The transmitter 200 includes a signal control unit 21, an error correction code addition unit (encoding unit) 22, an interleaver (interleave device) 23, a modulator 24, an OFDM subcarrier allocation unit 25, and an IFFT (Inverse Fast Fourier Transform) unit 26. And a wireless transmission unit 27.

  The signal control unit 21 generates transmission data. The error correction code adding unit 22 encodes transmission data generated by the signal control unit 21 and adds an error correction code. The interleaver 23 rearranges the data in order to provide resistance against burst errors in the transmission path with respect to the encoded data (codeword). The modulator 24 performs modulation processing on the interleaved data. The OFDM subcarrier allocation unit 25 allocates the modulated signal to subcarriers used in OFDM transmission. The IFFT unit 26 converts data assigned to subcarriers from frequency domain data to time domain data for each OFDM symbol (Orthogonal Frequency-Division Multiplexing symbol). The wireless transmission unit 27 converts the data converted into the time domain into a format that can be transmitted wirelessly and inputs the data to the transmission antenna 20. The transmission antenna 20 radiates the input data to the antenna.

  FIG. 3 is a diagram illustrating a configuration example of the receiver 300 included in the reception device 3 according to the present embodiment. The receiver 300 includes a reception antenna 30, a radio reception unit 31, an FFT unit 32, a demodulator 33, a parallel / serial converter 34, a deinterleaver 35, an error correction unit 36, and a signal control unit 37.

  The reception antenna 30 receives a signal transmitted from the transmission device 2. The wireless reception unit 31 converts the reception signal received by the reception antenna 30 into data that can be demodulated. The FFT unit 32 converts the data converted by the wireless reception unit 31 from the time domain to the frequency domain. The demodulator 33 demodulates the data converted by the FFT unit 32 (that is, data for each subcarrier) for each subcarrier. The parallel-serial converter 34 rearranges the data for each subcarrier in series. The deinterleaver 35 performs processing (deinterleaving) opposite to the rearrangement performed by the interleaver 23 of the transmitter 200. The error correction unit 36 detects and corrects errors in the data after deinterleaving. The signal control unit 37 outputs data after error correction.

  In the case of the configuration example in FIG. 1A, the radio stations 1-1 and 1-2 may include the transmitter 200, the transmission antenna 20, the receiver 300, and the reception antenna 30, respectively. As described above, a part of the transmitter and the receiver may be integrated. Hereinafter, when the radio stations 1-1 and 1-2 are shown without being distinguished, they are referred to as a radio station 1. FIG. 1A shows an example in which the wireless station 1 has this integrated configuration example, and includes a transmission / reception antenna 10.

  FIG. 4 is a diagram illustrating a configuration example of the wireless station 1 in which a part of the transmitter and the receiver are integrated. The radio station 1 illustrated in FIG. 4 includes a transmission processing unit 201 and a reception processing unit 301. The transmission processing unit 201 includes a signal control unit 21, an error correction code addition unit 22, an interleaver 23, a modulator 24, an OFDM subcarrier allocation unit 25, and an IFFT unit 26 similar to those of the transmitter 200. The reception processing unit 301 includes an FFT unit 32, a demodulator 33, a parallel / serial converter 34, a deinterleaver 35, an error correction unit 36, and a signal control unit 37 similar to the receiver 300. The wireless transmission / reception unit 11 converts the data converted into the time domain into a format that can be transmitted wirelessly and outputs the data to the transmission / reception antenna 10. The wireless transmission / reception unit 11 converts the reception signal received by the transmission / reception antenna 10 into data that can be demodulated. In the transmission processing unit 201 and the reception processing unit 301, components having the same functions as those of the transmitter 200 and the receiver 300 are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 5 is a diagram illustrating a configuration example of the interleaver 23 according to the present embodiment. As illustrated in FIG. 5, the interleaver 23 includes a rearrangement unit 230, a first storage device (first storage unit) 231, a second storage device (second storage unit) 232, and a cyclic shift amount storage register (register). 233 and a reading position calculation device (reading unit) 234.

  The interleaver 23 according to the present embodiment stores the input data in the first storage device 231 in the row direction. The rearrangement unit 230 exchanges the data stored in the first storage device 231 in the row direction. The data in which the row direction is exchanged is stored in the second storage device 232. The cyclic shift amount storage register 233 stores a cyclic shift amount set in advance. The readout position calculation device 234 divides the matrix data stored in the second storage device 232 into each time zone for transmission, and based on the value stored in the cyclic shift amount storage register 233, The data reading position is calculated, and the data is read from the second storage device 232 in the column direction from the calculated reading position.

  Next, the operation of transmitter 200 of the present embodiment will be described. The operation of the transmission processing unit 201 is the same as the operation of the transmitter 200 except that the operations of the wireless transmission unit 27 and the transmission antenna 20 are performed by the wireless transmission / reception unit 11 and the transmission / reception antenna 10, respectively.

  In the transmitter 200, first, the signal control unit 21 collects transmission data for one codeword (that is, information data in one codeword) and passes it to the error correction code adding unit 22. The error correction code adding unit 22 encodes the data to be transmitted. As this encoding, for example, convolutional encoding can be used. FIG. 6 is a diagram illustrating an example of data after convolutional coding. The numbers in each rectangle in FIG. 6 indicate the order from the first bit, and do not indicate the transmission data value.

  Next, the interleaver 23 performs two interleaving processes on the encoded transmission data. Data input to the interleaver 23 is sequentially stored in the first storage device 231 in the row direction. FIG. 7 is a diagram illustrating an example of a storage method in the first storage device 231. FIG. 7 shows an example in which the 32-bit codeword illustrated in FIG. 6 is stored. Data is input and stored in the row direction, and when a certain number (number of columns) is input, the head of the next row is stored. Is input. By repeating this, data is stored in a matrix as shown in FIG. In FIG. 7, since the number of columns is eight, 32-bit codewords are stored in a matrix of 4 rows and 8 columns. In FIG. 7, the number of columns is eight, but the number of columns is not limited to this.

  The rearrangement unit 230 performs rearrangement in units of columns as the first interleave process (first interleave process). FIG. 8 is a diagram illustrating an example of the first interleaving process. In the example of FIG. 8, the first column data is moved to the second column, the second column data is moved to the seventh column, the seventh column data is moved to the first column, and the third column data is moved. Is moved to the sixth column, the fourth column data is moved to the third column, the fifth column data is moved to the eighth column, the sixth column data is moved to the fifth column, the eighth column Are moved to the fourth column. The specific order of column rearrangement is not limited to the example of FIG.

  The matrix-like data rearranged in units of columns in this way is transferred to the second storage device 232, and the second storage device 232 stores the transferred data. As the second interleaving process (second interleaving process), the reading position calculation device 234 divides the matrix-like data stored in the second storage device 232 for each time zone in which the data is transmitted. A read position is calculated based on the cyclic shift amount stored in the cyclic shift amount storage register 233, and a process of reading data from the second storage device 232 in the column direction from the calculated read position is performed. That is, the read position calculation device 234 groups for each time zone in which matrix data is transmitted, and sequentially reads out the position in the bit string for outputting the bit string in each group for each group.

  FIG. 9 is a diagram illustrating an example of the read position calculated by the read position calculation device 234 and the output direction from the second storage device 232. The read position calculation device 234 divides the data in the form of a matrix stored in the second storage device 232 for each time zone (for one OFDM symbol, that is, one symbol time). In the example of FIG. 9, it is divided into four time zones of time # 1, time # 2, time # 3, and time # 4. Then, the read position calculation device 234 obtains a read position (a position to start reading) based on the cyclic shift amount stored in the cyclic shift amount storage register 233 for each time period. A position surrounded by a circle in FIG. 9 indicates a reading position. FIG. 9 shows an example in which the cyclic shift amount is 1 (1 bit), and the reading position is shifted by 1 bit for each time slot. The read position calculation device 234 outputs the data read and read from the second storage device 232 in the column direction starting from the read position for each time zone. Reading is performed for each time zone until all data corresponding to the time zone is read. That is, for example, for time # 1, the bit numbers are read in the order of 7, 15, 23, 31, 1, 9, 17, 25, and for time # 2, the bit numbers are 12, 20, 28, 4 , 16, 24, 32, 8 in this order.

  The cyclic shift amount stored in the cyclic shift amount storage register 233 can be freely set, can be appropriately changed from the outside, and may be set according to the use environment of the system to be applied.

  In the present embodiment, the first interleaving process for rearranging the matrix composed of transmission data (codeword) in the column direction is realized by the rearrangement unit 230 and the first storage device 231. The configuration of the first interleave processing unit that performs one interleave processing is not limited to this example. For example, the rearrangement unit 230 and the first storage device 231 may be implemented as one component. In addition, the second interleaving process in which the reading position is determined based on the cyclic shift amount for each transmission time period and read in the column direction is performed by the cyclic shift amount storage register 233, the second storage device 232, and the read position calculation device 234. However, the configuration of the second interleave processing unit that performs the second interleave processing is not limited to this example. For example, the cyclic shift amount storage register 233 and the read position calculation device 234 may be mounted as one component.

  In addition, the matrix-shaped transmission data stored in the first storage device 231 is transmitted in the same time zone in two columns as shown in FIG. Also, 8 data transmitted in the same time zone are assigned to 8 subcarriers, respectively. Therefore, in the first interleaving process, rearrangement is performed so that a plurality of columns (two in the examples of FIGS. 8 and 9) in the same time zone are transmitted in different time zones. Thus, in the first rearrangement, interleaving is performed in the time direction. In addition, when the input direction (that is, the output order of the codewords) is set to the row direction, interleaving is simultaneously performed in the frequency direction in order to perform allocation to subcarriers in order in the column direction as shown in FIG. It will be. In FIG. 9, two columns are set as one time zone, but three or more columns may be set as one time zone.

  FIG. 10 is a diagram illustrating an example of data output when the interleave processing according to the present embodiment is applied. The vertical axis in FIG. 10 indicates time, and the horizontal axis indicates frequency. The frequency (subcarrier) on the horizontal axis conceptually shows the frequency after the subcarrier is assigned.

  The modulator 24 modulates the signal interleaved by the interleaver 23. As a modulation method, for example, QPSK (Quadrature Phase Shift Keying) can be used. When QPSK is used, the input signal is read and modulated two bits at a time.

  The OFDM subcarrier allocation unit 25 rearranges the modulated signals in parallel for each OFDM symbol and allocates the modulated signals to the subcarriers, and inputs them to the IFFT unit 26. The IFFT unit 26 performs IFFT on each input symbol for each OFDM symbol, thereby converting the signal assigned to the subcarrier from data in the frequency domain to data in the time domain. The wireless transmission unit 27 converts the data output from the IFFT unit 26 into data that can be transmitted wirelessly, and transmits the data as a radio wave via the transmission antenna 20.

  Next, an operation at the time of reception of the receiver 300 will be described. The operation of the reception processing unit 301 is the same as the operation of the receiver 300 except that the operations of the wireless reception unit 31 and the reception antenna 30 are performed by the wireless transmission / reception unit 11 and the transmission / reception antenna 10, respectively.

  In the receiver 300, first, the radio reception unit 31 converts the radio wave received by the receiving antenna 30 into a format that allows signal processing and the like. Then, the FFT unit 32 divides the reception signal converted by the radio reception unit 31 for each OFDM subcarrier, and the demodulator 33 demodulates each subcarrier.

  The parallel / serial converter 34 rearranges the demodulated data for each subcarrier in series. And the deinterleaver 35 performs the process of the reverse procedure to the process which the interleaver 23 of the transmitter 200 performed, and performs the deinterleave process which rearranges data.

  Next, the error correction unit 36 performs error correction processing on the data that has been subjected to deinterleaving processing, for example, by Viterbi decoding processing using a Viterbi algorithm. The signal control unit 37 outputs the data after error correction processing to the outside of the receiver 300 as received data.

  As described above, in this embodiment, after performing interleaving using a matrix at the time of transmission, the bits are distributed in the frequency direction and the time direction by reading sequentially from the designated position. For this reason, even if subcarriers at the same position in a plurality of OFDM symbols receive interference due to impulsive noise, the possibility of being able to be decoded by the Viterbi decoding process increases. By changing the reading start position during the interleaving process according to the convolutional code and the characteristics of the interference signal, a radio apparatus having higher interference resistance can be made.

  In the embodiment of the present invention, wireless communication has been described as an example. However, any transmitter / receiver that uses OFDM can be applied to various forms, such as a mobile terminal such as a mobile phone, a fixed terminal that does not move, a PLC ( It can also be used for wired communication such as Power Line Communication.

  Even when a code other than the convolutional code is used, if the matrix shown in FIG. 7 is configured with a plurality of codewords, consecutive errors are dispersed in each codeword, so that more codewords can be decoded. For this reason, interference resistance can be improved even when a code other than the convolutional code is used.

  As described above, the interleave device, the transmission device, the reception device, and the communication system according to the present invention are useful for a communication device that performs OFDM transmission.

  1-1, 1-2 radio station, 2 transmitter, 3 receiver, 10 transmit / receive antenna, 11 radio transmitter / receiver, 20 transmit antenna, 21 signal controller, 22 error correction code adding unit, 23 interleaver, 24 modulator 25 OFDM subcarrier allocation unit, 26 IFFT unit, 27 radio transmission unit, 30 reception antenna, 31 radio reception unit, 32 FFT unit, 33 demodulator, 34 parallel-serial converter, 35 deinterleaver, 36 error correction unit, 37 Signal control unit, 200 transmitter, 201 transmission processing unit, 230 rearrangement unit, 231 first storage device, 232 second storage device, 233 cyclic shift amount storage register, 234 reading position calculation device, 300 receiver, 301 Reception processing unit.

Claims (7)

An interleaving device that performs an interleaving process on the transmission data in a transmission device that transmits transmission data by Orthogonal Frequency-Division Multiplexing transmission,
A first interleave processing unit for performing a first interleave process for rearranging the transmission data in the time and frequency directions;
The transmission data after the first interleaving process is grouped for each Orthogonal Frequency-Division Multiplexing symbol time, and the bit string of each group is output by cyclically shifting the output start position in the bit string for each group. A second interleave processing unit for performing interleave processing;
An interleaving device comprising: The first interleave processing unit includes:
The input direction of the transmission data is set to the row direction, the transmission data is sequentially stored in the row direction in order of input of the transmission data, and the transmission data is stored in the next row for every input of a fixed number of bits, so that the fixed bit number is the number of columns. A first storage unit that stores the transmission data in the form of a matrix as a transmission data matrix;
Multiple columns of the transmission data matrix are transmitted in the same Orthogonal Frequency-Division Multiplexing symbol time, and columns transmitted in the same Orthogonal Frequency-Division Multiplexing symbol time in the transmission data matrix are adjacent before rearrangement. A rearrangement unit that rearranges the columns of the transmission data matrix stored in the first storage unit so as to be columns other than the first column;
The interleaving apparatus according to claim 1, further comprising: The second interleave processing unit includes:
A register for storing a preset cyclic shift amount;
A second storage unit for storing transmission data after the first interleaving process;
The transmission data stored in the second storage unit is grouped for each Orthogonal Frequency-Division Multiplexing symbol time, the bit string of each group is stored in the register, and the output start position in the bit string for each group is stored in the register. A readout unit that reads out the data by shifting based on the cyclic shift amount being;
The interleaving apparatus according to claim 1, further comprising:   The interleaving apparatus according to claim 1, 2 or 3, wherein the transmission data is convolutionally encoded data. A transmission device that transmits transmission data by Orthogonal Frequency-Division Multiplexing transmission,
A first interleave processing unit for performing a first interleave process for rearranging the transmission data in the time and frequency directions;
The transmission data after the first interleaving process is grouped for each Orthogonal Frequency-Division Multiplexing symbol time, and the bit string of each group is output by cyclically shifting the output start position in the bit string for each group. A second interleave processing unit for performing an interleaving process;
A transmission device comprising: A receiving device that receives a signal transmitted from the transmitting device according to claim 5,
A receiving apparatus comprising: a deinterleaving apparatus that performs a process reverse to an interleaving process performed by the transmitting apparatus on a signal received from the transmitting apparatus. A transmission device according to claim 5;
A receiving device according to claim 6;
A communication system comprising:

Images