JP2003101504A - Transmission apparatus and method, communication system, recording medium and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable easy modification on the allocation of a subcarrier affected by fading. SOLUTION: In step S1, a transmission side transmits a reference signal to a reception side. In step S11, the reception side analyzes signal intensity from the received reference signal on a subcarrier basis, and detects the fading information of the transmission line. In step S2, the transmission side determines an appropriate mapping scheme, based on the received fading information. In step S3, the transmission side transmits the determined mapping scheme to the reception side. In step S4, the transmission side sets a parameter of the newly determined mapping scheme. In step S5, according to the newly set mapping scheme, the reception side maps a parity bit, with priority given to the subcarrier affected by fading.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission device and method, a communication system, a recording medium, and a program, and in particular, for example, OFDM (Orthogonal Frequency Divis).
The present invention relates to a transmission device and method, a communication system, a recording medium, and a program suitable for use in the case of performing communication by the ion multiplex) method.

[0002]

2. Description of the Related Art Recently, an OFDM modulation system (orthogonal frequency division multiplexing system) has been attracting attention as a transmission system for digital broadcasting using terrestrial waves.

Here, an OFDM modulation method (orthogonal frequency division multiplexing method) will be described.

Generally, in the OFDM modulation communication, as a typical standard thereof, IEEE (Institute of Electrica)
l and Electronics Engineers) 802.11a and HiperLAN / 2.

FIG. 1 is a diagram showing an arrangement example of subcarriers of one OFDM symbol in a normal state of the HiperLAN / 2 standard. As shown in the figure, the frequency bandwidth of each subcarrier (carrier wave) is 1/64 of the OFDM signal bandwidth,
The number of actually used subcarriers is 52 except for both ends and the center of the frequency band of the OFDM signal. Of the 52 subcarriers, there are four subcarriers called pilot subcarriers, and the remaining 48 subcarriers are used for data transmission. The pilot subcarrier is known data that serves as a phase reference for correctly identifying the phase of the subcarrier, and is inserted at regular intervals.

In general, the IEEE802.11a and HiperLAN / 2 standards use a convolutional code as an error correction code. Convolutional coding is defined by two parameters, a coding rate R and a constraint length K. The coding rate is R
= 1/2, 1/3 or 1/4 is used, and the constraint length is selected in the range of K = 3 to 14, but normally, considering the processing amount on the decoding side, K = 7 or 9 is used.

FIG. 2 is a diagram showing an example of the configuration of a convolutional encoder adopted in the IEEE 802.11a and HiperLAN / 2 standards.

In the figure, a convolutional encoder having a code rate R = 1/2 and a constraint length K = 7 is shown. This convolutional encoder is composed of shift registers 1-1 to 1-6 and adders 2-1 and 2-2. As a result, the information bits (source signal) input to the convolutional encoder are stored in the encoder (that is, the shift register 1) by the constraint length K, and the information bits stored in the shift register 1 are added. The adder 2 performs addition (logical addition), and the addition result is generated as a coded bit. In this case, 2-bit coded bits X and Y are generated from the input 1-bit information bit IN.

The coded bits with a coding rate of 1/2 output from the convolutional encoder have high error correction capability but poor transmission efficiency. Therefore, in general, the coded bits with the coding rate of 1/2 output from the convolutional encoder are punctured (decimated) according to a predetermined rule, and output as punctured codes.

FIG. 3 is a diagram for explaining the puncturing process. 3A represents a 3-bit source signal, FIG. 3B represents a convolutionally encoded signal, and FIG. 3C represents a punctured signal.

As shown in the figure, 3-bit source signals IN1, IN2, IN3 (FIG. 3A) are convolutionally coded at a coding rate of 1/2, and 6-bit signals X1, X2, X3, Y1, Y2, Y3 are generated and output (FIG. 3B). Then, the 6-bit signals X1, X2, X3, Y1, Y2, Y3 are punctured at a coding rate of 3/4 (in this case, the 2-bit signals X3, Y2 are thinned out). It is output as 4-bit signals X1, X2, Y1, Y3.

As described above, the punctured code characteristically deteriorates as compared with the coding rate 1/2, but the transmission efficiency is improved. Therefore, for example, at a coding rate of 1/2 for the convolutional encoder and a coding rate of 3/4 for the punctured section, the transmission efficiency is improved by about 33%. Therefore, the S / N (Signa
These coding rates are properly used according to (l to Noise: signal-to-noise ratio).

A turbo code is known as a code having a high error correction capability, which is close to the Shannon limit (the limit of the channel capacity that can be transmitted without error in digital communication).
The turbo encoder outputs the source signal itself and two convolutional code bits that are the parity.

By the way, in radio communication under a multipath environment, comparison is made by direct waves (signals directly coming from a transmitting station) and reflected waves (signals reflected from obstacles) or radio wave interference between reflected waves. A phenomenon called fading occurs in which the signal strength of a specific frequency part in a relatively narrow band is significantly deteriorated.

Therefore, when fading occurs in communication using an OFDM modulation system in which a large number of mutually orthogonal subcarriers are phase- or amplitude-phase modulated and multiplexed, only S / N of some subcarriers is generated. It will get worse.

Therefore, for example, "Adaptive Modulation
For the HIPERLAN / 2 Air Interface ”, a method using an adaptive modulation method has been proposed.

FIG. 4 is a diagram showing an example of the configuration of an OFDM transmitter using the adaptive modulation method.

The turbo encoder 11 performs error correction processing such as convolutional coding on the input source signal (IN), and the source signal itself (IN) and two convolutional coded bits (X, Y) is output. The convolutionally coded bits output from the turbo encoder 11 have high error correction capability, but have poor transmission efficiency, and thus are supplied to the punctured unit 12.

The punctured section 12 is a turbo encoder 11
The convolutionally coded bits supplied from P.S.A. are regularly subjected to puncturing processing (thinning-out processing), and the punctured code bits are supplied to the frequency interleaver 3. The frequency interleaver 3 interleaves input coded data so that continuous data is not assigned to the same or adjacent subcarriers.

Specifically, when the received power of 2 or 3 subcarriers out of 48 subcarriers becomes extremely weak due to the effect of fading, continuous data is assigned to that subcarrier. In that case, in the receiving device, after demodulation, a continuous error may occur and the error may be input to the decoder (error corrector), and the error correction process may not be performed. Therefore, the frequency interleaver 3
Thus, if the continuous input data is arbitrarily rearranged and assigned to each subcarrier, even if 2 or 3 subcarriers cannot be used, the error is generated by the frequency deinterleaver of the receiving device. The data is input to the decoder in a separated state, which facilitates error correction processing.

The control unit 15 acquires in advance information on fading of the transmission path, and supplies the fading information to the subcarrier mapping unit 14 and the amplitude / phase modulation unit 16, respectively.

The subcarrier mapping section 14 assigns an appropriate modulation method to each subcarrier based on the fading information supplied from the control section 15. The subcarrier mapping unit 14 maps (modulates) the frequency-interleaved data sequence supplied from the frequency interleaver 13 according to the modulation scheme assigned to each subcarrier.

That is, subcarriers with fading have a relatively low required S / N QPSK (Quarterar).
y Phase Shift Keying: 4 phase PSK) or BPSK (Binary Phas)
e Shift Keying: Two-phase PSK) is used, and other subcarriers use 16QA with good transmission efficiency.
A multi-level amplitude phase modulation method such as M (Quadrature Amplitude Modulation) or 64QAM is used.

The amplitude / phase modulator 16 amplitude-phase modulates the data sequence mapped by the subcarrier mapping unit 14 on the basis of the fading information supplied from the controller 15, and IFFT (Inverse Fast Fourier Transform:
It is supplied to the inverse fast Fourier transform processing unit 17. IFFT section 1
Reference numeral 7 performs an inverse fast Fourier transform process on the data series that has been amplitude-phase modulated by the amplitude-phase modulator 16.

In this way, the subcarrier mapping unit 1
4 indicates, for example, that all subcarriers should be modulated by a 16QAM modulation scheme with a coding rate of 3/4, but for subcarriers affected by fading, a QPSK modulation scheme with a coding rate of 1/2. Modulate with. As a result, compared to the case where all subcarriers are modulated by the same modulation method as in the past, the transmission capacity is larger when compared with the same S / N, and lower when compared with the same transmission capacity. Communication with S / N becomes possible.

[0026]

However, in the above-mentioned adaptive modulation method, since it is not possible to allocate all the data of the packet to be transmitted, which is allocated from the upper layer (the part that performs so-called radio transmission / reception control), the S There is a problem that it is necessary to adjust the book edge by changing the modulation method of the subcarrier with good / N to the modulation method of 64QAM, which requires complicated processing.

The present invention has been made in view of such a situation, and makes it possible to easily change the allocation of subcarriers affected by fading.

[0028]

A first transmitting apparatus of the present invention is a coding means for coding a signal, an acquiring means for acquiring fading information of a transmission path, and a fading acquired by the acquiring means. Setting means for setting an allocation pattern of subcarriers based on the information, and encoding coded by the encoding means for the subcarrier having fading based on the allocation pattern set by the setting means And an allocation unit that preferentially allocates a parity portion of the data.

The encoding means in the first transmitting apparatus of the present invention may be constituted by a turbo encoder.

It is possible to further provide notifying means for notifying the receiving device of the allocation pattern set by the setting means.

According to the first transmission method of the present invention, an encoding step for encoding a signal, an acquisition control step for controlling acquisition of fading information on a transmission path, and an acquisition control step are executed to control acquisition. Based on the fading information, a setting step of setting an allocation pattern of subcarriers, and based on the allocation pattern set by the processing of the setting step, the subcarrier with fading is processed by the processing of the encoding step. An allocation step of preferentially allocating the parity part of the encoded data that has been encoded.

The program recorded on the first recording medium of the present invention comprises an encoding step for encoding a signal, an acquisition control step for controlling acquisition of fading information on a transmission path, and an acquisition control step. Based on the fading information acquisition is controlled by the setting step to set the subcarrier allocation pattern, based on the allocation pattern set by the processing of the setting step, for the subcarriers fading,
An allocation step of preferentially allocating the parity part of the coded data coded by the processing of the coding step.

A first program of the present invention is an encoding step for encoding a signal, an acquisition control step for controlling acquisition of fading information on a transmission path, and a fader whose acquisition is controlled by the processing of the acquisition control step. A setting step of setting an allocation pattern of subcarriers based on the fading information, and a code of the subcarrier in which fading has occurred by the processing of the encoding step based on the allocation pattern set by the processing of the setting step. And a step of allocating the parity part of the encoded data that has been preferentially allocated to the computer.

In the first transmitting apparatus and method and the program of the present invention, a signal is encoded, fading information of a transmission path is acquired, and a subcarrier allocation pattern is obtained based on the acquired fading information. Is set, and based on the set allocation pattern,
The parity part of the encoded data that has been encoded is preferentially assigned to the subcarrier in which fading has occurred.

The second transmitting apparatus of the present invention comprises a coding means for coding a signal, an acquisition means for acquiring a subcarrier allocation pattern, and a fading based on the allocation pattern acquired by the acquisition means. The present invention is characterized by comprising an assigning unit that preferentially assigns a parity part of the encoded data encoded by the encoding unit to the generated subcarriers.

The encoding means in the second transmitting apparatus of the present invention may be constituted by a turbo encoder.

The second transmission method of the present invention is a coding step for coding a signal, an acquisition control step for controlling acquisition of a subcarrier allocation pattern, and an allocation whose acquisition is controlled by the processing of the acquisition control step. An allocation step of preferentially allocating a parity part of the coded data coded by the processing of the coding step to subcarriers having fading based on the pattern.

The program recorded on the second recording medium of the present invention is composed of a coding step for coding a signal, an acquisition control step for controlling acquisition of a subcarrier allocation pattern, and an acquisition control step. An allocation step of preferentially allocating the parity part of the encoded data encoded by the processing of the encoding step to the subcarrier in which fading has occurred, based on the allocation pattern whose acquisition is controlled. It is characterized by

A second program of the present invention is a coding step for coding a signal, an acquisition control step for controlling acquisition of a subcarrier allocation pattern, and an allocation pattern whose acquisition is controlled by the processing of the acquisition control step. Based on the above, the computer is caused to perform an allocation step of preferentially allocating the parity part of the encoded data encoded by the processing of the encoding step to the subcarrier in which fading has occurred. To do.

In the second transmitting apparatus and method and the program of the present invention, signals are coded, subcarrier allocation patterns are acquired, and sub-fading in which subfading is occurring is performed based on the acquired allocation patterns. The parity portion of the encoded data that has been encoded is preferentially assigned to the carrier.

In the first transmission system of the present invention, the transmitting device obtains the encoding means for encoding the signal, the obtaining means for obtaining the fading information of the transmission path notified from the receiving device, and the obtaining means. Setting means for setting a subcarrier allocation pattern based on the generated fading information, first notifying means for notifying the receiving device of the allocation pattern set by the setting means, and allocation pattern set by the setting means Based on the above, the assigning means preferentially assigns the parity part of the encoded data encoded by the encoding means to the subcarrier in which fading has occurred. Detecting means for detecting the fading information and a second communication for notifying the transmitting device of the fading information detected by the detecting means. Characterized in that it comprises a means.

In the first transmission system of the present invention,
The transmitting device encodes the signal, and the subcarrier allocation pattern is set based on the fading information of the transmission path notified from the receiving device. The set allocation pattern is notified to the receiving device and set. Based on the allocation pattern, for the sub-carriers that are fading, the parity part of the encoded data that has been coded is preferentially allocated, and the receiving device detects the fading information of the transmission path, The detected fading information is notified to the transmission device.

In the second transmission system of the present invention, the transmitting device obtains the encoding means for encoding the signal, the obtaining means for obtaining the subcarrier allocation pattern notified from the receiving device, and the obtaining means. Based on the allocation pattern, the allocation means preferentially allocates the parity part of the coded data encoded by the encoding means to the subcarrier in which fading has occurred. Detecting means for detecting fading information of the road, setting means for setting the subcarrier allocation pattern based on the fading information detected by the detecting means, and notifying the transmitting device of the allocation pattern set by the setting means And a notification means for performing the notification.

In the second transmission system of the present invention,
The transmitting device encodes the signal, and based on the subcarrier allocation pattern notified by the receiving device, the parity part of the encoded data that has been fading is given priority to the subcarrier with fading. Of the transmission path is detected by the receiving device, the subcarrier allocation pattern is set based on the detected fading information, and the transmitting device is notified of the set allocation pattern. .

[0045]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 5 is a diagram showing a configuration example of a transmission system according to the OFDM communication system to which the present invention is applied. Transmitter 3
1 performs convolutional coding or the like on the input digital data at a predetermined coding rate, and transmits the convolutionally coded coded bits together with the source signal to the receiving device 33 via the transmission medium 32. . The receiving device 33 receives the convolutionally encoded data transmitted via the transmission medium 32 and decodes it.

FIG. 6 is a block diagram showing a configuration example of the transmitting device 31 of FIG. The parts corresponding to those of the related art are designated by the same reference numerals, and the description thereof will be appropriately omitted.

The turbo encoder 11 performs error correction processing such as convolutional coding on the input source signal (IN), and the source signal itself (IN) and two convolutional coded bits (X, Y) is output.

FIG. 7 is a block diagram showing a configuration example of the turbo encoder 11.

The source signal (IN) is output as it is through the delay device 51. The source signal is also recursive systematic convolutional (RSC).
It is supplied to the encoder 53-1 and is supplied to the random interleaver 52, where the source signals are randomly interleaved and then supplied to the recursive systematic convolutional encoder 53-2.

The recursive systematic convolutional encoder 53 has a structure in which a recursive (circular) part and a non-recursive part are combined, as shown in FIG. That is, the output of the delay unit 62 and the outputs of the delay units 62 and 63 are input to the adder 61, and the adder 64 is input to the adder 64.
The output of 1 and the outputs of the delay device 62 and the delay device 63 are input. The configuration of the recursive systematic convolutional encoder shown in FIG. 8 is called an IIR (Infinite Impulse Response) format.

Thus, the recursive systematic convolutional encoder 5
From 3, the current input information i and the past input information p are both combined, and a convolutionally encoded bit (parity bit) obtained by systematically encoding is output.

Returning to the explanation of FIG. Convolutional coded bits (X) generated by the recursive systematic convolutional encoder 53-1
Is output via the delay unit 54, and the convolutional coded bits (Y) generated by the recursive systematic convolutional encoder 53-2 are output as they are.

As described above, from the turbo encoder 11,
The source signal (IN) itself, coded at a coding rate of 1/3, and the two convolutional coded bits (X, Y), for a total of 3
The encoded bits of the bit are output.

Returning to the explanation of FIG. Puncture part 12
Performs puncturing processing on the convolutionally coded bits supplied from the turbo encoder 11, and supplies the punctured code bits to the subcarrier mapping unit 14.

FIG. 9 is a diagram for explaining the puncturing process. 9A shows a 3-bit source signal, FIG. 9B shows a convolutionally coded signal, and FIG. 9C shows a punctured signal.

As shown in the figure, the 6-bit source signals IN1, IN2, IN3, IN4, IN5, IN6 (FIG. 9A) are convolutionally coded at a coding rate of 1/2 to obtain a 12-bit signal. X1, X2, X
3, X4, X5, X6, Y1, Y2, Y3, Y4, Y5, Y6 are generated and output (FIG. 9B). And the 12-bit signals X1, X2, X3, X4, X
5, X6, Y1, Y2, Y3, Y4, Y5, Y6 are punctured at a coding rate of 3/4 (in this case, 10-bit signal X
1, X2, X4, X5, X6, Y1, Y2, Y3, Y4, Y5 are thinned out) and output as 2-bit signals X3, Y6. In this way, the source signal IN having a large deterioration in characteristics is not thinned out, and only the parity bit is thinned out.

The control unit 15 acquires in advance information regarding fading of the transmission path from the receiving device 33, determines an appropriate mapping setting method based on the fading information, and determines each mapping setting method according to the determined mapping setting method. The parameters of the subcarrier mapping unit 14 are set so that the subcarriers are mapped. Control unit 15
Notifies the receiving device 33 of the determined mapping setting method.

The subcarrier mapping unit 14 follows the appropriate mapping method set by the control unit 15 with respect to the subcarriers in which fading has occurred.
The parity bits supplied from the punctured unit 12 are preferentially mapped.

The amplitude / phase modulator 16 amplitude-phase modulates the data sequence mapped by the subcarrier mapping unit 14 and supplies it to the IFFT unit 17. The IFFT unit 17 performs an inverse fast Fourier transform process on the data sequence amplitude-phase modulated by the amplitude-phase modulator 16.

FIG. 10 is a block diagram showing a configuration example of the receiving device 33 of FIG.

The FFT unit 81 performs fast Fourier transform processing on the coded data transmitted from the transmission device 31 via the transmission medium 32, and supplies it to the amplitude / phase demodulation unit 82. The amplitude / phase demodulation unit 82 performs amplitude / phase demodulation on the encoded data subjected to the fast Fourier transform processing, and the subcarrier demapping unit 8
Supply to 3.

The subcarrier demapping section 83 has previously acquired the mapping setting method from the transmission device 31,
Based on the mapping setting method, the demodulated data that has been amplitude-phase demodulated is demapped (demodulated). The fading detection unit 84 detects information regarding fading of the transmission path for each subcarrier from the demodulated data of the reference signal supplied from the subcarrier demapping unit 83,
The transmitter 31 is notified of the detection result (fading information).

The punctured decoding unit 85 performs punctured decoding processing (interpolation processing) on the demodulated data of the parity portion demapped by the subcarrier demapping unit 83, and outputs it to the turbo encoder 86.

The turbo encoder 86 is composed of, for example, a Viterbi decoder and the like, and the source signal supplied from the subcarrier demapping unit 83 and the coded bits as the parity supplied from the punctured decoding unit 85. Is decoded and the decoded data is output.

Next, the data transmission process will be described with reference to the flowchart of FIG. Note that the transmission device 31 will be described here as a base station and the reception device 33 as a mobile station.

In step S1, the transmitter 31
A reference signal for setting (determining) the mapping method,
It is transmitted to the receiving device 33 via the transmission medium 32.

In step S11, the receiving device 33
Receives the reference signal transmitted from the transmission device 31 via the transmission medium 32, performs fast Fourier transform processing in the FFT unit 81, performs amplitude phase demodulation in the amplitude phase demodulation unit 82, and in the subcarrier demapping unit 83. Demapping is performed for each subcarrier, and the fading detection unit 84
Supply to. The fading detection unit 84 analyzes the signal strength for each subcarrier from the demodulated data of the reference signal supplied from the subcarrier demapping unit 83, and detects fading information on the transmission path. In step S12, the fading detection unit 84 transmits (notifies) the fading information detected in the process of step S11 to the transmission device 31.

In step S2, the control unit 15 of the transmitting device 31 receives the fading information notified from the receiving device 33, and based on the fading information,
Determine the appropriate mapping method. In step S3, the control unit 15 transmits (notifies) the mapping method determined in the process of step S2 to the receiving device 33. In step S4, the control unit 15 sets the parameters of the subcarrier mapping unit 14 so that each subcarrier is mapped according to the new mapping method determined in the process of step S2.

In step S13, the subcarrier demapping section 83 of the receiving device 33 receives the mapping method notified from the transmitting device 31 and sets its parameters.

As described above, by the processing of steps S1 to S4 and steps S11 to S13,
An appropriate mapping method is negotiated between the transmitting device 31 and the receiving device 33.

In step S5, the turbo encoder 11 of the transmission device 31 performs error correction processing such as convolutional coding on the signal to be transmitted, and the source signal itself and 2
Outputs two convolutionally encoded bits. The punctured unit 12 performs puncturing processing on the convolutionally coded bits and supplies the convolutionally coded bits to the subcarrier mapping unit 14. The subcarrier mapping unit 14 preferentially maps the parity bit supplied from the punctured unit 12 to the subcarrier in which fading has occurred, according to the new mapping method set by the control unit 15. The amplitude / phase modulator 16 amplitude-phase modulates the data sequence mapped by the subcarrier mapping unit 14 and supplies it to the IFFT unit 17. The IFFT unit 17 performs inverse fast Fourier transform processing on the amplitude-phase modulated data series. Then, the encoded data is transmitted to the receiving device 33 via the transmission medium 32.

At step S6, the transmitter 31
It is determined whether or not a predetermined time (for example, tens of ms or tens of μs) has elapsed. If it is determined that the predetermined time has not elapsed, the process returns to step S5 and the above-described processing is repeatedly executed. If it is determined in step S6 that the predetermined time has elapsed, the process proceeds to step S7, it is determined whether the transmission is completed, and if it is determined that the transmission is not completed, the process returns to step S1 and the above-described process is performed. Repeat the process.

That is, in the process of step S6, since the receiving device 33 is a mobile station, the situation of the transmission path may change. Therefore, a reference signal is transmitted at every predetermined time and a new mapping method is always set. Done to be able to.

In step S14, the receiver 33
The FFT unit 81 performs fast Fourier transform processing on the encoded data transmitted from the transmission device 31, and the amplitude / phase demodulation unit 82.
Supply to. The amplitude / phase demodulation unit 82 performs amplitude / phase demodulation on the coded data subjected to the fast Fourier transform processing, and supplies the demodulated data to the subcarrier demapping unit 83. The subcarrier demapping unit 83 demaps the demodulated data according to the parameter (mapping method) set in the process of step S13.

If it is determined in step S7 that the transmission has ended, the transmission processing ends.

In this way, the transmitter 31 and the receiver 33
Since signals are transmitted and received according to the mapping method arranged between the subcarrier and the subcarrier, even if any of the 48 subcarriers is affected by fading, By preferentially allocating the parity part, efficient transmission can be achieved.

Further, in the above, the fading information detected by the receiving device 33 is notified to the transmitting device 31,
Although the transmitter 31 determines the appropriate mapping method, the receiver 33 may determine the mapping method.

FIG. 12 is a block diagram showing another configuration example of the receiving device 33 of FIG. The parts corresponding to those in FIG. 10 are designated by the same reference numerals, and the description thereof will be omitted as appropriate. In the case of the example in FIG. 12, a mapping setting unit 91 is further provided in the configuration of the receiving device 33 shown in FIG.

The mapping setting unit 91 determines an appropriate mapping setting method based on the fading information supplied from the fading detection unit 84, and performs subcarrier demapping so as to perform demapping according to the determined mapping setting method. The parameters of the section 83 are set.
The mapping setting unit 85 notifies the transmission device 31 of the determined (set) mapping setting method.

Next, the data transmission process will be described with reference to the flowchart of FIG.

The processing of steps S31 and S41 is the same as the processing of steps S1 and S11 described with reference to the flowchart of FIG. 11, and therefore the description thereof is omitted.

In step S42, the mapping setting section 91 of the receiving device 33 determines an appropriate mapping method based on the fading information detected in the process of step S41. In step S43, the mapping setting unit 91 transmits (notifies) the mapping method determined in the process of step S42 to the transmission device 31.

In step S32, the control unit 15 of the transmitting device 31 receives the mapping method notified from the receiving device 33 and confirms it. In step S33, the control unit 15 transmits (notifies) the confirmation of the mapping method to the reception device 33. In step S34, the control unit 15 sets the parameters of the subcarrier mapping unit 14 so as to map each subcarrier according to the new mapping method notified from the reception device 33.

In step S44, the mapping setting unit 91 of the receiving device 33 receives the confirmation notification from the transmitting device 31 and performs subcarrier demapping so as to perform demapping according to the new mapping setting method determined in the process of step S42. The parameters of the section 83 are set.

As described above, steps S31 to S3
4 and the processing of steps S41 to S44,
An appropriate mapping method is decided in advance between the transmitting device 31 and the receiving device 33.

The processes of steps S35 to S37 and step S45 are the same as the processes of steps S5 to S7 and step S14 described with reference to the flowchart of FIG. 11, and therefore the description thereof will be omitted.

As described above, the convolutional coded bits, which are the parity part, of the coded data output from the turbo encoder 11 are preferentially mapped to the subcarriers in which fading has occurred. Because I did
A source signal that occupies a large weight in the error correction process is transmitted on a subcarrier with little deterioration. Then, even if there is an error, the convolutionally coded bits, which is a parity part that has little influence, are transmitted on subcarriers with degraded S / N.

Therefore, the data transmission from the transmission device 31 has apparently almost the same characteristics as the transmission in which the thinning-out of the parity part is slightly larger, and is deteriorated as compared with the transmission without fading at all, but the fading The transmission characteristics are significantly improved as compared with the case where the source signal is mapped to the subcarriers without considering the coding.

Next, the transmission method by the adaptive modulation method and the transmission method by the method to which the present invention is applied will be compared and described.

FIG. 14 is a diagram showing the number of transmission data per OFDM symbol and the number of transmission data per subcarrier in each modulation scheme.

As shown in the figure, the BPS with the coding rate of 1/2
In the case of the K modulation method, 24 bits of data can be transmitted per 1 OFDM symbol and 0.5 per 1 subcarrier.
Bits of data can be transmitted. Code rate 3/4 B
In the case of PSK modulation method, 36 bits of data can be transmitted per 1 OFDM symbol, and 0 per subcarrier.
It can transmit 75 bits of data. Code rate 1 /
In the case of the 2 QPSK modulation method, 48-bit data can be transmitted per 1 OFDM symbol, and 1.0-bit data can be transmitted per 1 subcarrier. 72 per 1 OFDM symbol in case of QPSK modulation method with code rate 3/4
Bit data can be transmitted, and 1.5 bit data can be transmitted per subcarrier.

Also, in the case of the 16QAM modulation system with the coding rate of 9/16, 108-bit data can be transmitted per 1 OFDM symbol and 2.25-bit data can be transmitted per 1 subcarrier. In the case of the 16QAM modulation scheme with the coding rate of 3/4, 144 bits of data can be transmitted per 1 OFDM symbol and 3.0 bits of data can be transmitted per subcarrier. 64QAM with 3/4 code rate
In the case of the modulation method, 216 bits of data can be transmitted per 1 OFDM symbol and 4.5 per subcarrier.
Bit data can be transmitted.

For example, in the case of a BPSK modulation method with a coding rate of 3/4, data of 3 bits (= 0.75 × 4) can be transmitted with four subcarriers, and QPSK with a coding rate of 3/4. In the case of the modulation method, 3 bits (= 1.5 × 2 subcarriers)
2) Minute data can be sent.

Here, the case of transmitting data by the QPSK modulation method with the coding rate of 3/4 will be described. Normally, when fading does not occur in the transmission path, the coded bits output from the turbo encoder 11 have a ratio of the source signal to the parity portion of 3: 1, and the parity of the parity is set to one in four. Subcarriage exists. If the subcarriers of this parity are evenly allocated, for example, FIG.
As shown in.

In subcarrier allocation as shown in FIG. 15, assuming that 7 subcarriers out of 48 subcarriers are affected by fading and their amplitudes are reduced, the conventional adaptive modulation method is used. When used, the modulation scheme of each subcarrier is changed as shown in FIG.

Specifically, first, for subcarriers affected by fading, BPSK with a coding rate of 1/2 is used.
Let's say you want to assign a modulation scheme. However, the coding rate
In the ½ BPSK modulation method, it is necessary to allocate subcarriers in units of two, so eight subcarriers including the subcarriers that are affected by fading are code rate 1/2 BPSK modulation method. Change (replace) to.

By this change, the number of transmission data is reduced by 8 bits (= (1.5−0.5) × 8), so that the coding rate is 3/4.
The data transmission efficiency is higher than that of QPSK modulation system, and if the 16QAM modulation system with a coding rate of 3/4 is attempted to make up for the shortfall, the number of transmission data per subcarrier increases by 1.5 (= 3−1.5) bits. To do. Therefore, 6 subcarriers are coded
When changing to 3/4 16QAM modulation system, the number of transmission data is 9
The number of bits (= 1.5 × 6) increases, and conversely there is one bit left. Furthermore, in order to eliminate the remainder of 1 bit, the number of transmission data is 1 bit (= (1.5−1.0) ×
2) It can be reduced and the total number of transmission bits can be matched.

As described above, the conventional adaptive modulation method is 48
Of these subcarriers, a BPSK modulation scheme with a coding rate of 1/2 is assigned to 8 subcarriers (the number of transmission bits by this modulation scheme is 8 bits), and a coding rate of 3/4 is assigned to 6 subcarriers. 16QAM modulation scheme of (the number of transmission bits by this modulation scheme is 6 bits), QPSK modulation scheme of coding rate 1/2 is assigned to two subcarriers (the number of transmission bits by this modulation scheme is 2 bits), A QPSK modulation scheme with a coding rate of 3/4 is assigned to the remaining 32 subcarriers (the number of transmission bits by this modulation scheme is 48 bits), and processing for adjusting the number of transmission data is performed.

On the other hand, when the present invention is applied, as shown in FIG. 17, the parity data in the vicinity of the subcarrier is preferentially assigned to the subcarrier affected by the fading. To do so. As a result, it is possible to perform transmission at exactly the same transmission rate as normal transmission without performing complicated processing for adjusting the number of transmission data as in the adaptive modulation method.

The series of processes described above (for example, the transmission process of the transmitter 31 and the receiver 33 of the transmission system)
Can be executed by hardware, but can also be executed by software. When a series of processes is executed by software, a program that constitutes the software can execute various functions by installing a computer in which dedicated hardware is installed or various programs. It is installed from a program storage medium into a possible general-purpose personal computer or the like.

FIG. 18 is a diagram showing an internal configuration example of a general-purpose computer. Computer CPU (Central Pro
The cessing unit) 101 is a ROM (Read Only Memory) 1
No. 02 stored in the program, or the storage unit 108
Various processes are executed according to the program loaded from the RAM (Random Access Memory) 103. RAM10
In addition, data and the like necessary for the CPU 101 to execute various processes are also stored in the area 3 as appropriate.

CPU 101, ROM 102, and RAM 103
Are mutually connected via a bus 104. An input / output interface 105 is also connected to the bus 104.

The input / output interface 105 includes an input unit 106 composed of buttons, switches, a keyboard, a mouse, etc., and a CRT (Cathode Ray Tub).
e), a display such as an LCD (Liquid Crystal Display), an output unit 107 including a speaker, a storage unit 108 including a hard disk, and a communication unit 10 including a modem and a terminal adapter.
9 is connected. The communication unit 109 performs communication processing via a network including the Internet.

The input / output interface 105 also includes
A drive 110 is connected as necessary, a magnetic disk 121, an optical disk 122, a magneto-optical disk 123, a semiconductor memory 124, or the like is mounted as appropriate, and a computer program read therefrom is stored in the storage unit 10.
Installed on 8.

As shown in FIG. 18, a program storage medium for storing a program installed in a computer and put into a state executable by the computer includes a magnetic disk 121 (including a flexible disk) and an optical disk 122 (CD-ROM). (Compact Disc-Read
Only Memory), DVD (including Digital Versatile Disc)), magneto-optical disk 123 (including MD (Mini-Disc) (registered trademark)), or semiconductor memory 124 or a package medium including It is configured by a ROM 102, a storage unit 108, and the like in which a program is provided to a user in a state of being pre-installed in a computer and in which a program is temporarily or permanently recorded.
To store the program in the program storage medium, a wired or wireless communication medium such as a public line network, a local area network, the Internet, or digital satellite broadcasting is used via the communication unit 109 such as a router or a modem as necessary. Is done.

In the present specification, the steps for describing the program stored in the program storage medium need not necessarily be performed in time series according to the order described, but may not necessarily be performed in time series. It also includes processing executed in parallel or individually.

Further, in this specification, the system means
It represents the entire apparatus composed of a plurality of devices.

[0109]

According to the first transmitting apparatus and method and the program of the present invention, a signal is encoded, fading information of a transmission path is acquired, and subcarriers of a subcarrier are acquired based on the acquired fading information. Since the allocation pattern is set, and based on the set allocation pattern, the parity part of the coded coded data is preferentially allocated to the subcarriers having fading, fading It is possible to easily change the allocation of subcarriers affected by, and to efficiently transmit data.

According to the second transmitting apparatus and method and the program of the present invention, a signal is coded, a subcarrier allocation pattern is acquired, and sub-fading occurs in the subcarrier based on the acquired allocation pattern. Since the parity part of the encoded data that has been encoded is preferentially assigned to the carriers, it is possible to easily change the assignment of the subcarriers that are affected by fading, and efficiently transfer the data. Can be transmitted.

According to the first transmission system of the present invention, the transmitter encodes the signal, sets the subcarrier allocation pattern based on the fading information of the transmission path notified from the receiver, and sets the subcarrier allocation pattern. Notify the receiving device of the allocated pattern, and based on the set allocation pattern, preferentially allocate the parity part of the coded data that has been coded to the subcarriers that are fading and receive. Since the device detects fading information on the transmission path and notifies the detected fading information to the transmitting device, data can be efficiently transmitted even when the fading is affected.

According to the second transmission system of the present invention, the transmitting device encodes the signal, and based on the subcarrier allocation pattern notified from the receiving device, for the subcarrier with fading, The parity part of the coded coded data is preferentially allocated, the receiving device detects fading information of the transmission path, and the subcarrier allocation pattern is set based on the detected fading information. Since the set allocation pattern is notified to the transmitting device, data can be efficiently transmitted even when affected by fading.

[Brief description of drawings]

FIG. 1 is a diagram showing an arrangement example of subcarriers of one OFDM symbol in a normal state.

FIG. 2 is a diagram illustrating a configuration example of a convolutional encoder.

FIG. 3 is a diagram illustrating a puncturing process.

[Fig. 4] Fig. 4 is a diagram illustrating a configuration example of an OFDM transmitting apparatus using an adaptive modulation method.

FIG. 5 is a diagram showing a configuration of a transmission system of an OFDM communication system to which the present invention is applied.

FIG. 6 is a block diagram showing a configuration example of the transmission device of FIG.

7 is a block diagram showing a configuration example of the turbo encoder in FIG.

8 is a diagram showing a configuration example of the recursive systematic convolutional encoder in FIG. 7. FIG.

FIG. 9 is a diagram illustrating puncturing processing.

10 is a block diagram illustrating a configuration example of the receiving device in FIG.

FIG. 11 is a flowchart illustrating a data transmission process.

FIG. 12 is a block diagram illustrating another configuration example of the receiving device in FIG.

FIG. 13 is a flowchart illustrating a data transmission process.

FIG. 14 is a diagram showing the number of transmission data per OFDM symbol and the number of transmission data per subcarrier in each modulation scheme.

[Fig. 15] Fig. 15 is a diagram for describing subcarrier allocation in a QPSK modulation scheme with a coding rate of 3/4.

[Fig. 16] Fig. 16 is a diagram for describing a change in modulation method of subcarriers affected by fading when an adaptive modulation method is used.

FIG. 17 is a diagram illustrating allocation of subcarriers affected by fading when the present invention is applied.

FIG. 18 is a diagram illustrating an internal configuration example of a general-purpose computer.

[Explanation of symbols]

11 turbo encoder, 12 punctured section, 14
Subcarrier mapping unit, 15 control unit, 16
Amplitude and phase modulator, 17 IFFT, 31 transmitter,
32 transmission medium, 33 receiving device, 53-1, 5
3-2 Recursive systematic convolutional encoder, 81 FFT section,
82 amplitude / phase demodulation section, 83 subcarrier demapping section, 84 fading detection section, 85 punctured decoding section, 86 turbo encoder, 91 mapping setting section, 121 magnetic disk, 122
Optical disk, 123 magneto-optical disk, 124 semiconductor memory

Claims (13)

[Claims] 1. A transmission device for transmitting a signal in an OFDM system, an encoding means for encoding the signal, an acquisition means for acquiring fading information of a transmission path, and the fading acquired by the acquisition means. Setting means for setting an allocation pattern of subcarriers based on the information, and based on the allocation pattern set by the setting means, for the subcarriers having fading, encoded by the encoding means And a allocating unit that preferentially allocates a parity part of the encoded data. 2. The transmission device according to claim 1, wherein the encoding unit is configured by a turbo encoder. 3. The transmitting apparatus according to claim 1, further comprising notifying means for notifying a receiving apparatus of the allocation pattern set by the setting means. 4. A transmission method of a transmission device for transmitting a signal in an OFDM system, an encoding step of encoding the signal, an acquisition control step of controlling acquisition of fading information of a transmission path, and the acquisition control step. Based on the fading information, the acquisition of which is controlled by the process of, a setting step of setting a subcarrier allocation pattern, and fading has occurred based on the allocation pattern set by the process of the setting step. An allocation step of preferentially allocating a parity part of the coded data coded by the processing of the coding step to the subcarriers. 5. A program for controlling a transmission device for transmitting a signal in an OFDM system, comprising: an encoding step of encoding the signal; an acquisition control step of controlling acquisition of fading information on a transmission path; Based on the fading information acquisition is controlled by the processing of the acquisition control step, a setting step of setting the subcarrier allocation pattern, based on the allocation pattern set by the processing of the setting step, of fading A computer-readable program is recorded, which comprises an allocation step of preferentially allocating a parity part of the encoded data encoded by the processing of the encoding step to the generated subcarriers. Recording medium. 6. A computer for controlling a transmission device for transmitting a signal by the OFDM system, a coding step for coding the signal, an acquisition control step for controlling acquisition of fading information of a transmission path, and the acquisition control. Based on the fading information, the acquisition of which is controlled by the processing of step, a setting step of setting an allocation pattern of subcarriers, and based on the allocation pattern set by the processing of the setting step, fading occurs A program that causes an allocation step of preferentially allocating a parity part of the encoded data encoded by the processing of the encoding step to the existing subcarriers. 7. A transmission device for transmitting a signal in an OFDM system, comprising: an encoding unit that encodes the signal, an acquisition unit that acquires an allocation pattern of subcarriers, and an allocation pattern acquired by the acquisition unit. Based on the above, the transmitting device is characterized by further comprising: an assigning unit that preferentially assigns a parity part of the encoded data encoded by the encoding unit to the subcarrier in which fading has occurred. 8. The transmission apparatus according to claim 7, wherein the encoding means is configured by a turbo encoder. 9. A transmission method of a transmission device for transmitting a signal by an OFDM method, comprising: an encoding step of encoding the signal, an acquisition control step of controlling acquisition of a subcarrier allocation pattern, and an acquisition control step. Allocation preferentially allocating the parity part of the coded data coded by the process of the coding step to the subcarriers having fading, based on the allocation pattern whose acquisition is controlled by the process. And a step of transmitting. 10. A program for controlling a transmission device for transmitting a signal in an OFDM system, comprising: an encoding step of encoding the signal; an acquisition control step of controlling acquisition of a subcarrier allocation pattern; Based on the allocation pattern whose acquisition is controlled by the processing of the control step, the parity part of the coded data coded by the processing of the coding step is preferentially applied to the sub-carrier where fading has occurred. A recording medium having a computer-readable program recorded thereon, which comprises: 11. A computer for controlling a transmission device for transmitting a signal in the OFDM system, a coding step for coding the signal, an acquisition control step for controlling acquisition of a subcarrier allocation pattern, and the acquisition control step. On the basis of the allocation pattern whose acquisition is controlled by the processing of step 1, the parity part of the coded data coded by the processing of the coding step is preferentially allocated to the subcarrier in which fading has occurred. A program that causes allocation steps and to be performed. 12. A communication system comprising a transmitter that transmits a signal in the OFDM system and a receiver that receives the encoded signal transmitted from the transmitter, wherein the transmitter encodes the signal. A setting unit that sets a subcarrier allocation pattern based on the fading information acquired by the acquisition unit, and an acquisition unit that acquires fading information of a transmission path notified from the reception device. Means, first notifying means for notifying the receiving device of the allocation pattern set by the setting means, and based on the allocation pattern set by the setting means, to subcarriers in which fading has occurred On the other hand, the parity part of the encoded data encoded by the encoding means is preferentially assigned. The receiving device includes a detecting device for detecting fading information of the transmission path, and a second notifying device for notifying the transmitting device of the fading information detected by the detecting device. A communication system comprising: 13. A communication system, comprising: a transmitter for transmitting a signal by an OFDM system; and a receiver for receiving the encoded signal transmitted from the transmitter, wherein the transmitter encodes the signal. Encoding means to obtain, acquisition means for acquiring the allocation pattern of the subcarriers notified from the receiving device, based on the allocation pattern acquired by the acquisition means, for the subcarriers fading, The receiving device includes a detecting means for detecting fading information of a transmission path, and an assigning means for preferentially assigning a parity part of the encoded data encoded by the encoding means. Setting means for setting the subcarrier allocation pattern based on the detected fading information; Communication system, comprising a notification means for notifying the allocation pattern set by the setting means to the transmission device.