JPH07112166B2 - Fading distortion compensation method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fading distortion compensating method, and more particularly to a fading distortion compensating method used in a digital radio communication method for multicarrier transmission using a multilevel quadrature amplitude modulation method or a multiphase phase modulation method. Regarding

[0002]

2. Description of the Related Art Conventionally, in the field of digital radio communication, the frequency band width of each modulated wave is narrowed by dividing the data to be transmitted into a plurality of carriers and modulating them, and delay dispersion occurs in the transmission line. A multi-carrier method has been proposed which improves transmission characteristics when amplitude deviation occurs. (Ichikawa, Murase: Frequency diversity effect in multi-carrier digital radio system, IEICE Transactions B-II voI.J73-B-II, 8,
See pp 349-356. ) In addition, the transmitter side periodically inserts a pilot signal into the data string, and the receiver side measures the distortion due to fading in the transmission path from the pilot signal and interpolates on the time axis to distort all symbols. A method of estimating and compensating for is proposed. (Sanbin: 1 for land mobile communication
6QAM fading distortion compensation method, IEICE Transactions B-II Vol. J72-B-II,
1, pp 7-15. 2) FIG. 2 shows an example of a conventional pilot signal arrangement in a 4-carrier multicarrier system. Here, the data signals 101 to 132 are distributed to four carriers, and the pilot signals 133 to 140 are periodically inserted for each carrier. However, the first subcarrier and the second subcarrier, and the third subcarrier and the fourth subcarrier are inserted. In the subcarrier,
The pilot signals are arranged at different positions on the time axis, and the first
Pilot signals are arranged at the same position on the time axis in the subcarrier and the third subcarrier, and in the second subcarrier and the fourth subcarrier.

Further, FIG. 4 shows an example of the configuration of the receiving side of the conventional fading compensation system when transmitting with the signal arrangement shown in FIG.

In FIG. 4, modulated waves of the first to fourth subcarriers are input from input terminals 25 to 28, demodulated and sampled and quantized in demodulators 7 to 10, and first to fourth demodulated symbol strings are obtained. Is output. Strain detector 29 ~
32 inputs the first to fourth demodulated symbol sequences, measures the distortion in the pilot signal, and outputs it. The distortion estimator 33 inputs the second and fourth demodulated symbol sequences and extrapolates the distortion in the pilot signals at the same position on the time axis, thereby
Estimate the distortion at the corresponding symbol on the time axis,
Output. In addition, the distortion estimation unit 34 inputs the first and third demodulated symbol sequences and interpolates the distortion in the pilot signals at the same position on the time axis to obtain the second
The distortion in the corresponding symbol on the time axis in the subcarrier is estimated and output. Similarly, the distortion estimation unit 35 inputs the second and fourth demodulated symbol sequences and interpolates the distortions in the pilot signals at the same position on the time axis to obtain the time axis in the third subcarrier. Estimate and output the distortion in the corresponding symbol above. In addition, the distortion estimation unit 36 inputs the first and third demodulated symbol sequences and extrapolates the distortion in the pilot signal at the same position on the time axis, so that on the time axis in the fourth subcarrier. Estimate and output the distortion in the corresponding symbol. The interpolators 37 to 40 receive the outputs of the strain detectors 29 to 32 and the outputs of the strain estimators 33 to 36, and perform interpolation to output the first to fourth compensation signal sequences. The compensators 19 to 22 receive the first to fourth demodulated symbol sequences and the first to fourth compensation signal sequences and output the first to fourth compensated signal sequences.
The parallel-serial converter 41 inputs the first to fourth compensated symbol sequences, removes pilot signals, and outputs demodulated data sequences.

Here, the shorter the interval between pilot signals that are periodically inserted and the shorter the interval at which distortion due to fading is measured, the faster the fading can be tracked. In this fading compensation method in the multi-carrier method, as shown in FIG. 2, the positions of pilot signals to be inserted between adjacent subcarriers are shifted so that not only pilot signals in each subcarrier but also adjacent subcarriers The pilot signal of the carrier is also used.

For example, assuming that the vector of the pilot signal to be transmitted is P and the vector of the signal received as the pilot signal is Pr, the strain Pd is the strain detectors 29-3.
In 2, the following is obtained.

Pd = Pr / P Now, distort the pilot signals 133 to 136 by P
Assuming d1 to Pd4, in the distortion estimation unit 34, the distortions Pd1 and Pd2 at the same position on the time axis are interpolated on the frequency axis as shown in FIG. Estimate the strain Pdi at.

Further, in the strain estimation unit 36, Pd1
And Pd2 are extrapolated on the frequency axis as shown in FIG. 6 to estimate the distortion Pdo in the data signal 104 in the fourth subcarrier.

Similarly, the data signal 109 is obtained by extrapolating and interpolating Pd3 and Pd4 on the frequency axis.
And the strain at 111 is estimated.

The distortion of each symbol is estimated by interpolating in the interpolators 37 to 40 using the distortion thus estimated and the distortion measured in the pilot signal in each subcarrier.

In the compensating units 19 to 22, the first to fourth demodulated symbol sequences are input, and the distortion is compensated by dividing by the distortion corresponding to each symbol output from the interpolating units 37 to 40.

As described above, not only the pilot signal in each subcarrier but also the pilot signal of the adjacent subcarrier is used to shorten the interval of distortion to be measured and perform interpolation to improve the tracking characteristic to fading. ing.

[0013]

As described above, in the conventional fading compensation system, the distortion measured in a plurality of pilot signals arranged in the same position on the time axis in a plurality of subcarriers is eliminated. Interpolation or extrapolation is performed to estimate the distortion at that position within the subcarrier where the pilot signal is not located at the corresponding position on the time axis. The use of insertion has a drawback that accurate estimation cannot be performed and sufficient compensation characteristics cannot be obtained.

An object of the present invention is to solve the above-mentioned drawbacks and to provide a fading distortion compensating system capable of obtaining a sufficient compensation characteristic for fading distortion even when a large delay dispersion occurs.

[0015]

A first fading distortion compensating method of the present invention uses N subcarriers as the first to Nth subcarriers in order according to the frequency level.
On the transmission side, the input data sequence is distributed to the first to Nth subcarriers, and the first data corresponding to both ends on the frequency axis is distributed.
And a serial-to-parallel converter that outputs a first to Nth symbol sequence by inserting a pilot signal into the Nth subcarrier at the same position on the time axis, and inputs the first to Nth symbol sequences. Then, the first to N-th modulators that perform modulation at the first to N-th sub-carrier frequencies and output the first to N-th modulated waves, and the receiving side inputs the first to N-th modulated waves, First to N-th demodulation units that output first to N-th demodulated symbol sequences, a first distortion detection unit that inputs the first demodulated symbol sequences and outputs distortion in a pilot signal, and the N-th demodulation unit A second distortion detector for inputting the post symbol sequence and outputting the distortion in the pilot signal, and for inputting the first and Nth demodulated post symbol sequences, and for inputting the time axis in the second to (N-1) th subcarriers. On the pilot signal A first to (N-2) th distortion estimating section for outputting the distortion of the symbol corresponding to the position of the symbol, and the pilot signal in the first to the Nth subcarriers or the symbol corresponding to the position of the pilot signal on the time axis. The first to N-th interpolators that input distortion and output the first to N-th compensation signal sequences, the first to N-th demodulated symbol sequences and the first to N-th compensation signal sequences are input. , A first to Nth compensating section for outputting first to Nth post-compensation symbol sequences, and a parallel-serial conversion for inputting the first to Nth post-compensation symbol sequences, removing pilot signals, and outputting data sequences Prepare the city.

According to a second fading distortion compensation method of the present invention, the data sequence input on the transmission side is first to Nth subcarriers in order according to the frequency of N subcarriers. A serial-parallel conversion unit that distributes to the Nth subcarrier, inserts pilot signals into the first and Nth subcarriers corresponding to both ends on the frequency axis, and outputs first to Nth symbol sequences; 1st to Nth modulation units for inputting 1st to Nth symbol sequences, modulating at 1st to Nth subcarrier frequencies, and outputting 1st to Nth modulated waves; Nth
First to N-th demodulation units for inputting modulated waves and outputting first to N-th demodulated symbol sequences, and first distortion detection units for inputting the first demodulated symbol sequences and outputting distortion in pilot signals By inputting the N-th demodulated symbol sequence and outputting the distortion in the pilot signal, and the outputs of the first and second distortion detecting sections, and interpolating on the time axis, The first and second interpolators that estimate the distortion in each symbol in the first and Nth subcarriers and output the first and Nth compensation signal sequences, and the first and Nth compensation signal sequences Input,
A first to a (N-2) -th distortion estimation unit that estimates distortion in each symbol in the second to (N-1) th subcarriers and outputs a second to (N-1) th compensation signal sequence; , The first to Nth demodulated symbol sequences and the first
To the Nth compensation-like signal sequence and outputs the first to Nth compensated symbol sequences and the first to Nth compensated symbol sequences and remove the pilot signal. And a parallel-serial conversion unit that outputs a data string.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the first fading distortion compensation system of the present invention will be described with reference to the drawings.

FIG. 3 shows an example of arrangement of pilot signals according to the present invention by a 4-carrier multi-carrier system. It should be noted that the first to fourth subcarriers are arranged in ascending order of subcarrier frequency. Here, the data signals 201 to 232 are distributed to four carriers, and the pilot signals 233 to 240 are inserted while being concentrated on the first and fourth carriers at both ends on the frequency axis.

FIG. 1 is a block diagram showing an embodiment of the configuration of the fading distortion compensation system of the present invention when the signals are arranged as shown in FIG.

On the transmitting side, the data string input from the terminal 1 is distributed to the subcarriers in the serial-parallel converter 2 as shown in FIG. 3, and the pilot signal is inserted to output the first to fourth symbol strings. To be done.

In the modulators 3 to 6, the first to fourth parts are used.
Input a symbol string, modulate at each subcarrier frequency,
The first to fourth modulated waves are output.

On the receiving side, the demodulators 7 to 10 receive the first to fourth modulated waves, demodulate and sample quantize them, and output first to fourth demodulated symbol sequences.

In the distortion detector 11, the first demodulated symbol string is input, and the distortion in the pilot signal is measured and output. In the strain detector 12,
The fourth demodulated symbol sequence is input, and the distortion in the pilot signal is measured and output.

In the distortion estimation unit 13, the first and fourth demodulated symbol sequences are input, and by interpolating the distortion in the pilot signal at the same position on the time axis, the second subcarrier Estimate and output the distortion at the corresponding symbol on the time axis. Further, in the distortion estimation unit 14, by inputting the first and fourth demodulated symbol sequences and interpolating the distortions in the pilot signals at the same position on the time axis, on the time axis in the third subcarrier. Estimate and output the distortion in the corresponding symbol at.

The interpolators 15 to 18 measure and output the distortion in each symbol by interpolating using the distortions measured or estimated by the distortion detectors 11 and 12 and the distortion estimators 13 and 14.

In the compensating units 19 to 22, the first to fourth demodulated symbol sequences are input, and the distortion is compensated by dividing by the distortion corresponding to each symbol output from the interpolating units 15 to 18. The 1st to 4th compensated symbol sequences are output.

The parallel-serial converter 23 inputs the first to fourth compensated symbol sequences, removes pilot signals, and outputs demodulated data sequences.

Here, assuming that the distortions in the pilot signals 233 to 236 are Pd5 to Pd8, the distortion estimating unit 1
3, the distortions Pd5 and Pd6 at the same position on the time axis are interpolated on the frequency axis as shown in FIG. 5 to estimate the distortion Pi1 in the data signal 201 in the second subcarrier.

Further, in the strain estimation unit 14, Pd5
And Pd6 are interpolated on the frequency axis as shown in FIG. 5 to estimate the distortion Pi2 in the data signal 202 in the third subcarrier.

Similarly, Pd7 and Pd8 are interpolated on the frequency axis to obtain the data signals 211 and 21.
Estimate the strain in 2.

In this way, the transmitter side concentrates the pilot signals on the subcarriers at both ends on the frequency axis, and the receiver side interpolates the distortion measured in the pilot signal on the frequency axis. Estimate the distortion of the corresponding symbol in each subcarrier of.

Next, an embodiment of the second fading distortion compensation system of the present invention will be described with reference to the drawings.

In FIG. 7, demodulation sections 7 to 10 receive the first to fourth modulated waves, demodulate and sample quantize them, and output first to fourth demodulated symbol sequences.

In the distortion detector 11, the first demodulated symbol sequence is input, and the distortion in the pilot signal is measured and output. In the strain detector 12,
The fourth demodulated symbol sequence is input, and the distortion in the pilot signal is measured and output.

In the interpolators 42 to 43, the outputs of the distortion detectors 11 to 12 are input and interpolated on the time axis to estimate the distortion in each symbol in the first and fourth subcarriers, and the first and fourth subcarriers are estimated. The fourth compensation signal train is output.

In the estimation units 44 to 45, the first
And the fourth compensation signal sequence are input and interpolated on the frequency axis to estimate the distortion in each symbol in the second to third subcarriers and output the second to third compensation signal sequences.

In the compensators 19 to 22, the first to fourth demodulated symbol sequences and the first to fourth compensation signal sequences are input, distortion is compensated, and first to fourth compensated symbol sequences are output. To do.

The parallel-serial converter 23 inputs the first to fourth compensated symbol sequences, removes pilot signals, and outputs demodulated data sequences.

As described above, the distortion in each symbol in the subcarriers at both ends where the pilot signals are arranged is first obtained by interpolation on the time axis, and the distortion is interpolated on the frequency axis to obtain the inside of the subcarrier. It is also possible to perform compensation by estimating the distortion in each symbol of.

[0040]

As described above, according to the fading distortion compensation method of the present invention, pilot signals are arranged on subcarriers on both ends of the frequency axis on the transmitting side, and pilot signals are arranged on the subcarriers on both ends on the receiving side. By interpolating the obtained distortion and estimating the distortion at that position in other subcarriers, the fluctuation of the phase and amplitude relationship between each carrier can be accurately estimated even when large delay dispersion occurs in the transmission path. Therefore, there is an effect that a sufficient compensation characteristic can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a fading distortion compensation method according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a conventional arrangement of data signals and pilot signals.

FIG. 3 is a diagram showing an embodiment of an arrangement of data signals and pilot signals according to the present invention.

FIG. 4 is a block diagram showing a configuration of a receiving side of a conventional fading distortion compensation system.

FIG. 5 is a diagram for explaining the operation of the strain estimation units 13 and 14 of the present invention.

FIG. 6 is a diagram for explaining the operation of conventional strain estimation units 33 to 36.

FIG. 7 is a block diagram showing a configuration of a receiving side of a fading distortion compensation system according to a second embodiment of the present invention.

[Explanation of symbols]

 1 Input Terminal 2 Serial-Parallel Converter 3-6 Modulator 7-10 Demodulator 11-12 Distortion Detector 13-14 Distortion Estimator 15-18 Interpolator 19-22 Compensator 23 Parallel-Serial Converter 24 Output Terminal 25 28 Input terminal 29-32 Strain detection part 33-36 Strain estimation part 37-40 Interpolation part 41 Parallel-serial conversion part 42-43 Interpolation part 44-45 Strain estimation part 101-132 Data signal 133-140 Pilot signal 201-232 data Signal 233-240 Pilot signal

Claims (2)

[Claims] 1. A fading distortion compensation system used in a digital wireless communication system in which data to be transmitted to N subcarriers (N is an integer of 3 or more) is divided and pilot signals are periodically inserted and transmitted. The first N subcarriers are sequentially arranged according to the frequency
To Nth subcarriers, the input side distributes the input data sequence to the first to Nth subcarriers, and on the time axis within the first and Nth subcarriers corresponding to both ends on the frequency axis. , A serial-to-parallel converter that outputs the first to Nth symbol sequences and the first to Nth symbol sequences are input, and is modulated at the first to Nth subcarrier frequencies. And outputs the first to Nth modulation waves and the receiving side receives the first to Nth modulation waves and outputs the first to Nth demodulated symbol sequences. The first to Nth demodulation units, the first distortion detection unit that inputs the first demodulated symbol sequence and outputs the distortion in the pilot signal, and the Nth demodulated symbol sequence that inputs the distortion in the pilot signal Output And 2 strain sensor, inputs the first and second N demodulation after symbol sequence, the second to (N-
1) First to (N-2) th distortion estimation units that output the distortion of symbols corresponding to the positions of pilot signals on the time axis in the subcarriers, and the pilot signals in the first to Nth subcarriers, or Input the distortion of the symbol corresponding to the position of the pilot signal on the time axis, and
Through 1st to Nth interpolator, which outputs the 1st to Nth compensation signal sequences, the 1st to Nth demodulated symbol sequences and the 1st to Nth compensation signal sequences, and receives the 1st to Nth compensation signals. A first serial to Nth compensation unit for outputting a rear symbol sequence; and a parallel-serial conversion unit for inputting the first to Nth compensated symbol sequences, removing pilot signals, and outputting a data sequence. Fading distortion compensation method. 2. A fading distortion compensation system used in a digital wireless communication system in which data to be transmitted to N subcarriers (N is an integer of 3 or more) is divided and pilot signals are periodically inserted and transmitted. The first sub-sequence is sequentially set according to the frequency of the N subcarriers
To the Nth subcarrier, the input side distributes the input data sequence to the first to Nth subcarriers,
A serial-to-parallel converter that inserts pilot signals into first and Nth subcarriers corresponding to both ends on the frequency axis and outputs first to Nth symbol sequences, and the first to Nth symbol sequences are input. , A first to N-th modulation section that performs modulation at the first to N-th sub-carrier frequencies and outputs first to N-th modulated waves, and a receiving side that inputs the first to N-th modulated waves, First to N-th demodulators for outputting the 1st to Nth demodulated symbol sequences, and 1st for inputting the first demodulated symbol sequences and outputting distortion in a pilot signal
The distortion detector and the N-th demodulated symbol string are input,
A second distortion detector that outputs distortion in the pilot signal and the outputs of the first and second distortion detectors are input and interpolated on the time axis to obtain the symbols in each of the first and Nth subcarriers. First and second interpolators that estimate distortion and output first and Nth compensation signal sequences, and the first and Nth compensation signal sequences are input to the second to (N-1) th sub-units. First to (N-2) th distortion estimation units that estimate distortion in each symbol in the carrier and output second to (N-1) th compensation signal sequences, and the first to Nth demodulated symbols Column and the first to Nth compensation signal sequences, and outputs first to Nth compensated symbol sequences, and the first to Nth compensated symbol sequences. , Pilot signal removed, data string Fading distortion compensation method characterized by comprising a parallel-serial conversion unit for outputting.