JPH07112165B2 - 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 bandwidth of each modulated wave is narrowed by dividing the data to be transmitted into a plurality of carriers for modulation.
A multi-carrier method has been proposed which improves the transmission characteristics against the amplitude deviation that occurs during selective fading.
(Ichikawa, Murase: Frequency diversity effect in multi-carrier digital radio system, IEICE Transactions B-II Vol. J73-B-II, 8, pp34
See 9-356. ) 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 for all symbols. A method of estimating and compensating for distortion has been proposed (Sanbin: Fading distortion compensation method of 16QAM for land mobile communication, IEICE Transactions B-II Vo.
l. J72-B-II, 1, pp7-15).

FIG. 2 shows an example of an arrangement of pilot signals in a multicarrier system with four carriers. Here, the data signals 101 to 132 are distributed to four carriers, and the pilot signals 133 to
Although 140 is inserted, pilot signals are arranged at different positions on the time axis between the first subcarrier and the second subcarrier, and the third subcarrier and the fourth subcarrier, and the first subcarrier and the third subcarrier are arranged. Pilot signals are arranged at the same position on the time axis in the subcarrier, the second subcarrier, and the fourth subcarrier.

Further, FIG. 3 shows an example of the configuration of a conventional fading compensation system when the signals are arranged as shown in FIG.

In FIG. 3, the sample-quantized first to fourth symbol sequences after demodulation of the first to fourth subcarriers are input from the first to fourth input terminals 1 to 4.
The first to the fourth strain detectors 5 to 8 are the first to the fourth.
Input a symbol string, measure the distortion in the pilot signal, and output it. The first interpolator 13 inputs the distortion in the pilot signals in the first and second symbol strings,
The first compensation signal train is output. Similarly, the second interpolation unit 14
Inputs distortion in pilot signals in the first and second symbol sequences and outputs a second compensation signal sequence. Further, the third interpolator 15 inputs the distortion in the pilot signals in the third and fourth symbol sequences and outputs the third compensation signal sequence. Similarly, the fourth interpolation unit 16 is
The distortion in the pilot signal in the symbol sequence is input and the fourth compensation signal sequence is output. The first to fourth compensators 22 to 25 receive the first to fourth symbol sequences and the first to fourth compensation signal sequences, and output the signal sequences after fading distortion compensation to the first to fourth output terminals. 26-29
Output to.

[0006] Here, the shorter the interval between the pilot signals inserted periodically 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 obtained in the strain detecting sections 5 to 8 as follows.

Pd = Pr / P Pilot signals 133 and 137 in the first subcarrier
Let Pd1 and Pd3 be the distortions measured at, and Pd2 and Pd4 be the distortions measured at pilot signals 135 and 139 in the second subcarrier.
The interpolator 13 includes Pd1 to Pd4 as distortions in the pilot signal 133, the data signal 109, the pilot signal 137, and the data signal 129 in the first subcarrier.
Is entered.

The interpolator 13 inputs Pd1 to Pd4 and interpolates them to estimate the distortion in each symbol as shown in FIG. Similarly, when estimating the distortion in the data signal in the second to fourth subcarriers, the interpolation units 14 to 16 perform interpolation using the distortions measured by the pilot signals in the adjacent subcarriers. Estimate the distortion on the symbol.

In the compensators 17 to 20, the first to fourth symbol sequences are input and divided by the corresponding distortions output from the interpolators 13 to 16 to compensate the distortion.

As described above, by using not only the pilot signals in each subcarrier but also the pilot signals of the adjacent subcarriers, the interval of the measured distortion is shortened and interpolation is performed to improve the tracking characteristic with respect to fading. ing.

[0012]

As described above, in the conventional fading compensation system, the fading distortion measured in the pilot signal in another subcarrier is used as it is in the data signal between the pilot signals. The strain is estimated. Therefore, when delay dispersion occurs in the transmission line and the phase or amplitude relationship between each subcarrier fluctuates, the compensation characteristic deteriorates rather than the case where compensation is performed using only pilot signals in each subcarrier. It has drawbacks.

An object of the present invention is to solve the above-mentioned drawbacks and to provide a fading distortion compensation system which can obtain a sufficient compensation characteristic even when delay dispersion occurs.

[0014]

According to the fading distortion compensation method of the present invention, data to be transmitted is divided into N (N is an integer of 3 or more) subcarriers, and at least 1 of the N subcarriers is divided. The groups are classified into k (k is an integer of 2 or more) groups that include two or more subcarriers, and pilot signals that are periodically inserted are arranged on the time axis between subcarriers in the same group. In the same position,
In a fading distortion compensation system used in a digital radio communication system in which subcarriers of different groups are arranged and transmitted at different positions on the time axis, sample quantization corresponding to each of the N subcarriers is performed. The N symbol examples after demodulation are input, the distortion in the pilot signal is detected, and the N distortion detection units that output and the outputs of the N distortion detection units are input,
Outputs of N first interpolators that estimate distortion between pilot signals in the N subcarriers and output N first distortion compensation signal sequences, and N distortion detectors Within each group among the subcarriers included in the (k-1) groups in which the pilot signals in the N subcarriers are distorted and the pilot signals are arranged at different positions on the time axis. Then, the distortion in the pilot signal in one subcarrier is used as the distortion in the corresponding symbol on the time axis to interpolate to estimate the distortion in the symbol between the pilot signals in the N subcarriers. Between the N second interpolators that output the second distortion compensation signal sequences and the N symbol sequences, and between the subcarriers in the same group. By comparing the distortions of the pilot signals arranged at the same position on the intermediate axis, it is possible to judge the magnitude of the delay dispersion in the transmission path and output a delay dispersion determination signal, and the N first delay dispersion detectors. Distortion compensation signal sequence and the Nth distortion compensation signal sequence are input, and the N first distortion compensation signal sequence or the Nth distortion compensation signal sequence is controlled by the control of the delay dispersion determination signal. N selection units for outputting the distortion-compensating signal sequence of 2;
It is characterized in that it is provided with N symbol arrays and N compensating sections that receive the outputs of the N selecting sections and output the symbol arrays after distortion compensation.

[0015]

Embodiments of the present invention will now be described with reference to the drawings.

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

In FIG. 1, sample-quantized first to fourth symbol sequences after demodulation of the first to fourth subcarriers are input from first to fourth input terminals 1 to 4.
The first to the fourth strain detectors 5 to 8 are the first to the fourth.
Input a symbol string, measure the distortion in the pilot signal, and output it.

The first to fourth interpolators 9 to 12 receive the outputs of the first to fourth distortion detectors 5 to 8, estimate the distortion between pilot signals in the subcarrier, and perform interpolation. , And outputs the first to fourth compensation signal sequences. The fifth to eighth interpolation units 13 to 17 perform the interpolation by the same method as the conventional technique. That is, the fifth interpolator 13 inputs the outputs of the first and second distortion detectors 5 and 6 and outputs the fifth compensation signal sequence. Similarly, the sixth interpolator 14 inputs the outputs of the first and second distortion detectors 5 and 6 and outputs a sixth compensation signal sequence. Also, the seventh interpolation unit 1
Reference numeral 5 inputs the outputs of the third to fourth distortion detectors 7 and 8 and outputs a seventh compensation signal sequence. Similarly, the eighth interpolation unit 1
Reference numeral 6 inputs the outputs of the third to fourth distortion detectors 7 and 8 and outputs an eighth compensation signal sequence.

The delay dispersion detector 17 inputs the first to fourth symbol sequences, checks the delay dispersion based on the dispersion of distortion in pilot signals at the same position on the time axis, and delays the delay more than a predetermined threshold value. It is determined whether the dispersion is large, and a delay dispersion determination signal is output.

The first to fourth selectors 18 to 21 are connected to the first
To the fourth to fifth compensation signal trains and the fifth to eighth compensation signal trains, and by controlling the delay dispersion determination signal, outputs the first to fourth compensation signal trains when the delay dispersion is large,
When the delay dispersion is small, the fifth to eighth compensation signal sequences are output.

The first to fourth compensating units 22 to 25 have the first
To the fourth symbol sequence and the outputs of the first to fourth selectors, and outputs the first to fourth compensated signal sequences to the first to fourth output terminals 26 to 29.

In this way, the delay dispersion detector 17 determines the magnitude of the delay dispersion in the transmission path, and when the delay dispersion is large, the distortion of each symbol is estimated using only the pilot signal in each subcarrier, and the delay dispersion is calculated. When is small, the pilot signals in other subcarriers are also used to estimate the distortion of each symbol and perform compensation.

[0023]

As described above, according to the fading distortion compensation method of the present invention, when the delay dispersion is large and the delay dispersion is small, the method of estimating the distortion in the data signal between the pilot signals is switched so that Even if delay dispersion occurs, there is an effect that sufficient compensation characteristics 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 an arrangement of data signals and pilot signals.

FIG. 3 is a block diagram showing a conventional fading distortion compensation method.

FIG. 4 is a diagram for explaining the operation of interpolators 13 to 16.

[Explanation of symbols]

 1-4 1st thru | or 4th input terminal 5-8 1st thru | or 4th distortion detection part 9-12 1st thru | or 4th interpolation part 13-16 5th thru | or 8th interpolation part 17 Delay dispersion | variation detection part 18-21st 1st thru | or 4th selection part 22-25 1st thru | or 4th compensation part 26-29 1st thru | or 4th output terminal 101-132 Data signal 133-140 Pilot signal

Claims (1)

[Claims] 1. The data to be transmitted is divided into N (N is an integer of 3 or more) subcarriers, and the N subcarriers are k such that at least one group includes two or more subcarriers. (K is an integer of 2 or more), the pilot signals that are periodically inserted are placed at the same position on the time axis between subcarriers in the same group, and on the time axis between subcarriers in different groups. In a fading distortion compensation method used in a digital wireless communication method in which signals are arranged and transmitted at different positions, sample-quantized demodulated N symbol strings respectively corresponding to the N subcarriers are generated. The N subcarriers that are input and detect the distortion in the pilot signal and output the N distortion detectors and the outputs of the N distortion detectors are input. The distortion between pilot signals of N, and outputs the N first interpolation units that output N first distortion compensation signal sequences and the outputs of the N distortion detection units, Of the distortion in the pilot signal in the sub-carrier and the sub-carriers included in the (k-1) groups in which the pilot signals are arranged at different positions on the time axis, within one sub-carrier in each group The distortion in the pilot signal is estimated by using the distortion in the pilot signal as the distortion in the corresponding symbol on the time axis to estimate the distortion in the symbol between the pilot signals in the N subcarriers.
N second interpolators for outputting the distortion-compensating signal sequence and the N symbol sequences are input, and pilot signals are arranged in the same position on the time axis between subcarriers in the same group. By comparing the distortions, the magnitude of the delay dispersion in the transmission path is determined, and a delay dispersion detection unit that outputs a delay dispersion determination signal, the N first distortion compensation signal sequences, and the N first distortion compensation signal sequences. N distortion output signal sequence is input, and the N first distortion compensation signal sequence or the N second distortion compensation signal sequence is output by controlling the delay dispersion determination signal. Fading, characterized by comprising: a number of selecting units; N number of symbol sequences; and N compensating units that receive the outputs of the N number of selection units and output a symbol sequence after distortion compensation. Distortion compensation method.