Pulse or digital communications – Receivers – Particular pulse demodulator or detector
Reexamination Certificate
2000-03-13
2004-06-22
Chin, Stephen (Department: 2634)
Pulse or digital communications
Receivers
Particular pulse demodulator or detector
C375S316000, C375S340000
Reexamination Certificate
active
06754291
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and a device of receiving digital signals and a receiver and more particularly, to a method and a device of outputting the demodulation result in soft-decision decoding that enhances the decoding capability of error-correcting codes, which makes it possible to output necessary reliability information with high accuracy, and a receiver using the method or device.
2. Description of the Prior Art
The soft-decision decoding technique is a technique that estimates the original digital signal from a noise-containing digital signal that has been sent through transmission lines by deciding the level of the noise-containing digital signal as a multi-valued signal (not a two-valued signal) using a plurality of threshold values. In other words, this technique is one that estimates the two-valued (i.e., “0” and “1”), original information through the multi-valued decoding by deciding the level of the noise-containing digital signal using a plurality of threshold values. This technique has an advantage that the error correction rate is better than that of the hard-decision decoding technology that estimates the two-valued, original information through the two-valued decoding by deciding the level of the noise-containing digital signal using a single threshold value.
An example of the prior-art soft-decision decoding systems is shown in the Japanese Non-Examined Patent Publication No. 8-317006 published in November 1996. In this system, the level reliability information on the basis of the received signal level and the phase reliability information on the basis of the received signal phase are used as the reliability information necessary for soft decision decoding. This prior-art system is explained below with reference to FIG.
1
.
As shown in
FIG. 1
, the prior-art soft-decision decoding system comprises an input terminal
1000
, a demodulation circuit
1001
, a level detection circuit
1002
, a level normalization circuit
1003
, a soft-decision result calculation circuit
1004
, a phase-reliability detection circuit
1006
, and an output terminal
1005
.
A received signal RS inputted through the input terminal
1000
is applied to the demodulation circuit
1001
. The circuit
1001
demodulates the signal RS to generate a demodulated signal and then, decodes the demodulated signal using the soft-decision decoding technique. Thus, the circuit
1001
outputs a decision result, i.e., the demodulated data DD, to the level normalization circuit
1003
, the soft-decision result calculation circuit
1004
, and the phase-reliability detection circuit
1006
.
The received signal RS is further applied to the level detection circuit
1002
and the phase-reliability detection circuit
1006
. The level detection circuit
1002
detects the level of the signal RS thus applied and outputs a receiving level signal RSL to the level normalization circuit
1003
. The level normalization circuit
1003
normalizes the level of the receiving level signal RSL on the basis of the decision result or demodulated data DD, outputting a receiving level reliability data LR. The “receiving level reliability” means the reliability relating to the receiving level of the received signal RS. The normalization operation of the circuit
1003
is necessitated by the following reason.
Since the decision result or demodulated data DD is a multi-valued demodulated data having different levels, the receiving level reliability is unable to be correctly estimated or evaluated from the receiving level itself. In other words, the receiving level reliability needs to be normalized.
On the other hand, the phase-reliability detection circuit
1006
detects the phase difference between the received signal RS and the demodulated data or decision result DD, outputting the level-based reliability data PR to the soft-decision result calculation circuit
1004
.
The soft-decision result calculation circuit
1004
receives the demodulated data DD, the phase-based reliability data PR, and the level-based reliability data LR, outputting a demodulation data DR applicable to the subsequent decoding operation.
With the prior-art soft-decision decoding system shown in
FIG. 1
, normalization is essential for calculating the level-based reliability data LR on the basis of the decision result or demodulated data DD, which raises a problem that the circuit scale of the system becomes large.
Also, if the decision result or demodulated data DD is incorrect due to noise, there arises a problem that the reliability of the level-based reliability data LR, which is dependent upon the decision result DD, is lowered and as a result, the decoding capability of the error-correction codes degrades.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a method and a device of outputting a demodulation result in soft-decision decoding that make it possible to output necessary reliability information with high accuracy using a simple circuit configuration.
Another object of the present invention is to provide a receiver having an enhanced decoding capability of error-correcting codes.
The above objects together with others not specifically mentioned will become clear to those skilled in the art from the following description.
According to a first aspect of the present invention, a method of outputting a demodulation result in soft-decision decoding is provided, which is comprised of the steps of:
(a) demodulating a received signal and deciding the received signal thus demodulated using a soft decision technique, outputting a decision result;
(b) estimating a distortion of the received signal generated in a communication channel, outputting a channel distortion data; and
(c) calculating a demodulation result on the basis of the decision result and the channel distortion data.
With the method of outputting a demodulation result in soft-decision decoding according to the first aspect, the distortion of the received signal generated in the communication channel is estimated to output the channel distortion data and then, the demodulation result is calculated on the basis of the decision result and the channel distortion data. This means that the channel distortion data (instead of the level of the received signal) is used as the level reliability information. Thus, the level reliability information can be obtained independent of the decision result, which simplifies the circuit configuration.
As a result, the necessary reliability information can be outputted with high accuracy using a simple circuit configuration.
According to a second aspect of the present invention, another method of outputting a demodulation result in soft-decision decoding is provided, which is comprised of the steps of:
(a) detecting a channel distortion of a received signal generated in a communication channel using a training signal contained in the received signal and a reference training signal, outputting a channel distortion data;
(b) generating a distortion-based reliability data from the channel distortion data;
(c) compensating the received signal using the channel distortion data, generating a compensated, received signal;
(d) demodulating the compensated, received signal and deciding the received signal thus demodulated using a soft decision technique, outputting a decision result; and
(e) outputting a demodulation result using the decision result and the distortion-based reliability data.
With the method of outputting a demodulation result in soft-decision decoding according to the second aspect, the channel distortion of the received signal generated in the communication channel is detected using the training signal contained in the received signal and the reference training signal. Also, the distortion-based reliability data is generated from the channel distortion data of the received signal. The received signal is compensated using the channel distortion data to thereby generate the compensated, received signal. Using the compensated, received signal, t
Okanoue Kazuhiro
Yamamoto Takeshi
Ahn Sam K.
Chin Stephen
Dickstein , Shapiro, Morin & Oshinsky, LLP
NEC Corp
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