Pulse or digital communications – Receivers – Particular pulse demodulator or detector
Reexamination Certificate
1998-01-30
2001-10-16
Ghayour, Mohammad H. (Department: 2634)
Pulse or digital communications
Receivers
Particular pulse demodulator or detector
C375S341000, C375S262000, C375S265000
Reexamination Certificate
active
06304616
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods of reception of a coded data signal by a receiver and, more particularly, to methods for producing and providing assisting signals to a demodulator in the receiver to improve decoding of the received coded data signal.
2. Description of Related Art
In data signal transmission, coding is often employed, for instance to enable reducing the required transmission energy per data bit for the same error rate. The main task of a data decoder downstream of a demodulator in the receiver is to determine a train of data bits d′
k
from the train of estimated values c′
i
, possibly provided with quality standards, for the channel symbols c
i
actually sent, so that the error probabilities of these data bits d′
k
, referred to the actual data bits d
k
of the source, are as low as possible.
One example of such a decoder is the one described in reference
1
(paper by Forney, “The Viterbi Algorithm”, Proceedings of the IEEE, Volume 61, No. 3, March 1973, pages 268-278), which is also known as a Viterbi decoder.
A second task of the data decoder can be to support the demodulator in determining the estimated values c′
i
from the received signal r(t). One example of such support is described in reference
2
(paper by Ungerboeck, “Channel Coding with Multilevel/Phase Signals”), IEEE IT-28, No. 1, January 1982, pages 55-67, especially FIG.
17
). In addition to the train of data bits d′
k
, the data decoder determines a train of improved estimated values c″
i
for the channel symbols, but this train is delayed compared to the train of estimated values c′
i
furnished by the demodulator. The estimated values for the channel symbols furnished by the channel symbols are also known as tentative decisions. The feedback of the estimated values c″
i
to the demodulator, however, creates a closed-loop control circuit, or control loop, in which the aforementioned delay is problematic. The feedback also creates problems in the initial synchronization, because the closed-loop control circuit under some circumstances can remain for relatively long periods in unstable states of equilibrium, known as “false locks”.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide improved methods of receiving a coded data signal by a receiver including a demodulator followed by a data decoder, which does not have the above-described disadvantages.
According to the invention the method of reception of a coded data signal by the receiver, the data signal being encoded by means of a channel symbol alphabet having M stages, the receiver including a demodulator that generates estimated symbols from the coded data signal and a data decoder following the demodulator, comprises the steps of:
a) forming a number of groups from channel symbols of the channel symbol alphabet, at least one of the groups comprising more than one channel symbol;
b) continuously making estimations of probabilities of group membership of received symbols in the respective groups;
c) furnishing these estimations of probabilities of group membership to the demodulator in the form of assisting signals; and
d) generating the estimated symbols with the help of the assisting signals.
Alternatively, according to the invention the method of reception of a coded data signal by the receiver, the data signal being encoded by means of a state transition diagram including a number of states, the receiver including a demodulator that generates estimated symbols from the coded data signal and a data decoder following the demodulator, comprises the steps of:
a) forming a number of groups from the states of the state transition diagram;
b) continuously making estimations of probabilities of group membership of a current state of the data decoder in the respective groups;
c) furnishing these estimations of probabilities of group membership to the demodulator in the form of assisting signals; and
d) generating the estimated symbols with the help of the assisting signals.
With these methods according to the invention, it is possible to keep the length of the delay in the resultant control loop of the demodulator and data decoder as short as possible. Fast initial synchronization is also attained.
The invention is based on the recognition that estimated values for the channel symbols are not absolutely necessary for the support of the demodulator. In the parallel patent application entitled “Verfahren zur Synchronisation” [Method for Synchronization], filed on the same date as the present application and by the same Applicant, it is shown that even estimated values for the membership in a channel symbol group can be used to support the demodulator. The feedback of estimated values for the membership in a channel symbol group, instead of for the channel symbols, according to the present invention has the following advantages: These estimated values can be determined with a shorter delay time, thus rendering the problems of the control loop transit time less critical. There are fewer channel symbol groups than channel symbols, so there are fewer unstable equilibrium states and therefore the initial synchronization is improved. Moreover, the decision regarding a group membership is easier and thus takes less effort. In addition, this makes the interface between the data decoder and the demodulator simpler and thus less complicated.
REFERENCES:
patent: 5031195 (1991-07-01), Chevillat et al.
patent: 5541955 (1996-07-01), Jacobsmeyer
patent: 5633881 (1997-05-01), Zehavi et al.
patent: 5862156 (1999-01-01), Huszar et al.
patent: 93 01 170 U1 (1994-07-01), None
Magee, F., Proakis, J.: “Adaptive Maximum-Likelihood Sequence . . . ”, IEEE Transactions On Information Theory, Jan. 1973, pp. 120-124.
Kamel, R., Bar-Ness, Y.:Reduced-State Sequence Estimation . . . , Electronics Letters, Jan. 6, 1994, vol. 30, No. 1, pp. 14-16.
Battail, G.: “Ponderation Des Symboles Decodes Par . . . ”, Ann. Telecommun., 42, 1987, pp. 31-38.
Hagenauer, J., Hoeher, P.: “A Voterbi Algorithm With Soft-Decision . . . ”, Proceedings of the Globecom Conference, 1989, p. 47.1.1-47.1.7.
Ghayour Mohammad H.
Robert & Bosch GmbH
Striker Michael J.
LandOfFree
Method for reception of coded data by a receiver does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for reception of coded data by a receiver, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for reception of coded data by a receiver will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2553923