Telecommunications – Transmitter and receiver at separate stations – Having measuring – testing – or monitoring of system or part
Reexamination Certificate
1999-05-13
2002-07-16
Trost, William (Department: 2683)
Telecommunications
Transmitter and receiver at separate stations
Having measuring, testing, or monitoring of system or part
C455S063300, C455S501000, C455S226300, C375S227000
Reexamination Certificate
active
06421527
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to wireless communications and more particularly to a system for dynamic adaptation of data/channel coding.
BACKGROUND OF THE INVENTION
Transmission of digitally encoded speech over wireless channels in a cellular environment usually requires the use of error control techniques to combat the noisy nature of such channels. In cellular applications, however, the characteristics of the channel are highly non-stationary, that is, periods of relatively error-free signal alternate with periods of strongly deteriorated signal. The traditional solution to this problem is to allocate to error detection and correction enough bandwidth to deal with the “average channel”, sacrificing optimality for the two extreme cases of good and bad channels.
This static approach is clearly not optimal: in good channel conditions most of the resources employed by error control are redundant, and could be better used to increase the speech quality, while in bad channels, error control should be reinforced by using resources made available by a lower bit rate speech codec. Moreover, the cellular channel is quite bipolar, that is, oscillates in time between good and bad channels, passing only a fraction of the time of a call in the “average channel” condition for which the static solution was designed. Unequal Error Protection is used in most cellular standards. In Unequal Error Protection, speech bits are divided into classes of decreasing perceptual importance and each class is encoded with appropriate rates of protection including no protection. Although the Unequal Error Protection approach used in most cellular standards somewhat mitigates the flaw of using the “average channel” approach, a better solution is desirable.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the present invention, a system is presented that allows one station to communicate with a second station. The station monitors the quality of the channels connecting them and adapts their data and error control rates accordingly.
REFERENCES:
patent: 4939731 (1990-07-01), Reed et al.
patent: 5818826 (1998-10-01), Gfeller et al.
patent: 5839077 (1998-11-01), Kowaguchi
patent: 5857147 (1999-01-01), Gardener et al.
patent: 5923679 (1999-07-01), Itoh et al.
patent: 6108374 (2000-08-01), Balachandran et al.
patent: 6141388 (2000-10-01), Servais et al.
Anandakumar Krishnasamy
DeMartin Juan-Carlos
McCree Alan V.
Ferguson Keith
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
Troike Robert L.
Trost William
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