Multiplex communications – Diagnostic testing – Determination of communication parameters
Reexamination Certificate
1997-04-25
2001-02-27
Nguyen, Chau (Department: 2739)
Multiplex communications
Diagnostic testing
Determination of communication parameters
C370S318000, C370S465000
Reexamination Certificate
active
06195337
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an encoding mode control method and a decoding mode determining apparatus in a digital cellular radio communication system, as well as a power control method and system that utilize the inventive idea.
BACKGROUND
In present digital cellular communication systems a speech encoder rate is chosen at call setup and is fixed throughout the call. This strategy is used in the D-AMPS and GSM systems. However, this strategy gives good performance with respect to channel robustness and speech quality over only a limited range of channel conditions.
In CDMA systems, such as IS-95, there is a variable speech and channel encoder scheme, but the speech and channel coder mode decision for one link is based on speech signal characteristics and is independent of the mode of a return link.
It has also been suggested as described in Dunlop J, Irvine J and Cosimini P. “Estimation of the Performance of Link Adaptation in Mobile Radio”, IEEE Vehicular Technology Conference, VTC-95, Chicago 1994, to use dynamically changing encoding modes with different mixes of speech/channel encoding suitable for different radio environments. However, these methods are too slow, since they need to keep signaling overhead as low as possible.
WO 94/07313 assigned to ANT NACHRICHTENTECHNIK GMBH, and Yuen E, Ho P and Cuperman V, “Variable Rate Speech and Channel Coding for Mobile Communication”, IEEE Vehicular Technology Conference, VTC-95, Stockholm 1994 describe systems in which a receiver may request a mode change from a transmitter over a dedicated back channel.
It would be desirable to dynamically allocate speech and channel coder rates depending upon local radio conditions on a frame by frame basis in order to achieve a close to optimum performance in a larger range of conditions, and to let the coding mode of one link control the allocation of coding mode for the return link.
SUMMARY
An object of the present invention is to provide an encoding mode control method that dynamically adapts the coding rate to prevailing radio conditions on a frame by frame basis and allows at least one party to base its transmission mode decision at least partially on the mode received on the other link.
Another object of the present invention is to provide a decoding mode determining apparatus that synchronizes the receiver decoding mode with the transmitter encoding mode.
A further object is a power control method and system based on these mode switching capabilities.
Briefly, the present invention achieves the above objects by monitoring the local radio environment around the transmitter and dynamically selecting a speech-/channel encoding rate combination suitable for the current radio environment, all combinations having the same total gross bit rate (the total bit rate available for information transfer on a given channel if no channel protection is provided). In a preferred embodiment the receiver trial decodes all possible speech/channel coding combinations and selects the most probable one for actual speech decoding. Finally the receiver selects the same encoding mode for the return link to the transmitter. This encoding scheme is very fast (frame by frame) and requires no handover. Furthermore, the coding gain/loss obtained by this mode switching may be utilized for power adjustments that reduce the overall interference level of the communication system.
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Jansson Fredrik
Minde Tor Bjorn
Nystrom Johan
Burns Doane Swecker & Mathis L.L.P.
Nguyen Chau
Nguyen Phuongchau Ba
Telefonaktiebolaget LM Ericsson (publ)
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