Multiplex communications – Communication over free space – Combining or distributing information via code word channels...
Reexamination Certificate
1998-04-06
2001-08-07
Marcelo, Melvin (Department: 2663)
Multiplex communications
Communication over free space
Combining or distributing information via code word channels...
C370S465000
Reexamination Certificate
active
06272123
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a CDMA (Code Division Multiple Access) transmitter-receiver capable of varying a transmission rate.
2. Description of the Background Art
A CDMA communication system must minimize transmission power per channel to increase its capacity in terms of the number of subscribers because they communicate using the same frequency band.
A conventional CDMA system like that recommended in the United States (IS-95) varies the transmission rate per channel by applying to voice encoding a block coding scheme that varies the bit rate of the voice encoding, and controls the transmission power in accordance with the transmission rate.
Such a conventional CDMA system has a drawback of being inapplicable to the voice encoding without using the block coding such as PCM (Pulse Code Modulation) and ADPCM (Adaptive Differential PCM). In addition, the block coding of the conventional CDMA system requires very complicated coding and decoding.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a CDMA transmitter-receiver capable of varying the transmission rate of the voice encoding on a sample by sample basis, thereby eliminating the drawbacks of the conventional technique.
To solve the foregoing problems, according to an aspect of the present invention, there is provided a CDMA transmitter-receiver comprising: a voice encoder for encoding an input voice signal on a sample by sample basis; an information distributor for splitting a signal encoded by the voice encoder into first bits to be subjected to error correcting coding and second bits not to be subjected to error correcting coding; an error correcting encoder for carrying out the error correcting coding of the first bits; and a controller for generating transmission rate information indicative of a number of transmitted bits, wherein the information distributor varies the number of the first bits in accordance with the number of transmitted bits indicated by the transmission rate information.
According to another aspect of the present invention, there is provided a CDMA transmitter-receiver comprising: a plurality of error correcting encoders for carrying out error correcting coding of input data, the plurality of error correcting encoders having different error correcting capabilities; a selector for selecting one of the plurality of error correcting encoders; and a controller for generating transmission rate information indicative of a number of transmitted bits, wherein the selector brings the selected one of the plurality of error correcting encoders into operation for a transmitted bit sequence designated by the transmission rate information.
REFERENCES:
patent: 5416787 (1995-05-01), Kodama et al.
patent: 5659579 (1997-08-01), Herzberg
patent: 5761223 (1998-06-01), Ando et al.
patent: 5953324 (1999-09-01), Adachi
patent: 6009553 (1999-12-01), Martinez et al.
Marcelo Melvin
OKI Electric Industry Co., Ltd.
Rabin & Champagne, P.C.
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