Automobile on-board and/or portable telephone system

Abstract

In an automobile on-board and / or portable telephone system capable of increasing the capacity of subscribers easily on the basis of changing of the information transmission bit rate, spread codes obtained by multiplying orthogonal spread codes (m in number) by a pseudo-random noise series are assigned to individual channels in the same cell in such a manner that the orthogonal spread codes are multiplied by some types of pseudo-random noise series having different phases, thereby making it possible to maintain the number of channels in the same cell at a value which is a multiple of the number of the orthogonal spread codes. Through this, in the case where the transmission bit rate is halved as compared to the presently existing rate in the future, assignment of spread codes which are increased in number to as large a value as necessary can be achieved and the subscriber's capacity can be increased within a range in which the necessary quality can be maintained even when link paths for m or more channels are set up in one cell from the viewpoint of Signal to Interference Ratio.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001]This is a continuation of application Ser. No. 09 / 337,403, now patented as RE37,420, which was filed on Jun. 21, 1999, to seek reissue of U.S. Pat. No. 5,677,292. That patent issued on Oct. 14, 1997 on application Ser. No. 08 / 272,156, filed on Jul. 8, 1994.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to an automobile on-board and / or portable telephone system in which the number of channels can be increased easily.[0004]2. Description of the Related Art[0005]In recent years, automobile on-board and / or portable telephone systems of the code division multiple access (CDMA) type have been developed for practical use as described in a paper “On the System Design Aspects of Code Division Multiple Access (CDMA) Applied to Digital Cellular and Personal Communications Networks”, May 19-22, 1991, IEEE Vehicular Technology Conference. A conventional example of the construction of the automobile on-boa...

AI Technical Summary

Benefits of technology

[0013]The present invention is achieved in the light of the above problems and it is an object of the present invention to provide an automobile on-board and / or portable telephone system which can increase the capacity of subscribers easily on the basis of, for example, changing of the information transmission bit rate.

[0015]In the present invention having the above construction, the PN series are subjected to multiplication while keeping the series unchanged but changing only the time phase to generate spread codes and the thus generated spread codes are assigned to the channels, thereby ensuring that the number of channels in the same cell can be twice the number of the orthogonal spread codes. Accordingly, for example, when aif voice signal codedcoding having a rate which is half the existing rate becomes applicable in the future, series which are as large in number as necessary can be assigned to increase the capacity of subscribers within a range in which the necessary quality can be maintained even when link paths in excess of m channels are set up in one cell from the viewpoint of the requisite SIR.

Problems solved by technology

In the aforementioned conventional automobile on-board and / or portable telephone system, however, the maximum channelnumber of channels of the outbound link path (a link path bound from the base station to an automobile on-board telephone or a portable telephone) in one cell is limited to the number of orthogonal spread codes (assumingassumed to be m) and, for example, even when aif voice signal codedcoding (coding / decoding unit) having a rate which is half the presently existing rate becomes applicable in the future in the field of communication, there will be a disadvantage in that the subscriber capacity of subscribers cannot be increased because of a shortage of the number of assigned codes or series in spite of the fact that link paths in excess of m channels arecould be set up in one cell from the viewpoint of the necessary SIR and the requisite quality cancould be maintained for performing communication.

Accordingly, if the capacity of subscribers is not increased but is left to be the existing one, then the automobile on-board and / or portable telephone system will be used wastefully.

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