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 <INS-S DATE="20011023" ID="INS-S-00001">the <INS-E ID="INS-S-00001">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

BACKGROUND OF THE INVENTION1. Field of the InventionThe present invention relates to an automobile on-board and / or portable telephone system in which the number of channels can be increased easily.2. Description of the Related ArtIn recent years, automobile on-board and / or portable telephone systems of .Iadd.the .Iaddend.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-board and / or portable telephone system .Iadd.the .Iaddend.of CDMA type is shown in FIG. 3. In the Figure, reference numeral 1 designates units at the transmitter side such as a base station and 2 units at the receiver side such as an automobile on-board telephone or a portable telephone. Denoted by reference nume...

AI Technical Summary

Benefits of technology

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.

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 a.]. .Iadd.if .Iaddend.voice signal .[.coded.]. .Iadd.coding .Iaddend.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

[.of subscribers.]. cannot be increased because of a shortage of

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