Overzone switching communication method of code division multiple access mobile communication system

Abstract

CDMA mobile communication method and system for realizing an autonomous distributed control of radio channel allocation, a synchronization control for a smooth establishment / switching, and a VOX control for a capacity increase. At either one station of each base station and the mobile station, one of a plurality of prescribed short spread codes is selected, and data sequence to be transmitted is spread by using the selected short spread code and a prescribed long spread code and then transmitted, while at another one station, the data sequence before spreading is reproduced and received by despreading the data sequence from that either one station by using the selected short spread code and the prescribed long spread code. At a time of the handover, each one of data to be communicated between a handover source base station and the mobile station and data to be communicated between a handover target base station and the mobile station is spread by using both a long spread code and a short spread code, and the received data are composed by adjusting timings at each of the mobile station and the base station. Also, a VOX control is carried out for transmission frames to be transmitted through a radio channel in at least one of each base station and the mobile station, and transmitted by randomly allocating an offset with respect to a transmission timing for each channel from a plurality of prescribed offset amounts.

Description

[0001] (This application is a divisional application, and the parent application number is 95190181.8) technical field [0002] The present invention relates to a method and system for mobile communication between a mobile station and a base station in a Code Division Multiple Access (CDMA) scheme. Background technique [0003] In mobile communication systems, the same radio channel is reused by several base stations spaced sufficiently apart in order to efficiently utilize the radio channel. In this case, in order to prevent mutual interference of the same radio channel, there is now a fixed channel allocation scheme in which the radio propagation state in the service area is estimated based on actual measurement, theoretical calculation, etc., and in each A base station provides a fixed radio channel. There is also a dynamic channel allocation scheme in which radio channels available in a system as a whole are available at any base station. [0004] In the fixed channel ...

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Problems solved by technology

[0006] However, in the conventional dynamic channel allocation scheme, which uses centralized control at the control station to control the radio channels allocated to the base stations in order to suppress the call loss rate or interference blocking probability to a minimum, it requires a large amount of data and complicated control, and there is a Disadvantage: increased signal traffic between each base station and the control station

[0017] However, in a mobile communication system using such a conventional mobile communication scheme, since it must use mutually different codes having a small correlation with each other as spreading codes provided on corresponding communication channels, it is necessary when the number of communication channels increases. Use long spreading codes, and there is a problem: until the phase of the spreading code obtained by the code generation circuit in the adjustable correlator or the matched filter circuit provided in each transceiver circuit and the modulated received signal It takes too much time until the phase of the spreading code is consistent

[0018] For this reason, there is now a problem that it takes too much time until the communication channel is established

[0026] However, in such a mobile communication system using the conventional CDMA mobile communication scheme, in addition to the above-mentioned problem that it takes too much time to perform synchronization for the purpose of communication channel establishment, there is a problem that there is In the case of out-of-synchronization of the base station, the acquisition of synchronization is almost impossible

[0027] For this reason, there is now a problem that communication is disconnected because the handoff target base station fails to perform synchronization acquisition at the time of handoff, or even if it succeeds in synchronization acquisition, it takes too much time until synchronization is established. time, so that smooth handover, etc.

[0031] Here, although a plurality of radio channels are established as shown in FIG. 4, when the VOX control is performed, the radio channels are synchronized with each other in a base station, so that the average transmission power can be made smaller by using the VOX control, but the synchronization words partially overlap each other. and the reception quality of the sync word portion degrades the

In other words, even if the interference to the other is made smaller by purposely turning off the transmission of the data part, the capacity is determined by the sync word part, and there is a disadvantage that the capacity increase cannot be obtained even when VOX is used

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