Multiplex communications – Communication over free space – Combining or distributing information via code word channels...
Patent
1995-10-05
1997-09-30
Safourek, Benedict V.
Multiplex communications
Communication over free space
Combining or distributing information via code word channels...
375208, 455 332, H04B 7216
Patent
active
056732600
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method and a system for making a mobile communication in a CDMA (Code Division Multiple Access) scheme between mobile stations and base stations.
BACKGROUND ART
In a mobile communication, in order to utilize radio channels effectively, the identical radio channel is repeated utilized at base stations which are sufficiently distanced spatially. In such a case, in order to prevent a mutual interference of that identical radio channel, there are a fixed channel allocation scheme in which a radio propagation state within a service area is conjectured by an actual measurement, a theoretical calculation, etc., and a radio channel is fixedly provided at each base station, and a dynamic channel allocation scheme in which a radio channel that is available in a system as a whole is made available at any base station.
In the fixed channel allocation scheme, even when a radio channel which is allocated to a neighboring base station is available at an own base station, it is impossible to allocate that radio channel to a new radio channel allocation request within the own base station, so that a radio channel utilization efficiency is insufficient in that regard, and a considerable amount of efforts are required for a re-designing in a case of additionally providing a base station, etc., so that the adaptivity to a system expansion is low.
On the other hand, in the dynamic channel allocation scheme, it is possible to allocate the radio channel flexibly to some extent with respect to the temporal variation, the spatial bias, etc. of the traffic, and it is possible to suppress a call loss rate or an interference obstruction probability to be minimum.
However, in a conventional dynamic channel allocation scheme, a centralized control of allocations of the radio channels to the base stations at a control station is used, so that in order to suppress the call loss rate or the interference obstruction probability to be minimum, it requires an enormous amount of data and a complicated control, and there has been a drawback that the traffic of the signals between each base station and the control station increases.
Also, presently, as an automobile telephone or portable telephone system, a mobile communication system for making communications by a communication scheme such as a CDMA mobile communication scheme between mobile stations and base stations is considered.
Such a mobile communication system using the CDMA mobile communication scheme is equipped with base stations provided in cells constituting an area in which communications are possible, and mobile stations, and at a time of starting a communication between a mobile station and a base station or carrying out a channel switching, etc., after a frequency to be used in a communication and a spread code in the CDMA scheme are determined by using an upward control channel, a downward control channel, etc., between a mobile station and a base station, a communication is made by establishing a synchronization of an upward communication channel and a downward communication channel between a mobile station and a base station.
The base station is equipped with an antenna for making transmission and reception of radio link signals, a common amplifier circuit for amplifying the radio link signals to be transmitted or received through this antenna, a plurality of transceiver circuits for carrying out a radio link signal transmission and reception processing through this common amplifier circuit and a processing for communicating with an exchanger side through each wire link, and a base station control circuit for controlling transmission and reception operation of each of these transceiver circuits.
At a time of starting a communication with a mobile station or carrying out a channel switching, etc., after a frequency to be used in a communication and a spread code in the CDMA scheme are determined by using an upward control channel, a downward control channel, etc., between a mobile station and a base station, this base sta
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patent: 5103459 (1992-04-01), Gilhousen et al.
patent: 5179571 (1993-01-01), Schilling
Higashi Akihiro
Hiroike Akira
Kaiyama Akira
Umeda Narumi
NTT Mobile Communications Network Inc.
Safourek Benedict V.
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