Telecommunications – Transmitter and receiver at separate stations
Patent
1989-04-26
1992-03-10
Eisenzopf, Reinhard J.
Telecommunications
Transmitter and receiver at separate stations
455 56, H04B 700
Patent
active
050955314
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a communication method and system for mobile communication. The present invention further relates to a communication method for mobile communicatin that employs a cellular system (which means the service area is covered by many circular or hexagonal shape small zones uniformly) which enables recovery of the communication quality when deteriorated as a result of movement of the mobile unit which is engaged in communication, and also to a system for this communication method.
More specifically, the present invention provides a communication method and system which are superior in the frequency effective utilization factor, communication quality, radiotelephone control capacity, etc.
2. Description of the Related Art
In mobile communication effected in a wide service area, a system in which a single radiotelephone base station covers the entire area to communicate with a mobile unit which is within the service area is generally called "large zone system". On the other hand, in "cellular system", the service area is divided into a plurality of small circular or hexagonal shape areas in each of which a single radiotelephone base station is installed, and a mobile unit which is present in each area effects communication with the ratiotelephone base station installed therein.
The conventional cellular system is adopted, for example, in the mobile telephone system of NTT (Nippon Telegraph & Telephone Corp.) which is now in commercial service. In this case, when a mobile unit which is loaded on an automobile moves away from the radiotelephone base station with which it is in communication, for example, when the distance from the radiotelephone base station is greater than a distance of from 5 to 7 km, the electric field intensity of the received radio wave lowers and, therefore, the speech quality deteriorates. For this reason, in the cellular system, radiotelephone base stations are installed in the service area at regular intervals of from 10 to 12 km so that, in the above-described case, another radiotelephone base station is always present near (within from 5 to 6 km) the current position of the automobile, thereby enabling the communication to continue between the new radiotelephone base station and the mobile unit by use of another radio channel.
In the NTT system, a radiotelephone control station for controlling setting and release of the radiotelephone speech channel is installed to control a large number of radiotelephone base stations and mobile units, and the radiotelphone control station is connected to a public telephone network through a gateway exchanger that serves as an interface. When the speech quality has deteriorated, the radiotelephone control station instructs a plurality of radiotelephone base stations around the mobile unit concerned to receive the radio waves transmitted from the mobile unit and, when it is judged that a desired level of speech quality can be maintained if a new radio channel is set up between the mobile unit and a specific one of the instructured radiotelephone base stations, the radiotelephone control station effects control such that a new channel is set up between the mobile unit and the specified radiotelephone base station.
FIG. 1 is a schematic block diagram of a conventional system that performs the above-described operation. The prior art will be explained below with reference to FIG. 1.
Referring to FIG. 1, four circular zones (cells) 14A, 14B, 14C and 14D each having a radius of about 5 to 7 km are defined as service areas of a mobile telephone system. It is assumed that a mobile unit 15 loaded on an automobile is in communication with a radiotelephone base station 13A in the zone (cell) 14A. Since the automobile is traveling within the zone (cell) 14A toward the zone 14C, the relative distance between the radiotelephone base station 13A and the mobile unit 15 is increasing. Assuming that the radio communication is continuing and the automobile has moved into the zone (cell)
REFERENCES:
patent: 4308429 (1981-12-01), Kai et al.
patent: 4670899 (1987-06-01), Brody et al.
patent: 4696052 (1987-09-01), Breeden
patent: 4882766 (1989-11-01), Akaiwa
Eisenzopf Reinhard J.
Iwatsu Electric Co. Ltd.
Urban Edward
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