Radio frequency communication system with a repeater that operat

Multiplex communications – Communication over free space – Repeater

Patent

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Details

370328, 370336, H04B 714

Patent

active

059302402

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL AREA

The present invention relates to an arrangement for, in a digital mobile radio communication system comprising on the one hand densely positioned base stations working with a short range and on the other hand mobile units, extending the range by means of repeating functions.


STATE OF THE ART

In radio systems, preferably digital radio systems, which are used in local applications, the coverage between a base station forming part of the system and a mobile unit belonging to the base station is limited to the area of coverage of the base stations. In general public radio-relay systems, it is already known, through patent specification EP A 2 092 237, to utilize a repeating function. The repeating function repeats a first sequence of downward time slots, in a first time frame, from the first to the second station as a second sequence of downward time slots, in a second time frame. The repeater function also transmits a first series of increasing time slots to the first station which answers a second series of upward time slots received from the second station.
In association with mobile radio systems belonging to this category with poor range in relation to the median in length of the radio link, a number of methods have been proposed for improving the coverage between the mobile units and the base stations. The proposals which have been put forward have, however, resulted in drawbacks with delays of the speech or data connections. No known technology for improving the range between mobile units and a base station in local networks which results in high capacity, adequate range, security and quality has previously existed.


DESCRIPTION OF THE INVENTION



TECHNICAL PROBLEM

The modern local radio systems of today presuppose the greatest possible range between the transmitter and receiver of the base stations and the mobile units at the same time as the greatest possible consideration can be given to radio systems being assigned to work in high frequency bands, preferably above 100 MHz, which gives a poor range in relation to the median attenuation of the radio link. On the other hand, a small part of the radio link has very high attenuation. In order to obtain adequate signal strength, the low attenuation link must therefore be significantly reduced as the high attenuation link cannot be changed for application reasons.
The problem can be exemplified with the radio-based local network application OMA (area-limited mobile access). The application means that the terminated cord connection to the subscriber is replaced by radio. The telephone exchange is connected to a radio base at a suitable distance from the subscriber, e.g. 500 meters. The radio base can connect a large number of subscribers within the coverage area. The subscriber, whose usual cord telephone is replaced by one or more cordless telephones, is offered an area-limited mobility. This means that costs for maintenance and running cables can be minimized. This presupposes, however, that adequate range can be obtained. Ongoing testing activity has shown that this type of system gives OMA ranges of less than 100 meters. The explanation for this relatively low range is that the signal strength is greatly damped when the radio wave is to penetrate the building or the ground. The invention intends to solve these problems among others.
In one embodiment of the subject of the invention, the use of a time multiplex protocol is utilized, in which protocol messages are to be capable of being transmitted in time slots divided in time frames in such a manner that drawbacks with delays of speech or data connections do not arise. The invention intends to solve this problem also.
In one embodiment of the subject of the invention, an influencing function is utilized, in which influencing function time slots are to be capable of being assigned in such a manner that capacity is increased in the critical coverage area of the mobile system. The invention intends to solve this problem also.
In one embodiment of the subject of the invention, the repe

REFERENCES:
patent: 4713809 (1987-12-01), Mizota
patent: 5113394 (1992-05-01), Kotzin
patent: 5365590 (1994-11-01), Brame
patent: 5371734 (1994-12-01), Fischer

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