Subscriber RF telephone system having distributed channel switch

Details Subscriber RF telephone system having distributed channel switch Subscriber RF telephone system having distributed channel switch

1997-12-10

1999-06-29

Cumming, William

Telecommunications

Radiotelephone system

H04Q 700

Patent

active

059181710

DESCRIPTION:

BRIEF SUMMARY
The present invention relates generally to trounced radio telephone systems and more particularly, to a subscriber telephone system for providing multiple information signals simultaneously over at least one radio frequency (RF) channel.


BACKGROUND OF THE INVENTION

Many developing countries have begun to investigate the possibility of providing telephone service to a larger percentage of their respective citizenry. In many developing countries the number of telephones per person (telephone density) in rural regions is typically only one-fifth to one tenth of the telephone densities characteristic of urban areas. For example, telephone densities in China's urban centers typically exceed 30 telephones per 1,000 population, while telephone density in China's rural areas is roughly 4 telephones per 1,000 population.
In order to improve service to rural areas many developing countries have attempted to identify telephone systems enabling cost-effective switching, transmission, and distribution suitable for the low capacity requirements of rural installation. At the same time, however, it is desired that the system be expandable to accommodate higher traffic, a larger subscriber base, and allow for advanced billing and data communication functions to be supported as rural areas develop.
Radio equipment has been used, particularly in rural areas, for providing telephone service to a distributed set of users. The highly variable distribution requirements of the rural networks in developing countries has spurred efforts to develop cost effective radio telephone systems. Radio transmission offers several advantages relative to communication facilitated by satellite or cable networks. For example, it may be impractical to bury cable in regions having uncultivatable (e.g., rocky or hardpan) soil, and aerial cable has proven to be relatively costly to install and maintain. In contrast, the cost of microwave radio links is relatively insensitive to distance due to the extended coverage capability afforded by repeater stations.
Satellite telephone systems are often used to service remote rural areas, or to provide service over wide geographic regions of diffuse subscriber concentration. However, a minimum number of subscribers is required to justify the significant investment required by the provision of satellite base stations and related facilities. Low capacity radio links can be a less expensive alternative to satellite systems when providing service to remote areas (e.g., islands) with relatively low levels of telephone traffic. Moreover, radio links can meet the transmission demands of low density demand pockets, particularly those located off of larger demand routes.
In trunked radio communication systems a number of radio users (subscribers) share a group of communication channels, where typically each user will require a channel for only a small percentage of the time. A base station serves as an exchange between the subscribers and a set of dedicated lines, i.e., trunks, from the public network. Subscribers may use mobile or portable two way and fixed base communication modules, with radio repeaters generally being used to provide the communication channels over an extended range. Conventional repeaters do not perform any call switching functions, but rather merely relay information signals linearly between subscribers and the base station. It follows that when one subscriber desires to communicate with another located nearby, the call must nonetheless be transmitted to the base station and rebroadcast to the intended recipient subscriber. Accordingly, a radio telephone system operative to provide localized call routing among proximately located subscribers would allow a base station of a given traffic capacity to service a larger number of subscribers.
Each repeater unit within trunked systems typically receives communication signals from subscriber units on a first path, and rebroadcasts the signals at higher power on a second path to other subscriber units. Trunking systems generally use different assigne

REFERENCES:
patent: 3562431 (1971-02-01), Inose et al.
patent: 4675863 (1987-06-01), Paneth et al.
patent: 5050189 (1991-09-01), Cox et al.

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