Conceptual design of a multiple site 800 MHz trunked land mobile system

As the need to provide larger and larger coverage areas for 800 MHz Trunked Radio systems (both portable and mobile) emerges, a requirement to extend the trunked concept at multiple sites will become a necessity. This paper deals with one possible solution to the problem. The operational and relative cost trade-offs win also be examined. Basically, the fundamental problem to be examined will involve devising a means to share the 5 to 20 channels assigned to a trunked system and shared by the multiple sites which all have total assigned channel capability at every site. The RF channel assignment must be controlled in such a manner that simulcast of identical radio frequency signals into coverage overlap areas will always be avoided so that received signal interference zones for portables and/or mobiles will not occur. The analysis will explore the necessary RF hardware configuration required at each of the multiple sites as well as the required computer/logic functions that must be accomplished to control the assignment of the proper channel to the proper site. Perhaps the most difficult design features of the concept will be the requirement to enable assignment of a channel upon demand of a mobile unit at a given site and the attendent logic/ timing funtions necessary to prevent duplicate assignment at any other of the multiple sites. The operational and cost trade-offs of such a concept must be compared on the basis of the allowable portable/mobile unit loading in terms of units per channel versus the equivalent loading which would result were the channels not reused at every site. The trade-off analysis also must include an analysis of spectrum conservation resulting from the multiple reuse of the channels which produce the same unit loading per channel were the channels not reusable at all sites. A cost trade-off of recurring TELCO line charges necessary to implement the concept versus the use of RF radio links to tie the sites together will be made. A final conclusion as to the technical and economic feasibility of such a system being implemented will be presented in an effort to anticipate the future development of wide area coverage trunked 800 MHz systems.