Trunked RF communication systems are known. Such systems typically allocate communication resources to communication units upon perception of a need by a resource controller. The request for a communication resource is transmitted to a resource controller over a control communication resource, in some systems, reserved for that purpose. The communication unit, upon receiving the allocation, tunes to the allocated frequency and begins transmitting a message.
The resource controller in granting the resource allocation may also allocate a transceiver (repeater) at a base site in support of the communication transaction. The repeater receives transmissions from the requesting communication unit and re-transmits the message for the benefit of any target communication units present with the service coverage area of the base site.
The resource request transmitted by a requesting communication unit in addition to containing the requestor's ID may also contain an ID of a target or group of targets. In trunked dispatch communication systems the target may consist of a number of communication units located within the same service coverage area as the requestor or located within a number of different service coverage areas.
In communication systems where targets are typically located in a number of different service coverage areas a resource controller typically transmits a system-wide paging alert followed by a system-wide allocation of communication resources. Such allocation of resources may occur even in the absence of target units within specific service coverage areas.
The communication resource allocated in a system-wide call may consist of the same resource, as in a same frequency simulcast system, or of a different resource in each service coverage area, as in a different frequency simulcast system (for a description of simulcast systems, in general, see System Design Aspects of a Simulated Trunked System, by Michael Sasuta, Vehicular Technology Conference-IEEE 32, May 23--26, 1982, IEEE Ref. No. 82CH1720-2, Library of Congress Cat. No. 8184746). Same frequency simulcast systems, as is known, suffer from a number of disadvantages. Chief among the disadvantages of same frequency simulcast systems include dead spots and multi-path fading caused by multiple transmission paths.
Alternatives to simulcast systems exists. Alternatives include the allocation of a unique communication resource in each service coverage area as in a wide area cellular telephone system. Wide area cellular telephone systems (as with many Simulcast systems) are typically controlled by a resource controller. The resource controller upon allocation of a resource from a base site acts to preclude re-allocation of the resource in adjacent base sites. Such a preclusion is necessary to prevent the resultant interference experienced in same frequency Simulcast systems.
A disadvantage of the different frequency Simulcast system include a decrease in spectral efficiency caused by the simultaneous use of additional communication resources. An advantage of the different frequency simulcast system, on the other hand, lies in the increase in received signal quality over same frequency simulcast systems. During periods of heavy system activity, on the other hand, the different frequency simulcast system restricts system capacity over that provided by same frequency simulcast. A need exists for an alternative operating system providing fewer disadvantages than the different frequency simulcast system, on the one hand, and same frequency simulcast system on the other under the various system loading levels experienced within communication systems.
USPTO Backgrounds
USPTO Backgrounds