The pooled network resources utilized in a trunked private mobile radio (PMR) network consist primarily of the radio channels and the line-connected PCM channels which span the fixed base-stations. Some calls will not require any landline resource, only a radio path into and out of the local base-station. A single radio channel would meet the resource demands placed on the base-station for calls of this type. However, to set up a cross-network communications path between two mobile parties requires several resources which may not be available all at the same time. It is normal practice to allocate the available resources and queue for the remainder. During the busy hour it is not uncommon for both parties involved in the call to queue for the radio channel resource. In such cases the queueing times of the calling and called parties will generally differ. Thus a radio channel may be allocated to one party before the other and consequently remain idle until a radio channel becomes available for the other party. Other calls meanwhile might be unable to proceed for want of that idle radio channel. Bubenik and Turner (1989), for example, reports an increase in carried load in a packet switch as a result of relaxing the strict FIFO queueing discipline. This paper examines the effect of a queue-jumping algorithm which bypasses the FIFO discipline and reduces channel idle time. Provided certain criteria are met, it is shown that if one party is moved to the head of a queue as soon as the other party is allocated a radio channel, there is an overall reduction in channel idle time over the entire network.
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