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Original Publication Date: 1997-Mar-01
Included in the Prior Art Database: 2002-May-17

Publishing Venue


Related People

Mark Shaughnessy Pat Ekstrom Ed Tremko


Land mobile radio systems can be classified into two major categories, trunked and conventional (also called non-trunked.) Systems of the trunked type are more complex and generally use a resource controller or similar device to allocate communica- tions traffic channels to requesters from among a pool of available channels. This resource allocator acts as a system "brain" to efficiently allocate the Radio Frequency (RF) resources. It uses a so-called control channel, which is usually a dedicated signal- ing channel, to receive service requests from radio units and direct them to the appropriate traffic chan- nel resource. The resource allocator also maintains some level of privacy between system user groups, since it only assigns users involved in a particular conversation to a traffic channel, while all other system users wait in silence, monitoring the control channel. In the simpler conventional system type on the other hand, there is no system "brain," and users are left to select a traffic channel by themselves. Often with conventional systems, user groups are given a permanent channel assignment by a system administrator to help minimize user confusion. Also, with conventional systems there is generally only rudimentary privacy between user groups. Generally, all users tuned to a given channel will hear all conversations on that channel, though some conventional systems also provide so-called private line (PL) or digital private line (DPL) signaling so those user radios that do not recognize a transmitted PL tone or DPL code remain muted.