Importance

Loading Importance Indicators...

Abstract

In a trunked radio communications system, apparatus and methods are provided for transparently updating existing frequency division multiple access (FDMA) communications facilities to accommodate time division multiple access (TDMA) communications. TDMA channels are added to existing FDMA sites on an individual basis to increase spectral efficiency and capacity while still being compatible with existing FDMA equipment and protocols. For example, the existing FDMA control channel and protocols are used by dual mode sites and dual mode radios. A dual mode radio transceiver selectively participates in trunked radio communications in either an FDMA mode or in a TDMA mode. Each dual mode radio includes a memory for storing a mode identifier identifying each channel as an FDMA or a TDMA working channel. When a channel assignment is made, the dual mode radio determines from that channel mode identifier stored in memory whether to operate in the FDMA or TDMA mode for that particular communication. Moreover, dual mode radios expedite synchronization to a TDMA working channel (time slot) using a timing relationship established between the FDMA control channel and the TDMA working channels. In the context of multiple site, trunked radio communications, the present invention provides for interoperability between sites and radios which have TDMA communications capabilities and sites and radios which have only FDMA capabilities.

Loading the Abstract Image...

First Claim