| 摘要 |
A cellular telephone system includes a packet-switched digital data communication subsystem overlaying a circuit-switched (e.g., voice) communication subsystem, with voice and data services sharing the same voice channels. The voice communication subsystem provides voice services independently of the operation of the data communication subsystem. On the other hand, the data communication subsystem monitors use of the voice channels for voice communication, and, in response thereto, temporarily allocates one or more of the available voice channels for data service. In a preferred embodiment, each data basestation transmits, from time to time, an available-channel signature to identify those, if any, of the data-allocated channels that are not then being used to transmit voice or data. For data communication, a remote unit monitors selected voice channels in the coverage area of the cellular telephone system for available-channel signatures, selects one of the channels (if any) identified by the signature thereon as being available for data transmission, and transmits or receives digital information over that channel.
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