| 摘要 |
In an exemplary embodiment, a base station maintains RF communication with mobile units using a polling protocol which may communicate at a higher or lower data rate, depending on the channel conditions. The base station transmits a general polling message at the lower data rate, and, associated therewith, transmits a test pattern for evaluation by the mobile units. Upon receipt of the transmissions, the mobile units analyze the test pattern to determine whether communication at the higher data rate is possible. Based on the determination, the mobile units select the appropriate rate to transmit data messages. The test pattern can be associated with a query from a mobile unit having a message to send, or with a contention polling message from the base.
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