| 摘要 |
PROBLEM TO BE SOLVED: To reduce the power of a mobile station required for retrieving the coverage area of a ground base station or an orbit satellite station. SOLUTION: A CPU 13 gives a command to a DSP 12 for retrieving three frequencies at maximum in a TDMA frame when retrieving. The CPU 13 sequentially gives the three frequencies to be checked to the DSP 12 to retrieve all ground frequency bands. This cycle continues under the condition that there is a detection signal with power enough to be strong to set up an AGC in an RF stage 10 until an RSSI level is received. The CPU 13 arranges the frequencies in the order of higher RSSI levels. When the level is higher than a threshold level, the CPU 13 gives a command to the DSP 12 to be synchronous with the channel. The DSP 12 tries to decode a broadcast message by synchronizing its operation with respect to accurate transmission timing, and a frequency at first and then tries to decode a synchronization burst. When the trial is successful, the CPU 13 registers it, the mobile station completes the operation at the outside of its coverage and 'stays' in the found-out channel.
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