| 摘要 |
Communication systems and methods that mitigate false alarms due to Doppl er shift are disclosed. Received message data is mapped to orthogonal Walsh codes, interleaved and scrambled with appropriate PN sequence prior to trans mission. The transmitted message data is descrambled and deinterleaved upon reception. The energies associated with each of the Walsh code from various antennas and/or signal paths are combined to obtain a total energy for each Walsh code. If the total energy of the Walsh code exceeds a certain threshol d it is declared as the received message else an erasure is indicated. As th e data is interleaved prior to transmission, any phase ramp introduced due t o Doppler is transformed into random phase errors upon deinterleaving at the receiver thereby mitigating false alarms.
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