Method and apparatus for late entry in asynchronous frequency hopping systems using random permutation sequences

摘要

A wireless method and apparatus for late entry in frequency hopping systems that, during call setup, computes a random permutation sequence through a hop set of frequencies, chooses preamble frequencies to omit data thereon in lieu of preamble data, and swaps frequencies in the random permutation sequence such that synchronization frequencies lie next to the preamble frequencies with an expected delay such that late entrants can join. The wireless method and apparatus meets the FCC requirement of maintaining a pseudorandom hopping pattern and equal distribution of all frequencies in a hop set while guaranteeing late entry and having no effect on battery performance of radios.

主权项

1. A method for late entry in asynchronous frequency hopping wireless communications, the method comprising:
during a traffic phase of a call, generating a random permutation sequence of frequencies, 1 to N, in a hop set based on data exchanged in a connection establishment phase of the call, wherein the hop set comprises N frequencies; finding a selected preamble frequency in the generated random permutation sequence at which to transmit a late entrant preamble frame for late entrant devices; finding a selected synchronization frequency in the generated random permutation sequence at which to transmit a late entrant synchronization frame associated with the late entrant preamble frame; finding a subsequent frequency in the generated random permutation sequence after the selected preamble frequency, wherein the subsequent frequency is located in the generated random permutation sequence where late entrant devices expect to find the late entrant synchronization frame associated with the late entrant preamble frame relative to the location of the selected preamble frequency in the generated random permutation sequence; switching the subsequent frequency in the generated random permutation sequence with the selected synchronization frequency in the generated random permutation sequence to form a modified random permutation sequence; and transmitting traffic, the late entrant preamble frame, and the late entrant synchronization frame over the frequencies, 1 to N, in accordance with the modified random permutation sequence.