Patent ID: 8428009

Claim:
A mobile station for use in a broadband communication system that includes a plurality of base stations and mobile stations, the mobile station comprising: an apparatus configured to transmit a first signal within an uplink frequency band from the mobile station to a first base station in the system, wherein: the first signal contains data that is encoded and modulated with a QAM or PSK modulation scheme; the first signal is transmitted via a plurality of orthogonal frequency division multiplexing (OFDM) subcarriers; and the first signal is transmitted with a time frame structure that includes a plurality of frames, wherein each frame contains a plurality of subframes, each subframe contains a plurality of time slots, each time slot contains a plurality of OFDM symbols, and each OFDM symbol contains a cyclic prefix; an apparatus configured to transmit a second signal within the uplink frequency band from the mobile station to a second base station during a hand-off from the first base station to the second base station, wherein: the second signal is formed by adding guard period(s) to either or both end(s) of a time-domain sequence wherein the time-domain sequence has an autocorrelation with a high peak-to-sidelobe ratio and has a low peak-to-average ratio in the frequency domain, and wherein the guard period(s) of the second signal is sufficient to account for time alignment uncertainty between the second signal and other OFDM signals transmitted in the system; and the second signal has a duration of a least a number of OFDM symbol periods of the first signal and the second signal has a high spreading gain for enhanced detectability against noise and interference from other OFDM signals transmitted in the system; the second signal occupies a bandwidth that is narrower than the bandwidth of the uplink frequency band and some frequency components within the occupied bandwidth are not energized in order to reduce interference between the second signal and other OFDM signals transmitted in the system; and the transmission power of the second signal is controlled to reduce interference with other OFDM signals transmitted in the system; and an apparatus configured to receive signals from the base stations.