Timing systems and methods for forward link diversity in satellite radiotelephone systems

摘要

Downlink signal bursts are transmitted from a plurality of visible satellites to a plurality of user terminals in a downlink region that is serviced by the plurality of visible satellites. A first downlink signal burst is sent from a first one of the visible satellites to a first user terminal in the downlink region. A second downlink signal burst is sent from a second one of the visible satellites to the first user terminal to be received at a time that is a function of a separation distance of the first user terminal in the downlink region from the Time Alignment Center (TAC) of the downlink region. First downlink signal bursts and second downlink signal bursts also are sent to other user terminals in the downlink region. The first and second downlink signal bursts preferably are sent over respective first and second carrier frequencies. In preferred embodiments, the downlink signal bursts are transmitted in a plurality of repeating frames of downlink signal bursts of a predetermined frame repetition period. The second downlink signal burst is sent so that it will be received by the intended user terminal at a time offset from the first downlink signal burst that is one half the predetermined frame repetition period plus a delay time DeltaT that is a function of a separation distance of the first user terminal in the downlink region from the TAC of the downlink region.