| 摘要 |
<p>A point-to-multipoint radio system comprises a plurality of subscriber units, a beacon transmitter comprising a frequency reference, a modulator and a radio transmitter operable to transmit a radio frequency beacon signal for reception by the plurality of subscriber units, the frequency of the beacon signal being derived from the frequency reference and the modulator being arranged to modulate the beacon signal according to a predetermined modulation scheme, and a hub including a hub transceiver operable to receive radio signals from the subscriber units and to transmit radio signals to the subscriber units. Each subscriber unit including a subscriber transceiver arranged to receive the beacon signal and using the beacon signal, to generate a radio signal to be transmitted to the hub and to correct frequency errors in a radio signal received from the hub.</p> |
