System for adjusting a time axis by using a control and an adjustment time slot in a satellite station of a TDMA network

摘要

In a TDMA network wherein a central station sends signals towards satellite stations in downward frames (A), each comprising a control time slot (Td0) and speech time slots (Td1 to TdM), and receives signals from one to M satellite stations in upward frames (C) of a like format, the central station checks the number of idle time slots in each of the downward and upward frames. Only when the number exceeds a preselected number, one of the idle time slots is selected as an adjustment time slot. The ordinary number given to the adjustment time slot is transmitted in a number field (Nf) of the downward control time slot. Each satellite station generates a time axis indicative of local time slots (D) with a delay relative to the thereby received downward time slots (B). On adjusting the time axis in a selected satellite station, the station sends a short burst (ts) in the local time slot indicated by the received number field. In compliance with an error with which the burst reaches the central station, the delay is rendered equal to a prescribed frame delay (te) minus twice a propagation delay (td) between that satellite station and the central station.