Method and apparatus for synchronizing timing among radio ports in

Abstract

In a TDM/TDMA digital radio communications system a few selected ports are connected to a fixed common timing reference and designated as master ports. Each master port is assigned a hierarchical value of zero. Every other port is initialized a high hierarchical value before performing an autonomous iterative procedure to synchronize timing to its nearest master port. By demodulating downlink signals transmitted from other ports when its own transmitter is turned off, a receiving port selects only a fixed number of ports providing the best signal quality with respect to which to adjust its timing. The relative timings and the hierarchical values of the transmitting ports are compared with those of the receiving port. If the hierarchical value of the receiving port, H.sub.R, is greater than or equal to the lowest hierarchical value, H.sub.L, of the transmitting ports, it adjusts its timing based on the timing differences with respect to the set of ports having a hierarchical value of H.sub.L and which have the highest signal quality. Further, H.sub.R is set to H.sub.L +1 if H.sub.R is greater than H.sub.L. The master timing propagates rapidly in a hierarchical way, which results in time synchronization of the entire system without timing drift.