Patent ID: 7079549
Filing Date: 2006-07-18
Classification: H04L

Abstract:
1. In a bi-directional data transmission system that facilitates communications between a central unit and a plurality of remote units using a frame based discrete multi-carrier transmission scheme that has a multiplicity of discrete subchannels including an overhead bus having a plurality of overhead subchannels, a method of synchronizing frames transmitted from a selected remote unit to the central unit, the method comprising the steps of: (a) when the selected first remote unit desires to establish communications with the central unit, receiving a first signal from the central unit and loop timing a clock at the selected first remote unit with a clock signal carried in the first signal; (b) transmitting a remote initiated synchronization signal from the loop timed selected first remote unit to the central unit over an overhead subchannel in the overhead bus when the selected first remote unit desires to establish communications with the central unit; (c) transmitting a centrally initiated synchronization signal from the central unit to the selected first remote unit when the central unit receives the remote initiated synchronization signal, wherein the centrally initiated synchronization signal contains information indicative of a frame boundary phase shift required to better synchronize the selected first remote unit with other remote units that are currently communicating with the central unit; and (d) shifting the phase of the frames outputted by the selected first remote unit in response to the centrally initiated synchronization signal to better synchronize the frame boundaries of the frames outputted by the selected first remote unit with frame boundaries of frames output by the other remote units that are currently communicating with the central unit; whereby the synchronization is arranged such that when fully synchronized, the frame boundaries from the various remotes will substantially coincide when they are received at the central unit.