Patent ID: 6262997
Filing Date: 2001-07-17
Classification: H04J

Abstract:
A communications network comprising a central station and a plurality of outstations for transmitting signals on an upstream channel to the central station using time division multiple access and receiving signals on a downstream channel from the central station using time division multiplex, in which each outstation has timing means for applying to its transmissions a timing adjustment determined by a ranging operation for that station, to compensate for differing transmission delays from the outstations to the central station, and in which the network is operable:(a) in an operational mode in which the outstations transmit to the central station in a frame structure having a plurality of frames containing traffic data and at least one frame reserved for ranging operations; and(b) in a start-up mode in which ranging operations are performed, and in which outstations in respect of which the ranging operations has been performed refrain from transmitting traffic data until after the ranging operation has been performed in respect of further outstations, whereby capacity on said upstream channel is made available to permit more frequent ranging operations than is possible in said operational mode.