Communications in a distribution network

摘要

In an arrangement for transmitting traffic in asynchronous transfer mode (ATM) cells in downstream and upstream frames between an out station and a base station, upstream traffic cells are queued in each outstation in sequential order for subsequent transmission in upstream frames to the base station. Each outstation sends requests for allocation of timeslots to the base station, each said allocation request being transmitted to the base station in a respective time slot of a said upstream frame. The base station includes means for performing a periodic ranging measurement with each outstation whereby to determine a corresponding timing offset between the base station and that outstation and for communicating that timing offset to the outstation. Each outstation controls the timing of its cell allocation requests such that the cell allocation requests received by the base station in each upstream frame are each in a respective predetermined time slot of that frame. This avoids the need for a preamble sequence to be provided with each request.