Synchronisation in an unsynchronised or single carrier synchronised communication system

摘要

A plurality of frequency resources are employed in an unsynchronised or single carrier synchronised communication system, e.g. a TETRA (TErrestrial Trunked Radio) system employing direct mode operation (DMO) for direct communication between mobile stations and a mobile wireless communication unit comprises a transmitter for transmitting on a first frequency resource of the plurality of frequency resources, wherein the transmission on the first frequency resource dictates a timing of transmissions of one or more other wireless communication units on a second frequency resource of said plurality of frequency resources. Either the timing of the transmission on the first frequency resource is used as the basis for the timing of transmissions on the second frequency resource or the transmission on the first frequency resource is a wireless message (dedicated protocol data unit (PDU)) that indicates to wireless communication units affiliated to the mobile wireless communication unit that the mobile wireless communication unit is to initiate a call on the first frequency resource, wherein the message is characterised in that it further signifies to the other wireless communication units that they should monitor transmissions on the first frequency resource, in order to synchronise a timing of any of their transmissions on a second frequency resource to the transmission on the first frequency resource. In this manner the system supports self-synchronisation since wireless communication units, operational on an unsynchronised or single carrier synchronised system, monitor an active transmission on a first frequency and synchronise subsequent transmissions on any coupled frequency to the active transmission.