COMMUNICATION SYSTEM AND METHOD

摘要

A communication system comprises: mobile user equipment; and a communication network adapted to communicate with the user equipment, the communication network comprising: a first base station adapted to communicate with the user equipment using radio signals and according to a first defined radio frame format comprising a first sequence of radio frames each having the same length and each being allocated a respective first system frame number (SFN) such that the radio frames of the first sequence are sequentially numbered; and a second base station adapted to communicate with the user equipment using radio signals and according to a second defined radio frame format comprising a second sequence of radio frames each having said same length and each being allocated a respective second SFN such that the radio frames of the second sequence are sequentially numbered, the user equipment being adapted to receive radio signals from the first base station and to use said received signals to synchronise with the first sequence of numbered radio frames, such that the user equipment can transmit radio signals to the first base station in accordance with the first defined radio frame format, and determine the first SFN of a frame of the first sequence at a particular time, the communication network being further adapted to transmit a radio signal to the user equipment, the radio signal comprising first information indicative of a difference between the first and second SFNs at a particular time and second information usable with said first information to determine unambiguously at least a least significant bit of the SFN in binary form of a frame of the second sequence at a particular time from a knowledge of the SFN of a frame of the first sequence at a particular time, the user equipment being further adapted to receive said radio signal and, when synchronised with said first sequence, to use the first and second information to synchronise with the second sequence, such that the user equipment can transmit radio signals to the second base station in accordance with the second defined radio frame format. A corresponding communication method is provided.