Patent ID: 6415149
Filing Date: 2002-07-02
Classification: H04W

Abstract:
A method for handoff in a cellular radio communications system including a plurality of cells each having one or more sectors, one or more base transceiver stations (BTSs) in each cell, and a base station controller (BSC) coupled to said BTSs, in which communications to and from a subscriber unit such as a mobile station may be carried by signals in one or more sectors and/or one or more cells during a handoff, said method comprising the step of the BSC selecting signals for said handoff on the basis of signal strength and expected signal correlation, expected signal correlation being assessed by considering said sector or cell in which each signal is carried,in which pilot signals are transmitted in each of a plurality of sectors and/or cells and, during a call, a subscriber unit reports to said BSC the identities and strengths of any pilot signals it receives, said BSC arranges said reported pilot signals into groups of pilot signals likely to have high correlation with each other, ranks said pilot signals within each group in order of said reported strengths, modifies said reported strengths by reducing by a predetermined factor said reported strengths of said pilot signals except for a strongest pilot signal in each group, and then assesses candidate pilot signals for handoff according to said modified signal strengths by prioritising handoff with pilot signals having the highest modified signal strengths, in which said predetermined factor is preferably between about 1 dB and 10 dB and particularly preferably between about 3 dB and 6 dB.