Soft handoff and connection reliability in cellular CDMA downlinks

A two-phase soft handoff scheme, which includes an initial power allocation phase followed by a power redistribution phase, is proposed. The initial power allocation phase makes a handoff decision for each connection by assigning a connection to the BS with the best link quality and allocating a minimum amount of power from the BS for the connection. The initial handoff decisions are made for individual connections independent of other connections or the BS power availability. Therefore, there might be heavily loaded and lightly loaded BSs because (i) traffic load may not be equally distributed in all cells, and (ii) the channel condition of the connections is random. The power re-distribution phase is to smooth out the loading on the system by coordinating the power allocations among neighboring BSs so that more connections can receive reliable transmissions. We then develop an analytical model for studying the connection reliability with the proposed soft handoff scheme. Our results show that the proposed two-phase soft handoff scheme can significantly improve connection reliability and increase system capacity in downlink transmissions.