Handover protocol in BDMA communication system

Abstract

To satisfy the increasingly requirement of data traffic, beam division multiple access (BDMA) system which uses multiple beamforming to serve multiple users simultaneously is considered as a new promising technology. By using BDMA technology, the new wireless system can achieve much improvement compared with conventional system in the view of capacity, coverage and power consumption.

To support mobility in wireless communication system, handover is the most important function. Previously, handover protocol in cellular communication system has been designed effectively and accurately in the consideration of user mobility. However, due to the changes in the system characteristics, a new handover protocol must be designed to support mobility in BDMA communication system. In the BDMA system,the serving beamwidth and beam direction change from time to time. Thus, to support handover, the MS needs to acquire the information about received signal strength of serving beam and target beam.

An optimal handover scheme in which mobile station (MS) handovers directly from the serving beam of the serving BS to target beam of the target BS is proposed. However, this handover scheme requires much handover scanning time. It leads to too longer handover delay which causes the poor performance of system. Hence, we propose a new suboptimal handover scheme in which MS estimates the average received signal strength of target beam based on average received signal strength of target omni directional antenna and information about its serving beamwidth. After estimating the received signal strength of target beam, the handover decision will be made based on the estimated average received signal strength of target beam and average received signal strength of serving beam.

Through the usage of proposed suboptimal handover scheme, the system performance increases significantly. System outage probability of the proposed suboptimal scheme is much smaller than that of conventiona...