An apropos signal report and adaptive period (ASAP) scheme for fast handover in the fourth-generation wireless networks

摘要

In this paper, a medium access control (MAC) layer handover scheme is proposed to reduce the handover processing time. Two critical points of investigation are examined to improve the performance of the handover process. The first point is the exact point of time when the handover process should be triggered. This factor is highly related to the signal-to-noise ratio (SNR) the mobile station (MS) receives at that moment. The second point is the moving direction and current moving velocity of the MS. Based on these two factors, an apropos signal report and adaptive period (ASAP) handover scheme is proposed to reduce the handover processing time. ASAP is based on the concept that the received SNR is highly related to the point of time the MS reports and the circumstance the MS stays. If the variation between two reported SNR values is large, the time interval of receiving the next SNR report must be reduced, or increased when the variation is small, to accurately reflect the SNR change. ASAP adjusts the periodic ranging period dynamically according to the MS moving velocity and no additional control messages are introduced into ASAP. ASAP is a base station (BS) initiated handover scheme. Detailed comparisons reveal that ASAP can achieve a handover delay reaching 15 ms low at most, which is substantially smaller than the fastest legacy network-assisted handover mechanism (50 ms).