Influence of velocity on the handover delay associated with a radio-signal-measurement-based handover decision

Velocity has a non-neglectable influence on the handover delay experienced by a user if the handover is triggered on a radio-signal-measurement (RSM) based handover scheme. Assuming currently used RSM schemes employing signal averaging (low-pass filtering) and a hysteresis margin, the analytical description of the delay is derived as a function of the velocity. The latter is used to determine the minimal overlapping of two adjacent radio cells required for a seamless, i.e. interrupt-free handover. Results show that the required overlapping for a zero-delay handoff does not scale with the handover frequency. Especially for small radio cell sizes, the overlapping may easily exceed 60% of the cell's diameter. The improvement gained by dynamically adapting RSM-scheme's parameter, i.e. the hysteresis margin, to the current velocity is neglectably small. Hence, a RSM-based handover decision is not suitable for high handover frequency scenarios and should be supported by other handover trigger mechanisms.