Experimental Evaluation on Doppler Spread Based Mobility State Decision Considering Moving Scatterers Using Actual Radio Propagation Data

Abstract

In order to deal with the rapidly increasing mobile traffic, layered cellular networks, where small cells with low transmission power are densely deployed and overlaid onto the hot spot areas of existing macro- cell coverage area, have been receiving much attention. Unfortunately, such layered cellular networks suffer from frequent handovers (HOs) that occur between small cells when a high velocity mobile terminal (MT) travels through these small cells in a short period of time. Hence, to improve frequency utilization for layered cellular networks while avoiding the frequent HOs, an inter-layer HO control policy where MTs traveling at a high velocity are served by the macro-cell layer and MTs traveling at a low velocity are served by the small-cell layer, is effective. To realize such inter-layer HO control policy, mobility state decision techniques are essential. The authors investigate a Doppler spread based mobility state decision for MTs where the GPS function has been manually disabled by the user as well as for MTs without the GPS function. This paper first evaluates the performance of a Doppler-spread based MT velocity detection with the use of practical outdoor radio propagation data. Then, from the evaluation results, it is considered that the presence of moving scatterers may degrade the detection accuracy. Finally, this paper proposes a scheme to suppress the velocity detection error caused by moving scatterers and mobility state decision accuracy with the proposed scheme is evaluated using actual outdoor radio propagation data.