Performance comparison of signal strength and signal quality based Inter-RAT MRO

The Long Term Evolution (LTE) network is currently being deployed on top of the legacy radio access technologies (RATs) such as the second generation (2G) or third generation (3G) mobile networks. Inter-RAT mobility robustness optimization (MRO) is one of the most important use cases for self-organizing network (SON). Unlike the manual optimization methods, an inter-RAT MRO algorithm adjusts the handover thresholds of each cell in autonomous and automatic manner. An inter-RAT handover is triggered when a measurement event is received from a user equipment (UE). The measurement event can rely on different measurement quantities, namely either signal strength (SS) or signal quality (SQ), where SQ takes the interference experienced by the UE into account. This paper investigates the sensitivity of the two measurement quantities on the behavior of the inter-RAT MRO algorithm in terms of optimization performance. Results have shown that SS is a more robust measurement quantity than SQ as it yields lower numbers of inter-RAT handovers and mobility failure events. Moreover, inter-RAT MRO is needed to achieve the best performance in each cell for both SS and SQ measurement quantities even though the optimization range of the handover thresholds is relatively small for the latter case.