Inter-layer Mobility Optimization

This chapter summarizes some potentially useful concepts and information for handling mobility in multi‐layer long‐term evolution (LTE) networks. The mobility design problem can be split into two regimes: coverage and capacity‐limited cases. The chapter focuses on inter‐layer mobility of a classical cellular network without small cells. It elaborates the idle mode cell selection/reselection and measurement process in LTE. The chapter details the user equipment (UE) measurement process, with some examples of how commercial LTE UEs implement the sometimes mystifying third generation partnership project (3GPP) idle mode measurement requirements. It summarizes inter‐layer measurements in connected mode. The UE needs measurement gaps to perform inter‐frequency or inter‐radio access technologies (RATs) measurements. A UE supporting carrier aggregation may be able to do inter‐frequency measurements without gaps. To alleviate long‐term intra‐ and cross‐layer congestion, network capacity needs to be increased by physical optimization and addition of new cells.