On the performance of advanced receivers in unsynchronized small cell LTE networks

Abstract

Next generation long term evolution (LTE) systems evolve towards small cell networks to boost spectrum efficiency through extreme frequency reuse. To mitigate the impact of the resulting tremendous co-channel interference, advanced receivers supporting network assisted interference cancellation and suppression (NAICS) represent a promised technique to meet the ubiquitous cell edge free experience. However, as the interfering signals will reach the cell edge user equipment (UE) at varying delays, unsynchronized small cell networks might experience large timing offsets (TOs) and considerably limit the expected downlink (DL) performance. In this paper we focus on reliable channel estimation for diverse types of NAICS receivers operating in rich interfering small cell LTE networks. With analytical results we derive the impact of TOs on channel estimation, show that the promised performance of each of the NAICS receivers vanishes when neglecting the varying delays and against expectations perform worse than conventional linear interference suppression receivers. However, estimating and compensating the impact of the TOs, reliable channel estimation can be achieved and as a result the expected DL performance of each of the investigated NAICS receivers can be guaranteed in unsynchronized small cell LTE networks.