Protocol Impact of LTE Relays on User Performance

Abstract

Relays are introduced for LTE Rel-10 in order to improve cell edge bitrates and coverage. 3GPP has specified both inband and outband relays. In this paper, we study the protocol level aspects of relays as well as cell-edge performance of a mobile terminal with system simulations. The results indicate that when a user is performing TCP downloads and uploads, in addition to potential subframe split between the backhaul and access link, also the adopted protocol solution and increased delays have impact on the user performance. Due to this, the bitrates may degrade even with outband relays if the UE having decent macro coverage is connected to a relay. However, when the UE has bad macro coverage, then there are gains from both inband and outband relays.