LTE Advanced: 3GPP Solution for IMT-Advanced

9.1 Introduction

LTE and LTE-Advanced radio access can provide very high data rates, even beyond 1 Gbps, but only when the signal conditions are favourable. If the signal is weak, for example indoors, the data rates will be substantially lower than the theoretical peak data rates. The initial LTE rollout uses large macro cells and will not be able to provide full coverage for high data rates. There is a clear need to push the LTE coverage. The coverage can be pushed by installing more macro base stations or more small base stations. The additional base stations improve both coverage and capacity. The challenge with new base stations is typically to find the suitable base station site locations and to organize the transport connections. Another option for coverage improvement has been the use of RF repeaters which boost the signal level, but also boost interference. The interference control with repeaters has been a challenge in the existing networks. 3GPP Release 10 brings one more option for improving the network coverage: relays. The idea in the relay node is to use the same LTE air interface also for the backhaul connection, which makes the relay installation simple as no separate transport solution is required. Furthermore, the relays will be smaller equipment that makes it possible to deploy them on lamp posts, for example. The relay node is designed to be backwards compatible with Release 8, both from the UE and from the core network point of view. The relay node looks like ...