LTE Advanced: 3GPP Solution for IMT-Advanced

13.9 Summary

Practical LTE data rates are limited by inter-cell interference rather than by thermal noise. In particular, current systems bear the problem that cell edge data rates are often just a fraction of the theoretical peak rate. Coordinated Multipoint (CoMP) is an option to manage inter-cell interference and boost cell edge data rates, and consequently provide a more homogeneous quality of service from cell centre to cell edge.

In the downlink, a joint transmission from multiple cells to one or multiple terminals has the highest gain potential, but requires very low latency backhaul while coordinated scheduling and beamforming sets lower requirements. Intra-site downlink CoMP between multiple sectors is the most straightforward option without any further backhaul requirements and achieves the majority of the traditional CoMP gains. The downlink cell edge CoMP gains with four antenna base station transmission and including channel state imperfections are up to 10–20%. The downlink CoMP gains with two antenna transmissions are clearly lower than with four antennas. Further, the downlink CoMP is not a game-changer in terms of meeting the capacity growth demands since the average gains tend to be only modest. The simulations show that intra site CoMP benefits constitute most of the total CoMP gains. Therefore, intra-site CoMP could be an attractive option to enjoy CoMP gains without major changes to the network architecture. Further sectorization and additional RF heads can ...