Uplink comp and the applications in LTE heterogeneous networks: Principles and the field trial

Uplink Coordinated Multi-Point (CoMP) reception is one of the key technologies of LTE Advanced system. It has the potential to improve uplink capacity by joint processing the received signals from more antennas of the neighbor nodes. Uplink CoMP is implemented at the eNodeB side with no requirement on terminals or protocols and thus is easy to be introduced in the current networks. In future heterogeneous network deployment, low power remote radio units (RRU:s) are identified as one of the key components to increase the capacity of cellular networks in dense areas with high traffic demands. By coordinating low power RRU:s with macro RRU:s, uplink CoMP can get significant uplink gain from not only macro reception diversity but also uplink/downlink decoupling. This paper analyzes the principles of uplink CoMP and its applications in heterogeneous networks, and then a recent full scale field trial in Ericsson Beijing LTE trial network is introduced. The results demonstrate that best uplink reception (in a micro RRU) can be decoupled from best downlink transmission (from a macro RRU), enabling improved uplink throughput with maintained downlink throughput. Thus the problem of uplink and downlink imbalance in heterogeneous networks can be solved and moreover significant uplink reception macro diversity gain can be achieved, hence cell edge user experience can be greatly improved.