Joint interference coordination and relay cell expansion in LTE-Advanced networks

Deploying relay nodes is foreseen a cost-efficient solution to combat the severe propagation loss at cell edge. However, relay cell coverage is limited by the low transmit power, limited antenna capabilities and wireless backhaul link bottleneck which may lead to load imbalances and hence low resource utilization efficiency. Further challenges in relay deployments are attributed to increased interference levels in the network compared with macrocell-only deployments, causing degradation of the user throughput. In this context, relay cell coverage expansion and interference coordination techniques are expected to improve the performance of relay deployments. In this study, we analyze the impact of the additional interference due to the relay node transmissions. Jointly with our previous study on cell expansion, we show how the interference coordination mitigates the interference from relays and hence optimizes the system performance. Comprehensive system level simulations are carried out within the LTE-Advanced framework. Results confirm that the interference imposed by relay nodes can be reduced. Furthermore, both cell edge throughput gains and cell average throughput gains are observed.