Algorithm to reduce impact of LTE-A CSI-RS on LTE legacy UE in CoMP scenario

In LTE-A (Long Term Evolution-Advanced) network, CSI-RS (Channel State Information Reference Signal) is substituted for CRS (Common Reference signal) to perform higher order MIMO (Multiple Input Multiple Output). In CoMP (Coordinated Multiple Point Transmission) scenario, the number of REs (Resource Element) occupied by CSI-RS would be multiplied. However, LTE (Long Term Evolution) legacy UEs (User Equipment) cannot distinguish CSI-RS from data, which may deteriorate the LTE UE´s demodulation performance. Therefore it could be troublesome for LTE legacy UEs scheduled in LTE-A network with higher order MIMO equipped, and it is even more serious when CoMP technology is used. Investigation results by both link-level and system-level simulation reveal that LTE legacy UEs performance is seriously degraded due to the impact of CSI-RS when coding rate and modulation order go higher. To reduce the performance degeneration, an improved scheduling algorithm named AUP-AMCS (Advanced UE Prioritization combined with Adaptive Modulation Coding Scheme) is proposed in this paper. Compared to existing algorithm, AUP-AMCS algorithm takes UE priority into consideration and is compatible with the established specification. Simulation results indicate that the proposed algorithm can improve system performance obviously.