Performance Analysis of Downlink Inter-Band Carrier Aggregation in LTE-Advanced

Carrier aggregation (CA) is one of the most distinct features for LTE-Advanced systems, which can support a much wider transmission bandwidth up to 100 MHz by aggregating two or more individual component carriers (CCs) belonging to the same (intra-band) or different (inter-band) frequency bands. With CA, it is possible to schedule a user equipment (UE) on multiple CCs simultaneously. From radio resource management (RRM) perspective, CC selection plays an important role in optimizing the system performance, especially in the case of inter-band CA where the radio propagation characteristics of each CC can be different. In this paper, we investigate the downlink resource allocation for inter-band CA, i.e., how to assign carrier(s) to different UEs. A simple yet effective G-factor based carrier selection algorithm, which takes both traffic load and radio channel characteristics into considerations, is proposed with the objective to guarantee good coverage for Rel´8 UEs and robustness for Rel´10 UEs. Simulation results show that our proposed G-factor based carrier selection algorithm can achieve much better coverage performance compared to the least-load carrier selection in scenarios with relatively high inter-site distance and relatively high frequency separation between carriers, at the expense of some marginal average user throughput loss.