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.