Feedback Compression Schemes for Downlink Carrier Aggregation in LTE-Advanced

With full channel state information (CSI) available, it has been shown that carrier aggregation (CA) in the downlink can significantly improve the data rate experienced at the user equipments (UE) [1], [2], [3], [4]. However, full CSI feedback in all component carriers (CCs) requires a large portion of the uplink bandwidth and the feedback information increases linearly with the number of CCs. Therefore, the performance gain brought by deploying CA could be easily hindered if the amount of CSI feedback is not thoroughly controlled. In this paper we analyze several feedback overhead compression schemes in CA systems. To avoid a major re-design of the feedback schemes, only CSI compression schemes closely elated to the ones specified in LTE-Release 8 and LTE-Release 9 are considered. Extensive simulations at system level were carried out to evaluate the performance of these feedback schemes in various traffic load conditions. Different scenarios were considered to answer the questions of when and why these CSI feedback compression schemes can be applied in CA.