Experimental Evaluation on Throughput Performance of Asymmetric Carrier Aggregation in LTE-Advanced

This paper presents laboratory experimental results on the throughput performance of asymmetric carrier aggregation between the uplink and downlink using an LTE-Advanced testbed. The implemented base station (BS) and mobile station (MS) transceivers have transmission bandwidth capability of up to 100 MHz (5 component carriers (CCs)) and 40 MHz (2 CCs) in the downlink and uplink, respectively. The testbed also features CC-specific adaptive modulation and channel coding (AMC) and hybrid automatic repeat request (HARQ) functionalities based on the actually transmitted control signaling. The experimental results show that, in the uplink, CC-based AMC using up to 64QAM high-order modulation is effective in increasing the user throughput in multipath fading channels and achieves a throughput greater than 100 Mbps using carrier aggregation with 2 CCs and 1-by-2 SIMO. The results also show that when the uplink control information (UCI) corresponding to 5 downlink CCs is multiplexed onto the uplink shared channel (PUSCH), the required block error rate (BLER) of the UCI below 10-2 is almost satisfied by appropriately setting the offset value, , for adjusting the channel coding rate of UCI although AMC with high-order modulation is applied to the UCI as well. Furthermore, we show that when carrier aggregation with 5 CCs and 2-by-2 MIMO multiplexing are applied in the downlink, high throughput greater than 500 Mbps (thus, half of the 1 Gbps that can be achieved using 4-by-4 MIMO multiplexing) is achieved at the average received signal-to-noise power ratio (SNR) of approximately 25 dB when CC-specific AMC considering UCI error is applied.