Upload Your Data Faster: Driver-Queue based Congestion Control for Wireless Networks

Data upload applications such as streaming of live videos and cloud services bring convenience to our lives. However, the Quality of Experience in wireless networks is often unsatisfactory. One of the reasons is, wireless communication is vulnerable to unpredictable factors such as rapid change of channel and competition of channel resources, leading to hysteresis and inaccuracy when performing a congestion control algorithm. To mitigate this problem, we analyzed the relationship between the real-time length of the NIC driver queue at the sender and the end-to-end transmission performances, and found a strong correlation between them. The reason is, when the wireless link is the first hop of data upload, the bottleneck mostly occurs at this hop, thus causing the accumulation of packets on the NIC driver queue. Based on this observation, we designed QCC, a congestion control algorithm that adjusts the congestion window (cwnd) according to the residual queue length after each round of NIC transmission. Specifically, the cwnd will be quickly reduced when this queue length is large to mitigate congestion, and gradually increased when it is small to increase link utility. By this means, QCC can track the time-varying wireless links quickly and accurately to achieve both high throughput and low latency. We evaluate QCC on both real-world Wi-Fi and cellular network implementations. Our experiment results reveal that QCC can achieve 2.04X lower delays than that of BBR while ensuring the similar link utilization rate as BBR (99% of BBR's throughput).