Improving TCP performance over mobile data networks with opportunistic retransmission

Recent advances in high-speed mobile networks have revealed new bottlenecks in the ubiquitous TCP protocol deployed in the Internet. In addition to differentiating random loss from congestion loss, our experiments revealed that TCP´s flow control mechanism can become a significant bottleneck during TCP´s loss recovery phase, resulting in bandwidth efficiency as low as 0.05. To tackle this problem we develop a novel opportunistic retransmission algorithm to enable the TCP sender to transmit new packets even before the loss recovery phase is completed, resulting in significant improvement in TCP´s bandwidth efficiency. We applied the proposed mechanism to three TCP variants and developed system models to analyze their performance. Experimental results showed that TCP´s throughput can be improved by up to 56% in real-world settings.