Delay-based TCP considering the latency by data link layer of mobile broadband network

Mobile broadband networks are becoming increasingly popular, and they support many different IP based services. The Transmission Control Protocol (TCP) is a widely used protocol in the Internet. In this paper, we analyze the performance of the existing loss-based and delay-based congestion control algorithms for TCP on real mobile networks. The impact the loss-based algorithm has in terms of network latency is extremely heavy and degrades the communication quality of all flows which share the same bottleneck link. On the other hand, although delay-based TCP is able to maintain latency at a low level, its goodput is very small because the RTT increases independently of network congestion. We propose a new delay-based congestion control algorithm. To enable this algorithm to work well on mobile networks, we use a variable threshold which includes the delay caused by the data link layer. Experiments on emulated network and real network show that the algorithm can maintain the queue size and transmission delay at low levels without degrading goodput.