Abstract—Delivering streaming video over wired/wireless networks is challenging, since link errors commonly compromise throughput performance, smoothness, and eventually impair the perceptual video quality. We combine an efficient Additive Increase Multiplicative Decrease (AIMD) transport protocol with an end-to-end mechanism that effectively decouples wireless from congestion loss to abolish the damage of error-induced multiplicative decrease on flow throughput and smoothness. Based on simulation results, we show that our combined approach provides the desired functionality to bind operationally wired and wireless links, within the framework of bandwidth efficiency, smoothness and fairness. The proposed mechanism can be easily adapted and incorporated into existing AIMD protocols, allowing them to utilize more efficiently wireless resources. Index Terms—transport protocols, wireless networks, QoS, video streaming.

A Retransmission Time Out (RTO) is inevitable, when the retransmission of a packet fails to reach the receiver. An RTO compels TCP to reduce packet flow drastically. However, in case of an RTO resulting from retransmission failure caused by the channel noise, reduction in the flow is inappropriate. The problem is compounded when a TCP sender is forbidden to continue transmission till the occurrence of the timeout. In this paper, we investigate the impact of such RTOs with the help of an empirical mathematical analysis. The analysis presented in the paper calculates the idle period of the sender in terms of number of RTTs, which depends on the value of congestion window before the timeout. The mathematical analysis is supported by the results of simulation based experiments and the evaluation of a scheme that improves TCP performance in case of avoidable timeouts caused by the loss of retransmission on an erroneous wireless link.

With the growing demand of Internet services, network operators have put significant efforts to improve network error resilience and efficiency. Since there exist different wired/wireless technologies for Internet access such as digital subscriber line (DSL), Ethernet, and worldwide interoperability for microwave access (WiMax), a mobile host can use multiple access networks simultaneously with multipath transmission. Taking the advantage of heterogeneous environment, multipath transmission through the Internet can improve service reliability and network flexibility. Ensuring a reliable end-to-end connection-oriented communication with satisfactory quality of service (QoS) and maintaining congestion control and flow control are the main responsibilities of the Transmission Control Protocol (TCP), the dominant transport layer protocol in the Internet. In this paper, we survey the state-of-the-art of multipath transmission techniques for QoS provisioning in wireless Internet access, focusing on the end-to-end transport layer protocols. The main challenges for the design of multipath TCP are reviewed, and the existing transport layer congestion control schemes are categorized. Multipath TCP and stream control transmission protocol (SCTP)-based transport layer protocols are discussed, and their limitations and/or impractical assumptions are addressed. Open research issues on the development of an effective, efficient, and practical multipath TCP protocol are summarized.