Special Issue: Reliable Transport Protocols for Mobile Computing

In recent years mobile computing has experienced significant growth, mainly due to the integration of wireless networks with the wired Internet. This integration itself experienced several stages of evolution: from the functional issues of network heterogeneity to the optimization of the Internet protocols. Currently, the design issues of reliable protocols for mobile computing possess a fundamental locus. More precisely, performance evaluation, throughput optimization, energy saving, and network/device functionality within the layered Internet call for further attention. Within this context, this special issue addresses the design concerns of reliable protocols for mobile computing. We have selected seven papers for presentation in the special issue, from a large pool of submitted papers in response to our call for papers. The first paper, authored by the guest editors, discusses open issues on the design of the dominant Internet protocol, the Transmission Control Protocol (TCP). The paper classifies the recent work based on the functionality of the proposed modifications, realizes the need for new performance metrics and presents selected results of two recent approaches to mobile TCP, namely TCP-Probing and WTCP. The paper by Eckhardt and Steenkiste investigates the possibility of dealing with wireless link errors by combining a link-level local error control with error-sensitive link scheduling. Having a direct target the improvement of TCP over wireless networks, Chen, Hsiao, Hou, Ge, and Fitz propose the use of Syndrome. Syndrome is a light-weight approach to improving TCP’s throughput performance. The combination of TCP’s sequence numbers and the additional base station-attached numbers allow for detection of the error’s location (i.e., wired vs. wireless). This is a significant step toward error correction especially owing to the fact that the base station does not need to buffer packets or a significant amount of states. Vaidya, Mehta, Perkins, and Montenegro propose an alternative TCPunaware technique where the wireless client delays duplicate acknowledgments to avoid fast retransmit at the sender. This is in sharp contrast to TCP-aware techniques such as Snoop. Along the lines of performance evaluation, the paper by Xu and Saadawi compares the performance of various TCP versions over ad-hoc (multi-hop wireless) networks and suggests appropriate parameter tuning in order for those versions to behave appropriately. Emphasizing the energy/throughput tradeoff, Zorzi, Rossi, and Mazzini investigate the performance of TCP over wideband CDMA air interface. Such interfaces are typical of third-generation wireless networks. The authors introduce a universal throughput curve and exploit the possibility of selecting an optimal power control threshold thereby optimizing the tradeoff between throughput gains and energy expenditure. Finally, to deal with reliable handoffs, the paper by Jobin, Tripathi, Gokhale and Faloutsos quantifies the effectiveness of a predictive reservations scheme using metrics which characterize the mobility profile of users. We would like to offer special thanks to the reviewers and to the authors for their contribution to this special issue.