1. TCP Performance over EDGE 
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Contact Hwee-Pink Tan [tanhp(at)tcd(dot)ie], Anthony Lo [A(dot)Lo(at)ewi(dot)tudelft(dot)nl] and Winston K. G. Seah [winston(at)i2r(dot)a-star(dot)edu(dot)sg]

Context
Enhanced Data rates for Global Evolution (EDGE) provides an evolutionary path from existing cellular systems such as Global Systems for Mobile Communications (GSM) for delivering higher data bit rate services that facilitate wireless Internet access. Thus, EDGE only defines a new radio access technology to achieve higher bit rates.

Overview
We investigate the performance of Transmission Control Protocol / Internet Protocol (TCP/IP) over the enhanced packet-switched transmission mode of EDGE, i.e., Enhanced General Packet Radio Service (EGPRS). The Network Simulator (ns) tool was used in the simulation. The performance of TCP was examined under various channel conditions with and without the link adaptation scheme of EGPRS. The link adaptation scheme improves the TCP performance under poor channel conditions. In the simulation, two different methods, BLock Error Rate (BLER) and the average of measured Carrier-to-Interference ratio (C/I), were employed to determine the channel quality and subsequently to select the most appropriate coding scheme to maximize the TCP throughput. The TCP throughput obtained using the BLER method is higher under poor channel conditions, while the throughput based on the average of measured C/I out-performs BLER under good channel conditions. As a result, we proposed a hybrid method, which selects the BLER method for poor channel conditions and the average C/I for good channel conditions. The simulation results show that the throughput obtained using the hybrid method is superior compared to the individual methods.

Related Publications

  • Hwee-Pink Tan, Anthony Lo and Winston Seah. Performance Evaluation of TCP/IP over EDGE. To appear in Proc. of the Tenth International Conference on Computing and Information, Kuwait, Nov 2000.

  • Hwee-Pink Tan, Anthony Lo and Winston Seah. TCP Performance over EGPRS / EDGE . M.Sc. Research Thesis, National University of Singapore, June 2000.



    • 2. TCP Performance over Routing Protocols in Mobile Ad-Hoc Networks 
    Contact Hwee-Pink Tan [tanhp(at)tcd(dot)ie], Md. Abdullah-Al-Mamun [mamunict98(at)yahoo(dot)com] and M. Mahbubur Rahman [drmahbub_07(at)yahoo(dot)com]

    Context
    A mobile ad hoc network (MANET) is a collection of wireless nodes that can be set up dynamically anywhere and anytime without using any pre-existing network infrastructure. Due to node mobility and variability of link quality, the interconnections between nodes change on a continual and arbitrary basis, giving rise to changing network topology. An ad hoc routing protocol determines the way to route packets between computing devices in a MANET. Although many ad hoc routing protocols have been proposed, little is known about the actual performacne of these protocols, and very few attempts have been made to compare their performance in a realistic manner.

    Overview
    We investigate the performance of TCP of various (single-hop and multi-hop) routing protocols for MANETs. Using ns-2, we evaluate the TCP window size, throughput and packet delay over a single TCP connection. Our results suggest that the various performance metrics are tightly related, and that TCP performance is tightly coupled with the stability and length of the routing path of each routing protocol.

    Related Publications

  • M. Mamun, M. Rahman and Hwee-Pink Tan. Performance Evaluation of TCP over Routing Protocols for Mobile Ad-Hoc Networks. Proc. of 1st Chinacom, October 2006.