Design of a Transport Layer Protocol for 4G Wireless Systems, Mobility

Abstract

Mobility computing is the network-access paradigm of the future. Future network protocols will be 4G defined over an entirely packet-switched network with digital network elements, high bandwidth and built-in network security. The bandwidth provided will be 100Mbps for stationary objects and 20 Mbps while in motion. 4G wireless networks will support global roaming and service portability across multiple wireless and mobile networks, for example from a cellular network to a satellite-based network to a high-bandwidth wireless LAN. TCP Performance degrades severely on a wireless link due to higher Bit Error Rate, Mobility, Limited Capacity, Non Uniform Error Profile and frequent Disconnections. We propose a new transport layer protocol for 4G Wireless Systems, compatible with the existing TCP/ IP implementations that combines the best of the currently proposed algorithms and our own new congestion control algorithm. We designed an optimized congestion control algorithm for the wireless link that provides connection oriented, reliable data service with graceful handovers and ability to recover from frequent disconnections. The protocol deals with high bit error rate by implementing split connections with local fast retransmissions. It uses Zero Window Advertisement to accomplish smooth handover under inter-wireless cell mobility. Several other methods have been proposed to overcome TCP-over-wireless faults including split-TCP connection, triple-acknowledgements and acknowledgment caching. Each of these methods improves the efficiency of TCP by improving a single fault aspect, while our proposal combines compatible improvements into an efficient and reliable protocol.