Survey of TCP Improvement over Multi-Hop Wireless and Wired Hybrid Networks

Standard TCP (Transmission Control Protocol) has limitations when it is used in wired and multi-hop wireless hybrid networks environment. Transmission media carrying data present a wide range of characteristics in multi-hop wireless and wired hybrid networks, some of which may cause a degradation of TCP performance. Much work has been conducted on the performance of TCP under different networks environment. A lot of efforts are made to improve the performance of TCP over wireless and wired hybrid networks. Most of them adapt TCP to multi-hop wireless and wired hybrid networks by modifying the standard TCP. Two main approaches are proposed: one focuses on the modification of one layer of OSI model, namely layered design; and the other improves TCP performance by modifying multi-layer, namely cross-layer design. In this paper, some different characteristics between wireless networks and wired networks are analyzed, then some key factors that influence TCP performance under wireless networks are discussed, and some difficult issues are pointed out to improve the performance of TCP over wired and wireless hybrid networks. Some research work about TCP performance under wired and wireless networks environment is analyzed and summarized. Finally, some possible research trends of the development of TCP over multi-hop wireless and wired hybrid networks in the future are proposed.