Research On Congestion Control Of TCP In Wireless Network

Recently, with the development of mobile communication technology and Internet,wireless technology is more and more important in the wireless Internet. Mobile nodes and its wireless communication links are going to be an important part in the future Internet.TCP Protocol is the most widely used protocol in the Internet, which provides reliable, robust end-to-end data transmission service. And the congestion control mechanism in TCP is one of the key techniques to keep the Internet stable. But the traditional TCP assumes that any lost packet is due to congestion, so it cannot adapt to the wireless environment of low quality links. But wireless telecommunication is characterized by high error rates and low bandwidth compared to wired networks, so when random loss occurs in wireless networks, TCP mistakes the cause for congestion and reduces the transmission rate, leading to low performance. Therefore, how to improve TCP performance under wireless networks is currently a very important topic.TCP congestion control algorithm is introduced Four-fold mechanisms are included: Slow Start, Congestion Avoidance,Fast Retransmit and Fast Recovery,which are the basis of congestion control algorithm. TCP algorithms which exist at present have been conducted the classified research. The dissertation analysis the whole performance in view of different types, and provides several kind of common TCP improved algorithm the technical comparison.The dissertation has described TCP congestion control mechanism in wireless network, discussed the limitations of the TCP congestion control mechanisms in wireless network, proposes TCP ED-Vegas, the mechanism of detecting packet corruption based on Vegas in wireless network. ED-Vegas extends TCP Vegas header options and allows the receiver to return a special ACK generated in response to packed corruption. Extensive simulations show that the mechanism can make Vegas distinguish packet corruption from congestion, avoid lots of unwanted timeouts caused by retransmitted packed to be corrupted and hence, enhanced Vegas performance.