A Study Of TCP Key Technologies Over Wireless Networks

With the fast development of communication, the abilities of transmitting and catching information have been enhanced greatly. However, so far it hasn't been achieved to exchange information wherever. Obviously, it is only wireless communication to reach the goal for the reasons of cheaper cost, building network wherever, internetworking wherever and so on. Comparing to wired network, there are many different characteristics in wireless environments, such as higher error rate, longer delay, lower bandwidth, frequent mobility and so on, which result in difficulty to guarantee network performances and qualities of service. So traditional TCP/IP protocols can't be directly adapted to wireless networks. The study of key theories and technologies for wireless networks has been becoming an important task in communication field. This paper will focus on TCP key technologies over wireless networks. TCP, transmission control protocol for providing reliable service, has being widely used in Internet. TCP plays an important role in guaranteeing network performances. The design of TCP mainly aims at system stability, protocol compatibility, traffic fairness, resource utility, network congestion control and so on. As for the reasons presented above, TCP can't be directly adapted to wireless networks. The study of wireless TCP are as follows: I TCP strategies for wireless networks dealing with error control, congestion control and corruption-based TCP rate adjustment; II Technologies about TCP congestion verdict and implicit loss detection of TCP packet under wireless environment; III A novel explicit error bit notification mechanism. It is very efficient to adopt this mechanism to notify corruption loss information to TCP sender even under high bit error rate and multi-hop wireless environment; IV Two suits of congestion-based TCP congestion control mechanisms. One mechanism can efficiently mitigate the fluctuation of data sending rate in steady state while quickly tracing network state changes, and another can easily perform network resources allocation by weight between traffics under the similar communication environments. V Two suits of corruption-based TCP rate adjustment mechanisms respectively1`belonging to rate-based and window-based. Due to the mechanisms, unnecessary data lost by corruption can be greatly avoided through the decrease of data sending rate while heavy data loss rate by corruption lasts short time, which may lead to higher reliability, unnecessary energy consumption of mobile devices and less system overheads with light influence to throughput and delay. The paper is organized as follows: Chapter 1 briefly introduces wireless communication, overview of wireless TCP technologies and works in the paper. Chapter 2 outlines OSI reference framework and TCP/IP architecture. Chapter 3 briefly explains TCP in wired networks. Chapter 4 discusses TCP strategies over wireless networks dealing with error control, congestion control and corruption-based TCP rate adjustment. Chapter 5 discusses detection of data lost by corruption or congestion in wireless networks, and analyzes a novel explicit bit error notification mechanism for wireless networks. Chapter 6 details two suits of congestion-based TCP congestion control mechanisms. Chapter 7 gives two suits of corruption-based TCP rate adjustment mechanisms.