Research On Congestion Control Scheme For Satellite Network

With the growing demand for multimedia communications and growing bandwidth, next generation of Global Networks is developing towards a heterogeneously combination of next generation of Internet, Mobile Communication Networks and Satellite Communications Network. There is no doubt that Satellite Network will play a much more important role in Global Network. However, new QoS requirements of Satellite Network are made as the development of bandwidth. Ensuring the the efficiency, stability and robust of transmission over satellite become a crucial. Hence research on congestion control scheme over satellite network has a great signification.On the basis of studying congestion control theory, and from the characteristics of satellite network, a research into congestion control scheme for satellite network is carried out. Main contents are as follows:(1) On the basis of studying the inapplicable of traditional TCP over satellite and analysing classical TCP congestion algorithms for satellite network, a TCP algorithm base on Bandwidth estimation enhanced Window recover and Error distinction algorithm called TCP-BRE is proposed. TCP-BRE accelerate the increase speed of window value, which is based on Available Bandwidth Estimation. By importing a accelerate factor related to window value from last congestion, TCP-BRE increase the window recovery speed when packet is lost. A loss distinction is added to distinct the reason why packets lost. Simulation results in OPNET demonstrate that TCP-BRE spends less time to complete transimission of short fluid of small data, increase TCP stable throuput effectively, and keep good performance under high error rate enviroment in satellite network. TCP-BRE increase resoure utilization of satellite network.(2) After analysing classical Active Queue Management scheme, their inapplicablity for satellite network is show. Base on REM, an Error rate-based Adaptive REM (EAREM) algorithm is proposed for on-board satellite system. An error rate mismatch term is added into the EAREM’s price, meanwhile, parameter adjustment mechanism is improved when queue length is far away from the reference length. Simulation results in OPNET demonstrate that compared to REM and AREM, EAREM can significantly reduce the marking probability, keep the queue length stable, and allow properly allocation of bandwidth based on channel error rate condition in satellite network. Moreover, in the circumstances that error rate change, EAREM performs a good adaptation.(3) On the basis of analysing Stochastic Fluid Model thoery for buffer threshold optimization problem, an SFM dynamic buffer threshold optimization algorithm based on random experiment method. Stochastic Fluid Model with input feeback mechanism is proposed; in the balance of dropping rate and delay, an cost function is constructed; random experiment method is used to achieve dynamic buffer threshold optimization considering computing ability of on-board router in this algorithm. Simulation results in OPNET demonstrate that SFM dynamic buffer threshold optimization algorithm based on random experiment method has a great convergence performance, fast convergence is achieved when buffer threshold have different initial values. Less complexity of algorithm makes it easily to be deployed in on-board routers. Key parameters such as balance factor and feedback factor, ratio of input application rate’s influence is studied in depth in this paper. The algorithm has certain use for reference of buffer management in on-board routers.