The Design And Implementation Of Adaptive Congestion Control Strategy Of Intelligent Gateway In Heterogeneous Networks

Traditional TCP(Transmission Control Protocol) has good performance in wiredchannels with high bandwidth, low bit error rate (BER) and short delay. However, inwireless channels with low bandwidth, high BER and long delay, due to thecharacteristic of "Always Congestion" judgment on network packet loss, thetraditional TCP can’t distinguish the packet loss reason correctly. As a result, it causesexcessive activation of Congestion Avoidance Mechanism, which makes the sendingwindow stay in low level in most time, significantly affects the TCP transmissionperformance.To deal with the performance degradation of current TCP protocols in wired andwireless hybrid networks, caused by the factors such as long delay and high BER, thispaper proposes a novel, Feedback Theory-based adaptive traffic control algorithm—TCP-Adaptive algorithm. It firstly selects the network parameters, average PacketLoss Rate (PLR), round trip time Mean Deviation Product (MDP) and networkTransmission Performance Index (TPI), uses fuzzy method to make comprehensiveevaluation of network status, yielding the network transmission performance index TPI.Secondly, in accordance with the value of TPI, it adopts corresponding control strategyagainst network data sending rate. Finally, it brings TPI back to the parameter inputside for iteration, and compares it with expected (or optimal) target value and adaptsthe factors of the input parameters in order to improve the accuracy of algorithm. Theprocess above being executed repeatedly, at last it establishes an adaptive trafficcontrol algorithm.The simulation shows that the newly proposed TCP adaptive congestion controlalgorithm, based on fuzzy packet loss differentiation method, is able to bringsatisfactory reflection of the real congestion status of hybrid networks, has betternetwork adaptability, and has better congestion control result than current main TCP algorithms, i.e. TCP, TCP-Reno, TCP-New Reno and TCP-Vegas. Under differentBERs, the new proposed protocol has higher throughputs. Furthermore, the higher thewireless BER is, the more outstanding the algorithm’s performance superioritybecomes.