| With the development of wireless communications, people are not content to search, input and send information on an immobile place any longer. They hope to drop in the Internet anytime and anywhere. So mobile Internet was brought forward (mobile IP), it is the effective extension of the traditional Internet. After almost 30 years evolution of TCP/IP agreement, it has been effectively adapted to transfers, especially the TCP slow startup, the avoidance of congestion, the quick retransmission, the congestion control of quick, the resumption and the resumption mechanism. But under the mobile circumstance, the sudden error of wireless channels, the biggish changes of delayed time, the switch of mobile host computer exceeding the different zone, and the traditional TCP congestion control and resumption mechanism can't adapt to the wireless mobile environment. On the basis of this, how to improve TCP's capability in the wireless mobile environment is one of the open questions which is being discussed and studied all over the world at present. It presented the working theory of mobile IP and the traditional TCP. From data link layer, TCP itself, and application layer, three aspects it presented some methods to improve TCP's capability in wireless and mobile node and some aspects, which are in process of study. Analysed some projects according to their shortcomings.The main discussing and resolving problem of this text is analysis and simulation of improving the TCP's performance for mobile IP. As follows:1.Theoretics: On the basis of queuing, to make open feedforward network model and educe.2.programme simulation: Simulate the process of the queuing according to queue model M/M/1, programming language C, the four steps such as data coming, waiting in queue, link service and data leaving. In different parameter setting, noted down the times of data retransmission, resending the data package, the time of passing link layer, utilization ratio of link layer, average length of each queue etc. It presents the diagram of the main program and a brief instruction of the documents.3.contrast, analysis and conclusion: Analysis about the parameter of theory and simulation: the average time, the rate of retransmission, the rate of retransmission data packages, the utilization ratio, the average length of each queue. Analyse every group of data with, output graph of function and statistics to draw a direct and persuadable conclusion. The methods of analysis and simulation in estimating the enhancement of link layer have some universal significance and guiding effect.First from theory to practice: on the base of queuing and in the M/M/1 condition, it works out the simulation program; gets the simulation data through running program. According to queuing, makes a net model with retransmission and feedback, educes the expressions; then from practice to theory: Contrasts and analyses some simulation data and data in theory, proves it a correct derivation. Combine theory with practice I get the optimization value, and generalize the optimization value, suppose and forecast even point out something undecided; The third from theory to practice once more, regard the hypothesis and questions as new tasks pending further discussion and simulation. Thus move in circles, improve and perfect it gradually.In the analysis and theory derivation of quick retransmission about the mobile IP's TCP enhancement, discussed the influence of the switch of the mobile IP's exceeding the different zones for TCP 's transfers, and analysed the main reasons why the traditional TCP congestion control is not suitable for the switch of the mobile IP's exceeding the different zones.Through the period of quick retransmission to the switch of the mobile node's exceeding the different zones and the time from slow-start to stabilization (queuing and service), contrasted and analysed the two methods then drew a conclusion: The efficiency of adopting quick retransmission during the switch of mobile IP's exceeding the diff... |
PDF Full Text Request