Simulation And Improvement Of Back-off Algorithm In CSMA

In communication network, when two or more users share the same physicalchannel transmission of data, the information is superimposed, the destination cannot receive the correct data, then the sender must re-transmission until itis successfully received. However, any two terminals are built in the transmissionpaths is unrealistic, on the one hand, is costly and expand more difficult, on the otherhand is channel utilization will be very low. In communications network, randommultiple access protocol is a kind of technology that used to solve multiple users toefficient and fair use Shared communication resources.At present more popular random multi-access systems are used in bus EthernetCSMA/CD multi-access systems and in wireless LAN used CSMA/CA multi-accesssystems, this thesis shows the basic principle of CSMA/CA and CSMA/CD,thenCSMA/CD use truncated binary exponential backoff algorithm and CSMA/CA usedbinary exponential backoff algorithm to carry on the detailed analysis.CSMA/CD and CSMA/CA are widely applied to computer media access controlprotocol, in light of the network load, and has a good performance. But whennetwork, especially in negative truck real-time demand higher network, to channelutilization rate is lower, delay jitter more serious, bigger and can effectively dealwith dynamic network business of emergency. In order to effectively improve theEthernet delay jitter performance, the Ethernet adopt truncated binary exponentialbackoff algorithm was improved, the dynamic change according to the conflictsituation, the upper truncated binary exponential backoff algorithm. Given the statetransition and MAC process diagram, Network Simulation experimental results showthat delay reduced nearly50%, and basically eliminate the delay jitter. In addition tocapture effect in wireless LAN binary exponential backoff algorithm can’t guaranteeuser access of fairness to meet the growing demand of multimedia applications. Inthis thesis the binary exponential backoff algorithm, based on the development statusand existing agreement for the shortage, analyzed the common solutions. Finally,according to the change of network business forward algorithm, and the adaptivewithdrawn in data frames tail add bits of information, indicates other nodes updateretreats counter value to avoid collisions. With theoretical analysis and experimentalsimulation results show that the modified binary exponential backoff algorithm can effectively improve the user access the fairness of the information age, and meet themultimedia needs.