Dynamic Wlan Transmission Optimization Based On The Frame Aggregation Mechanisms

Along with wide use of wireless network, more attention is paid on the efficiency and performance. IEEE 802.11 n proposes a frame aggregation technology, which can increase the transmission bandwidth of wireless networks effectively. This paper researches on dynamic frame aggregation strategy, which has important theoretical and application value.First, the research status of the MAC layer frame aggregation is introduced, the performance of the fixed frame length frame polymerization is analysised. Then, based on the BER of WLAN, the best frame length is achieved in order to maximum the network throughput. An adaptive frame aggregation algorithm(Adaptive Frame Aggregative based on BER, AFABB) is put forward according to the current channel bit error rate, which can adjust the aggregation frame length dynamically to obtain the maximum throughput. Finally, 802.11 MAC of the NS2 simulation software is extended and improved. Simulation scenarios is built to verify the efficiency of proposed algorithm, simulation result shows the feasibility of the algorithm. Specific work is as follows:(1) By the model of Markov chain, the performance of fixed length frame aggregative is analysised for A-MSDU、A-MPDU and two stage frame aggregation. A-MPDU can achieve good performance between channel utilization and latency. Because the channel bit error rate changes dynamic, fix frame length aggregative algorithm can not get the maximum throughput.(2) According to the theoretical model, the optimum frame length can be achieved under a certain channel bit error rate to get the maximum channel utilization. On this basis, puts forward the adaptive frame aggregation algorithm, which adjusts the aggregation frame length by detecting the change of the current channel bit error rate to improve the channel utilization.(3) The original NS2 simulation software gets a packet each time, can not support frame aggregation. The NS2 simulation software is improved by increasing the cache on the 802.11 MAC to get more packets to supports frame aggregation. Simulation scenarios is built to verify the AFABB algorithm. The simulation results show that compared with the fixed frame length strategy, AFABB can get higher channel utilization according to some channel bit error rate.