IEEE 802.11n系统最优包长和聚合个数调节算法

为了在非理想信道和给定时延约束下提高IEEE 802.11n系统的吞吐量,推导了有传输差错条件下采用聚合后一次成功发送的平均数据量;将该数据量代入描述理想信道DCF系统的Markov模型的饱和吞吐量表达式,得到非理想信道下DCF系统的饱和吞吐量计算式;分析DCF机制下采用数据包聚合方案的平均时延及各退避阶的平均时延,将业务的时延约束转化为对平均时延的限制;在平均时延限制下,提出一种根据信道状态和所得计算式动态调节包长和聚合个数的算法,使系统的饱和吞吐量最大.仿真结果证实采用最优数据包长和聚合个数调节算法的系统饱和吞吐量明显高于用固定包长和聚合个数的方案.

Algorithm of optimal packet size and aggregation number for IEEE 802.11n system

In order to improve the system throughput of IEEE 802.11n under delay constraint,the average data quantity of one transmission with aggregation under non-ideal channel condition(when transmission error exists) is derived.The calculating formula of saturation throughput of distributed coordination function(DCF) system in non-ideal channel condition is obtained by inlaying the average data quantity into the mathematical expression of saturation throughput in Markov model which describes the DCF system in ideal channel condition.Analysis is presented on the average delay of system and each backoff stage of DCF with aggregation scheme to transform the delay constraint to the limit of average delay.To maximize the saturation throughput,the packet size and aggregation number are dynamically adjusted according to the variable channel conditions under the limit of average delay.The simulation results show that the system throughput from the adjusting algorithm is obviously higher than that from fixed packet size and aggregation number scheme.