Clients automatically try alternate servers; if all servers are down, clients do exponential backoff to avoid flooding the servers when they come back up 客戶端能自動對每個服務(wù)器輪流嘗試連接;如果所有的服務(wù)器都出問題了,客戶端會備份結(jié)果并暫停與服務(wù)器的連接,以免服務(wù)器恢復(fù)運作時對服務(wù)器造成泛洪式攻擊。
Analysis and simulation results show that, compared with the ieee802.11 binary exponential backoff ( beb ) algorithm and other algorithms that have been employed to address the fairness problem, the proposed qbwf algorithm is simpler and practical . also, by choosing appropriate parameters, the qbwf algorithm can effectively improve the channel access fairness and achieve a preferable trade-off between fairness and throughput 分析與仿真結(jié)果表明,與ieee802.11標準的二進制指數(shù)退避(beb)算法和其它改善信道接入公平性的算法相比,本文算法更為簡單實用,且對于合適的參數(shù)取值,本文算法能有效地改善信道接入的不公平性,并能在信道吞吐量的下降和信道接入公平性的改善之間達到一個較好的折衷。
Simulation is operated with ns2 under linux, and the simulation results show that, the presented algorithm is simpler and more practical, while it can improve the fairness index of ad hoc network to a large extent compared with the ieee802.11 binary exponential backoff ( beb ) algorithm . it can make better use of the wireless channel by dynamically adjusting its backoff timer according to the network's contest situation . in addition, service differentiation can be achieved among flows with different qos requirements and thus the qos for medium access control in ad hoc network is improved 通過在linux系統(tǒng)下利用networksimulator(ns2)仿真工具對算法進行計算機仿真分析,結(jié)果表明,與ieee802.11標準采用的二進制指數(shù)退避(beb)算法相比,該文所提算法更簡單、高效,它能在很大程度上提高adhoc網(wǎng)絡(luò)信道接入的公平性,并能動態(tài)地提供服務(wù)區(qū)分,保障對多媒體等多種實時業(yè)務(wù)的傳輸需求,同時,算法可以根據(jù)網(wǎng)絡(luò)當(dāng)前具體的競爭激烈情況,動態(tài)調(diào)整退避時間值,從而提高信道的利用率。