The mobility of the targets asks for high requirements of the locating speed in indoor positioning systems.The standard medium access control(MAC)algorithm will often cause lots of packet conflicts and high transmissi...The mobility of the targets asks for high requirements of the locating speed in indoor positioning systems.The standard medium access control(MAC)algorithm will often cause lots of packet conflicts and high transmission delay if multiple users communicate with one beacon at the same time,which will severely limit the speed of the system.Therefore,an optimized MAC algorithm is proposed based on channel reservation to enable users to reserve beacons.A frame threshold is set to ensure the users with shorter data frames do not depend on the reservation mechanism,and multiple users can achieve packets switching with relative beacon in a fixed sequence by using frequency division multiplexing technology.The simulation results show that the optimized MAC algorithm proposed in this paper can improve the positioning speed significantly while maintaining the positioning accuracy.Moreover,the positioning accuracy can be increased to a certain extent if more channel resources can be obtained,so as to provide effective technical support for the location and tracking applications of indoor moving targets.展开更多
A dynamic slots allocation algorithm is proposed for the MAC protocol in TDMA based wireless ATM networks, and it takes the status of the output buffer of the VBR video source, the slots currently occupied by the VBR...A dynamic slots allocation algorithm is proposed for the MAC protocol in TDMA based wireless ATM networks, and it takes the status of the output buffer of the VBR video source, the slots currently occupied by the VBR video source and the total slots allocation situation in the cell into consideration before the assignment of slots. The result of the simulation shows that by this algorithm the MAC protocol yields higher statistics duplex gain of the channel.展开更多
太赫兹无线局域网(Wireless Local Area Network,WLAN)是实现大带宽、短距离无线接入的重要技术途径,受太赫兹波束极窄特性影响,现有的低频WLAN媒体接入控制(Media Access Control,MAC)地址已不能直接复用于太赫兹WLAN。针对太赫兹波束...太赫兹无线局域网(Wireless Local Area Network,WLAN)是实现大带宽、短距离无线接入的重要技术途径,受太赫兹波束极窄特性影响,现有的低频WLAN媒体接入控制(Media Access Control,MAC)地址已不能直接复用于太赫兹WLAN。针对太赫兹波束极窄特性导致的信道利用率低问题,提出了负载自适应的混合接入MAC协议(Load-Adaptive Hybrid Access MAC Protocol,LAHA-MAC)。通过记录上一次工作扇区的节点数量自适应地选择信道接入方式。当工作扇区节点数量N小于接入方式选择阈值N*时,该机制采用基于竞争的接入方式,能够同时获得较高的吞吐量和较低的端到端时延;当节点数量N大于接入方式选择阈值N*时,该机制采用基于调度的接入方式,能够避免节点之间的碰撞,提高传输效率。考虑到可能出现的接入方式选择错误,该机制能够实现灵活地接入方式切换。当信道中节点碰撞次数N col大于切换阈值N*col时,将基于竞争的接入方式切换为基于调度的接入方式。仿真结果表明,该机制能够在网络负载动态变化的情况下有效提高信道利用率。展开更多
基金Supported by the National Natural Science Foundation of China(No.61771186)Outstanding Youth Project of Heilongjiang Natural Science Foundation(No.YQ2020F012)Undergraduate University Project of Young Scientist Creative Talent of Heilongjiang Province(No.UNPYSCT-2017125)。
文摘The mobility of the targets asks for high requirements of the locating speed in indoor positioning systems.The standard medium access control(MAC)algorithm will often cause lots of packet conflicts and high transmission delay if multiple users communicate with one beacon at the same time,which will severely limit the speed of the system.Therefore,an optimized MAC algorithm is proposed based on channel reservation to enable users to reserve beacons.A frame threshold is set to ensure the users with shorter data frames do not depend on the reservation mechanism,and multiple users can achieve packets switching with relative beacon in a fixed sequence by using frequency division multiplexing technology.The simulation results show that the optimized MAC algorithm proposed in this paper can improve the positioning speed significantly while maintaining the positioning accuracy.Moreover,the positioning accuracy can be increased to a certain extent if more channel resources can be obtained,so as to provide effective technical support for the location and tracking applications of indoor moving targets.
文摘A dynamic slots allocation algorithm is proposed for the MAC protocol in TDMA based wireless ATM networks, and it takes the status of the output buffer of the VBR video source, the slots currently occupied by the VBR video source and the total slots allocation situation in the cell into consideration before the assignment of slots. The result of the simulation shows that by this algorithm the MAC protocol yields higher statistics duplex gain of the channel.
文摘太赫兹无线局域网(Wireless Local Area Network,WLAN)是实现大带宽、短距离无线接入的重要技术途径,受太赫兹波束极窄特性影响,现有的低频WLAN媒体接入控制(Media Access Control,MAC)地址已不能直接复用于太赫兹WLAN。针对太赫兹波束极窄特性导致的信道利用率低问题,提出了负载自适应的混合接入MAC协议(Load-Adaptive Hybrid Access MAC Protocol,LAHA-MAC)。通过记录上一次工作扇区的节点数量自适应地选择信道接入方式。当工作扇区节点数量N小于接入方式选择阈值N*时,该机制采用基于竞争的接入方式,能够同时获得较高的吞吐量和较低的端到端时延;当节点数量N大于接入方式选择阈值N*时,该机制采用基于调度的接入方式,能够避免节点之间的碰撞,提高传输效率。考虑到可能出现的接入方式选择错误,该机制能够实现灵活地接入方式切换。当信道中节点碰撞次数N col大于切换阈值N*col时,将基于竞争的接入方式切换为基于调度的接入方式。仿真结果表明,该机制能够在网络负载动态变化的情况下有效提高信道利用率。
文摘着眼于IEEE802.11MAC协议的改进与优化。根据马尔可夫理论分析了MAC层性能,首次提出利用平均冲突次数来代替以往算法中对竞争终端个数的精确测量,在此基础上将冲突权值引入DCF(distributed coordi-nation function)机制中,从而提出了基于冲突权值的动态优化方案(dynamic optimization algorithm based on theconflict weights,DOBCW)。经仿真对比测试,改进方案DOBCW在系统吞吐量和系统时延方面很具优势,最高可提高两倍的系统吞吐量和降低80%的系统时延。而在对系统稳定性的考察中,改进方案DOBCW的吞吐率和系统时延也表现得比原有机制更为稳定。通过仿真实验,有效地证明了改进方案高效性。
