IEEE 802.11ah is a new Wi-Fi standard for sub-1Ghz communications,aiming to address the challenges of the Internet of Things(IoT).Significant changes in the legacy 802.11 standards have been proposed to improve the ne...IEEE 802.11ah is a new Wi-Fi standard for sub-1Ghz communications,aiming to address the challenges of the Internet of Things(IoT).Significant changes in the legacy 802.11 standards have been proposed to improve the network performance in high contention scenarios,the most important of which is the Restricted Access Window(RAW)mechanism.This mechanism promises to increase the throughput and energy efficiency by dividing stations into different groups.Under this scheme,only the stations belonging to the same group may access the channel,which reduces the collision probability in dense scenarios.However,the standard does not define the RAW grouping strategy.In this paper,we develop a new mathematical model based on the renewal theory,which allows for tracking the number of transmissions within the limited RAW slot contention period defined by the standard.We then analyze and evaluate the performance of RAW mechanism.We also introduce a grouping scheme to organize the stations and channel access time into different groups within the RAW.Furthermore,we propose an algorithm to derive the RAW configuration parameters of a throughput maximizing grouping scheme.We additionally explore the impact of channel errors on the contention within the time-limited RAW slot and the overall RAW optimal configuration.The presented analytical framework can be applied to many other Wi-Fi standards that integrate periodic channel reservations.Extensive simulations using the MATLAB software validate the analytical model and prove the effectiveness of the proposed RAW configuration scheme.展开更多
OFDM(orthogonal frequency division multiplexing)系统内存在多个正交子载波,其对于定时和频率偏移特别敏感,因此时间和频率同步显得尤为重要。参考IEEE802.11a物理层帧结构,分析了802.11a协议符号同步算法和其存在的问题,介绍了一种...OFDM(orthogonal frequency division multiplexing)系统内存在多个正交子载波,其对于定时和频率偏移特别敏感,因此时间和频率同步显得尤为重要。参考IEEE802.11a物理层帧结构,分析了802.11a协议符号同步算法和其存在的问题,介绍了一种改进的互相关同步算法。仿真结果表明,改进算法在接收信号存在频率偏移时,能改善原算法性能,提高定时估计的准确性。展开更多
IEEE 802.11ax系统中站点(Station,STA)数量众多和潜在的高数据包冲突率导致无线局域网通信效率显著降低,本文针对上行多用户传输中的无效帧填充问题,以每轮传输中用户组的传输延迟为优化目标,提出一种多用户调度和资源分配算法。基于OF...IEEE 802.11ax系统中站点(Station,STA)数量众多和潜在的高数据包冲突率导致无线局域网通信效率显著降低,本文针对上行多用户传输中的无效帧填充问题,以每轮传输中用户组的传输延迟为优化目标,提出一种多用户调度和资源分配算法。基于OFDMA上行调度接入中动态传输时间的帧交互方案,接入点(Access Point,AP)结合STA提供的信道状态信息(Channel State Information,CSI)和缓冲区状态报告(Buffer State Report,BSR)信息来确定各站点的传输延迟;针对最小化组内用户传输延迟差的优化问题,设计传输机会(Transmit Opportunity,TXOP)时长内用户分组策略及资源块(Resource Unit,RU)-STA匹配方案;进而以最大化信道利用率为目标,确定各站点的发射功率,同时保障每组用户的传输速率。与参考调度策略对比,本文提出的调度和资源分配算法在连续多帧传输的信道利用率上有10%~15%的提升,同时也保证了用户间传输速率的稳定性。展开更多
基金supported by the Spanish Ministry of Science,Education and Universities,the European Regional Development Fund and the State Research Agency,Grant No.RTI2018-098156-B-C52.
文摘IEEE 802.11ah is a new Wi-Fi standard for sub-1Ghz communications,aiming to address the challenges of the Internet of Things(IoT).Significant changes in the legacy 802.11 standards have been proposed to improve the network performance in high contention scenarios,the most important of which is the Restricted Access Window(RAW)mechanism.This mechanism promises to increase the throughput and energy efficiency by dividing stations into different groups.Under this scheme,only the stations belonging to the same group may access the channel,which reduces the collision probability in dense scenarios.However,the standard does not define the RAW grouping strategy.In this paper,we develop a new mathematical model based on the renewal theory,which allows for tracking the number of transmissions within the limited RAW slot contention period defined by the standard.We then analyze and evaluate the performance of RAW mechanism.We also introduce a grouping scheme to organize the stations and channel access time into different groups within the RAW.Furthermore,we propose an algorithm to derive the RAW configuration parameters of a throughput maximizing grouping scheme.We additionally explore the impact of channel errors on the contention within the time-limited RAW slot and the overall RAW optimal configuration.The presented analytical framework can be applied to many other Wi-Fi standards that integrate periodic channel reservations.Extensive simulations using the MATLAB software validate the analytical model and prove the effectiveness of the proposed RAW configuration scheme.
文摘OFDM(orthogonal frequency division multiplexing)系统内存在多个正交子载波,其对于定时和频率偏移特别敏感,因此时间和频率同步显得尤为重要。参考IEEE802.11a物理层帧结构,分析了802.11a协议符号同步算法和其存在的问题,介绍了一种改进的互相关同步算法。仿真结果表明,改进算法在接收信号存在频率偏移时,能改善原算法性能,提高定时估计的准确性。
文摘IEEE 802.11ax系统中站点(Station,STA)数量众多和潜在的高数据包冲突率导致无线局域网通信效率显著降低,本文针对上行多用户传输中的无效帧填充问题,以每轮传输中用户组的传输延迟为优化目标,提出一种多用户调度和资源分配算法。基于OFDMA上行调度接入中动态传输时间的帧交互方案,接入点(Access Point,AP)结合STA提供的信道状态信息(Channel State Information,CSI)和缓冲区状态报告(Buffer State Report,BSR)信息来确定各站点的传输延迟;针对最小化组内用户传输延迟差的优化问题,设计传输机会(Transmit Opportunity,TXOP)时长内用户分组策略及资源块(Resource Unit,RU)-STA匹配方案;进而以最大化信道利用率为目标,确定各站点的发射功率,同时保障每组用户的传输速率。与参考调度策略对比,本文提出的调度和资源分配算法在连续多帧传输的信道利用率上有10%~15%的提升,同时也保证了用户间传输速率的稳定性。
