LoRaWAN是低功耗广域网(LPWAN)中的一种无线通信标准,为物联网的发展提供了支撑。然而,受限于扩频因子(SF)间不完全正交性的特点和LoRaWAN不具备先听后发(LBT)机制的事实,基于ALOHA的传输调度方式会引发严重的信道冲突,极大降低了LoRa(L...LoRaWAN是低功耗广域网(LPWAN)中的一种无线通信标准,为物联网的发展提供了支撑。然而,受限于扩频因子(SF)间不完全正交性的特点和LoRaWAN不具备先听后发(LBT)机制的事实,基于ALOHA的传输调度方式会引发严重的信道冲突,极大降低了LoRa(Long Range Radio)网络的扩展性。为提高LoRa网络的扩展性,提出用非坚持型载波监听多路访问(NP-CSMA)机制替代LoRaWAN中ALOHA的介质访问控制机制,通过LBT协调LoRa网络中SF相同的各个节点接入信道的时间。不同SF之间的传输则采用多种SF信号并行传输,以减少共信道中同SF干扰和避免SF间干扰。为了分析NP-CSMA对LoRa网络扩展性的影响,通过理论分析和NS3仿真对LoRaWAN与NP-CSMA构建的LoRa网络进行比较。实验结果表明,在相同的条件下,与LoRaWAN相比,NP-CSMA在网络通信负载率为1的情况下,它的理论数据包交付率(PDR)性能比LoRaWAN高58.09%。在信道利用率方面,与LoRaWAN相比,NP-CSMA的饱和信道利用率提高了214.9%,容纳的节点数量也增加了60.0%。另外,NP-CSMA的平均时延在网络通信负载率小于1.7时也低于确认型LoRaWAN,而且在扩频因子为7和10时,它用于维持信道活动检测(CAD)模式所造成的额外能耗也比LoRaWAN用于接收来自网关确认消息所需的额外能耗低1.0~1.3 mJ和2.5~5.1 mJ;充分反映了NP-CSMA可以有效提高LoRa网络的可扩展性。展开更多
低压电力线通信(Low Voltage Power Line Carrier Communication,LVPLC)的介质访问控制(Medium Access Control,MAC)协议是影响网络吞吐量的重要因素。针对LVPLC精确人工蛛网网络中由于非对称PLC信道影响而导致吞吐量相对较低的问题,改...低压电力线通信(Low Voltage Power Line Carrier Communication,LVPLC)的介质访问控制(Medium Access Control,MAC)协议是影响网络吞吐量的重要因素。针对LVPLC精确人工蛛网网络中由于非对称PLC信道影响而导致吞吐量相对较低的问题,改进了已有的p-载波侦听多路访问协议(p-persistent Carrier Sense Multiple Access,p-CSMA),提出了一种自适应载波侦听多路访问(Adaptive Carrier Sense Multiple Access,ACSMA)协议来优化有限负载下的吞吐量。该协议可通过动态调整概率,降低了数据包的冲突概率,优化了电力线信道的传输状态,最大限度地提高了吞吐量。仿真实验结果表明,ACSMA显著提升了多种通信状态下的吞吐量。展开更多
This work proposes a Field Programmable Gate Array (FPGA)-oriented architecture for the IEEE 802. 11 Distributed Coordination Function (DCF) transceiver. We describe the functional blocks carrying out the Carrier Sens...This work proposes a Field Programmable Gate Array (FPGA)-oriented architecture for the IEEE 802. 11 Distributed Coordination Function (DCF) transceiver. We describe the functional blocks carrying out the Carrier Sense Multiple Accesses with Collision Avoidance (CSMA/CA), develop the interfaces to the application layer and the physical layer, and implement it on FPGA devices by utilizing Very-high-speed-integrated-circuit Hardware Description Language (VHDL). The novelty of our proposal is twofold. Firstly, all MAC parameters (i.e., Max/Min Contention Window, Data Unit Length, Fragmentation Threshold, Retry Limit, etc.) can be directly accessed and programmed from the application layer interface, which is necessary to achieve better network performance in dynamic environments. Secondly, the character based on FPGA makes the proposal more flexible and risk-reduced for the development of DCF-based wireless networks, such as MANETs and software-defined-radio-based cognitive ad hoc networks.展开更多
In this study, the transmission capacity of VANETs in a highway scenario is analysed on the basis of a 1D line model and the carrier sense multiple access with collision avoidance(CSMA/CA) protocol. We describe the CS...In this study, the transmission capacity of VANETs in a highway scenario is analysed on the basis of a 1D line model and the carrier sense multiple access with collision avoidance(CSMA/CA) protocol. We describe the CSMA/CA protocol used in IEEE802.11 p from the perspective of the geometric relationship amongst simultaneous transmitters. The desired channel and interfering channels are assumed to experience the same amount of path-loss and Rayleigh fading. On the basis of the proposed model, we analyse the attempted transmission probability of each road segment and the maximum intensity of active transmitters, including their theoretical values. Then, we employ the physical model to obtain the outage probability and derive the upper bound of the transmission capacity of a VANET, which is defined as the average spatial density of successful transmissions in the network. Simulation results indicate that the theoretical value offers a good bound on network capacity.展开更多
在LEACH协议的基础上进行改进提出了一种高能效无线传感器网络协议——LEACH-M。LEACH协议中,簇首节点与基站之间直接传送数据,离基站较远区域的簇首能耗较大,这影响了系统寿命。LEACH-M协议在簇首形成阶段采用CSMA/CA(carrier sense mu...在LEACH协议的基础上进行改进提出了一种高能效无线传感器网络协议——LEACH-M。LEACH协议中,簇首节点与基站之间直接传送数据,离基站较远区域的簇首能耗较大,这影响了系统寿命。LEACH-M协议在簇首形成阶段采用CSMA/CA(carrier sense multi-access with collision avoidance)作为MAC协议,并在簇首节点与基站之间引入了改进的多跳路由算法,使网络中各簇的能耗更加均匀。仿真结果表明,与LEACH相比,LEACH-M协议具有更好的能量有效性,并且提高了无线传感器网络的寿命。展开更多
文摘LoRaWAN是低功耗广域网(LPWAN)中的一种无线通信标准,为物联网的发展提供了支撑。然而,受限于扩频因子(SF)间不完全正交性的特点和LoRaWAN不具备先听后发(LBT)机制的事实,基于ALOHA的传输调度方式会引发严重的信道冲突,极大降低了LoRa(Long Range Radio)网络的扩展性。为提高LoRa网络的扩展性,提出用非坚持型载波监听多路访问(NP-CSMA)机制替代LoRaWAN中ALOHA的介质访问控制机制,通过LBT协调LoRa网络中SF相同的各个节点接入信道的时间。不同SF之间的传输则采用多种SF信号并行传输,以减少共信道中同SF干扰和避免SF间干扰。为了分析NP-CSMA对LoRa网络扩展性的影响,通过理论分析和NS3仿真对LoRaWAN与NP-CSMA构建的LoRa网络进行比较。实验结果表明,在相同的条件下,与LoRaWAN相比,NP-CSMA在网络通信负载率为1的情况下,它的理论数据包交付率(PDR)性能比LoRaWAN高58.09%。在信道利用率方面,与LoRaWAN相比,NP-CSMA的饱和信道利用率提高了214.9%,容纳的节点数量也增加了60.0%。另外,NP-CSMA的平均时延在网络通信负载率小于1.7时也低于确认型LoRaWAN,而且在扩频因子为7和10时,它用于维持信道活动检测(CAD)模式所造成的额外能耗也比LoRaWAN用于接收来自网关确认消息所需的额外能耗低1.0~1.3 mJ和2.5~5.1 mJ;充分反映了NP-CSMA可以有效提高LoRa网络的可扩展性。
文摘低压电力线通信(Low Voltage Power Line Carrier Communication,LVPLC)的介质访问控制(Medium Access Control,MAC)协议是影响网络吞吐量的重要因素。针对LVPLC精确人工蛛网网络中由于非对称PLC信道影响而导致吞吐量相对较低的问题,改进了已有的p-载波侦听多路访问协议(p-persistent Carrier Sense Multiple Access,p-CSMA),提出了一种自适应载波侦听多路访问(Adaptive Carrier Sense Multiple Access,ACSMA)协议来优化有限负载下的吞吐量。该协议可通过动态调整概率,降低了数据包的冲突概率,优化了电力线信道的传输状态,最大限度地提高了吞吐量。仿真实验结果表明,ACSMA显著提升了多种通信状态下的吞吐量。
基金the National Natural Science Foundation of China
文摘This work proposes a Field Programmable Gate Array (FPGA)-oriented architecture for the IEEE 802. 11 Distributed Coordination Function (DCF) transceiver. We describe the functional blocks carrying out the Carrier Sense Multiple Accesses with Collision Avoidance (CSMA/CA), develop the interfaces to the application layer and the physical layer, and implement it on FPGA devices by utilizing Very-high-speed-integrated-circuit Hardware Description Language (VHDL). The novelty of our proposal is twofold. Firstly, all MAC parameters (i.e., Max/Min Contention Window, Data Unit Length, Fragmentation Threshold, Retry Limit, etc.) can be directly accessed and programmed from the application layer interface, which is necessary to achieve better network performance in dynamic environments. Secondly, the character based on FPGA makes the proposal more flexible and risk-reduced for the development of DCF-based wireless networks, such as MANETs and software-defined-radio-based cognitive ad hoc networks.
基金supported in part by the National Natural Science Foundation of China under Grant No.61271184 and 61571065
文摘In this study, the transmission capacity of VANETs in a highway scenario is analysed on the basis of a 1D line model and the carrier sense multiple access with collision avoidance(CSMA/CA) protocol. We describe the CSMA/CA protocol used in IEEE802.11 p from the perspective of the geometric relationship amongst simultaneous transmitters. The desired channel and interfering channels are assumed to experience the same amount of path-loss and Rayleigh fading. On the basis of the proposed model, we analyse the attempted transmission probability of each road segment and the maximum intensity of active transmitters, including their theoretical values. Then, we employ the physical model to obtain the outage probability and derive the upper bound of the transmission capacity of a VANET, which is defined as the average spatial density of successful transmissions in the network. Simulation results indicate that the theoretical value offers a good bound on network capacity.
文摘在LEACH协议的基础上进行改进提出了一种高能效无线传感器网络协议——LEACH-M。LEACH协议中,簇首节点与基站之间直接传送数据,离基站较远区域的簇首能耗较大,这影响了系统寿命。LEACH-M协议在簇首形成阶段采用CSMA/CA(carrier sense multi-access with collision avoidance)作为MAC协议,并在簇首节点与基站之间引入了改进的多跳路由算法,使网络中各簇的能耗更加均匀。仿真结果表明,与LEACH相比,LEACH-M协议具有更好的能量有效性,并且提高了无线传感器网络的寿命。
