An interference avoidance MAC protocol design in mobile ad hoc networks

The multi-rate IEEE 802.11 DCF MAC protocol can transmit control signals at a basic transmission rate and data signals at various transmission rates. When the transmission rates of the control signals and the data signals differ, the transmission range of the lower transmission rate is larger than the transmission range of the higher transmission rate. Since a lower transmission rate increases the transmission range, it also increases the nodes in the Network Allocation Vector (NAV) status and decreases the network throughput. However, if a neighbor receiving the control signal of the ongoing communication pair communicates with another node, it may occur signal interference. This study proposes a Space Overlapping MAC (SO-MAC) protocol to increase the communication pairs and avoid interferences in single radio for multi-rate wireless network. The SO-MAC protocol uses a channel division mechanism to avoid interference between the data and control signals. This study also proposes a bandwidth allocation strategy for the sub-channels to maximize the utilization of the bandwidth of the divided sub-channels. To solve the interference between the data signals, SO-MAC allows a neighbor of the sender and the receiver to use the received signal strength to determine whether it can send or receive the data signal to increase the communication pairs. Simulation results show that, compared to the IEEE 802.11 DCF protocol and DCA protocol, the proposed SO-MAC protocol with the bandwidth allocation strategy can increase the communication pairs, achieve better throughput, reduce the number of handshake failures, and decrease the delay of transmitting a packet.     

适用于水声传感网络的多链路传输MAC协议

针对水声传感网络存在的高时延、低信道利用率等问题,提出一种新的多链路传输介质访问控制协议.该协议节点通过RTS/CTS握手协议交互时延信息和传输计划,实现多条链路传输数据.在汇聚节点接收多个节点的数据时,汇聚节点根据节点的时延和接收的数据帧大小规划节点之间的发送顺序,避免传输冲突造成的能量损失和低信道利用率,同时为得到...     

多跳分布式无线网络环境下自适应获取冲突避免的多址接入协议

该文为多跳移动的分布式无线网络提出了一种新型的媒质接入控制（MAC）协议，即公共－发送信道式自适应获取冲突避免（AACA－CT）协议，在该协议中，每个节点预先监测记录周邻节点的信道使用情况，从而自适应地为自己选择发送信道，并且利用在公共信道上发送的RTS分组唤起收方使用各自的发送信道而实现无冲突的通信，它的主要思想在于资源预约可以简便地利用半双工无线电台以异步方式灵活，有效地在多个频段，多个跳频（FH）码或多个直接序列扩频（DSSS）码上实现，而且不依赖于功能强大的基站或中心控制器以及有线骨干网的帮助，性能分析和仿真结果表明，它能有效地克服隐藏终端和暴露终端问题，并且可以完全解决侵入终端问题。     

基于跨层竞争的同步MAC协议研究

在无线传感器网络(WSNs)中,基于跨层竞争的同步媒体接入控制(MAC)在一周期内可安排多个数据包的多跳传输,传统的协议在同一个数据窗口传输请求数据包和确认数据包,降低了数据窗口的多跳流量的建立,也降低了在多跳场景中的数据包传输率和传输时延性能.本文提出了基于新的基于跨层竞争的同步MAC(CLC-MAC)协议,CLC-MAC协议引用新的周期结构,且其包含两个独立窗口,并由该窗口分别传输数据请求包和确认包,即请求包在数据窗口传输,而确认包在休眠窗口传输.实验数据表明:与先锋路由帧MAC(PRMAC)协议相比,CLC-MAC协议的端到端传输时延和数据包传输率的性能均得到了提高.     

接收方预约信道的水声传感器网络MAC协议

为了获得更高的网络吞吐量,更低的端到端时延,设计出了一种适用于分簇网络的水声传感器网络MAC协议,该协议采用接收方建立握手机制,有效的获取邻居节点通信时的状态,动态分配发送时隙,实现数据包以报文序列方式无冲突的到达接收端.仿真结果表明,与同类MAC协议(FERI, RIPT)相比,该协议提高了网络吞吐量,降低了数据丢失率和端到端时延.     

基于压缩感知的水下传感器网络预约多址接入协议

相比于陆地无线传感器网络, 水下传感器网络拥有更大的传播时延, 导致许多已经比较成熟的MAC协议不能直接应用于水下。提出了基于压缩感知的水下传感器网络预约多址接入协议, 充分利用水下环境中的长传播时延, 使网络中各节点能够在时间和空间上对信道资源进行共用, 实现多个用户同时进行信道预约, 提高了信道的利用率。在考虑多用户分集基础上, 该协议使成功预约到信道的用户可以利用有限的全部带宽资源进行高速传输, 以此来提高整个网络的吞吐性能。仿真结果表明, 与传统的RTS/CTS方案相比, 该协议具有更高效的信道预约能力, 更高的数据传输效率, 以及更好的吞吐性能。     

Opportunistic medium access control for maximizing packet delivery rate in dynamic access networks

One of the key challenges to enabling efficient cognitive radio (CR) communications is how to perform opportunistic medium access control (MAC) that maximizes spectrum efficiency. Several CRN MAC protocols have been designed assuming relatively static primary radio (PR) channels with average idle durations largely exceed CR transmission times. For such CR environment, typical multichannel MAC protocols, which select the best quality channel, perform reasonably well. However, when such mechanism is employed in a CRN that coexists with highly dynamic licensed PR networks (PRNs), where PR channel idle durations are comparable to CR transmission times, the forced-termination rate for CR transmission can significantly increase, leading to a reduction in network throughput. To reduce the forced-termination rate, many MAC protocols have been proposed to account for the dynamic time-varying nature of PR channels by requiring communicating CR users to consistently perform channel switching according to PR activities. However, such channel-switching strategy introduces significant overhead and latency, which negatively affect network throughput. Hence, in this paper, we propose a probabilistic channel quality- and availability-aware CRN MAC. Our protocol uses a novel channel assignment mechanism that attempts at maximizing the packet success probability of each transmission and hence avoids the significant overhead and latency of channel switching. Simulation results show that by being quality- and availability-aware, our protocol provides better spectrum utilization by decreasing the forced-termination rate and improving network throughput.     

移动Ad Hoc网络中基于ID的信道预约多址接入协议

为了在移动ad hoc网络中有效利用无线信道资源,提出一种基于ID的信道预约(ID-based channel reservation,简称IDBCR)多址接入协议.该协议在公共信道上发送Request-To-Send/Clear-To-Send(RTS/CTS)分组实现握手,采用基于节点ID的信道选择方案选择无冲突的业务信道传输数据分组,目的节点成功接收完数据分组后在另一个公共信道上回复acknowledgment(ACK)分组,有效避免了暴露终端问题.最后,仿真实现了IDBCR协议,并与CAM-MAC(cooperative asynchronous multi-channel MAC)多信道协议比较.结果表明,在总信道利用率、平均信道利用率和平均分组延迟性能上,IDBCR多址接入协议明显优于CAM-MAC协议.     

车载自组织网络协作MAC协议研究

车载自组织网络(Vehicular Ad Hoc Network,VANET)的关键技术之一就是 设计一个高效的媒体接入控制(Medium Access Control,MAC)协议。MAC协议因对网络的吞吐量、时延和丢包率等具有重大影响而成为研究热点。针对车载自组织网络对MAC协议的特殊性要求,提出了一种基于协作方案的TDMA MAC协议,即C-TDMA MAC。该协议中,当源节点到目的节点间直接传输失败时,其邻近辅助节点利用未被预留的时隙协作重传其先前侦听到的数据包到目的节点,而不影响其它数据包的正常传输。数值分析和仿真结果表明,所提出的协议提高了数据包成功传输的概率。     

一种分布式的基于预留的多信道MAC协议

无线传感器网络(wireless sensor networks,WSNs)已经广泛应用于各个领域。许多领域利用了周期性数据汇聚,传感器节点周期性地产生数据包,通过一系列中继节点传输到汇聚节点。提出了一种分布式的基于预留的多信道MAC协议,称为R-MMAC协议,其中利用了预留机制和多信道通信机制,在多信道条件下,每个节点传输数据包时都将预留下一个数据包的传输,根据接收信号强度指示(received signal strength indication,RSSI)值选择自己的最佳信道进行预留。另外,还提出了针对预留时发生冲突的解决算法,利用信干噪比(signal to interference and noise ratio,SINR)和数据包接收率(packet reception rate,PRR)得到了预留的传输时间,从而降低了传感器节点到汇聚节点的传输时延和未来数据包的冲突概率。利用OMNET++5.3仿真工具对R-MMAC协议、X-MAC和EM-MAC协议进行了比较,结果表明R-MMAC协议实现了更低的端到端时延。     

认知无线电网络双天线多信道MAC协议

在认知无线电网络中,媒体接入控制(MAC)协议的主要功能包括信道感知、选择和接入控制,其中感知时间和传输时间的长度对网络的性能有着重要的影响。在动态无线网络环境下,如何合理分配感知时间和传输时间是个挑战性问题。提出了一种双天线多信道分布式认知无线电MAC（TM-MAC）协议,不需要在传输之前对信道进行感知。节点可以在其它节点传输数据的同时对频谱资源进行检测,然后利用空闲的频谱资源通信。建立了数学模型分析在饱和网络状况下MAC协议的吞吐量。仿真分析表明TM-MAC协议能够有效提高网络的吞吐量。     

An adaptive directional MAC protocol for ad hoc networks using directional antennas

A directional antenna can bring benefits in terms of power consumption,spatial reuse,etc.To exploit the advantage of directional antennas and improve the transmission throughput highest,this paper proposes an adaptive directional MAC protocol(ADMAC).By varying the transmission strategy according to the usage of the channel,nodes can send RTS and CTS packets omni-directionally or directionally.Also,this paper proposes a calculation method of virtual carrier sensing with collision avoidance.By the method,ADMAC protocol makes more pairs of nodes transmit and receive data simultaneously without interferences than other MAC protocols for directional antennas.The paper compares the simultaneous delivering nodes and network throughput of ADMAC with DMAC,DVCS and SDMAC under different experiment parameters.The simulation results show that the throughput of ADMAC is higher than the throughput of DMAC,DVCS and SDMAC protocols.     

一种基于跨层功率控制的Ad hoc网络路由算法*

在无线Ad Hoc网络路由协议中引入功率控制不但可以降低网络能量消耗,同时还能改善网络的吞吐量、投递率等性能,已成为当前Ad Hoc网络的一个研究热点.本文提出了一种基于跨层功率控制的按需路由算法CPC-AODV(Cross-layer Power Control Ad hoc On-demand Distance Vector).算法按需建立多个不同功率级的路由,节点选择到目的节点最小功率级的路由来传递分组,并对网络层的数据分组、路由分组和MAC层控制帧的传输采用不同功率控制策略来降低能量消耗.仿真结果表明:算法有利于降低通信能量开销,延长网络寿命,提高网络投递率及改善网络时延.     

一种适用于Ad Hoc网络的多信道能量高效MAC协议

对多信道条件下MAC协议功率控制机制进行了分析,提出一种能够根据各个接收节点的通信状况,动态地调整数据信道上数据帧的传输功率和控制信道上CTS帧的发送功率的多信道Ad Hoc网络能量高效的MAC协议(MPEMAC).仿真表明,该协议有效的节省了节点能耗,延长了网络节点的生存时间,同时还能够增大空间信道的利用率,从而进一步提高网络的平均吞吐量.     

基于Nak-Only握手协议的WUSB系统的设计

在WUSB系统的设计中,针对ACK等短数据包在物理层是定长数据包时会浪费带宽的问题,提出了一种Nak-Only握手协议,其主要思想是通过一种消极等待机制来代替ACK的传输,从而节省了过长握手包造成的带宽浪费。这种方案在实现中需要WUSB物理层的收发转换延迟具有良好的稳定性,但在收发转换延迟跳动较大的情况下,也可以用发送端缓存3个数据包的方法来避免数据包丢失。通过仿真验证了Nak-Only握手协议会对WUSB带来吞吐率上的提升,效果可以接近物理层支持理想变长数据包时的性能。     

A hybrid MAC protocol for a metro WDM network using multiple free spectral ranges of an arrayed-waveguide grating

In this paper, we report on a novel quality-of-service supporting reservation-based medium access control (MAC) protocol for a reliable, scalable, and cost-effective switchless wavelength division multiplexing network. The network is completely passive and is based on an arrayed-waveguide grating (AWG). Each node at the network periphery is equipped with one single fast tunable transceiver for data and one low-cost broadband light source which is spectrally sliced for broadcasting control information. Direct sequence spread spectrum techniques are used to enable simultaneous transmission of data and control. All wavelengths are used for data transmission and signaling is done in-band. Each node has global knowledge and schedules variable-size data packets on a deterministic first-come-first-served and first-fit basis guaranteeing fairness and completely avoiding channel and receiver collisions. The proposed protocol provides both packet and circuit switching and supports multicasting. The network efficiency is significantly increased by spatially reusing wavelengths and exploiting multiple free spectral ranges (FSRs) of the AWG. The analysis accounts for propagation delay and protocol processing time. Results show that using three FSRs instead of one significantly decreases the mean delay and improves the mean throughput by up to 88%, resulting in a normalized mean throughput of approximately 78%. The analytical results are verified by simulation.     

一种水声通信中的自适应ARQ方案

在水声通信系统中,由于水声信道的半双工、时变和长传播时延等特性,导致用于水声通信中的停等自动重传请求(SW ARQ)方案的吞吐性能显著下降。本文首先利用扩频通信技术,将单个信道分成两个子信道：一个用于前向信道(从发送方到接收方),另一个用于反向信道(从接收方到发送方),充分地利用水声信道。在此基础上,结合选择自动重传请求(SRARQ)方案与返回-n自动重传请求(GBNARQ)方案的混合式自动重传请求(SR GBNARQ)方案的优良性能,提出了一种随水声信道的时变特性改变分组长度的自适应ARQ方案。仿真结果表明：该方案能有效地提高水声通信系统的吞吐性能。     

基于异构竞争窗口优化的水下传感器网络MAC协议

传统水下传感器网络的MAC协议具有能耗过大、带宽资源不足等缺点,通过研究基于竞争窗口CW(Contention Win-dow)的CW-MAC协议无法完全保障信道利用公平性的缺陷,提出了两种基于异构竞争窗口优化策略的HCW-MAC协议,根据传感器节点的欧式距离差异对各节点所分配CW值的进行优化调整.本文采用NS-3仿真平台对CW-MAC与HCW-MAC协议分别进行了仿真比较,仿真结果验证了HCW-MAC协议的吞吐量与能耗性能均优于传统的CW-MAC协议.     

e-MAC:一种面向Ad Hoc网络的高吞吐量MAC协议

解决ad hoc网络中隐藏节点问题、暴露节点问题的最终目的是减少节点间的冲突,提高网络空间复用率,从而提高网络吞吐量.现有MAC协议在解决隐藏节点问题时着重于彻底消除网络中的隐藏节点,忽略了网络空间复用率,即使能够彻底解决隐藏节点问题,也不能有效提高网络吞吐量.同样,现有协议在解决暴露节点问题时着重于如何允许暴露节点并行发送数据,忽略了暴露节点接收数据的问题,也影响了网络空间复用率.提出了一种高效的MAC协议e-MAC,协议采用两种方法提高网络空间复用率:首先,协议中接收节点根据接收到发送节点的信号强度动态调整忙音发射功率,使忙音恰好覆盖所有的隐藏节点,在彻底解决隐藏节点问题的同时,提高网络空间复用率;其次,隐藏节点接收到RTS消息后,通过判断RTS消息信号强度与信道中干涉信号的强度之比来决定是否接收数据,允许满足信噪比要求的接收节点接收数据,进一步提高网络空间复用率.仿真结果验证了协议的有效性,在任意拓扑结构下,e-MAC协议的平均吞吐量比DUCHA(dual channel access)协议高87%.     

水声传感网MAC协议综述

海洋在人类发展中扮演着越来越重要的角色。水下通信技术作为人类认识海洋的重要手段,成为研究界的热点与难点。由于水下通信技术有不同于陆地无线通信的信道特点和性能要求,传统无线通信MAC(medium access controD协议难以直接应用于水声通信,因此相继提出针对各种应用场景的水声MAC协议。在简述水声传感网(Undcrwatcr Acoustic Sensor Nctwork,UWASN)特点和MAC协议设计准则后,根据信道获取方式将当前典型协议分为基于竟争和基于调度两大类。根据冲突处置方式进一步将基于竞争的协议分为随机多址和冲突避免,根据信道分配的动态性将基于调度的协议分为动态分配和静态分配。在此分类基础上,描述了近期出现的典型协议的设计思想、主要机制,并比较了协议在能耗、信道利用、吞吐量等方面的差异,最后指出提高MAC协议性能的发展方向。