太赫兹网络中基于中继协作转发的高效双信道MAC协议

针对现有多输入多输出(Multiple-Input Multiple-Output, MIMO)太赫兹通信网络双信道MAC协议存在波束重叠干扰和冗余控制开销等问题,提出了一种太赫兹网络中基于中继协作转发的双信道MAC协议(High Efficiency Dual channel MAC Protocol Based on Relay Cooperative Forwarding in Terahertz Networks, HE-RCFMAC)。HE-RCFMAC协议包含动态帧聚合、基于位置信息自适应协作转发和精简RTS(Request To Send)/CTS(Clear To Send)帧三种机制。经三种机制处理后,可有效提升信道利用率,同时减小控制开销,提高数据传输成功率和整体网络吞吐量。仿真结果表明,所提协议与现有的MIMO太赫兹双信道MAC协议相比,MAC层吞吐量、数据传输成功率和信道利用率分别提升了12.82%、12.28%和8.73%,证明了所提协议的有效性。     

太赫兹网络中基于中继的高效双信道MAC协议

现有的太赫兹无线个域网双信道介质访问控制(MAC)协议工作在WiFi和太赫兹信道。由于这两种信道的频率相差极大,导致使用全向天线和定向天线的覆盖范围各不相同,这样便会使节点之间的消息传输成功率大大降低,同时也降低了网络整体的吞吐量。另外,在现有的太赫兹无线网络双信道MAC协议中还存在一定的冗余控制开销,这导致了信道利用率低。基于此,文章提出一种太赫兹无线网络中基于中继的高效双信道MAC协议(HE-BRMAC),HE-BRMAC分为中继辅助和自适应减少控制开销机制。通过这两种机制可达到提高消息传输成功率、提升网络整体吞吐量、减少控制开销和提高信道利用率的效果,尤其当节点数较多时,HE-BRMAC的效果更为显著。     

太赫兹无线个域网公平高效的MAC层优化机制

针对太赫兹无线个域网双信道媒体访问控制(Medium Access Control, MAC)协议中存在的信道资源分配公平性差、数据帧重传效率低和控制开销较高的问题,提出了一种公平高效的MAC层优化机制。新机制采用基于历史时隙申请信息的信道资源分配策略优化时隙分配公平性,根据信道质量自适应选择数据帧重传机制,控制节点从申请时隙的节点发送的控制帧中的“duration”字段提取时隙申请信息,省略时隙申请帧的发送,从而降低数据帧排队时延和控制开销,提高吞吐量。仿真结果表明,与TAB-MAC和MDP-MAC协议的机制相比,所提机制的数据帧平均排队时延降低了15%,吞吐量提高了5%。     

一种移动感知的太赫兹无线局域网定向MAC协议

现有太赫兹无线局域网定向MAC(Medium Access Control)协议中,节点移动情况下PNC(PicoNet)发送beacon帧时存在部分控制字段浪费、CTAP(Channel Time Allocation Period)中PNC与DEV(Device)进行波束赋形开销偏大等问题。为此,提出了一种移动感知的太赫兹无线局域网定向MAC(Mobility-aware Directional MAC,MA-MAC)协议。该协议采用基于卡尔曼算法的节点扇区预测机制对移动节点的扇区范围进行迭代预测,采用基于DEV扇区预测的beacon帧内容填充机制对beacon帧中时隙分配字段进行填充,采用基于节点扇区预测的快速波束赋形机制使得PNC与DEV之间波束赋形操作简化。通过仿真验证,与基于IEEE 802.15.3c的太赫兹无线局域网定向MAC协议和现有协议进行对比,MA-MAC协议下网络吞吐量得到了提升,网络平均时延、网络整体控制开销得到了改善。     

一种高效太赫兹无线个域网MAC协议

太赫兹无线通信技术越来越多地受到人们关注,MAC协议作为无线通信的关键,如何适应太赫兹超高速率的无线网络是一个急需解决的问题。文章提出了两种新的机制用于改进现有太赫兹MAC协议存在的不足,最大可能地利用了信道资源,除去了冗余的控制开销,从而提高了无线网络通信的吞吐量。最后通过实际验证结果,对太赫兹无线网络MAC协议的进一步研究提供了支持。     

应用于航空Ad Hoc网络的高负载优先级均衡MAC协议

针对航空Ad Hoc网络在高负载下的低时延信道接入问题,提出一种优先级与公平性协作的多信道MAC协议(PBLL/HL)。在多信道检测统计基础上加以改进,结合优先级机制,在高负载网络中适时截流低优先级业务,优化网络流量,保证高优先级业务低时延发送;设计公平性优先级阈值与冲突退避窗口算法(PCA),减小低优先级业务接入时延。仿真结果表明,PBLL/HL能够在高负载网络有效控制信道接入,维持良好的网络流量,降低网络平均接入时延(低优先级业务时延过载时降低10%以上),稳定高负载网络吞吐量(最大吞吐量88.1%,过载时吞吐量下滑平缓),解决了航空数据链高业务量带来的高时延和网络拥塞。     

基于太赫兹无线网络的高速MAC协议研究与实现

为解决现有无线网络的MAC协议无法匹配太赫兹无线网络物理层(PHY)的问题,提出了一种新的太赫兹无线网络MAC协议,并对该协议加以实现验证。该协议通过新的超帧结构,减少了数据发送的等待时间,加快了端到端数据的传输,从而获得更高的网络端到端吞吐量。通过实现结果表明,在带宽为3.125 Gbps下,采用新协议可以实现均值约2.78 Gbps的端到端吞吐量;同时,在端到端平均时延的性能上也有较大提升。该协议的实现为将来太赫兹无线网络MAC协议的进一步研究提供了有力的支持。     

一种快速传输的太赫兹无线个域网MAC协议

针对现有太赫兹无线个域网MAC协议存在信道利用率低的问题,提出一种快速传输的太赫兹无线个域网MAC(Fast Transmission MAC Protocol for THz Wireless Personal Area Network,FTP-MAC)协议,FTP-MAC协议采用多对节点并行传输机制,在信道互不干扰的情况下实现了多对节点在同一时刻内同时传输的功能,通过OPNET仿真工具进行仿真验证。相较于LODMAC协议和TAB-MAC协议,FTP-MAC协议在吞吐量、信道利用率和网络整体的数据传输效率等性能方面都有所提高。     

无线网状网中基于信道预留的多信道媒体接入控制方案

目前多信道无线Mesh网络WMN(Wireless Mesh Network)的MAC(Medium Access Contro)l仍然存在信道利用率低的问题,因此提出了具有控制信道和数据信道的多信道WMN的MAC方案。方案采用数据信道预留机制来提高系统的吞吐量,并降低接入时延。该方案通过减小控制信道上的碰撞概率可以有效降低系统接入时延并提高控制信道的利用率。理论分析和性能估计表明此方案具有高的吞吐量和低的接入时延,性能明显优于现有的公共信道控制方案CCC(Common Control Channel)。     

一种多信道的分簇式短波令牌协议

传统的短波令牌协议( HFTP)调度方式单一,在没有数据传送时,信道资源会被各节点间的令牌传递所占用,且令牌在通信质量较差时易丢失。基于此,提出一种多信道的分簇式短波令牌协议( CHFTP),通过以通信质量评估为标准的分簇算法和基于预约的动态令牌调度,减小了令牌丢失的概率和令牌传递、处理的开销,并给出了仿真分析。仿真结果表明,该协议的端到端平均时延和网络吞吐量明显优于短波令牌协议, CHFTP 的平均时延最多可减少75%,网络吞吐量最多可增加66.7%,适合在短波通信网络中使用。     

ATMAC: adaptive token‐based medium access control protocol for cognitive radio wireless mesh network

In next generation wireless communication, cognitive radio technology facilitates to utilize underutilized licensed frequency bands that help to enhance the spectrum utilization. Cognitive radio wireless mesh network (CRWMN) is a promising and reliable technology to experience high throughput with low cost. Existing IEEE 802.11 based medium access control (MAC) protocols offer high data rates with decreasing efficiency at the MAC layer. Hence, most of the researchers applied aggregation mechanisms to provide the solution to bandwidth craving applications. In CRWMN, MAC design is significant because stability, efficient resource utilization, and scalability are predominating problems; however, the specified MAC issues are not yet resolved. The proposed MAC is novel, which aims to ensure reliability and scalability for CRWMN. The common control channel is used to exchange handshaking frames between the transmitter and receiver. It helps us to schedule the data transmission as well as reserve the channel in a discrete time interval. It introduces a token‐based channel accessing mechanism with resource‐aware channel assignment, which resolves the problems of efficiency and stability. The proposed MAC simulated using the network simulator (ns‐2), and the simulation results demonstrate that the proposed protocol improved the performance compared with the existing protocols.     

Performance analysis of adaptive MAC protocol in VANETs considering the potential impact on throughput and transmission delays

The existing adaptive multichannel medium access control (MAC) protocols in vehicular ad hoc networks can adjust themselves according to different vehicular traffic densities. These protocols can increase throughput and guarantee a bounded transmission delay for real‐time safety applications. However, the optimized control channel interval is computed based on the maximum throughput while ignoring the strict safety packet transmission delay requirements. In this paper, we analyze the effects of the throughput and strict safety packet transmission delay with adaptive multichannel MAC protocols, such as connectivity‐aware MAC (CA MAC), adaptive multi‐priority distributed MAC (APDM), multi‐priority supported p‐persistent MAC (MP MAC), and variable control channel interval MAC (VCI) protocols. The performance and analysis results show that: (a) under a low data rate condition, CA MAC does not guarantee a strict safety packet transmission delay; (b) APDM not only satisfies the safety packet transmission requirement, but also provides the lowest safety packet transmission delay; (c) under a high data rate condition, we suggest APDM for use as an adaptive MAC protocol because it allows for high throughput for nonsafety packets and preserves low safety packet transmission delay; (d) under a low data rate condition with various data packet sizes, we suggest MP MAC for high throughput, which satisfies the safety packet transmission requirement; and (e) under low vehicle density and low data rate conditions, VCI can support high throughput. A balance between transmission delay and throughput must be considered to improve the optimal efficiency, reliability, and adaptability.     

A Scalable CSMA and Self-Organizing TDMA MAC for IEEE 802.11 p/1609.x in VANETs

vehicular ad hoc networks (VANETs) have been a key topic for research community and industry alike. The wireless access in vehicular environment standard employs the IEEE 802.11p/1609.4 for the Medium Access Control (MAC) layer implementation for VANETs. However, the carrier sense multiple access (CSMA) based mechanism cannot provide reliable broadcast services, and the multi-channel operation defined in IEEE 1609.4 divides the available access time into fixed alternating control channel intervals (CCH) and service channel (SCH) intervals, which may lead to the low utilization of the scarce resources. In this paper, a novel multichannel MAC protocol called CS-TDMA considering the channel access scheduling and channel switching concurrently is proposed. The protocol combines CSMA with the time division multiple access (TDMA) to improve the broadcast performance in VANETs. Meanwhile, the dwelling ratio between CCH and SCH changes dynamically according to the traffic density, resulting in the improvement of resource utilization efficiency. Simulation results are presented to verify the effectiveness of our mechanism and comparisons are made with three existing MAC protocols, IEEE MAC, SOFT MAC and VeMAC. The simulation results demonstrate the superiority of CS-TDMA in the reduction of transmission delay and packet collision rate and improvement of network throughput.     

RIM-MAC：一种适用于水下传感网接收者发起的多会话MAC协议

声通信是水下传感网的主要通信方式之一,但是它具有长延迟和低带宽的特点,这是水下传感网MAC（media access control）协议研究面临的主要挑战。为提高网络吞吐量,提出了一种接收者发起的多会话MAC协议（RIM-MAC）。它利用接收者发起会话,通过一次会话的4次握手完成所有邻居数据分组的传输,有效地减少握手次数。同时利用侦听到的本地信息（邻居延迟图和邻居的传输调度）避免信道冲突并发起多个会话,这解决了长传播延迟带来的信道利用率低的问题。RIM-MAC通过增强节点间并行传输的能力,在接收者和发送者两端提高时空复用率,与经典水下MAC协议比,网络吞吐量提高了至少36%。除此之外,基于自适应数据轮询策略提出了一种网络负载公平算法（FTA）,它保证了网络中竞争节点间的信道访问的公平性。仿真实验表明,在长传播延迟的场景下,RIM-MAC取得了比典型的水下传感网MAC协议更好的吞吐量性能。     

用于VANET紧急消息传输的改进二元分割广播协议

摘要：针对车辆自组织网络（vehicular Ad Hoc network,VANET）中紧急消息的传输,提出一个改进的二元分割广播（MBPAB）协议。协议将通信范围迭代划分成小的区域,寻找离发送节点最远区域内的车辆,对紧急消息执行转发,通过减少转发跳数,提高消息传播速度。通过引入MAC（medium access control）子层的微型分布式帧间间隔（mini-DIFS）,赋予对紧急消息以更高的优先级接入通信信道。仿真结果表明,在VANET 中, MBPAB协议与现有的广播协议相比,在通信时延和消息传播速度方面有更好的性能表现。     

RSU-coordinated multichannel MAC protocol in vehicular ad hoc network

A road side unit (RSU)-coordinated multichannel media access control (MAC) (RMM) protocol was proposed in vehicular ad hoc network,which aimed to improve the transmission efficiency of non-safety messages.Under the coordination of RSU,nodes had more opportunities to make SCH reservations on control channel,and the contention-free message transmissions were thus realized.The proposed RMM protocol could use the service channel during the whole synchronization interval for non-safety message transmissions,and thus the saturated network throughput and channel utilization were improved,and the transmission delay was reduced.Compared with other existing protocols,extensive analysis and simulation results demonstrate the superiority of the RMM protocol.     

Real Time Scheduling in TSCH for IoT Using Neurogenetic Algorithm

Internet of Things (IoT) is a widely adoptable technology in industrial, smart home, smart grid, smart city and smart healthcare applications. The real world objects are remotely connected through internet and it provides services with the help of friendly devices. Currently IEEE 802.15.4e Time Slotted Channel Hopping (TSCH) standard is gaining a part of consideration among the IoT research community because of its effectiveness to improvise the reliability of communication which is orchestrated by the scheduling. As TSCH is an emerging Medium Access Control (MAC) protocol, it is used in the proposed work to enhance the network scheduling by throughput maximization and delay minimization. The paper focuses on proper utilization of the channel through node scheduling. NeuroGenetic Algorithm (NGA) has been proposed for TSCH scheduling and its performance is evaluated with respect to time delay and throughput. The system is implemented in real time IoT devices and results are perceived and analyzed. The proposed algorithm is compared with existing TSCH scheduling algorithms.

     

Analytical modeling of bidirectional multi‐channel IEEE 802.11 MAC protocols

This paper presents an analytical approach to model the bi‐directional multi‐channel IEEE 802.11 MAC protocols (Bi‐MCMAC) for ad hoc networks. Extensive simulation work has been done for the performance evaluation of IEEE 802.11 MAC protocols. Since simulation has several limitations, this work is primarily based on the analytical approach. The objective of this paper is to show analytically the performance advantages of Bi‐MCMAC protocol over the classical IEEE 802.11 MAC protocol. The distributed coordination function (DCF) mode of medium access control (MAC) is considered in the modeling. Two different channel scheduling strategies, namely, random channel selection and fastest channel first selection strategy are also presented in the presence of multiple channels with different transmission rates. M/G/1 queue is used to model the protocols, and stochastic reward nets (SRNs) are employed as a modeling technique as it readily captures the synchronization between events in the DCF mode of access. The average system throughput, mean delay, and server utilization of each MAC protocol are evaluated using the SRN formalism. We also validate our analytical model by comparison with simulation results. The results obtained through the analytical modeling approach illustrate the performance advantages of Bi‐MCMAC protocols with the fastest channel first scheduling strategy over the classical IEEE 802.11 protocol for TCP traffic in wireless ad hoc networks. Copyright © 2010 John Wiley & Sons, Ltd.     

A hybrid reservation-based MAC protocol for underwater acoustic sensor networks

Due to the characteristics of underwater acoustic channel, such as long propagation delay and low available bandwidth, media access control (MAC) protocol designed for the underwater acoustic sensor network (UWASN) is quite different from that for the terrestrial wireless sensor network. However, for the contention-based MAC protocols, the packet transmission time is long because of the long preamble in real acoustic modems, which increase the packet collisions. And the competition phase lasts for long time when many nodes are competing for the channel to access. For the schedule-based MAC protocols, the delay is too long, especially in a UWASN with low traffic load. In order to resolve these problems, a hybrid reservation-based MAC (HRMAC) protocol is proposed for UWASNs in this paper. In the proposed HRMAC protocol, the nodes reserve the channel by declaring and spectrum spreading technology is used to reduce the collision of the control packets. Many nodes with data packets to be transmitted can reserve the channel simultaneously, and nodes with reserved channel transmit their data in a given order. The performance analysis shows that the proposed HRMAC protocol can improve the channel efficiency greatly. Simulation results also show that the proposed HRMAC protocol achieves better performance, namely higher network throughput, lower packet drop ratio, smaller end-to-end delay, less overhead of control packets and lower energy overhead, compared to existing typical MAC protocols for the UWASNs.