基于动态控制信道的认知无线电网络MAC协议

在认知无线电网络中,MAC协议主要用于信道资源的感知、选择以及接入控制从而保证公平性和有效的资源共享。针对认知无线电网络基于控制信道的研究现状,文中在认知无线电网络分布式多信道MAC(CR-MMAC)协议的基础上,引入同步机制,不等待传输机制和不重申机制,提出一种基于动态公共控制信道的认知无线电网络MAC(CR-DCMAC)协议。它能够减少信道资源开支,降低控制信道上的控制分组量。仿真结果表明,CR-DCMAC协议能提高系统总吞吐量和空闲频谱资源的利用率,综合性能优于CR-MMAC协议。     

一种基于全双工的分布式认知无线电MAC协议

现有的MAC协议在认知无线电环境下都存在"隐藏"终端和"暴露"终端问题,这降低频谱资源利用率和多信道环境下的系统性能,文章提出一种基于全双工的分布式认知无线电MAC(CR-MAC)协议,该协议在不影响授权用户前提下,认知用户通过侦听控制信道的消息,动态的使用授权信道,并通过两根天线同时进行发送数据和接收数据,以此解决"隐藏"终端和"暴露"终端的问题。通过仿真验证,并与现有的MAC协议进行比较,CR-MAC协议可以有效的提高系统的吞吐量。     

选用最优数据信道的认知无线电MAC协议

如何选择数据信道进行数据的传输是认知无线电网络MAC协议的重要环节,许多现有的MAC机制在选用数据信道没有考虑信道的可用概率,而可用概率对网络性能有着重要的影响。提出了一种最优信道传输的认知无线电MAC协议。次用户在频谱感知后,选用质量最优数据信道对数据进行传输,评价信道质量的标准中考虑了信道的可用概率。最后,使用ns...     

认知无线电网络的MAC协议机制

针对认知无线电网络可用信道资源随时间和空间环境变化的特点,分析了认知无线电网络MAC协议面临的问题,提出了一种基于全局控制信道的MAC协议方案,在此基础上阐述了两种接入方式及相应适用场合,实现了认知无线电节点对可用信道资源变化的感知,可为认知无线电MAC协议研究及应用提供参考.     

基于能量收集驱动和信道感知的CRN

针对能量采集器供电的认知无线电网络进行了研究。首先,在采用离散时间马尔可夫链的建模基础上,通过分析认知用户在收集到的能量包和电池容量的限制下有效地利用能量,以最大化当前时隙的吞吐量。然后,找到多个信道的最优感知顺序和对应于该感知顺序下信道的最优传输能量集,得到使认知无线电网络在多个时隙的预期吞吐量最大化的递归表达式。最后提出了一种基于该递归表达式实现最大化预期吞吐量的算法。仿真实验结果表明,所提出的方案相比于其他方案,不仅提高了认知无线电网络的吞吐量,而且降低了主信道上的平均碰撞比。     

太赫兹网络中基于优先级调度的低开销双信道MAC协议

针对现有太赫兹通信网络双信道MAC协议存在控制开销冗余和在竞争信道时缺少优先级调度策略等问题,提出了一种太赫兹网络中基于优先级调度的低开销双信道MAC协议（Low Overhead Dual-channel MAC Protocol Based on Priority Scheduling,LO-PSMAC）,包含通信距离预判、优先级调度策略的CSMA/CA和精简THz频段MAC帧三种机制,可有效提升信道利用率和整体网络吞吐量,同时减小控制开销和降低数据平均时延。仿真结果表明,所提协议与现有太赫兹双信道MAC协议相比,MAC层吞吐量和信道利用率分别提升了7.14%和14.75%,数据平均时延降低了14.21%。     

基于多信道预约的传感器网络MAC协议研究

针对传感器网络中三重隐终端问题,提出了一种基于自适应占空比的多信道MAC协议—MCR,MCR通过多信道预约机制高效地解决了该问题。在理论分析中,通过最小化节点平均信道切换次数的下界得出了节点的最优占空比。为验证MCR中多信道预约和自适应占空比机制的性能,进行了模拟和真实实验,实验结果表明,与其他MAC协议相比,随着信道数及网络负载的增加,MCR提高了网络吞吐量,降低了传输所消耗的能量。     

水声通信网络中的MACA-C介质访问控制协议

介质访问控制协议（Medium Access Control , MAC）是水声通信网络中的一种关键技术。与陆地无线通信系统使用无线电波有所不同,水声通信网络依靠水声进行通信。水声通信网络中的MAC协议设计面临许多挑战面,如:传播延迟大、带宽窄、电池不易更换或充电、节点发射功率受限等。因此,陆地无线通信系统的各MAC协议不能直接应用到水声通信网络。本文提出了一种适用于水声通信网络的MACA（MACA-C）协议,该协议主要将传输数据包和控制包结合使用,在每轮握手的过程中,该协议通过发送列的首数据包和RTS控制包来改善信道利用率。仿真结果也表明MACA-C能够达到较高的和稳定的吞吐量性能,同时在保持低碰撞率的前提下增加信道利用率。      

基于认知无线电的小卫星群通信动态频谱分配

文中以认知无线电技术(cognitive Radio, CR)为基础,提出了一种基于CR的小卫星群通信动态频谱分配MAC方案.该方案允许未授权用户自适应地选取可用带宽,实现了动态频谱接入,有效地提高了频谱利用率.提出一种动态信道的跳预约多址接入(DC-HRMA)协议,在不需要公共信道的情况下,解决了信道有效接入与退让问题.仿真结果表明,该协议性能和主次用户数目的合理搭配相关.     

基于MIMO技术的WMN MAC协议研究

分析了MIMO技术中由于通信链路间干扰导致网络吞吐量降低的问题,提出了一种基于多模多信道技术的改进MAC协议(MPRP-MAC),利用节点中的多个通信模块以及多个正交信道资源,使节点可以在无干扰的情况下实现接收与发送同时进行。实验结果表明,该技术可充分利用天线资源,有效提高系统容量。     

Channel allocation and medium access control for wireless sensor networks

Recent developments in sensor technology, as seen in Berkeley’s Mica2 Mote, Rockwell’s WINS nodes and the IEEE 802.15.4 Zigbee, have enabled support for single-transceiver, multi-channel communication. The task of channel assignment with minimum interference, also named as the 2-hop coloring problem, allows repetition of colors occurs only if the nodes are separated by more than 2 hops. Being NP complete, development of efficient heuristics for this coloring problem is an open research area and this paper proposes the Dynamic Channel Allocation (DCA) algorithm as a novel solution. Once channels are assigned, a Medium Access Control protocol must be devised so that channel selection, arbitration and scheduling occur with maximum energy savings and reduced message overhead, both critical considerations for sensor networks. The contribution of this paper is twofold: (1) development and analysis of the DCA algorithm that assigns optimally minimum channels in a distributed manner in order to make subsequent communication free from both primary and secondary interference and (2) proposing CMAC, a fully desynchronized multi-channel MAC protocol with minimum hardware requirements. CMAC takes into account the fundamental energy constraint in sensor nodes by placing them in a default sleep mode as far as possible, enables spatial channel re-use and ensures nearly collision free communication. Simulation results reveal that the DCA consumes significantly less energy while giving a legal distributed coloring. CMAC, our MAC protocol that leverages this coloring, has been thoroughly evaluated with various modes in SMAC, a recent protocol that achieves energy savings through coordinated sleeping. Results show that CMAC obtains nearly 200% reduction in energy consumption, significantly improved throughput, and end-to-end delay values that are 50–150% better than SMAC for our simulated topologies.     

Optimal designs for IEEE 802.15.4 wireless sensor networks

This paper investigates the maximum achievable channel throughput in a single‐channel and single‐hop wireless sensor network using IEEE 802.15.4 Medium Access Control (MAC) protocol. We introduce a simple mean‐field approach to model the Carrier Sense Multiple Access with Collision Avoidance mechanism of the 802.15.4 MAC protocol under unsaturated conditions. We derive a set of expressions such as optimal sensing rate of a sensor node, its corresponding failure probability, and the channel throughput for both saturated and unsaturated networks. With those expressions, we propose several network designs to achieve the optimal throughput by choosing the appropriate MAC parameters. We validate the proposed optimal designs using ns‐2 simulations. Furthermore, we evaluate the network lifetime expectancy of the optimal designs and compare it with the lifetime of network settings under saturated conditions that use the default MAC parameters of IEEE 802.15.4. Copyright © 2011 John Wiley & Sons, Ltd.     

A short-term fair MAC protocol for WLANs

Designing a medium access control (MAC) protocol that simultaneously provides high throughput and allows individual users to share limited spectrum resources fairly, especially in the short-term time horizon, is a challenging problem for wireless LANs. In this paper, we propose an efficient cooperative MAC protocol with very simple state information that considers only collisions, like the standard IEEE 802.11 MAC protocol. However, contrary to the IEEE 802.11 MAC, the cooperative MAC gives collided users priority to access the channel by assigning them shorter backoff counters and interframe-spaces than users who did not participate in the collision event. In other words, collided users are the only ones allowed to transmit in the following contention period. For the cooperative MAC protocol, we utilize an analytical throughput model to obtain the optimal parameter settings. Simulation results show that the cooperative MAC provides significant improvement in short-term fairness and access delay, while still providing high network throughput.     

基于信道状态感知的多信道认知多址接入协议

摘 要：针对多信道认知无线网络中预约信道与多个数据传输信道的状态不一致会降低认知多址协议性能的问题,提出了基于数据信道状态感知的多信道认知多址协议——CAM-MAC协议。该协议在预约信道上优化握手机制来减少平均成功预约时长;而在Nakagami衰落数传信道上采用跨层方法设计了基于瞬时SNR的自适应传输机制来提高数据传输速率。通过上述机制,CAM-MAC协议可以有效提升系统性能。分析与仿真均表明：该协议在饱和吞吐量上有较大提升,在特定场景下可提高约50%。     

Tone Dual‐Channel MAC Protocol with Directional Antennas for Mobile Ad Hoc Networks

The directional medium access control (MAC) protocol improves the throughput of mobile ad hoc networks but has a deafness problem and requires location information for neighboring nodes. In the dual‐channel directional MAC protocol [12], the use of omnidirectional packets does not require the exact location of destination node. In this letter, we propose a tone dual‐channel MAC protocol with directional antennas to improve the throughput of mobile ad hoc networks. In the proposed MAC protocol, we use a directional CTS and an out‐of‐band directional DATA tone with a new blocking algorithm to improve the spatial reuse. We confirm the throughput performance of the proposed MAC protocol by computer simulations using the Qualnet simulator.     

移动代理WSN网络中信道Sift MAC协议

介绍了一种采用移动代理的无线传感器(WSN)网络,该网络系统由移动代理节点负责复杂数据处理、接入处理、数据转发传输、路由维护等工作,与一般WSN网络相比具有节能优势。该网络系统MAC层采用S-ALOHA协议,不仅网络吞吐量低而且能耗大,依据网络结构特点提出了采用基于信噪比(SNR)的信道Sift协议。仿真验证该协议大大提高了网络吞吐量和降低了网络系统能耗。     

Stability analysis for cognitive radio with multi-access primary transmission

This letter analyzes the impact, from a networklayer perspective, of having a single cognitive radio transmitterreceiver pair share the spectrum with multiple primary users wishing to communicate to a single receiver in a multi-access channel (MAC). In contrast to previous work which assumes a time division multi-access strategy, here, we assume the set of primary users simultaneously access the channel to deliver their packets to a common destination. We derive the symmetric stable throughput regions, consisting of maximal arrival rates for primary and secondary (or cognitive radio) users under two investigated protocols. The first protocol is a conventional MAC scheme where the primary and secondary nodes operate independenly. The second protocol corresponds to a multi-access relay channel (MARC) which exploits user cooperation between primary and secondary nodes. We prove that cooperation is beneficial in the considered MARC as it enables higher throughputs for both primary and secondary users.     

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。     

DCR‐MAC: distributed cognitive radio MAC protocol for wireless ad hoc networks

The MAC protocol for a cognitive radio network should allow access to unused spectrum holes without (or with minimal) interference to incumbent system devices. To achieve this main goal, in this paper a distributed cognitive radio MAC (DCR‐MAC) protocol is proposed for wireless ad hoc networks that provides for the detection and protection of incumbent systems around the communication pair. DCR‐MAC operates over a separate common control channel and multiple data channels; hence, it is able to deal with dynamics of resource availability effectively in cognitive networks. A new type of hidden node problem is introduced that focuses on possible signal collisions between incumbent devices and cognitive radio ad hoc devices. To this end, a simple and efficient sensing information exchange mechanism between neighbor nodes with little overhead is proposed. In DCR‐MAC, each ad hoc node maintains a channel status table with explicit and implicit channel sensing methods. Before a data transmission, to select an optimal data channel, a reactive neighbor information exchange is carried out. Simulation results show that the proposed distributed cognitive radio MAC protocol can greatly reduce interference to the neighbor incumbent devices. A higher number of neighbor nodes leads to better protection of incumbent devices. Copyright © 2008 John Wiley & Sons, Ltd.     

A hybrid multi-channel MAC protocol for wireless ad hoc networks

In a regular wireless ad hoc network, the Medium Access Control (MAC) protocol coordinates channel access among nodes, and the throughput of the network is limited by the bandwidth of a single channel. The multi-channel MAC protocols can exploit multiple channels to achieve high network throughput by enabling more concurrent transmissions. In this paper, we propose a hybrid and adaptive protocol, called H-MMAC, which utilizes multi-channel resources more efficiently than other multi-channel MAC protocols. The main idea is to adopt the IEEE 802.11 Power Saving Mechanism and to allow nodes to transmit data packets while other nodes try to negotiate the data channel during the Ad hoc Traffic Indication Message window based on the network traffic load. The analytical and simulation results show that the proposed H-MMAC protocol improves the network performance significantly in terms of the aggregate throughput, average delay, fairness and energy efficiency.