MAC Protocol for Opportunistic Cognitive Radio Networks with Soft Guarantees

Cognitive radio (CR) is the key enabling technology for an efficient dynamic spectrum access. It aims at exploiting an underutilized licensed spectrum by enabling opportunistic communications for unlicensed users. In this work, we first develop a distributed cognitive radio MAC (COMAC) protocol that enables unlicensed users to dynamically utilize the spectrum while limiting the interference on primary (PR) users. The main novelty in COMAC lies in not assuming a predefined CR-to-PR power mask and not requiring active coordination with PR users. COMAC provides a statistical performance guarantee for PR users by limiting the fraction of the time during which the PR users' reception is negatively affected by CR transmissions. To provide such a guarantee, we develop probabilistic models for the PR-to-PR and the PR-to-CR interference under a Rayleigh fading channel model. From these models, we derive closed-form expressions for the mean and variance of interference. Empirical results show that the distribution of the interference is approximately lognormal. Based on the developed interference models, we derive a closed-form expression for the maximum allowable power for a CR transmission. We extend the min-hop routing to exploit the available channel information for improving the perceived throughput. Our simulation results indicate that COMAC satisfies its target soft guarantees under different traffic loads and arbitrary user deployment scenarios. Results also show that exploiting the available channel information for the routing decisions can improve the end-to-end throughput of the CR network (CRN).     

Cross-Layer Design for QoS in Wireless Mesh Networks

Cross-layer design for quality of service (QoS) in wireless mesh networks (WMNs) has attracted much research interest recently. Such networks are expected to support various types of applications with different and multiple QoS and grade-of-service (GoS) requirements. In order to achieve this, several key technologies spanning all layers, from physical up to network layer, have to be exploited and novel algorithms for harmonic and efficient layer interaction must be designed. Unfortunately most of the existing works on cross-layer design focus on the interaction of up to two layers while the GoS concept in WMNs has been overlooked. In this paper, we propose a unified framework that exploits the physical channel properties and multi-user diversity gain of WMNs and by performing intelligent route selection and connection admission control provides both QoS and GoS to a variety of underlying applications. Extensive simulation results show that our proposed framework can successfully satisfy multiple QoS requirements while it achieves higher network throughput and lower outage as compared to other scheduling, routing and admission control schemes.     

Performance Analysis of a New MAC Protocol for Wireless Cognitive Radio Networks

Wireless Personal Communications - In this study, network performance analysis of a newly proposed cognitive radio wireless network (CRWN) medium access control (MAC) protocol is investigated in...     

Cross-Layer Design for QoS Support in Multihop Wireless Networks

Due to such features as low cost, ease of deployment, increased coverage, and enhanced capacity, multihop wireless networks such as ad hoc networks, mesh networks, and sensor networks that form the network in a self-organized manner without relying on fixed infrastructure is touted as the new frontier of wireless networking. Providing efficient quality of service (QoS) support is essential for such networks, as they need to deliver real-time services like video, audio, and voice over IP besides the traditional data service. Various solutions have been proposed to provide soft QoS over multihop wireless networks from different layers in the network protocol stack. However, the layered concept was primarily created for wired networks, and multihop wireless networks oppose strict layered design because of their dynamic nature, infrastructureless architecture, and time-varying unstable links and topology. The concept of cross-layer design is based on architecture where different layers can exchange information in order to improve the overall network performance. Promising results achieved by cross-layer optimizations initiated significant research activity in this area. This paper aims to review the present study on the cross-layer paradigm for QoS support in multihop wireless networks. Several examples of evolutionary and revolutionary cross-layer approaches are presented in detail. Realizing the new trends for wireless networking, such as cooperative communication and networking, opportunistic transmission, real system performance evaluation, etc., several open issues related to cross-layer design for QoS support over multihop wireless networks are also discussed in the paper.     

带休眠算法的无线传感器网络MAC协议

由于无线传感器网络中每个传感器节点的能量有限,所以需要有效的MAC协议来保持能量的高效利用。在MAC协议中引入休眠算法是其中一种重要的节能方式。现有的带休眠算法的无线传感器网络MAC协议已有很多种,主要分为2大类:一类是以S-MAC协议为代表的基于休眠/监听排程方案来达到节能目的的MAC协议;另一类是以WiseMAC为代表的基于低功率信道检测方案的MAC协议。对现有的主要几种有代表性的带休眠算法的无线传感器网络MAC协议进行了描述,分析了它们各自的优缺点,并进行了对比和总结。     

Opportunistic Channel Selection Strategy for Better QoS in Cooperative Networks with Cognitive Radio Capabilities

Mission-oriented MANETs are characterized by implicit common group objectives which make inter-node cooperation both logical and feasible. We propose new techniques to leverage two optimizations for cognitive radio networks that are specific to such contexts: opportunistic channel selection and cooperative mobility. We present a new formal model for MANETs consisting of cognitive radio capable nodes that are willing to be moved (at a cost). We develop an effective decentralized algorithm for mobility planning, and powerful new Altering and fuzzy based techniques for both channel estimation and channel selection. Our experiments are compelling and demonstrate that the communications infrastructure-specifically, connection bit error rates-can be significantly improved by leveraging our proposed techniques. In addition, we find that these cooperative/opportunistic optimization spaces do not trade-off significantly with one another, and thus can be used simultaneously to build superior hybrid schemes. Our results have significant applications in high-performance mission-oriented MANETs, such as battlefield communications and domestic response & rescue missions.     

Comparing Energy-Saving MAC Protocols for Wireless Sensor Networks

Applications for wireless sensor networks have notably different characteristics and requirements from standard WLAN applications. Low energy consumption is the most important consideration. The low message rate that is typical for sensor network applications and the relaxed latency requirements allow for significant reductions in energy consumption of the radio. In this article we study the energy saved by two MAC protocols optimized for wireless sensor networks, S-MAC and T-MAC, in comparison to standard CSMA/CA, We also report on the effects of low-power listening, a physical layer optimization, in combination with these MAC protocols. The comparison is based on extensive simulation driven by traffic that varies over time and location; sensor nodes are inactive unless they observe some physical event, or send status updates to the sink node providing the connection to the wired world. T-MAC} in combination with low-power listening saves most energy, but can not handle the same peak loads as CSMA/CA and S-MAC.Gertjan Halkes earned a B.Sc. and an M.Sc. in computer science from the Delft University of Technology in 2002 and 2004 respectively. He is currently working as a Ph.D. student in the Parallel and Distributed Systems group at that same university.Tijs van Dam received an M.Sc. in computer science from Delft University of Technology, The Netherlands in 2004. He is now working for IBM.Koen Langendoen is an associate professor in the Parallel and Distributed Systems group at Delft University of Technology, The Netherlands. He earned an M.Sc. in computer science from the Vrije Universiteit, Amsterdam in 1988 and a Ph.D. in computer science from the Universiteit van Amsterdam in 1993. His research interests include system software for parallel processing, wearable computing, embedded systems, and wireless sensor networks.     

Cross-Layer Based Asymmetric Resource Allocation in Relay-Aided Cognitive Radio Networks

Wireless Personal Communications - Cross-layer based asymmetric resource allocation in relay-aided cognitive radio networks (CRN) is proposed in this paper. Existing cross-layer schemes on...     

基于粗糙集的认知无线网络跨层学习

 认知学习是认知无线网络(CRN)跨层设计中非常重要的一环,它要求通信网络能利用已知跨层环境参数进行知识提取学习,并根据需要重配置网络.本文提出了一种基于粗糙集的CRN跨层学习技术,构建了案例事件库、知识库与规则匹配器,该模型结合数据离散、属性约简、值约简与规则生成算法来解决CRN的跨层学习问题.通过典型测试数据集的仿真比较,选出一组适合于所提出模型的粗糙集算法集合.仿真结果表明,该算法集能有效解决CRN跨层学习中知识提取与规则生成的准确性及有效性等问题,提出的跨层学习模型能有效用于CRN中的知识学习.     

Opportunistic Routing Protocols in Wireless Sensor Networks

Wireless Personal Communications - Research on wireless sensor network (WSN) has mainly involved the use of a portable and limited power source, namely batteries, to power the sensors. Without...     

基于跨层设计的无线网络QoS技术

随着多媒体业务的不断发展,如何保证无线网络上的QoS成为一个很重要的问题.基于传统的分层设计方法很难适应快速变化的无线通信环境.主要研究无线网络QoS的跨层设计技术,分析了无线网络的特点及其QoS需求,在此基础上阐述跨层设计的思想和方法,讨论了QoS跨层设计目前存在的问题,对QoS跨层设计技术进行了展望.     

Designing a MAC Algorithm for Equitable Spectrum Allocation in Cognitive Radio Wireless Networks

Spectrum sharing is one of the most important stages in cognitive radio wireless networks, responsible for the opportunistic allocation of free channels to unlicensed users (SUs) to be utilized in data transmission. One of the critical issues at this stage, is related to the absence of a module capable of allocating the available resources fairly to all network users. In this sense, the paper develops a media access control protocol (MAC) for cognitive networks based on infrastructure called CRUD-MAC, which allows to take advantage of channel access in a more equitable and efficient way; for this purpose two algorithms we designed within the MAC standard (using ANFIS and FAHP) for the ranking or classification of SUs by score when assigned channels based on network usage historical metrics, so that nodes with better ranking have priority in the allocation. Validation of the proposals was made by comparing the performance of CRUD-MAC with ANFIS, FAHP, and a channel assignment algorithm, not including ranking. The results show that the system is more efficient from the standpoint of fair allocation of resources.     

认知无线网络随机接入MAC协议建模与性能分析

该文采用马尔科夫链构建了认知无线网络随机接入MAC协议的数学模型,提出了一种协议分析的理论方案。该方案建立了信道的三状态马尔科夫链模型,通过引入授权信道限制率和稳态可用授权信道数的概念,解决了信道状态时变特性给理论分析带来的挑战;建立了基于离散2维马尔科夫链的信道协商模型,并考虑控制信道容量限制等约束条件,给出了协议饱和吞吐量的理论分析算法。仿真验证了所提方案的有效性,分析了协议性能与网络参数之间的数值关系。     

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WSN的能量高效MAC协议研究

介质访问控制(medium access control,MAC)协议能效性直接影响着无线传感器网络的寿命.在阐述能量消耗分布及造成无效功耗原因的基础上,分析了MAC协议的性能评价指标和分类方法;重点围绕能量高效,比较研究了当前一些重要的MAC协议,结果表明不存在满足所有要求的协议,仅仅是在各性能间优化折中;最后展望了无线传感器网络MAC协议进一步的研究趋势.     

无线传感器网络MAC协议研究

本文首先从应用需求和业务特性两方面分析了无线传感器网络MAC协议设计面临的挑战.然后,结合现有典型协议,对无线传感器网络MAC协议的研究现状和趋势、节能策略及协议其他特点进行了分析与总结.最后,探讨了无线传感器网络MAC协议的待研究问题.     

认知无线Mesh网络跨层设计研究

传统网络的分层设计不能满足具有特殊QoS需求的无线宽带业务,无法应对动态频谱接入的无线通信环境。采用联合开放、架构灵活的跨层设计研究无线Mesh网络接入技术日渐成为热点。本文首先介绍了跨层设计的起源、分类,然后分析了认知无线Mesh网络跨层研究的挑战、难点及最新进展,并提出利用跨层设计实现路由及频谱管理的一种构想,最后展望了认知无线Mesh网络跨层研究的新方向。     

CL-MAC: A Cross-Layer MAC protocol for heterogeneous Wireless Sensor Networks

In duty cycled MAC protocols, multi-packet, multi-flow and multi-hop traffic patterns experience significant latencies, which are partially due to duty cycling. Several cross-layer routing/MAC schemes have been proposed to mitigate this latency. However, they utilize routing information from a single flow and/or a single packet perspective, thus limiting their adaptation to varying traffic loads and patterns. In this paper, we propose a novel Cross-Layer MAC protocol (CL-MAC) for WSNs, to efficiently handle multi-packet, multi-hop and multi-flow traffic patterns while adapting to a wide range of traffic loads. CL-MAC’s scheduling is based on a unique structure of flow setup packets that efficiently utilize routing information to transmit multiple data packets over multiple multi-hop flows. Unlike other MAC protocols, supporting construction of multi-hop flows, CL-MAC considers all pending packets in the routing layer buffer and all flow setup requests from neighbors, when setting up a flow. This allows CL-MAC to make more informed scheduling decisions, reflecting the current network status, and dynamically optimize its scheduling mechanism accordingly. We evaluate CL-MAC through extensive ns-2 simulations and compare its performance to the state of the art, over various networks and for a wide variety of traffic loads and patterns. In all our experiments, CL-MAC substantially reduces end-to-end latency, increases delivery ratio while reducing the average energy consumed per packet delivered.     

一种简单的适合无线Mesh网络的机会协作MAC机制

针对IEEE802．11MAC（medium access control）协议中通信模式的缺陷,提出了一种新的协作MAC机制。该机制重点研究了分布式中继节点的选择算法,并定义了一种新的控制帧（retran）。目的节点通过发送retran帧启动协作机制,收到该帧的节点根据中继选择算法设置自身定时器,从而竞争产生“机会中继”,使其在源节点与目的节点之间搭建通信桥梁,该方法简单可行。仿真表明,随着网络中节点数的增加,新的机制对网络吞吐量和误比特性能的改善效果明显,从而提高了通信质量。     

Cross-Layer QoS Scheduling for Layered Multicast Streaming in OFDMA Wireless Networks

The conventional multicast scheme of wireless networks, though establishing a bandwidth-saving means for point-to-multipoint transmission, is very conservative by limiting the throughput of short-range communications. The multicast performance can be significantly improved if some low-rate users are pruned. In this paper, we investigate the subchannel assignment mechanism of multicast streaming services in the emerging WiMax/802.16e systems, where each multimedia stream is composed of a basic layer and an enhancement layer. The former affords a low-resolution video image to all the subscribers, while the latter only serves those with preferable channel states. Optimization frameworks are formulated to characterize the QoS requirements of multicast flows: pruned proportional rate ratio (PPRR), pruned stream rate guarantee (PSRG) and pruned user proportional fairness (PUPF). Three cross-layer algorithms are presented to perform channel assignment for different QoS requirements. Analytical study shows that the proposed algorithms have polynomial-time computational complexity. Numerical experiments validate that our proposals significantly outperform the conventional peer schedulers in terms of system throughput.