认知无线网络中基于业务区分的自适应MAC协议

为了提高认知用户的接入效率,同时兼顾其QoS需求,提出了一种应用于认知无线网络的基于业务区分的自适应MAC协议。对不同业务采取不同的最优频谱检测时间,实时业务(RT)以最小化接入时延为目的确定最优的频谱检测时间,而非实时用户(NRT)则以最大化吞吐率为目标确定最佳的频谱检测时间。根据所确定出的最佳频谱检测时间,结合当前的业务到达速率和调度策略,不同业务以时隙Aloha的方式接入空闲频谱。理论分析和仿真表明,所提出的自适应MAC协议能够自适应地为认知用户的不同业务确定最优频谱检测时间,从而有效地提高频谱使用效率,保证不同业务的QoS需求。     

An auction‐based MAC protocol for cognitive radio networks

Cognitive radio and dynamic spectrum sharing systems use innovative spectrum management techniques that allow different systems to share the same frequency band to utilize the radio spectrum in an efficient way. In this paper, we propose a novel cognitive media access control protocol for cognitive radio networks under the property‐rights model, in which secondary users are divided into several nonoverlapping groups, and each group uses the proposed auction algorithm to bid for required channels from the auctioneer appointed by primary users. Simulations indicate that our proposed media access control protocol can effectively utilize spectrum resources, achieve high system efficiency, and guarantee the fairness of channel allocation among groups. Copyright © 2011 John Wiley & Sons, Ltd.     

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.     

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%。     

An improved fair channel hopping protocol for dynamic environments in cognitive radio networks

Wireless Networks - Rendezvous is a fundamental challenge in cognitive radio networks where users can find each other on a specific channel and hence establish a communication link. Most previous...     

A fair MAC protocol for resource sharing in ad-hoc cognitive networks

Cognitive Radio (CR) technology allows an opportunistic use of the licensed spectrum by the CR users, avoiding harmful interference to Primary Users (PUs). To perform their activity, secondary users (SUs) have particular features compared to the PUs; sensing is one of the principal. Specifically the CR users must detect the spectrum holes left by PUs by performing sensing. All the protocol stack need to be redesigned taking into account the specificity of the cognitive environment. In this paper a novel MAC protocol for cognitive radio wireless ad-hoc networks is presented and analysed. The introduced protocol is distributed, collision-free and guarantees a fair channel assignment, also taking into account the requests of Quality of Service (QoS) of the CR nodes. The performance of the protocol has been studied through statistical computations. In particular, a Markov chain has been introduced to study the global performance of the protocol. In addition a simulation tool has been developed to validate the mathematical model and to prove the fairness of the resource sharing mechanism. The results prove the protocol efficiency and the high fairness, measured with the help of the Jain’s fairness index.     

认知无线Mesh网络中基于马氏决策模型的MAC协议

为解决认知无线Mesh网络中专用控制信道较难获得的问题,提出一种基于POMDP的机会式频谱接入MAC协议,在不需要中心控制器和专用控制信道的协调下,实现动态频谱感知和接入。仿真结果表明,基于POMDP的接入策略能够有效提高网络频谱利用率和吞吐量,性能最优,而基于贪心算法的接入策略,在降低计算复杂度的同时,获得了较好的性能,实用性较强。     

Cooperative and fair MAC protocols for cognitive radio ad-hoc networks

Wireless Networks - A secondary user (SU) in multichannel cognitive radio ad hoc network (CRAHN) has a limited transmission range, which may raise a hidden multichannel sensing problem. In...     

Hopping control channel MAC protocol for opportunistic spectrum access networks

Opportunistic spectrum access （OSA） is considered as a promising approach to mitigate spectrum scarcity by allowing unlicensed users to exploit spectrum opportunities in licensed frequency bands. Derived from the existing channel-hopping multiple access （CHMA） protocol,we introduce a hopping control channel medium access control （MAC） protocol in the context of OSA networks. In our proposed protocol,all nodes in the network follow a common channel-hopping sequence; every frequency channel can be used as control channel and data channel. Considering primary users＇ occupancy of the channel,we use a primary user （PU） detection model to calculate the channel availability for unlicensed users＇ access. Then,a discrete Markov chain analytical model is applied to describe the channel states and deduce the system throughput. Through simulation,we present numerical results to demonstrate the throughput performance of our protocol and thus validate our work.     

认知无线电网络的分布式路由协议的研究

分布式路由算法广泛应用于认知无线电网络(CRNs)。为此,分析多跳CRNs的路由问题,利用无中心的Markov决策过程(DEC-POMDP)建立问题模型,并确保次级用户对主级用户的干扰少于预定阈值,进而控制端到端时延。最后引用多智能体学习算法解决此问题模型,进而形成基于多智能体学习的路由(MALR)。实验结果表明,提出的路由能够控制时延,并降低了干扰率。     

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。     

A distributed network coded control channel for multihop cognitive radio networks

Designing a solution for multihop cognitive radio networks poses several challenges such as the realization of the control channel, the detection of primary users, and the coordination of secondary users for dynamic spectrum access purposes. In this article we discuss these challenges and propose a solution that aims to meet most of them. The proposed solution is completely distributed, and does not need dedicated spectrum resources for control purposes, but rather leverages on a virtual control channel that is implemented by having users exchange control information whenever they meet in a particular channel, using network coding techniques for better dissemination performance. Due to these aspects, our proposal represents a significant improvement over existing dynamic spectrum access and multichannel MAC solutions. We discuss the effectiveness of our scheme in multihop cognitive ad hoc networks, where secondary users need to opportunistically access the spectrum at those locations and times at which it is not used by primary users. Finally, we report the results of an evaluation study assessing the performance of the proposed scheme with respect to different system and scenario parameters.     

Cooperative Q-learning based channel selection for cognitive radio networks

Wireless Networks - This paper deals with the jamming attack which may hinder the cognitive radio from efficiently exploiting the spectrum. We model the problem of channel selection as a Markov...     

TFRC-CR: An equation-based transport protocol for cognitive radio networks

Reliable and high throughput data delivery in cognitive radio networks remains an open challenge owing to the inability of the source to quickly identify and react to changes in spectrum availability. The window-based rate adaptation in TCP relies on acknowledgments (ACKs) to self trigger the sending rate, which are often delayed or lost owing to intermittent primary user (PU) activity, resulting in an incorrect inference of congestion by the source node. This paper proposes the first equation-based transport protocol based on TCP Friendly Rate Control for Cognitive Radio, called as TFRC-CR, which allows immediate changes in the transmission rate based on the spectrum-related changes in the network environment. TFRC-CR has the following unique features: (i) it leverages the recent FCC mandated spectrum databases with minimum querying overhead, (ii) it enables fine adjustment of the transmission rate by identifying the instances of true network congestion, as well as (iii) provides guidelines on when to re-start the source transmission after a pause due to PU activity. TFRC-CR is evaluated through an extensive set of module additions to the ns-2 simulator which is also released for further investigation by the research community.     

Adaptive power-controlled MAC protocols for improved throughput in hardware-constrained cognitive radio networks

Cognitive radios (CRs) are emerging as a promising technology to enhance spectrum utilization through opportunistic on-demand access. Many MAC protocols for cognitive radio networks (CRNs) have been designed assuming multiple transceivers per CR user. However, in practice, such an assumption comes at the cost of extra hardware. In this paper, we address the problem of assigning channels to CR transmissions in single-hop and multi-hop CRNs, assuming one transceiver per CR. The primary goal of our design is to maximize the number of feasible concurrent CR transmissions, and conserve energy as a secondary objective, with respect to both spectrum assignment and transmission power subject to interference constraint and user rate demands. The problem is formulated under both binary-level and multi-level spectrum opportunity frameworks. Our formulation applies to any power-rate relationship. For single-hop CRNs, a centralized polynomial-time algorithm based on bipartite matching that computes the optimal channel assignment is developed. We then integrate this algorithm into distributed MAC protocols that preserve fairness. For multi-hop ad hoc CRNs, we propose a novel distributed MAC protocol (WFC-MAC) that attempts to maximize the CRN throughput, assuming single transceiver radios but with “dual-receive” capability. WFC-MAC uses a cooperative assignment that relies only on information provided by the two communicating users. The main novelty in WFC-MAC lies in requiring no active coordination with licensed users and exploiting the dual-receive capability of radios, thus alleviating various channel access problems that are common to multi-channel designs. We conduct theoretical analysis of our MAC protocols, and study their performance via simulations. The results indicate that compared with CSMA/CA variants, our protocols significantly decrease the blocking rate of CR transmissions, and hence improve network throughput.     

A distributed spectrum handoff MSRV protocol for the cognitive radio ad hoc networks

Wireless Networks - Cognitive radio technology provides opportunistic wireless spectrums access for the secondary users (SUs) while primary users (PUs) are dormant. By emergence of a PU in the...     

An energy aware event-driven routing protocol for cognitive radio sensor networks

Cognitive radio sensor network (CRSN) is an intelligent and reasonable combination of cognitive radio technology and wireless sensor networks. It poses significant challenges to the design of topology maintenance techniques due to dynamic primary-user activities, which in turn decreases the data delivery performance of the network as well as it’s lifetime. This paper aims to provide a solution to the CRSN clustering and routing problem using an energy aware event-driven routing protocol (ERP) for CRSN. Upon detection of an event, the ERP determines eligible nodes for clustering according to local positions of CRSN nodes between the event and the sink and their residual energy levels. Cluster-heads are selected from the eligible nodes according to their residual energy values, available channels, neighbors and distance to the sink. In ERP, cluster formation is based on relative spectrum awareness such that channels with lower primary user appearance probability are selected as common data channels for clusters. For data routing, ERP employs hop-by-hop data forwarding approach through the CHs and primary/secondary gateways towards the sink. Through extensive simulations, we demonstrate that the proposed ERP provides with better network performances compared to those of the state-of-the-art protocols under a dynamic spectrum-aware data transmission environment.     

An efficient routing protocol for cognitive radio networks of energy-limited devices

Telecommunication Systems - In the era of Internet-of-things (IoT), the future 5G networks are supposed to provide ubiquitous connectivity, high speed, as well as low latency and energy efficiency...