共查询到20条相似文献,搜索用时 15 毫秒
1.
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。 相似文献
2.
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. 相似文献
3.
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. 相似文献
4.
5.
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... 相似文献
6.
7.
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. 相似文献
8.
9.
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... 相似文献
10.
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. 相似文献
11.
12.
13.
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. 相似文献
14.
Slimeni Feten Chtourou Zied Scheers Bart Nir Vincent Le Attia Rabah 《Wireless Networks》2019,25(7):4161-4171
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... 相似文献
15.
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. 相似文献
16.
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. 相似文献
17.
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... 相似文献
18.
19.
Madiha Tabassum Md. Abdur Razzaque Md. Nazmus Sakib Miazi Mohammad Mehedi Hassan Abdulhameed Alelaiwi Atif Alamri 《Wireless Networks》2016,22(5):1523-1536
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. 相似文献
20.
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... 相似文献