Cognitive Radio (CR) technology was introduced to effectively exploit the under-utilization portions of the licensed spectrum. A primary challenge in enabling CR networking is how to coordinate the CR communications, in which CR users need to exchange their control information before data exchange can take place. Providing a reliable coordination mechanism in CR networks (CRNs) is not an easy task because of the dynamic nature of primary radio (PR) activities and the heterogeneity of both spectrum availability and CR users’ distribution. In this paper, we propose a dynamic-size clustering with CSMA/CA-based algorithm to overcome the challenge of achieving reliable coordination in CR networks (CRNs). CR users in our scheme are organized into dynamic size clusters and cooperate in selecting common control channels (CCCs) and use them for cluster coordination. The proposed scheme called Dynamic-hop virtual clustering distributed coordination (DH-VCDC). This scheme provides a dynamic-hop virtual clustering based on the traffic condition of both PR and CR users while achieving a minimum number of common available data channels per cluster, in which a better trade-off between the number of common idle channels per cluster and the cluster size is achieved. DH-VCDC scheme exploits the advantages of using Multi-packet Multi-channel Discontinuous Orthogonal Division Multiplexing (DOFDM) to reduce neighbor discovery time, allow CR users to have several cluster memberships, select multiple CCCs and simplify the inter-cluster coordination. CR users in our scheme are grouped to form virtual clusters each contains at least 2 CCCs (primary and backup CCCs). Three modes of DH-VCDC are presented: one-, two- and three-hop modes. Each CR must continuously monitor both PR and CR traffic loads and accordingly chooses the appropriate DH-VCDC mode. The performance of DH-VCDC is compared with reference schemes, in which significant performance improvement is reported.

引入了认知无线电（CR）技术以有效利用许可频谱中未充分利用的部分。启用CR网络的主要挑战是如何协调CR通信，其中CR用户需要先交换其控制信息，然后才能进行数据交换。在CR网络（CRN）中提供可靠的协调机制并非易事，因为主要无线电（PR）活动的动态性质以及频谱可用性和CR用户分布的异质性。在本文中，我们提出了一种基于CSMA / CA的动态大小聚类算法，以克服在CR网络（CRN）中实现可靠协调的挑战。我们方案中的CR用户被组织成动态大小的集群，并合作选择公共控制信道（CCC），并将其用于集群协调。所提出的方案称为动态跳跃虚拟群集分布式协调（DH-VCDC）。该方案基于PR和CR用户的流量状况，提供了一个动态跃点虚拟群集，同时实现了每个群集的最小可用公共数据通道数，其中，每个群集的公共空闲通道数与群集大小已达到。DH-VCDC方案利用了使用多数据包多信道不连续正交分割多路复用（DOFDM）的优势，以减少邻居发现时间，允许CR用户拥有多个集群成员，选择多个CCC并简化集群间协调。我们的方案中的CR用户被分组以形成虚拟集群，每个虚拟集群至少包含2个CCC（主CCC和备用CCC）。介绍了DH-VCDC的三种模式：一跳，二跳和三跳模式。每个CR必须连续监视PR和CR流量负载，并相应地选择适当的DH-VCDC模式。将DH-VCDC的性能与参考方案进行了比较，其中报告了显着的性能改进。