Advances in cognitive radio networks: A survey <s> F. Control Channel Management <s> Device coordination in open spectrum systems is a challenging problem, particularly since users experience varying spectrum availability over time and location. We propose a distributed coordination approach that handles spectrum heterogeneity without relying on the existence of a preassigned common control channel. Our approach carries potential to provide robust operation under network dynamics. While this approach can be implemented by upgrading the legacy protocol stack without modifying the MAC protocol, we also describe modifications to the MAC protocol that address spectrum heterogeneity and significantly improve system performance. Experimental results show that the proposed distributed coordination scheme outperforms the existing coordination schemes by 25-35% in throughput and provides 50% of delay reduction <s> BIB001 </s> Advances in cognitive radio networks: A survey <s> F. Control Channel Management <s> As the radio spectrum usage paradigm shifting from the traditional command and control allocation scheme to the open spectrum allocation scheme, wireless mesh networks meet new opportunities and challenges. The open spectrum allocation scheme has potential to provide those networks more capacity, and make them more flexible and reliable. However, the freedom brought by the new spectrum usage paradigm introduces spectrum management and network coordination challenges. In this paper, we study the network formation problem in cognitive radio based mesh networks. A cluster-based approach is proposed to form a mesh network in the context of cognitive radio scenario. Moreover, a topology management algorithm is developed to optimize the cluster configuration with regard to the network topology. The prominent feature of the proposed approach lies in the capability to adapt the cluster configuration to network and radio environment changes. <s> BIB002 </s> Advances in cognitive radio networks: A survey <s> F. Control Channel Management <s> In this paper we address the control channel assignment problem in a cognitive radio based wireless network, namely the CogMesh. Such a network is featured by the dynamic spectrum sharing of the secondary users coexisting with the primary users. The opportunistic nature of the spectrum utilization among the secondary users makes a global control channel infeasible. The self-coordination of the network, hence, becomes a challenge task. Considering the fact that common channels may temporarily exist among a local group of secondary users, we propose an adaptive approach that selects local common control channels independently by each secondary user according to the qualities of the detected spectrum holes and the choices of its neighbors. To achieve this, a swarm intelligence-based algorithm is used to facilitate the common control channel selection. The idea is to use HELLO messages periodically broadcasted by neighbors as the pheromone to rank the common channels so as to expedite the channel selection process. The algorithm is completely distributed and therefore scalable. Moreover, it is simple, flexible, adaptive, and well balanced on the exploitation and exploration of the radio resources. The behaviors and performance of the proposed algorithm are verified by simulation. <s> BIB003 </s> Advances in cognitive radio networks: A survey <s> F. Control Channel Management <s> Cognitive networks enable efficient sharing of the radio spectrum. Multi-hop cognitive network is a cooperative network in which cognitive users take help of their neighbors to forward data to the destination. Control signals used to enable cooperation communicate through a common control channel (CCC). Such usage introduces conditions like channel saturation which degrades the overall performance of the network. Thus, exchanging control information is a major challenge in cognitive radio networks. This paper proposes an alternative MAC protocol for multi-hop cognitive radio networks in which the use of a CCC is avoided. The scheme is applicable in heterogeneous environments where channels have different bandwidths and frequencies of operation. It inherently provides a solution to issues like CCC saturation problem, Denial of Service attacks (DoS) and multi-channel hidden problem. The proposed protocol is shown to provide better connectivity and higher throughput than a CCC based protocol, especially when the network is congested. <s> BIB004
The majority of the DSA systems use a dedicated global control channel to coordinate the spectrum allocation. However, this assumption is not realistic in opportunistic spectrum access since there may be no permanent channel available for secondary users. A distributed group coordination solution is proposed in BIB001 , where a common control channel is only required locally by the neighbor nodes sharing common channels. A cluster based approach is presented in BIB002 , where a dynamic one-hop cluster is formed by users sharing common channels and the spectrum is managed by cluster heads. A distributed swarm intelligence based control channel assignment scheme is proposed in BIB003 , which selects local common control channels among a local group of secondary users according to the quality of the detected spectrum holes and the choice of the neighboring users. Potential control channel saturation will degrade the network performance severely. An alternative MAC protocol without requiring a common control channel for multi-hop CR networks is proposed in BIB004 . By dividing the time into fixed-time intervals and have all users listen to a channel at the beginning of each slot, the proposed protocol ensures that control signals can be exchanged among users.