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The exploitation of spectrum opportunities in the dimension of height will bring another transmission degree of freedom for wireless networks. Besides, the modern wireless networks are deployed in the three dimensional (3D) space, which need cognitive radio technologies to enhance their performances. With these motivations, the capacity of 3D cognitive radio networks (CRNs) is addressed in this paper...
Global time synchronization is an important function that enables all devices in a network to have a unified time. In traditional wireless ad hoc networks, since the spectrum is always available, the global time synchronization process usually can be performed without any interruption. However, in cognitive radio (CR) ad hoc networks, the global time synchronization process among secondary users may...
In this paper, we investigate the connectivity of a two-tier network, which is composed of a primary tier and a secondary tier according to their different spectrum access priorities. The primary nodes and secondary nodes are both distributed over the same Euclidean space following two independent Poisson point processes of densities λP and λS, respectively. The two tiers operate over a synchronized...
Recently, multichannel protocols have been proposed and shown to significantly improve the aggregate throughput compared to single channel protocols. However, some existing proposals still suffer from low channel utilization or unfair bandwidth allocation between different flows in a multihop wireless network. In this paper, we design an asynchronous multichannel MAC called the cooperative multichannel...
As we know, secure communication is the key of success for any wireless network. Denial of Service (DoS) attacks is severe in all the attacks in security of wireless network. Furthermore, cognitive radio networks are vulnerable to DoS attack due to their own characteristics. This paper analyzed the architecture of cognitive radio networks and emphatically discussed the possible various DoS attacks...
When the crypto-period is expired or the key is compromised, trusted third party (TTP) broadcasts the materials of key update. The method cannot guarantee that all the nodes access to key materials in time if nodes work on different spectrums in cognitive radio networks. This paper presents a new algorithm based on the logistic model (KULCR) which reduces the demand for network synchronization and...
This paper proposes a novel reconfiguration management scheme to dramatically improve spectral efficiency and performance in cognitive radio networks. It is very suitable for efficient wireless services in dense spectrum environment. A specific distributed spectrum etiquette protocol called ASCP (Adaptive Spectrum Coordination Protocol) is designed and analyzed. With proposed opportunistic collaboration...
How to realize the cognitive capability is a key point to realize the cognitive wireless network. The research of cognitive wireless network is still at the primary stage, even not having a unique, accepted network architecture and implementation method. The construction of knowledge base in cognitive wireless network based on network situation-aware in the paper is deeply investigated in unfixed...
We study two distinct, but overlapping, networks which operate at the same time, space and frequency. The first network consists of n randomly distributed primary users, which form either an ad hoc network, or an infrastructure supported ad hoc network in which l additional base stations support the primary users. The second network consists of m randomly distributed secondary or cognitive users....
Opportunistic spectrum access (OSA) allows unlicensed users to share licensed spectrum in space and time with no or little interference to primary users, which bring new research challenges in MAC design. In this paper, we firstly introduce the differences between the conventional multi-channel MAC protocols and the MAC protocols for OSA as well as the requirements for OSA MAC protocols, and then...
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