Hybrid Cognitive Network Research Articles

Cluster‐based spectrum access scheme selection and optimal relay link selection for hybrid overlay/underlay cognitive radio networks

SummaryCognitive radio (CR) network is the effective technique for the optimum utilization of the spectrum. The hybrid cognitive network (HCN) has been implemented to increase the utilization of the spectrum, by using both (overlay/underlay) modes of spectrum sharing. In overlay mode, cognitive radio (CR) opportunistically uses the spectrum, whereas in underlay mode, the CR uses the spectrum simultaneously with primary user (PU) with transmit power limitation. The HCN tries to use advantages of both modes of spectrum sharing. Its performance is based on the accuracy of the method used to find the PU status. Hence, in this paper, “clustering‐based spectrum access scheme selection and optimal relay link selection for hybrid overlay/underlay cognitive radio networks” have been proposed to improve the performance of the hybrid cognitive radio network. In this proposed method, the scheme selection is done in two levels. In the first level, spectrum sharing scheme is selected based on the cluster in which the SU is present, and in the second level, scheme is selected based on the PU status. The cluster‐based cooperative spectrum sensing method has been used to find the status of the PU. Compared with cooperative spectrum sensing, a cluster‐based cooperative spectrum sensing has a huge effect on sensing accuracy. While the underlay scheme is used by SU, best relay link has been selected by using particle swarm optimization technique. Thus, the best scheme selection and relay selection improve the performance of hybrid cognitive radio network. The simulation result shows that the proposed method improves the throughput of the HCN.

Capacity of hybrid cognitive network with outage constraints

The concept of cognitive radio is to exploit efficiently the spectrum resources by allowing the coexistence of the primary and secondary users in the same bandwidth without interfering the performance of primary users. Three coexisting models (overlay, underlay and interleave) were presented in recent literature. In this study, the authors propose a hybrid cognitive network model with overlay and underlay models, whereby a primary link leases its fractions of transmission time to the secondary users for their cooperation (i.e. these nodes form as a virtual multiple input multiple output (VMIMO) group) under the outage constraints of the primary and secondary systems. A new cooperative protocol between primary and secondary users is presented. The authors attempt to achieve the maximum transmission capacity of the secondary users under the primary and secondary outage constraints, which depend on the secondary density in the cognitive network. This study gives the upper bound density of the secondary transmitters that are modelled as a homogeneous marked Poisson point process. The maximum density is achieved by computing an optimal set of system parameters such as power control factor of the secondary user and the dirty paper coding (DPC) parameter. Simulation results illustrate that the maximum secondary density obtained using VMIMO is superior to that obtained by direct primary transmission.

Queuing network modeling of the psychological refractory period (PRP).

The psychological refractory period (PRP) is a basic but important form of dual-task information processing. Existing serial or parallel processing models of PRP have successfully accounted for a variety of PRP phenomena; however, each also encounters at least 1 experimental counterexample to its predictions or modeling mechanisms. This article describes a queuing network-based mathematical model of PRP that is able to model various experimental findings in PRP with closed-form equations including all of the major counterexamples encountered by the existing models with fewer or equal numbers of free parameters. This modeling work also offers an alternative theoretical account for PRP and demonstrates the importance of the theoretical concepts of "queuing" and "hybrid cognitive networks" in understanding cognitive architecture and multitask performance.