For efficient spectrum utilization in cognitive radio networks it requires appropriate allocation of idle frequency spectrum among coexisting cognitive radios while maximizing total bandwidth utilization and minimizing interference. The fixed spectrum allocation scheme leads to low spectrum utilization across the whole spectrum. This paper is an attempt to overcome the problem in such wireless ...

Cognitive radio plays a vital role in wireless communication. The cognitive radio composed of a transceiver which is used to check the channel vacancy for communication and avoids busy channels by shifting into unused channel. The scope for spectrum vacancy and area of coverage is increased by using cognitive radio. In cooperative relay network to transmit the primary traffic the primary users ...

The rapid proliferation of wireless systems makes interference management more and more important. This paper presents a novel cognitive coexistence framework, which enables an infrastructure system to reduce interference to ad-hoc or peer-to-peer communication links in close proximity. Motivated by the superior resources of the infrastructure system, we study how its centralized resource alloc...

A fundamental problem in dynamic frequency reuse is that the cognitive radio is ignorant of the amount of interference it inflicts on the primary license holder. A model for such a situation is proposed and analyzed. The primary sends packets across an erasure channel and employs simple ACK/NAK feedback (ARQs) to retransmit erased packets. Furthermore, its erasure probabilities are influenced b...

We present a cognitive spectrum access solution for FH-CDMA ad hoc networks. Building on a cluster-based split phase multi-channel MAC protocol, we propose a mechanism for local interference avoidance through distributed hopset adaptation. Its goal is to identify and substitute channels not suitable for reliable communication. Substitution rules replace channels by locally unused hopsets. This ...

Traditional power allocation schemes in Orthogonal Frequency Division Multiplexing (OFDM) based Cognitive Radio Networks (CRNs) are achieved under perfect channel state information (i.e., exact parameter information). Due to channel estimation errors and feedback delays, however, channel uncertainties are inevitable in practical CRNs. In this paper, considering bounded channel uncertainties, a ...

This paper considers a spectrum-sharing cognitive network in which a secondary user shares spectrum with an existing primary user as long as the interference caused by the secondary user to the primary user is below permissible levels. We investigate the delay quality-of-service (QoS) guaranteed capacity gains with imperfect channel state information (CSI) between the secondary transmitter and ...

Abstract—Dynamic spectrum networks enable fast deployment of new wireless technologies by effectively utilizing allocated yet unused wireless spectrum. By sensing and utilizing available wireless channels, cognitive radio devices can provide high throughput, low latency communication. Existing schemes for channel assignment suffer drawbacks in throughput and reachability in the presence of loca...

This thesis focuses on the performance of terrestrial communication systems that use channel assignment schemes to allocate base stations in a scenario that implements the coexistence of mixed terrestrial communication systems based on cognitive radio technology. Interaction and coexistence of different channel assignment schemes is investigated. Reinforcement learning is applied into multicast...

Cognitive Radio Ad Hoc Networks (CRAHNs) constitute a viable solution to solve the current problems of inefficiency in the spectrum allocation, and to deploy highly reconfigurable and selforganizing wireless networks. Cognitive Radio (CR) devices are envisaged to utilize the spectrum in an opportunistic way by dynamically accessing different licensed portions of the spectrum. However the phenom...