Adaptive Modulation and Coding and Cooperative ARQ in a Cognitive Radio System

In this paper, a joint cross-layer design of adaptive modulation and coding (AMC) and cooperative automatic repeat request (C-ARQ) scheme is proposed for a secondary user in a shared-spectrum environment. First, based on the statistical descriptions of the channel, closed-form expressions of the average spectral efficiency (SE) and the average packet loss rate (PLR) are presented. Then, the cross-layer scheme is designed, with the aim of maximizing the average SE while maintaining the average PLR under a prescribed level. An optimization problem is formed, and a sub-optimal solution is found: the target packet error rates (PER) for the secondary system channels are obtained and the corresponding sub-optimal AMC rate adaptation policy is derived based on the target PERs. Finally, the average SE and the average PLR performance of the proposed scheme are presented

Dynamic channel selection for multi-user video streaming over cognitive radio networks

Due to the dynamic nature of cognitive radio networks, multi-user video streaming (with various video traffic characteristics and QoS requirements) requires efficient dynamic channel selection schemes to exploit available spectrum resources. To do this, a wireless user needs to effectively model the dynamic wireless environment and estimate the delay of video packet transmission when selecting a specific frequency channel. In this paper, we apply the priority virtual queue model for these wireless users to adapt their channel selection and maximize video qualities. The simulation results show that the proposed channel selection solution based on priority scheduling outperforms the conventional dynamic channel selection scheme by 2 dB (PSNR). Index Terms — Video streaming, cognitive radio networks, priority queuing analysis

Radio network management in cognitive LTE-Femtocell Systems

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London.There is a strong uptake of femtocell deployment as small cell application platforms in the upcoming LTE networks. In such two-tier networks of LTEfemtocell base stations, a large portion of the assigned spectrum is used sporadically leading to underutilisation of valuable frequency resources. Novel spectrum access techniques are necessary to solve these current spectrum inefficiency problems. Therefore, spectrum management solutions should have the features to improve spectrum access in both temporal and spatial manner. Cognitive Radio (CR) with the Dynamic Spectrum Access (DSA) is considered to be the key technology in this research in order to increase the spectrum efficiency. This is an effective solution to allow a group of Secondary Users (SUs) to share the radio spectrum initially allocated to the Primary User (PUs) at no interference. The core aim of this thesis is to develop new cognitive LTE-femtocell systems that offer a 4G vision, to facilitate the radio network management in order to increase the network capacity and further improve spectrum access probabilities. In this thesis, a new spectrum management model for cognitive radio networks is considered to enable a seamless integration of multi-access technology with existing networks. This involves the design of efficient resource allocation algorithms that are able to respond to the rapid changes in the dynamic wireless environment and primary users activities. Throughout this thesis a variety of network upgraded functions are developed using application simulation scenarios. Therefore, the proposed algorithms, mechanisms, methods, and system models are not restricted in the considered networks, but rather have a wider applicability to be used in other technologies. This thesis mainly investigates three aspects of research issues relating to the efficient management of cognitive networks: First, novel spectrum resource management modules are proposed to maximise the spectrum access by rapidly detecting the available transmission opportunities. Secondly, a developed pilot power controlling algorithm is introduced to minimise the power consumption by considering mobile position and application requirements. Also, there is investigation on the impact of deploying different numbers of femtocell base stations in LTE domain to identify the optimum cell size for future networks. Finally, a novel call admission control mechanism for mobility management is proposed to support seamless handover between LTE and femtocell domains. This is performed by assigning high speed mobile users to the LTE system to avoid unnecessary handovers. The proposed solutions were examined by simulation and numerical analysis to show the strength of cognitive femtocell deployment for the required applications. The results show that the new system design based on cognitive radio configuration enable an efficient resource management in terms of spectrum allocation, adaptive pilot power control, and mobile handover. The proposed framework and algorithms offer a novel spectrum management for self organised LTE-femtocell architecture. Eventually, this research shows that certain architectures fulfilling spectrum management requirements are implementable in practice and display good performance in dynamic wireless environments which recommends the consideration of CR systems in LTE and femtocell networks

Cognitive Radio Systems

Cognitive radio is a hot research area for future wireless communications in the recent years. In order to increase the spectrum utilization, cognitive radio makes it possible for unlicensed users to access the spectrum unoccupied by licensed users. Cognitive radio let the equipments more intelligent to communicate with each other in a spectrum-aware manner and provide a new approach for the co-existence of multiple wireless systems. The goal of this book is to provide highlights of the current research topics in the field of cognitive radio systems. The book consists of 17 chapters, addressing various problems in cognitive radio systems

Application of Cognitivе Radio in Smart Grid Communication

Wireless communication is fast becoming the most common mode of communication. Invention of Bluetooth, WI-Fi, WiMAX, etc. have aided in popularizing wireless communication. Now wireless communication is being sought at for achieving communication in smart grid network .In a conventional power distribution system the power which was generated was being transmitted through the transmission link without taking into account the demand of the user. In a smart grid we address that issue. There is a flow of information from both sides. There are devices communicating with each other in sharing information. Advanced mitring scheme, dynamic pricing scheme have become new paradigm in smart grid. Research is going on for application of cognitive radios in smart grid communication .The spectrum used for communication is limited. Out of the channels available some have been licensed to certain users who are known as primary users. The other users are known as secondary users. The secondary users are large in number and the frequency channels available for them to communicate is limited in number. But the primary user use their allotted channels for very small amount of time. So, the secondary users can tap into those frequencies whenever it is idle. This can achieve efficiency in communication and help in reducing communication blockage of secondary users. Cognitive radios help in sensing the availability of the primary users in a channel and relay the data to secondary users so that they could use them. They also perform the task of switching the secondary users into another channel whenever a primary user uses that channel. In my work I have tried to find out an effective dynamic traffic scheduling scheme for effective communication purposes. First I had taken a scheme in which priority levels were assigned to different groups of secondary users without considering QoS of the channels. In my work I have tried to find out an еffеctivе dynamic traffic scheduling scheme for еffеctivе communication purposes. First I had taken a scheme in which priority levels wеrе assigned to different groups of secondary users without considering QoS of the channels. Thеn wе took QoS into consideration and calculated the system utilization, blocking probability in both cases for diffеrеnt sеcondary usеrs. Finally, I calculated the end to end delay using an optimal algorithm and comparеd it with thе еnd to еnd dеlay calculatеd without thе algorithm