Spectral Resource Management In Cognitive Radio Networks

Cognitive radio(CR)is the hopeful technology of 21st century in terms of radio spectrum exploitation,as it offers enhanced the quality of service(QoS)and throughput to users and is the excellent way to optimizing spectrum allocation.This technology enables a terminal to become acquainted with its radio environment and to have the ability to adapt to its environment.The CR terminals are capable of detecting unused portions of the spectrum and to adapt their transmission characteristics to the usage free of space bands.In recent years,the researchers have given a lot of interest to the study of this new technology.However,dynamic spectrum access in a cognitive radio system raises several challenges including the detection of free spectrum bands,equitable sharing of resources,conflict and interference management,and user mobility management.Each research community focuses its studies on one of these issues in order to achieve effective spectrum management.Nevertheless,certain parameters of essential functioning of this technology are not yet sufficiently studied such as spectrum detection,mobility management,tradeoff management between energy and spectral efficiency and the trading aspect of the spectrum between a cognitive user(CU)and a primary user(PU).In this thesis,we have studied the spectral management relating to cognitive radio networks(CRNs),which allows complete integration of CR technology with existing networks.First,a cooperative mode spectrum detection framework based on multi-user diversity is developed to increase the spectrum detection capability while satisfying the interference constraints,which can be extended to the CR networks.Spectrum detection is the very first step in implementing CR networks.By using multi-antenna system,it is easy to obtain diversity gain.In the detection of the PU signal,the major challenge is the detection of its low power as a noise level signal under the constraint of fading channels due to multiple paths.The most effective methods for avoiding fading channels due to multiple paths is to use a diversity receptor.The results of the simulation show that the proposed spectrum detection scheme provides better equity and higher network capacity compared to conventional spectrum sharing methods.Second,the CRNs technical framework for mobility management related to spectrum handoff is analyzed.CRNs attempt to dynamically use the spectrum while allowing radio terminals to operate in the most accessible spectral band,to maintain the QoS requirements concerning the transparent communication during handoff to a better frequency band.This thesis makes a significant contribution by proposing a very effective method that reduces information loss,and latency of spectrum handoff between a primary and secondary user.Reducing unnecessary and multiple handoffs of SUs,which improves the communication system stability of CUs.For this purpose,protocols have also been initiated to promote the smooth operation of the proposed scheme.The proposed scheme is implemented through simulation and compared to other handoff schemes following various simulation experiments.Thirdly,a compromise management framework is proposed between energy and spectral efficiency.A joint optimization of efficiency is possible between energy efficiency and spectral efficiency in spectral resource management.Overall energy efficiency is generally considered to be the strongest constraint involved in the design and analysis of wireless cognitive radio networks.This specific constraint is added to the challenges related to spectral efficiency.It is proven in this section that there is a trade-off between energy and spectral efficiency in the management of CRNs,Finally,after detection of the spectral hole nearby PUs the use of the spectral band by the SUs is not free.A trading aspect of the spectrum is developed in this thesis in order to make effective its management.This operation consists of selling a portion of the spectrum from PU to an SU to earn money.The PU is the one who has a license on the spectrum,the SU is the opportunistic user.Several models of spectrum pricing are presented.Given that the radio spectrum is a very scarce resource and requires an efficient allocation to meet the primary operators(POs)and the SUs,the economic issues raised in the dynamic spectrum sharing have an importance.The numerical results show the proposed scheme efficiency.