Performance Improvement of Cognitive Radio Systems through Advanced Spectrum Sensing Interference Management and Modulation Techniques

Abstract

The tremendous growth in wireless communication applications and services made it essential to newlineaddress the spectrum scarcity problem. With the static spectrum allocation strategy, licensed spectrum newlinebands are not used at full capacities resulting in a very low utilization ratio. The idea of cognitive radios newline(CRs) enables unlicensed users to exploit these underutilized spectral resources with the help of newlinedynamic spectrum access. Spectrum sensing provides the necessary information about the existence of newlinelicensed primary users in a particular spectrum band that is very useful in the CR deployment without newlineany harmful interference. However, in the case of erroneous detection of the primary user, secondary newlineusers may interfere with the primary users when both primary and secondary users are active simultaneously. newlineAlso in the case of the underlay spectrum sharing scenario, it is necessary to control the newlinetransmission parameters of the secondary users to avoid the harmful interference to the primary users. newlineTherefore, understanding the interference and its consequences on the achievable capacity for the underlay newlinecognitive radio network is critical. It is required for CR systems to develop efficient techniques to newlineenhance the capacities of both primary user (PU) and secondary user (SU) along with the efficient management newlineof the mutual interference that SUs cause to a PU receiver and the hindrance that PU causes newlineto SUs. The present thesis contributes to three major research areas, i.e. spectrum sensing, interference newlinemanagement, and modulation technique to improve the performance of a cognitive radio system. newlineTo opportunistically access the licensed bands, a reliable spectrum sensing capability is required to newlineidentify the available vacant frequency bands at a particular instance of time and specific geographic location. newlineVarious narrowband spectrum sensing techniques are explored with major emphasis on classical newlineenergy detection technique due to its simple structure and low computational complexity. newline