LOWERING THE SNR WALL USING ADAPTIVE TECHNIQUES

Abstract

As wireless applications having growth rapidly in its services it becomes essential to deal with spectrum shortage problem. If we take a small part of radio spectrum and scan that portion including revenue rich urban areas, we will find that for some band of frequencies spectrum is overloaded on the same time other frequencies band are some frequency bands in the spectrum are vacant, there will also some range of frequencies available which are moderately occupied. This leads to generate a concept of underutilization of radio spectrum; Cognitive radio (CR) technology takes part in to improve this problem through improved utilization of radio spectrum. Cognitive radio is called secondary users in the wireless communication in which a transceiver can smartly sense in which RF channels primary users (licensee users) are present or absent, and it has capability to move into vacant channels or out of the channel without disturbing the occupied ones. Spectrum sensing plays an important role in cognitive radio concept. Various spectrum sensing techniques have been already discussed in past research work in wireless communication field. The main role of spectrum sensing is to detect the unused spectrum called white hole. In this thesis we analyze the performance of energy based detection spectrum sensing scheme in cognitive radio. By considering the uncertainty presence in wireless channel, degrade performance of energy detector is showed called “SNR wall”. This limitation can be improved by adopting a new adaptive technique to reduce SNR wall as shown in the simulation results. Computer simulation showed that detection performance for schemes are sensitive in lower signal-to-noise under noise uncertainty environment. Improved results obtained from new technique are shown in simulation.