Different power loading allocation schemes for ofdm based cognitive radio system
International Journal of Latest Trends in Engineering and Technology · 2016
Now a day we are facing many problems regarding spectrums due to the growing application in wireless fields.Lot of wireless applications is sharing the same medium and due to this there is overburden which leads to shortage of spectrum in given frequency bands.On the other hand, measurement show that many spectrum bands are rarely used most of the time, whereas other bands are used heavily crowded and as we know the radio frequency is limited natural resource and its efficient use is of the almost very importance.Moreover, most spectrum bands are allocated to certain services but spectrum occupancy measurements show that only some portions of the spectrum band are heavily used.The use of radio spectrum can be improved by means of the cognitive radio (CR) technology.In some case, the spectrum bands are not been efficiently utilized because licensed user are absent and cannot occupy their spectrum and unlicensed users are not allowed to operate in same spectrum bands.Spectral efficiency can be improved significantly by giving Opportunistic access of the frequency bands to a group of required users (secondary CR users) for whom the band has not 1 Department of Electronics & Telecommunication D. Y.