Research On Spectrum Sensing Technology In Spectrum Sharing Radio Systems

As a smart spectrum sharing technology, cognitive radio can significantly improve the spectrum utilization. Spectrum sensing is recognized as one of the key technologies to implement cognitive radio. The classification of spectrum sensing technology is introduced in chapter 2. Generally, spectrum sensing technology can be classified as single-user spectrum sensing including transmitter spectrum sensing, receiver spectrum sensing and multi-users cooperative spectrum sensing. For the transmitter spectrum sensing, energy detection is introduced in details.The energy sensing scheme exploiting the cyclic prefix of an OFDM symbol is studied in chapter 3, which can improve the performance of detection compared with the conventional sensing scheme not exploiting the cyclic prefix. An improved scheme is proposed to reduce energy consumption for sensing and improve the achievable throughput for the secondary network by means of increasing sensing period. In the proposed scheme, the sensing period is limited to interference between primary user and secondary user and the time required to find spectrum holes. It is also analyzed through simulation results.Energy detection with multiple antennas is studied in chapter 4. In wireless multi-path fading channels, energy detection with multiple antennas is able to achieve reliable detection. Compared with multi-users cooperative spectrum sensing, it does not need extra communication bandwidth. Energy detection with multiple antennas can be classified as multiple antennas with single energy detector and multiple antennas with multiple energy detectors. For multiple antennas with single energy detector, three data fusion rules are analyzed including AND rule, OR rule and K/N rule. For multiple antennas with multiple energy detectors, maximum ratio processing and selection ratio processing are studied. The performance of multiple antennas with single energy detector and multiple antennas with multiple energy detectors are analyzed and compared through simulation results.