ABSTRACT
In the present era, wireless communication is going in a big way and cognitive radio network (CRN) is one of the future-based technologies in wireless communication system. The concept of cognitive radio (CR) was first proposed by Joseph Mitola III at the Royal Institute of Technology (KTH) in Stockholm, Sweden, in 1998. CR is an intelligent wireless communication system, which is aware of its surrounding environment, learns from the environment, and adapts its internal states to statistical variations in the incoming radio-frequency (RF) stimuli by making corresponding changes in certain operating parameters in real time. A CR comes under the Institute of Electrical and Electronics Engineers (IEEE) 802.22 wireless regional area network (WRAN) standard and has the ability to detect the channel usage, analyze the channel information, and make a decision whether and how to access the channel. The US Federal Communications Commission (FCC) uses a narrower definition for this concept: “Cognitive radio: A radio or system that senses its operational electromagnetic environment and can dynamically and autonomously adjust its radio operating parameters to modify system operation, such as maximize throughput, mitigate interference, facilitate interoperability, and access secondary markets.” The primary objective of the CR is to provide highly reliable communication whenever and wherever needed and to utilize the radio spectrum efficiently. Static allocation of the frequency spectrum does not meet the needs of current wireless technology, so dynamic spectrum usage is required for wireless networks. CR is
6.8 Collaborative Spectrum Sensing Technique Based on ED Implies Multiple Antennas with ADTs in CRNs (CSS_ED_MA_ADT) 227
6.9 Simulation Results and Analysis for CSS_ED_MA_ADT 229 6.10 Conclusion and Future Work 231 Acknowledgments 231 References 231 Biographical Sketches 233
considered as a promising candidate to be employed in such systems as they are aware of their operating environments and can adjust their parameters. It can sense the spectrum and detect the idle frequency bands; thus, secondary users (SUs) can be allocated in those bands when primary users (PUs) do not use those bands in order to avoid any interference to PUs by SUs. In the CRN literature, PU and SU are considered as shown in Figure 6.1. The PU is a licensed user that has an allocated band of spectrum for exclusive use. The SU is unlicensed user that does not have an allocated band of spectrum. We use spectrum sensing techniques to detect the presence of PU licensed signal at low signal-to-noise ratio (SNR).
