Spectrum sensing detection methods in cognitive radio systems

Wireless technology is the key technology to eliminate the dense wire ropes from hospitals and far access to medical devices. In order to overcome the problem of bandwidth scarcity, cognitive radio driven hospitals are introduced. Cognitive radio is the most effective technology to solve spectrum scarcity problem in contrast to high speed data transfer need. In cognitive radio systems, non-licensed users are permitted to use an idle licensed spectrum bandwidth. Whenever the license holder begin to use its spectrum, non-licensed user stops its communication and waits until the licensed user finish its communication. In cognitive radio driven hospitals, devices are divided in two categories just as the one in cellular communication. Primary devices has very high priority and their communication is vital for the hospital and patients, so that no interference should be made with such devices. Secondary devices are the ones which has lower priority and they can wait until the primary devices do their communication and then, they begin to use the allocated spectrum. The most important parameter in cognitive radio driven hospitals is a reliable spectrum sensing method. This method should be a simple one to be able to implement it in the secondary devices. Among all the sensing methods, energy detection based spectrum sensing and covariance based spectrum sensing is very popular. Maximum to minimum eigen-value based spectrum sensing is the best known of the covariance based spectrum sensing. In order to improve the performance of energy detection, double threshold concept is introduced. Double threshold energy detection method is introduced in literature to improve energy detection method performance. In this thesis, we used this concept in maximum to minimum eigen-value based spectrum sensing to improve its performance. The problem with covariance based spectrum sensing is its complexity. These complex methods can not be used in real systems of cognitive radio driven hospitals. The other method to improve the sensing algorithms performance is cooperative concept. The main reason of wireless hospitals is eliminating complexity and dense ropes that by using cooperative system for the devices, again this ropes and complexity will be used again. We have suggested to use memory concept in energy detection based spectrum sensing methods. Two new algorithms are introduced with considerably better performance with the cost of delay in secondary communication which is bearable. These new methods are memory based double threshold energy detection and memory based energy detection with their pros and cons.