One of the emerging technology in Wireless communication is cognitive radio in which a wireless network changes its transmission or reception parameters to communicate efficiently avoiding interference with licensed or unlicensed users it enables cognitive terminals which are also called secondary unlicensed users to share spectrum with the primary licensed users to enhance the spectrum utilisation and important thing in its designing is spectrum sensin. A secondary cognitive user under the effect of shadowing or channel fading might not be able to sense the primary user's signal accurately. Collaboration among the secondary users in such a case enhances the overall spectrum sensing performance, where the individual observations of the secondary users are collected at a common receiver and a global conclusion is drawn. Thus, the selection of the appropriate secondary users is of importance, this will also in turn reduce the overall battery consumption, as fewer users would take part in collaboration.
In the past decade, there has been a great deal of increase growth in wireless communications. This can be seen by the phenomenal increase in the mobile and personal communication devices. The development of Wi-Fi , WiMax and other broadband wireless technologies for services like web surfing,mobile computing and mobile TV assures the future growth of wireless systems. Moreover, the use of mobile phones and other wireless systems have increased. All wireless systems require a range of spectrum, allocated by the government in order to operate. With the growing popularity of wireless systems, the problem of spectrum scarcity increased.
The main reason of spectrum scarcity is because of its underutilisation of allocated spectrum, as observed by the Spectrum Policy Task Force working for the FCC. This shows that the spectrum is mostly underutilized with a lot of empty spaces (white spaces) are available in-between. It is clear that the spectrum scarcity is mainly due to the under utilisation caused by fixed frequency assignment. If the spectrum is efficiently used, the problem of spectrum scarcity can be reduced to a large extent .To overcome the problem of spectrum being under utilised, various technical terms have been coined, among them Opportunistic Spectrum Access is of interest. The broad term Cognitive Radio enables secondary users to opportunistically access a licensed spectrum whenever it is not in use by a primary licensed user. The secondary user accessing a licensed spectrum for its use should not cause any interference to the primary user and vacate the spectrum as soon as a primary user arrives. In order to reduce the chances of secondary users causing interference to the primary users, the secondary users have to accurately identify the presence or absence of a primary user's signal in the first place. This alleviates the importance of spectrum sensing in cognitive radios. So different techniques are used for this purpose such as Energy detection which is a simple technique and does not require any prior knowledge about the primaryas user's signal, hence ideal for implementation in secondary user hardware. However, its performance is degraded in the presence of fading and shadowing. Collaboration among more than one secondary user was suggested to cope with this degradation in performance.
PROJECT GOALS AND CONTRIBUTIONS:
The project aim and goals are that we will analyze the short comings of the cognitive radio and how the spectrum sensing different techniques works such as using energy detection method. Also the constraint such as the presence of shadowing and fading would also be examine and to analyze that how the secondary user have achieved the better spectrum sensing performance using appropriate simulaion tool such as MATLAB to perform an optimisation scheme using Genetic Algorithm.
This is a research oriented project in which a comparative study will be conducted for the three basic cooperative strategies. The first step would be literature review so that good understanding of the domain is grabbed. It is also necessary to have good idea of the current status of the research going in this area. In the second step, a simulation platform will be developed in MATLAB. It will consist of implementation of the cooperation Algorithm. After this, the simulation will be performed. The simulation results will then be studied to identify the specific goals how much it have been achieved and also the pros and cons of each cooperation strategy.