| Author | Gautam, Manya |
| Call Number | AIT Thesis no.TC-08-10 |
| Subject(s) | Cognitive radio networks
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| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Telecommunications, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. TC-08-10 |
| Abstract | Cognitive Radio (CR) is an emerging wireless technology based on Software Defined Radio (SDR) that is aware of its environment and location and can make decisions on reusing the available frequency band dynamically. The efficiency of CR totally depends on its sensing ability so that it does not create interference to the primary or licensed user of that frequency. Various techniques have been proposed for spectrum sensing out of which cooperative sensing provides a much reliable result of the presence or absence of primary users (PUs) by combating the effect of fading or shadowing. Recent works on cooperative detection techniques have shown the improvements in the probability of detection and false alarm. However, the performance of cooperative sensing is severely degraded due to the presence of malicious secondary users (SUs). The security aspect of CR is a subject of research. In this thesis the effect of malicious users in CR networks is studied in a cooperative sensing environment. The capacity degradation of the PUs due to the interference created by such malicious act of the SUs is evaluated by calculating the signal to interference ratio (SIR). Due to this SIR the capacity of the primary gets degraded. In order to upgrade the performance of the PU a power control algorithm, in which transmit power of the PU is increased to minimize the effect of the interference, is applied. However, the increase in this power level ofthe PU should not cause interference to other adjacent PUs. A fixed-step power control technique is applied to the PU in which the power level of the PU is increased with a step size of 1 dB. Results show a significant increase of 4-5% in the capacity of the PU for small increment of 1 dB power level, still maintaining the SIR level of the neighboring PUs. However, for a larger increment the interference becomes prominent. In order to protect the PU's transmission from SUs a protected distance for the primary user can be selected within which the SUs are not allowed to transmit. The simulation is carried out to calculate the protection distance for the primary user. Results show that as the probability of detection is high the required protection distance is low and vice-versa. All the simulations are implemented in a MATLAB simulator. |
| Year | 2008 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. TC-08-10 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Department of Information and Communications Technologies (DICT) |
| Academic Program/FoS | Telecommunications (TC) |
| Chairperson(s) | Ahmed, Kazi M. |
| Examination Committee(s) | Rajatheva, R. M. A. P.;Erke, Tapio J. |
| Scholarship Donor(s) | AIT Fellowship |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2008 |