Resource allocation and interference mitigation for OFDMA based wireless hierarchical networks | |
| Author | Gamage, Amila Pradeep Kumara Tharaperiya |
| Call Number | AIT Thesis no.TC-11-07 |
| Subject(s) | Cognitive radio networks Wireless communication systems Orthogonal frequency division multiplexing |
| 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-11-07 |
| Abstract | Recent studies have revealed vast underutilization of the statically allocated licensed spectrum bands across space and time. Cognitive radio (CR) technology is an evolutionary concept for efficient radio spectrum utilization that performs detection of the unused bands and temporarily uses them without inflicting any serious interference to primary user (PU) of such bands. We consider energy detector based PU sensing using multiple correlated antenna CR deploying a square law combiner operating under Nakagami-m faded, AWGN corrupted channels from PU to CR. We derive the average probability of detection explicitly for two, three and four correlated antenna CR and also illustrate a generalized approach for L correlated antennas. We take this scenario further to a cooperative detection network that has a number of multiple correlated antenna CRs assuming Nakagami-m faded and AWGN corrupted channels from each CR to a fusion center (FC) which produces the ultimate decision regarding the spectrum vacancy. We derive an optimal log-likelihood ratio (LLR) at the FC for two, three and four antenna CR and generalize the results for any number of antennas. Our analysis suggests that the existence of correlation among antennas degrades the detection performance of each individual CR and of the overall cognitive network. However, the improvement in detection capability due to antenna diversity is more pronounced than the deterioration in it due to antenna correlation. Hence, antenna diversity is beneficial for boosting the individual as well as the overall detection capability of co-operative CRs even in presence of antenna correlation. We next consider an optimal allocation of the total transmit power of a PU in a bid to maximize the capacity of PU to base station (BS) such that the m out of N fused probability of detection of PU by an N number of collaborating CRs is above a certain threshold guaranteeing a reliable cooperative detection performance. We formulate and solve the problem after proving it to be convex to analyze the effect of m out of N fusion rule on both the optimal capacity and the corresponding fused detection probability. The MAJORITY rule has the best detection probability whereas the OR rule tends to somewhat balance the tradeoff between high PU capacity and high fused detection probability requirements. |
| Year | 2011 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. TC-11-07 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Telecommunications (TC) |
| Chairperson(s) | Rajatheva, R.M.A.P. |
| Examination Committee(s) | Teerapat Sanguankotchakorn;Poompat Saengudomlert |
| Scholarship Donor(s) | Thailand (HM King) |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2011 |