Jayasinghe, Laddu Keeth Saliya creator Rajatheva, R.M.A.P Chairperson Ahmed, Kazi Mohiuddin Examination Committee Poompat Saengudomlert Examination Committee The Government of Finland Scholarship donor text series technical report th Pathum Thani, Thailand Asian Institute of Technology 2010 continuing eng 68 leaves : ill. Here, we analyze the relay networks with cognitive radio (CR), physical layer networkcoding (PNC) and multiple-input multiple-output (MIMO) communications.First, we investigate the optimal power allocation of relaynodes which are usedin the secondary user (SU) communication of a CR network. Thepower allocationproblem solves for regenerative, non-regenerative, N series and diversity relay modelsunder Rayleigh fading. The outage probability of SU communication is limited by theinterference power threshold (IPT) constraints of PUs and is affected significantly bythe IPT levels of PUs.An optimal power allocation problem is developed with IPT constraints to max-imize the sum-rate of the two-way communication. Similar behavior is observed as inthe one way transmission.Finally, we investigate OSTBC MIMO transmission with non-coherent amplify-and-forward relaying when the source-relay and relay-destination channels undergoRayleigh and Rician fading respectively. We derive expressions for the moment gener-ating function (MGF), moments, PDF of the SNR at the destination. We analyze thesystem performance by deriving new analytical expressionsfor the BER and amount offading. These performance metrics reveal that strong line of sight component betweenrelay-destination link always limit the performance promised by MIMO scattering en-vironment only when both nodes have multiple antennas. A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Telecommunications, School of Engineering and Technology Thesis (M.Eng.) - Asian Institute of Technology, 2010 Cognitive radio networks MIMO systems Wireless communication systems Asian Institute of Technology. http://203.159.5.9/ait-thesis/detail.php?q=B04074 http://203.159.5.9/ait-thesis/detail.php?q=B04074 110219 20260817162322.0