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Oklahoma State University

Random Subcarrier Allocation in OFDM-Based Cognitive Radio Networks

Monday, February 8, 2016 - 3:00pm to 4:00pm
103 ATRC

Refreshments and discussion following.  Open to the public.

SPEAKER:  Dr. Sabit Ekin

ABSTRACT:   Advances in communications technologies entail demands for higher data rates. One of the popular solutions to fulfill this requirement was to allocate additional bandwidth, which unfortunately is not anymore viable due to spectrum scarcity. In addition, spectrum measurements around the globe have revealed the fact that the available spectrum is under-utilized. One of the most remarkable solutions to cope with the under-utilization of radio-frequency spectrum is the concept of cognitive radio (CR) with spectrum sharing features, also referred to as spectrum sharing systems.

This work investigates the performance of an orthogonal frequency-division multiplexing (OFDM)-based CR spectrum sharing communication system that assumes random allocation and absence of the primary user’s (PU) channel occupation information, i.e., no spectrum sensing is employed to acquire information about the availability of unused subcarriers or the PU's activity. Due to the lack of information about PUs' activities, the secondary user (SU) randomly allocates the subcarriers of the primary network and collide with the PUs' subcarriers with a certain probability. The average capacity of SU with subcarrier collisions is employed as performance measure to investigate the proposed random allocation scheme for both general and Rayleigh channel fading models. In the presence of multiple SUs, the multiuser diversity gain of SUs is also investigated. The main benefit of proposed random subcarrier utilization is to uniformly distribute the amount of SUs' interference among the PUs' subcarriers, also termed as interference spreading. The analysis and performance of such a communication set-up provides useful insights and can be utilized as a valid benchmark for performance comparison studies in CR spectrum sharing systems that assume the availability of spectrum sensing information. Further, the complexity of the proposed random access method with respect to the methods based on spectrum sensing is much lower due to the elimination of spectrum sensing mechanism and minimal cooperation between primary and secondary base stations.

Sabit Ekin received his B.Sc. degree in the Department of Electrical and Electronics Engineering from Eskisehir Osmangazi University in Eskisehir, Turkey, in 2006, the M.Sc. degree from the Department of Electrical Engineering from New Mexico Tech, Socorro, NM, in 2008, and the Ph.D. degree from the Department of Electrical and Computer Engineering, Texas A&M University, College Station, TX in 2012.

He was working as a visiting research assistant in Electrical and Computer Engineering Program at Texas A&M University at Qatar (2008–2009). During the summer of 2012, he worked with the Femto-cell interference management team in the Corporate R&D at New Jersey Research Center, Qualcomm Inc. After his Ph.D. study, he joined in Qualcomm Technologies Inc., San Diego, CA, where his is currently working as a senior modem system engineer at the Department of Qualcomm Mobile Computing. His research interests are in the areas of design and performance analysis of communications systems, particularly interference management and statistical modeling of interference in next-generation wireless and cognitive radio networks.