Browsing by Author "Kurt, G. K."

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Diversity-multiplexing tradeoff for network coded cooperative OFDMA systems
(IEEE, 2015) Heidarpour, Ali Reza; Kurt, G. K.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Heidarpour, Ali Reza
Network coded cooperation (NCC) is an effective method to improve the throughput efficiency in cooperative wireless networks. In an effort to have further gains over the initial works, which build upon the assumption of time division multiple access, the combined use of orthogonal frequency division multiplexing (OFDM) with NCC has been proposed in the literature. In this paper, we consider orthogonal frequency division multiple access (OFDMA), an extension of the OFDM to a multiuser system where subsets of carriers are assigned to different users. We derive a closed-form expression for the outage probability of the system under consideration and present the diversity-multiplexing tradeoff (DMT) analysis. Our results demonstrate that NCC-OFDMA system is able to fully exploit both frequency and spatial diversity. Simulation results are presented to verify our theoretical analysis.
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Implementation of network coding in wireless systems
(Springer Nature, 2018) Basaran, S. T.; Heidarpour, A. R.; Gokceli, S.; Kurt, G. K.; Uysal, Murat; Altunbas, I.; Electrical & Electronics Engineering; UYSAL, Murat
In this chapter, we target to give extensive performance analyses about application of network coding (NC) in wireless systems, referred to as network coded cooperation (NCC), brings both diversity and multiplexing gains. We use the diversity-multiplexing trade-off (DMT) to determine performance bounds of NCC systems. Within the scope of this study, NCC is integrated with orthogonal frequency division multiple access (OFDMA) and the corresponding system model is characterized by specifically focusing on frequency diversity gain. DMT expressions of the NCC-OFDMA system is given. A real-time implementation of the NCC-OFDMA system is presented by creating a testbed NI USRP-2921, NI PXIe-5644R, NI PXI-6683H software defined radio (SDR) modules and LabVIEW software. Obtained real-time performance measurements are essential to demonstrate the practical advantages or disadvantages of the usage of the NCC-OFDMA system. Overall, we aim to present a detailed overview of the fundamental performance bounds of NCC and its extension to the practical applicability of NCC in wireless networks.
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On the performance of NCC-OFDMA systems in the presence of carrier frequency offset
(IEEE, 2017) Heidarpour, Ali Reza; Kurt, G. K.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Heidarpour, Ali Reza
Network coded cooperative (NCC) systems have recently gained increasing attention due to their high power and spectral efficiency. For high speed data transmission over frequency-selective channels, NCC is further combined with orthogonal frequency division multiple access (OFDMA). In this paper, we derive outage probability and diversity gain of NCC-OFDMA systems in the presence of carrier frequency offset (CFO). Our results demonstrate that NCC-OFDMA system is capable to achieve full spatial and frequency diversity in noise limited system where the CFO variance σ2ε → 0. However, in interference limited case where the CFO variance σ2ε > 0, error floor occurs leading zero diversity gain. Numerical results are further presented to validate our analytical findings.