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In this study, real-time software defined radio implementation of the point to point multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) system using pre-fast Fourier transform (pre-FFT) beamforming technique in both the transmitter and the receiver is done for the first time in the literature. By taking benefit of the MIMO system's spatial multiplexing property, the performance of the implemented pre-FFT beamforming approach is demonstrated in terms of bit error rate and error vector magnitude measurements. As a result of the test results, the effect of the beamforming methods on the performance of communication systems are clearly observed.

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In this article, performance of a multi‐user downlink non‐orthogonal multiple access system in dual‐hop full‐duplex amplify‐and‐forward relaying networks is investigated over Nakagami‐m$$ m $$ fading channels in the presence of channel estimation error and feedback delay. The base station applies transmit antenna selection (TAS)/Alamouti space‐time block coding scheme, while the users exploit maximum‐ratio combining to utilize benefits of receive diversity. To demonstrate superiority of the proposed system, outage probability (OP) is investigated, and tight lower bound expression is derived to support the exact OP. Moreover, asymptotic analyzes are also conducted for ideal and practical conditions to provide further insights into the OP in high signal‐to‐noise ratio region. In addition, software defined radio based test‐bed implementation is realized to confirm the analysis and show feasibility of the proposed system. Theoretical analyzes verified by simulations and practical implementations demonstrate that more performance improvement can be achieved for the weakest user (with the lowest channel gain) in the case of practical conditions when compared to ideal cases. Also, both diversity order and array gain are dominant in achieving minimum OP (based on relay location) in ideal conditions, while only array gain has effect in practical manner.

In this paper, the performance of a power domain downlink multiple-input multiple-output non-orthogonal multiple access system in dual-hop full-duplex (FD) relaying networks is investigated over Nakagami-𝑚 fading channels by considering the channel estimation error and feedback delay. Particularly, in the investigated system, the base station equipped with multiple antennas transmits information to all mobile users by applying conventional transmit antenna selection/Alamoutispace-time block coding scheme with the help of a dedicated FD amplify-and-forward relay. The received signals at mobile users are combined according to maximal-ratio combining technique to exploit benefits of receive diversity. In order to demonstrate the superiority of the proposed system, outage probability (OP) is investigated and tight lower bound expressions are derived for the obtained OP. Moreover, asymptotic analyses are also conducted for ideal and practical conditions to provide further insights about the outage behavior in the high signal-to-noise ratio region. Finally, theoretical analyses are validated via Monte Carlo simulations and software defined radio based test-bed implementation.