Browsing by Author "Eren, Tuncay"

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Citation - WoS: 6
Citation - Scopus: 9
Null Subcarrier Index Modulation in Ofdm Systems for 6g and Beyond
(Mdpi, 2021) Eren, Tuncay; Akan, Aydin
Computational complexity is one of the drawbacks of orthogonal frequency division multiplexing (OFDM)-index modulation (IM) systems. In this study, a novel IM technique is proposed for OFDM systems by considering the null subcarrier locations (NSC-OFDM-IM) within a predetermined group in the frequency domain. So far, a variety of index modulation techniques have been proposed for OFDM systems. However, they are almost always based on modulating the active subcarrier indices. We propose a novel index modulation technique by employing the part of the transmitted bit group into the null subcarrier location index within the predefined size of the subgroup. The novelty comes from modulating null subcarriers rather than actives and reducing the computational complexity of the index selection and index detection algorithms at the transmitter and receiver, respectively. The proposed method is physically straightforward and easy to implement owing to the size of the subgroups, which is defined as a power of two. Based on the results of our simulations, it appeared that the proposed NSC-OFDM-IM does not suffer from any performance degradation compared to the existing OFDM-IM, while achieving better bit error rate (BER) performance and improved spectral efficiency (SE) compared to conventional OFDM. Moreover, in terms of computational complexity, the proposed approach has a significantly reduced complexity over the traditional OFDM-IM scheme.
Citation - WoS: 1
Citation - Scopus: 1
System Architecture Design for Low-Complexity Downlink Receivers in MU-OFDM Systems
(IEEE-inst Electrical Electronics Engineers inc, 2025) Eren, Tuncay; Janjua, Muhammad Bilal; Akan, Aydin
This study introduces a novel resource allocation approach and a simplified receiver design tailored for power- and processing-constrained devices within an orthogonal frequency division multiplexing (OFDM) system accommodating both mobile and static users. Specifically, pilot symbols are selectively allocated to high-mobility users to facilitate frequent updates of channel state information (CSI). In contrast, static users are excluded from regular pilot updates to enhance resource utilization and minimize unnecessary overhead. To further reduce computational load and make the receiver design simple, we implement $N/2$ -point fast Fourier transform (FFT) for processing a large number of subcarriers. This approach effectively addresses the computational limitations associated with traditional OFDM systems. The proposed design significantly reduces processing overhead while maintaining system reliability. Comprehensive simulations demonstrate that the proposed system achieves bit error rate (BER) performance, and spectral efficiency comparable to conventional methods while significantly reducing computational complexity.