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Electrical and Computer

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Now showing 1 - 4 of 4
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    RIS-Assisted Receive Generalized Space Shift Keying and Receive Generalized Spatial Modulation
    (IEEE, 2024) Marin, Porfirio; Hanif, Muhammad; Bedeer, Ebrahim
    In this paper, we enhance the performance of wireless communication systems by utilizing reconfigurable intelligent surface (RIS) and index modulation (IM). In particular, we introduce two schemes: RIS-assisted receive generalized space-shift keying (RIS-RGSSK) and RIS-assisted receive generalized spatial modulation (RIS-RGSM). In the RIS-RGSSK scheme, information bits are conveyed through selection of multiple receive antennas. The RIS-RGSM scheme takes RIS-RGSSK a step further by conveying information bits not only through the selection of multiple receive antennas, but also through embedding information bits in the phase of the received signals using M - ary phase shift keying (PSK) modulation. We also present simple yet efficient greedy detectors (GDs) for non-coherent detection of both schemes. Simulation results demonstrate the advantages of our proposed methods over existing schemes such as the RIS-assisted receive quadrature space-shift keying (RIS-RQSSK).
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    Low Complexity Lookup Table Aided Soft Output Semidefinite Relaxation based Faster-than-Nyquist Signaling Detector
    (Institute of Electrical and Electronic Engineers, 2024) Çiçek, Adem; Marsland, Ian; ÇAVUS, ENVER; Bedeer, Ebrahim; Yanikomeroglu, Halim
    Spectrum scarcity necessitates innovative, spectral- efficient strategies to meet the ever-growing demand for high data rates. Faster-than-Nyquist (FTN) signaling emerges as a compelling spectral-efficient transmission method that pushes transmit data symbols beyond the Nyquist limit, offering en- hanced spectral efficiency (SE). While FTN signaling maintains SE with the same energy and bandwidth as the Nyquist sig- naling, it introduces increased complexity, particularly at higher modulation levels. This complexity predominantly arises from the detection process, which seeks to mitigate the intentional intersymbol interference generated by FTN signaling. Another challenge involves the generation of reliable log-likelihood ratios (LLRs) vital for soft channel decoders. In this study, we introduce a lookup table (LUT) aided soft output semidefinite relaxation (soSDR) based sub-optimal FTN detector, which can be extended to higher modulation levels. This detector possesses polyno- mial computational complexity, given the negligible complexity associated with soft value generation. Our study assesses the performance of this soft output detector against that of the optimal FTN detector, Bahl, Cocke, Jelinek and Raviv (BCJR) algorithm as the benchmark. The likelihood values produced by our LUT aided semidefinite relaxation (SDR) based FTN signaling detector show promising viability in coded scenario.
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    Performance Evaluation and Low-Complexity Detection of the PHY Modulation of LR-FHSS Transmission in IoT Networks
    (Institute of Electrical and Electronics Engineers (IEEE), 2024-06-24) Maleki, Alireza; Bedeer, Ebrahim; Barton, Robert
    Long-range frequency-hopping spread spectrum (LR-FHSS) is a new transmission protocol introduced under the long-range wide area network (LoRaWAN) specifications to tackle the issue of extremely long-range and large-scale internet of things (IoT) deployment scenarios. Unlike the other LoRaWanscheme, i.e., the one based on the chirp spread spectrum (CSS) modulation, the physical layer of LR-FHSS exploits a 488 Hz Gaussian minimum shift keying (GMSK) modulation. In this paper, we investigate and model the FHSS-GMSK modulation and evaluate its bit error rate (BER) performance in the LR-FHSS system using simulations. We also propose a low-complexity GMSK signal detection scheme that can be used at the gateway (GW) of an IoT network with a massive number of IoT end devices (EDs). Using computer simulations, we show that our proposed detector can offer a tradeoff between the complexity of the receiver and the bit error rate (BER) performance.
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    Widely-Linear Processing of Faster-than-Nyquist Signaling in the Presence of IQ Imbalance
    (IEEE, 2025-09-25) Ismael, Fouad; Bedeer, Ebrahim
    Faster-than-Nyquist (FTN) signaling is a promising approach to increase the spectral efficiency (SE) of next-generation wireless communication systems. In this paper, we investigate the detection of FTN signaling in the presence of in-phase and quadrature (IQ) imbalance in frequency-selective fading channels. We show that IQ imbalance at the transmitter and the receiver of FTN signaling results in an image of the transmit and the received signal, respectively, and this image represents an additional interference. We use concepts from widely linear processing to exploit the correlation between the received signal and its complex conjugate. In particular, we propose a widely-linear minimum mean square error (WL-MMSE) algorithm to estimate the transmit FTN signaling in the presence of IQ imbalance and frequency-selective channels. We additionally prove that the mean square error (MSE) of the proposed WL-MMSE is small than its counterpart of the linear-MMSE (L-MMSE). Simulation results verify our findings in terms of bit error rate (BER) and MSE performance.