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    A decentralized dynamic relaying-based framework for enhancing lora networks performance
    (2024) Haif, Hamza; Arous, Abdelali; Arslan, Hüseyin
    Long-Range (LoRa) technology holds tremendous potential for regulating and coordinating communication among Internet of Things (IoT) devices due to its low-power consumption and cost-effectiveness. However, LoRa faces significant obstacles, such as reduction in coverage area, a high packet drop ratio (PDR), and an increased likelihood of collisions, all of which result in substandard data rates. In this article, we present a novel approach that employs a relaying node capable of allocating resources dynamically based on signal parameters. In particular, the geometric placement of the relay node is determined by a genetic algorithm that maximizes signal-to-noise ratio (SNR) and signal-to-interference ratio (SIR) success probabilities. Using equal-area-based (EAB) spreading factor (SF) distance allocation scheme, the coverage area is sliced into distinct regions in order to derive the success probabilities for different communication stages. Furthermore, we present a frequency channel shuffling algorithm to prevent collisions between end devices (EDs) without increasing the complexity of the relaying nodes. Through extensive simulations, we demonstrate that our proposed scheme effectively expands the coverage area, conserves transmission resources, and enhances the system's throughput. Specifically, our approach extends the range by up to 40%, increases the throughput by up to 50% compared to conventional methods, and achieves a 40% increase in success probability. To validate the practicality of our approach, we implement our algorithm in an active LoRa network utilizing an ESP32 LoRa SX1276 module, showcasing its compatibility in real-world scenarios.
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    Novel ocdm transceiver design for doubly-dispersive channels
    (2024) Haif, Hamza; Zegrar, Salah Eddine; Arslan, Hüseyin
    Orthogonal chirp division multiplexing (OCDM) is a new multi-carrier scheme that has been emerging as a new candidate for 6G waveform taking advantage of the unique features of the chirp spread spectrum that makes it immune to intersymbol interference raised due to delay spread. However, a thorough analysis of OCDM under doubly-dispersive channels has not been conducted yet to verify its robustness against Doppler spread as well. In this paper, we investigate the input-output relationship of an OCDM system under doubly-selective channel, where we demonstrate that the circular convolution property of OCDM partially holds even under Doppler spread. Building on previous results, we show the difficulties and problems associated with estimating and equalizing the channel at the receiver side in conventional OCDM systems, especially in case of having fractional delay and Doppler shifts. Then, we propose a new OCDM transceiver by adding fast Fourier transform (FFT) and windowing blocks to ensure channel tap separability and reduce the effect of fractional Doppler shift, respectively. Accordingly, a new channel estimation scheme is developed for the proposed OCDM system. The numerical and simulation results validate the advantages of the proposed OCDM system performance under doubly-dispersive channels over the conventional where the proposed leverages a bit-error-rate (BER) gain in perfect channel state information (CSI) of 2 dB and 3 dB for minimum mean squared error (MMSE) and message passing (MP) equalizers, respectively, and show that it holds great promise as an emerging radio access technology for 6G wireless systems.
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    Otfs-based isac for super-resolution range-velocity profile
    (2024) Zegrar, Salah Eddine; Haif, Hamza; Arslan, Hüseyin
    The recently popularized ISAC paradigm attempts carry out both communication and sensing functionalities uses the same time-frequency resources to combat the scarcity of these resources. However, high-resolution range and velocity radars require wideband long-duration transmission, which implies complex, costly receivers to sample at a high-frequency rate. In this paper, we propose an orthogonal time-frequency space (OTFS)-based ISAC system which enables achieving highly accurate range-velocity profiles without the need for large bandwidth transmissions or long-duration frames. This approach relaxes the constraints on bandwidth and time while still providing precise sensing information. The proposed scheme exploits a single OTFS carrier with rectangular pulse shaping as a pilot to estimate both simultaneous accruing delay and Doppler, thereby determining range and velocity, respectively. By leveraging the sidelobes of the physical pulse shape of the pilot signal, we propose an algorithm that allows the detection of the range and the velocity of radar targets beyond the resolution limitation set by the time duration and the bandwidth of the transmitted signal. The conducted simulation results along with the real experimental results demonstrate that the proposed design can achieve accurate low-complexity radar parameter estimation.