Optimal Power and Resource Allocation for Transmit Power Minimization in OFDMA-based NOMA Networks

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Waveform comparison in the presence of Gaussian Phase Noise in the sub-THz context

International audienceDriven by the need of more available frequency bands, an increasing attention has been paid to the use of sub-THz bands, as shown by the author in [1]. In this review of the advances in the THz communications, the author explained that publications have been numerous since early 2000. Communication systems using all-electronics or photonics are using carrier frequencies in the unexpected range of 100 GHz-700 GHz, though the most studied frequency bands lies between 200 GHz and 400 GHz. From this review, researchers have reached over 100 Gbps. These systems used only OOK, QPSK and 16-QAM modulation schemes. Our sudy here is relevant, because it presents an extended study of waveforms in this context

Performance Comparison of Digital Modulations in the Presence of Gaussian Phase Noise in the Sub-THz Context

International audienceDriven by the need of more available frequency bands, an increasing attention has been paid to the use of sub-THz bands. In such high frequency bands, the signal is expected to be impaired by phase noise, I/Q mismatch, power amplifier non linearities, etc. It has been shown that at such frequencies, with possibly large bandwidth (∼ 50 GHz), Gaussian phase noise models accurately the phase noise. This paper studies the effect of Gaussian phase noise on several waveforms. Here, five performance metrics are used to compare them: Bit Error Rate (BER), Peak-to-Average Power Ratio (PAPR), Adjacent Channel Power Ratio (ACPR), spectral efficiency (SE) and Error Vector Magnitude (EVM). The aim of this comparison is to give recommandations on which waveform to use in this context, depending on the impact of the phase noise on the performance of such transmissions

Preamble Design for Data-Aided Synchronization of Single Side Band Continuous Phase Modulation

International audienceIn this paper, we calculate the Cramer-Rao bound (CRB) for single side band continuous phase modulation signals (SSB-FSK). The CRB is useful to design an optimum preamble sequence to jointly estimate the frequency offset, symbol timing, and carrier phase. The goal is to find preamble sequences that minimize the CRBs of all estimated parameters. The results provide some useful preambles, which can be added to data packets for synchronization in burst-mode SSB-FSK transmissions. © 2020 URSI

Power Allocation for Minimizing Energy Consumption of OFDMA Downlink with Cell DTx

International audienceWith Cell DTx, a base station can dynamically be switched to sleep mode during very short periods (inferior to frame duration) in order to reduce its energy consumption. In this paper, we study the problem of energy consumption minimization with Cell DTx for the downlink of an Orthogonal Frequency Division Multiple Access (OFDMA) base station. We show that this problem can be rewritten as a convex problem. Then, we derive interpretable expressions for the transmit power and sleep mode duration which minimize the energy consumption. Besides, we show that resource allocation algorithms already proposed for transmit power minimization have near optimal performance. Simulation results show that up to 38% of base station energy consumption can be saved with Cell DTx

Optimal Power and Resource Allocation for Transmit Power Minimization in OFDMA-based NOMA Networks

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When Asymmetry Helps: Joint Power and Blocklength Optimization for Non-Orthogonal Multiple Access in Downlink Communications

International audienceThis paper investigates downlink non-orthogonal multiple access (NOMA) in short-packet communications, specifically focusing on a scenario where an Access Point (AP) serves two users with varying channel conditions. The study explores the finite blocklength regime in order to support low latency scenarios. In this context, the conventional Shannon’s capacity theorem becomes inadequate due to the non-negligible decoding error probability, resulting from finite blocklengths that do not approach infinity, which is the case of the asymptotic regime of the capacity theorem. NOMA has great potential to improve spectral efficiency compared to orthogonal multiple access by adapting power allocation to take benefit from the asymmetrical channel conditions between served users. In this study, we take the concept further by suggesting that, in the finite blocklength regime, the user with the worst communication channel can benefit from a longer blocklength. The approach considers both power and blocklength partitioning as the degrees of freedom to be tuned to enhance overall system performance. In particular, we derive the maximum achievable rates of both users when different blocklengths are assumed. We are evaluating the impact of promoting the user with the worst channel condition not only through higher power but also through a longer block on its maximum achievable rate while ensuring a minimum achievable rate for the other user. Numerical results of the exact resolution are provided. The comparative analysis of the proposed scheme with the conventional one where both users have the same blocklength shows that the asymmetry of blocklengths is as beneficial as the asymmetry in power. This observation has been verified by the achievable rate region analysis, using Pareto Frontier and genetic algorithm tools

Optimal Power Allocation for Minimizing the Energy Consumption of a NOMA Base Station with Cell DTx

International audienceIn this paper, we consider a base station that jointly employs Non-Orthogonal Multiple Access (NOMA) and Cell Discontinuous Transmission (Cell DTx) in order to reduce its power consumption and we study the problem of optimal power allocation. We show first that this problem is convexand can be solved using only single variable root finding algorithms. Then, we employ numerical simulations in order to assess the performance of the proposed power allocation

Green Communication via Cooperative Protocols using Message-Passing Decoder over AWGN Channels

International audienceIn wireless networks, the cooperative diversity is an implicit form of space diversity commonly used when other conventional transmit diversity methods might not be practical. It was largely proved that cooperative transmission, where a source and a relay cooperate to communicate with a unique destination, is power-efficient compared to the point-to-point transmission. However, the model considered when stating this conclusion is counting only the transmission power consumption. In this paper, we study the effect of taking into account not only the transmission power at each transmission node but also the processing power consumed in each reception node on the overall end-to-end performance. We formulate the optimization problem aiming to minimize the total power consumption in order to achieve a target performance constraint, where the total power consumption stands for the sum of the transmission power and the processing power consumed in the decoding (neglecting other forms of power consumption). Our analysis relies on the characterization of an information-theoretic bound on the decoding power of any modern code to achieve a specified bit error probability while operating at a certain gap from the capacity. As this bound is built on the sphere-packing analysis, the present study focuses on message-passing decoders. Using this theoretical framework, the improvement of well-known cooperative protocols over the original non-cooperative point-to-point system system is reinvestigated in terms of total power consumption. Thanks to this theoretical framework, a new classification of the studied cooperative protocols is given revealing some surprizing conclusions. In particular, the selective decode-and-forward protocol is no more constantly prefered to its simpler alternative, i.e. the decode-and-forward protocol