In this article, we show how using modulo ADCs in full-duplex transceivers can alleviate quantization errors.

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Channel charting is a data-driven baseband processing technique consisting in applying unsupervised machine learning techniques to channel state information (CSI), with the objective of reducing the dimension of the data and extracting the fundamental parameters governing the distribution of CSI samples observed by a given receiver. In this work we develop an efficient learning architecture on real-world data from commercial base station. Results indicate that channel charting can indeed be achieved in production.

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I am giving a talk and sharing my experience this month with Ph.D. students about careers in the industry. You can find the slides for the talk here!

The majority of modern communication systems adopt quadrature amplitude modulation (QAM) constellations as transmission schemes. Due to their square structure, however, QAM do not provide satisfying protection to phase noise effects, as the number of constellation points grows, increasing at the same time their peak-to-average-power ratio. This requires an expensive power amplifier and an oscillator at the transmitter to guarantee low distortion, complicating the adoption of dense transmission schemes in practical high-data rate systems. In this paper, we construct a coded modulation scheme based on regular amplitude and phase shift keying modulations. We propose a novel multilevel coding labeling for the constellation points separating the amplitude and phase domains. We provide a novel multistage decoding scheme allowing for a low-complexity log-likelihood ratio calculation for soft-input decoding of component codes, along with a suitable rate design. Finally, we compare the proposed scheme with the state-of-the-art QAM constellations and optimize the constellations in the presence of phase noise.

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In this lecture, we cover multiple access techniques and background, up to most recent multi-user MIMO, massive MIMO, and non-orthogonal multiple access for modern cellular networks and wireless local area networks.

In this lecture, we present the premises of 5G, the key drivers behind the future standards. We then develop 2 of the technologies that are expected to answer part of the challenges put forth in the standards's development, namely massive MIMO and mm-Wave communications.

In this lecture, we present the premises of 5G, the key drivers behind the future standards. We then develop 2 of the technologies that are expected to answer part of the challenges put forth in the standards's development, namely massive MIMO and mm-Wave communications.

The output of oscillators is usually not stable over time. In particular, phase variations—or phase noise—corrupts the oscillations. In this letter, we describe a circuit that is designed to average the phase noise processes and frequency offsets in frequency-matched oscillators. The basic circuit uses the independence of two phase noise processes to provide a cleaner oscillating output with a lower phase noise variance. We describe extensions of the circuit designed to average out more than two oscillators, as well as a single one through delay elements. In all the examples covered, we provide a theoretical analysis of the resulting phase noise process when the input phase noise processes follow a Wiener model.

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With the advent of 5G, standardization and research are currently defining the next generation of the radio access. Considering the high constraints imposed by the future standards, disruptive technologies such as Massive MIMO are being proposed. At the heart of this process are wireless channel models, that now need to cover a massive increase in design parameters to consider, a large variety of frequency bands, and very heterogeneous deployments. This tutorial describes how channel models address this new level of complexity and which tools the community prepares to efficiently but accurately capture the upcoming changes in radio access design. We analyze the main drivers behind this overhaul of channel modeling tools, the challenges they pose to the community, and survey the current approaches to overcome them.

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Modern cellular networks in traditional frequency bands are notoriously interference-limited especially in urban areas, where base stations are deployed in close proximity to one another. The latest releases of Long Term Evolution (LTE) incorporate features for coordinating downlink transmissions as an efficient means of managing interference. Recent field trial results and theoretical studies of the performance of joint transmission (JT) coordinated multi-point (CoMP) schemes revealed, however, that their gains are not as high as initially expected, despite the large coordination overhead. These schemes are known to be very sensitive to defects in synchronization or information exchange between coordinating bases stations as well as uncoordinated interference. In this article, we review recent advanced coordinated beamforming (CB) schemes as alternatives, requiring less overhead than JT CoMP while achieving good performance in realistic conditions. By stipulating that, in certain LTE scenarios of increasing interest, uncoordinated interference constitutes a major factor in the performance of CoMP techniques at large, we hereby assess the resilience of the state-of-the-art CB to uncoordinated interference. We also describe how these techniques can leverage the latest specifications of current cellular networks, and how they may perform when we consider standardized feedback and coordination. This allows us to identify some key roadblocks and research directions to address as LTE evolves towards the future of mobile communications.

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In this lecture, we present the premises of 5G, the key drivers behind the future standards. We then develop 2 of the technologies that are expected to answer part of the challenges put forth in the standards's development, namely massive MIMO and mm-Wave communications.

In this course, over 20 hours, we cover advanced MAC and PHY algorithms aimed at improving the performance of wireless communications. We study the specificities of the wireless medium, the impact on performances, and the difference between wireless algorithms and relevant wireline equivalents.

The packet error rate (PER) is a metric of choice to compute the practical performance of communication systems experiencing block fading, e.g., fading processes whose coherence time is relatively slow when compared to the symbol transmission rate. For these types of channels, we derive a closed-form asymptotic expression which approximates the value of the PER for high signal-to-noise ratio (SNR). We also provide another approximation based on a unit-step formulation of the symbol error rate (SER). We show that the two approximations are related and may be derived from one another, thereby allowing us to obtain closed-form approximations of the block fading PER in both coded and uncoded systems. We then show how these approximations may be used in practice, through the derivation of a packet error outage (PEO) metric covering the case where the links experience shadowing on top of block fading, as well as asymptotically optimal power allocations in relay channels under a block fading hypothesis.

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Working in the Signal and Information Processing team in Paris, at Huawei's newly opened French Research Center.

Qualified for Associate Processor positions in sections 61 (Signal processing and Automatic Control) and 27 (Computer Science).