Vahid Meghdadi

• professor
• Professor at University of Limoges

The Cell-Free Massive Multiple-Input Multiple-Output (CF-mMIMO) system, incorporating nonlinear power amplifiers (PAs) at both access points (APs) and user equipment (UEs), is analyzed to ensure high and consistent data rates for sixth-generation (6G) networks while maintaining economic feasibility. Specifically, Minimum Mean Squared Error (MMSE) c...

Cell-free Massive multiple-input multiple-output (CF-mMIMO) is one of the most promising technologies. It is crucial to examine the performance of CF-mMIMO systems in real-world scenarios, particularly the hardware impairments caused by nonlinear power amplifiers (PAs). This paper’s main objective is to thoroughly examine CF-mMIMO under PA non-line...

The evolution from 5G to the upcoming 6G has spotlighted the limitations of the available wireless spectrum, which has become more pronounced. Thereby, efficient spectrum allocation through the design of appropriate multiple access methods is a critical challenge in addressing the demands for massive connectivity, broadband services, and facilitati...

With the evolution of 5G networks, optimizing resource allocation has become crucial to meeting the increasing demand for massive connectivity and high throughput. Combining Non-Orthogonal Multiple Access (NOMA) and massive Multi-Input Multi-Output (MIMO) enhances spectral efficiency, power efficiency, and device connectivity. However, deploying MI...

To achieve low probability of intercept (LPI) in radar networks for multiple target detection, it is necessary to find the optimal assignment of distributed radars to targets. The multi-radar to multi-target assignment (MRMTA) problem aims to find the best radar combination, but its brute-force (BF)-based approach over all possible sensor combinati...

La transition énergétique passera notamment par l’autoconsommation et l’autoproduction. L’utilisation de sources d’origines solaire et/ou éolienne permettront d’atteindre les objectifs bas carbone (atteindre la neutralité carbone à l’horizon 20250). Cette production étant intermittente, il est indispensable de les stocker pour pouvoir les utiliser...

The hybrid beamforming (BF) technique has been put forward to reduce required radio frequency (RF) chains in massive MIMO systems. Nevertheless, it requires an analog network to implement the complex coefficients of the analog BF in the analog domain. Deploying fixed PSs with switch networks is {a simple} architecture in which the BF coefficients a...

Beamforming is the fundamental concept of wireless communications to serve several users through multiple-antenna transceivers. The advent of massive multiple-input multiple-output (MIMO) systems leads to an investigation into beamforming to reach optimal performance. However, fully-digital beamforming implementation has to face important challenge...

Abstract In cell‐free massive multiple‐input‐multiple‐output (CF‐MMIMO) systems, a massive number of access points, mastered by central processing units are distributed in a coverage area to serve much smaller number of user equipments (UEs) simultaneously over the same time/frequency resources. In opposition to the centralized MMIMO, CF‐MMIMO part...

In the context of a massive MIMO system, the number of RF chains increases prohibitively. To solve the problem, hybrid beamforming (BF) has been proposed. Nevertheless, the amplitude constraint of the analog part in hybrid BF limits achieving the optimal performance given by the optimal digital BF. Some studies have been conducted recently to relax...

The exact expressions and simple tight lower bounds for end-to-end average symbol error rate (ASER) and outage probability (OP) are derived in amplify-and-forward (AF) source-relay-destination cooperative link, provided that source-destination path is correlated with the source-relay path. Afterward, an optimum power allocation (PA) and relay locat...

In this paper, we are interested in the data gathering for Wireless Sensor Networks (WSNs). In this context, we assume that only some nodes are active in the network, and that these nodes are not transmitting all the time. On the other side, the inactive nodes are considered to be inexistent or idle for a long time period. Henceforth, the sink shou...

Due to the ageing population and the dramatically increasing of the number of patient or disabled person living alone at home, remote health monitoring has become a critical demand for society, and has attracted the attention of researchers. We implemented an Internet of Things (IoT)–based remote health monitoring prototype using the integration be...

The aim of this research work is to develop a wearable and IoT-based fall detection system that can potentially be integrated within a smart home or a community health center to improve the quality of life of the elderly. This system would enable caregivers to remotely monitor the activities of their dependents and to immediately be notified of fal...

Cooperative relay system (CRS) is an efficient wireless communication approach, with the advantage of creating diversity. In order to minimize the average symbol error rate (ASER) of a CRS with amplify-and-forward relaying protocol (AF-CRS) in the Nakagami-m fading channel, the optimum relay location and allocating optimal power is determined. To a...

In the Wireless Sensor Networks (WSNs), ensuring long-term survival of the sensor devices is crucial, especially for non-energy harvesting networks where the sensors have to deal with the available limited power. Thus, there is a huge need to efficiently select, in each time-slot, a small set of source nodes to monitor the network area and deliver...

Due to the ageing population and the dramatically increasing of the number of patient or disabled person living alone at home, remote health monitoring has become a critical demand for society, and has attracted the attention of researchers. We implemented an Internet of Things (IoT)-based remote health monitoring prototype using the integration be...

This book constitutes the refereed proceedings of the 5th International Symposium on Ubiquitous Networking, UNet 2019, held in Limoges, France, in November 2019. The 17 revised full papers presented together with 1 short paper were carefully reviewed and selected from 41 submissions. The papers are organized in topical sections: ubiquitous communic...

This paper investigates cooperative data exchange (CDE) scheme using instantly decodable network coding (IDNC) across energy-constrained devices over wireless channels. In fact, enabling the CDE brings several challenges, such as how to extend the network lifetime and how to reduce the number of transmissions in order to satisfy urgent delay requir...

In this study, the authors demonstrate the potentiality of the integration of low‐density parity‐check codes with a full self‐seeded optical architecture using advanced optical and electrical models. This study aims to show the performances that one can expect from this association in the context of cloud radio access network (C‐RAN). Different dec...

In this work, joint optimization of Power Allocation (PA) and Relay Location (RL) is investigated for Amplify-and-Forward (AF) cooperative relaying in order to minimize the Average Symbol Error Rate (ASER). First, a closed-form expression of the ASER is derived for different modulations in Rayleigh fading channel at a high signal-to-noise ratio reg...

Future wireless communication systems will consist of multiple networks with various capabilities. Wireless networks may encounter severe distortions due to the presence of interfering signals generated at some power stations dedicated to smart grid applications. In fact, severe environmental effects of high voltage substations must be considered,...

In the field of smart home and smart building, there is a wide range of products using various proprietary and open standards for their interconnection. However, the coexistence of those standards imposes serious constraints because of the inherent nature of the radio frequency propagation. A way to investigate this issue is to study the interferen...

This paper considers the uplink pilot overhead in a time division duplexing (TDD) massive Multiple Input Multiple Output (MIMO) mobile systems. A common scenario of conventional massive MIMO systems is a Base Station (BS) serving all user terminals (UTs) in the cell with the same TDD frame format that fits the coherence interval of the worst-case s...

This paper considers the uplink pilot overhead in a time division duplexing (TDD) massive Multiple Input Multiple Output (MIMO) mobile systems. A common scenario of conventional massive MIMO systems is a Base Station (BS) serving all user terminals (UTs) in the cell with the same TDD frame format that fits the coherence interval of the worst-case s...

We demonstrate field trial CPRI3 error-free transmission over field fibre at 2.5 Gbit/s with DWDM self-seeded RSOAs in the O-band. The use of FEC in transponders enables to achieve 30 dB optical budget and up to 70 km reach.

Powerline network is recognized as a favorable infrastructure for Smart Grid to transmit information in the network thanks to its broad coverage and low cost deployment. The existing works are trying to improve and adapt transmission techniques to reduce Powerline Communication (PLC) channel attenuation and exploit the limited bandwidth to support...

We investigate the use of Low Rank Parity Check Codes, originally designed for cryptography applications in the context of Power Line Communication. Particularly, we propose a new code design and an efficient probabilistic decoding algorithm. The main idea of decoding Low Rank Parity Check Codes is based on calculations of vector spaces over a fini...

We investigate the use of Low Rank Parity Check Codes (LRPC), originally designed for cryptography applications in the context of Power Line Communication (PLC). Particularly we propose a new code design and an efficient probabilistic decoding algorithm. The main idea of decoding LRPC codes is based on calculations of vector spaces over a finite fi...

In this paper we study the design of LDPC decoding scheme for very high throughput optical communications for a full self-seeded optical architecture dedicated to cloud radio access network (C-RAN). The objective of this paper is to demonstrate the potentiality of Bit Flipping (BF) algorithms. It is shown that the Gradient Descent Bit Flipping (GDB...

This paper introduces a new family of rank metric codes: the Low Rank Parity Check Codes (LRPC) for which we propose an efficient probabilistic LRPC decoding algorithm concatenated with convolutional code associated with an interleaver. The main idea of decoding LRPC codes is based on calculations of vector spaces over a finite field F(q). This fam...

On the Optimizing of Wireless Networks and toward improving the future 5th Generation mobile Network Infrastructure, we propose a novel infrastructure that can be the next Smart City Network. Our proposed Infrastructure takes into consideration most future demands and challenges, includes Capacity, Reliability, Scalability, and Flexibility. To deal...

This paper deals with the improvement of energy efficiency in wireless sensor networks (WSN).Taking into consideration the power saving problem which is of crucial importance when the sensors are supplied by a limited power source, this paper proposes a method that optimizes as much as possible the transmission power of the sensors. Under the assum...

Massive MIMO brings both motivations and challenges to develop the 5th generation Mobile wireless technology. The promising number of users and the high bitrate offered per unit area are challenged by uplink pilot contamination due to pilot reuse and a limited number of orthogonal pilot sequences. This paper proposes a solution to mitigate uplink p...

Sufficient wireless coverage is necessary to initiate communication with mobile terminals. Mobile network operators must guarantee good radio coverage. Telecommunication regulatory services (TRS) and technicians are assigned the duty of regularly verifying the conformity of the radio coverage at least once a year. However, it is not possible to col...

The paper presents an evaluation of the performances and the coexistence of standard home automation radiofrequency protocols such as KNX-RF Multi, Zigbee and EnOcean with Bluetooth Low Energy protocol available in smartphone and tablets in the domain of smart grid and smart home. This work allows describing an overall interoperable and efficient r...

This paper describes a novel approach for combining Luby Transform (LT) codes and Network Coding (NC) in the context of PowerLine Communications (PLC) smart grid networks. Multihop transmissions of LT-encoded data on PLC networks are considered and algorithms to combine data at relay nodes are proposed. Without the need to decode and then re-encode...

This paper studies the Power Line Communications (PLC) and tackles the problem of criss-cross noise. In the literature, it is proposed to use Reed-Solomon code concatenated with convolutional code associated with an interleaver. For instance in the context of smart grid, some standards like G3 and IEEE 1901.2 use this scheme. However, the narrowban...

Low Voltage (LV) Narrowband (NB) Power-Line Com-munications (PLC) for future smart grid networks are considered in this paper. From early investigations, it is known that their channel is impaired by coloured background noise, frequency selectivity along with impulsive and narrowband noise. Signals of multi-carrier transmissions systems like PLC ca...

Power Line Communication (PLC) remains the most appropriate communication architectures and technology for Smart Grid (SG) deployment. A major challenge for researchers in SG, is how to supply robust and efficient communication since PLC channel is a fading channel whose characteristics vary considerably over long distances and at high frequencies....

Maximizing the lifetime of sensor networks is a major challenge. In a sensor network, the nodes communicate with each other to pass the information to a data sink. These nodes have limited energy resource, and to increase the lifetime of the network, it is necessary to design communication protocols which aim at reducing the consumed power. Several...

Smart grids have attracted considerable interest in the research community and among market actors. The main interest of smart grid is to continuously monitor the whole system energy and optimize it in order to increase the overall energy efficiency. To this purpose, a power energy manager like Linky (ERDF project - France) is needed to ensure the...

Les Courant Porteur en Ligne (CPL) Basse Tension (BT) à bande étroite pour les futurs réseaux “intelligents” de distribution d’électricité sont considérés dans le présent document. Les signaux provenant de transmissions multi-porteuses comme ceux rencontrés dans le CPL peuvent être représentés sous forme matricielle où les erreurs peuvent se produi...

A dual capacitive feed antenna solution is proposed to address the new challenges, on the RF front end, that LTE Carrier Aggregation has introduced. The antenna covers the frequency bands 690 MHz to 964 MHz and 1700MHz to 2700 MHz. The antenna has two feeding elements that are capacitively coupled to the same grounded folded loop, allowing an effic...

A new distributed coding scheme is proposed to achieve diversity in a network comprising multiple sources, multiple relays, and a single destination. This scheme is based on a distributed implementation of linear block codes, where each relay is assigned to a subset of the source nodes using the channel state information (CSI) of the source-relay (...

Low voltage narrow band (NB) power-line communications (PLC) for future smart grid networks are considered in this paper. We investigate a cooperative communication scheme, where both transmissions from the source to the relays and from the relays to the destination use fountain codes. Because of the broadcast property of the PLC channel, intermedi...

Optimization of sensor network architecture in order to improve the overall system performance at the end processing station is an important challenge. A lot of architectures have been designed to optimize the bit error rate. Conventionally, this optimization is done by inserting relays between sensors and destination. These relays insert redundant...

SUMMARY Optimization of large sensor network architecture in order to improve the overall system performance at the end processing station is an important challenge. Many architectures have been designed to optimize the bit error rate. Conventionally, this optimization is performed by inserting relays between sensors and destination. These relays i...

In this paper, we consider relay assignment in cooperative networks based on the sum-rate criterion. We show that this scheme achieves full diversity, assuming that all the end-to-end (E2E) channels are independent. Our analysis is motivated by the fact that there are many algorithms in the literature to find the permutation that maximizes sum rate...

This paper addresses the problem of transmitting data to multiple mobile stations using a decode-and-forward strategy. Precoding vectors are used in relays to cancel out multiple access interference at the mobile stations. The diversity gain of the system has been analytically calculated for the case of two mobile stations. The system performance f...

Mobile Sensor networks have become a hot topic of research in the last decade. There are a lot of new applications which employ this kind of network architecture. For example, Body Area Network (BAN) is a new application where multiple sensors on different body parts simultaneously transmit their data to a monitoring unit. In the case of numerous s...

Due to the existing frequency-selectivity in PLC channels, data transmission over long distance can exhibit serious difficulties in PLC systems. In order to reduce the attenuation effect for long transmission distances between two nodes (a transmitter and a receiver), we use a relay in PLC systems. Many considerations are taken into account in this...

In a distributed cooperative communication system, as the distances between different relay nodes and the receiving nodes may be different, so the performances of distributed space time codes at receiving nodes may badly be degraded if timing synchronization is not assured. In this article, extending the work of Damen et al. we introduce the design...

- L’idée principale de cette étude est d’utiliser le codage LDPC dans les systèmes de codage de deux sources distribuées. L’objectif est de diminuer la distorsion du système et de se rapprocher des bornes théoriques de Wyner-Ziv. Une application aux systèmes de compression d’images utilisant la transformée en ondelettes est proposée. Les résul...

This paper investigates linear beamforming techniques in relay networks with one source and multiple relays and destinations. The goal is to determine the beamforming matrix so that the signal to noise plus interference ratio at the destination is maximized while respecting power constraints. The considered power constraint here is a total (source...

This paper proposes a new simple precoding solution based on the Gram–Schmidt orthonormalization to be used at the relay station of a multirelay wireless networks where the different mobile stations belong to the same network, in order to mitigate the multiuser interference at each mobile station. The strength of this method is that it only require...

In this paper, we address the relay assignment in cooperative networks based on order statistics. We consider a network comprising a cluster of transmitting sources, a cluster of relay nodes and a single destination. This is motivated by the fact that the existing relay assignment schemes don't achieve diversity for the network configuration under...

Optimizing architecture of sensor networks is a current topic of research. This research field can be applied in several contexts such as environmental monitoring or body area network. Performance improvement in terms of bit error rate is a major challenge. Reducing processing time and simplifying the operations of the network are the two main key...

This paper deals with the problem of relay assignment in cooperative networks. We consider a network which consists of N nodes and a single destination. Each node is a potential relay to help other nodes to communicate with the destination. The problem is how to assign some nodes (as relays) to some nodes (as sources) in order to optimize a conveni...

This paper deals with relay assignment in cooperative networks based on the max-min criterion. A simple algorithm is proposed in order to find the optimum relay assignment permutation to avoid brute-force prohibitive search method. It is assumed that there are N source-destination pairs and M relays in the network. The problem is how to assign each...

Recently, some works have shown that it was possible to obtain quite good bit error rate performances over an additive white Gaussian noise channels with chaotic systems. In this research field, this paper proposes new insights for the chaos-coded modulation (CCM) schemes originally proposed by Kozic et al. (2003; IEEE Trans Circuits Syst Regul Pap...

This paper addresses the problem of transmitting data to multiple mobile stations using a decode-and-forward strategy. Precoding vectors are used in relays to cancel out multiple access interference at the mobile stations. Statistical distribution of signal to noise ratio (SNR) is approximated by an expectation maximization algorithm. Based on this...

This paper offers the statistical analysis of relay assignment in cooperative Decode-and-Forward (DF) networks based on order statistics. By assuming a set of N independent Rayleigh fading channels, first the channel with r-th biggest SNR is analyzed. The diversity order and average error probability for this channel are calculated. Then it is assu...