Eigenvalue-Based Spectrum SensingWith Two Receive Antennas

National audience"Le concept de la radio intelligente définit deux types d’utilisateurs: les utilisateurs primaires (UP) qui ont accès aux ressources spectrales d’une façon prioritaire et les utilisateurs secondaires (US) qui exploitent les opportunités de communication laissées vacantes parles UPs. Dans ce papier on s’int´eresse au probl`eme de d´etection des ressources spectrales libres en utilisant les distributions du nombre deconditionnement (NDC) de la matrice de covariance des signaux reus par l’US. Une nouvelle formule math´ematique est propos´ee pour ladistribution du NDC dans le cas d’absence des UPs permettant ainsi de d´evelopper un nouveau algorithme de d´etection. Les r´esultats dessimulations nous permettent de valider la formulation th´eorique et les hypoth`eses de bases.

Complexity gain of QR Decomposition based Sphere Decoder in LTE receivers

ISBN: 978-1-4244-2515-0International audienceIt has been widely shown that the Sphere Decoding can be used to find the Maximum Likelihood (ML) solution with an expected complexity that is roughly cubic in the dimensions of the problem. However, the computational complexity becomes prohibitive if the Signal-to-Noise Ratio is too low and/or if the dimension of the problem is too large. That is why another technique denoted as Fixed-complexity Sphere Decoder (FSD) is an interesting approach. This algorithm needs a preprocessing step, and in this paper the QR-Decomposition-based preprocessing technique, which is not inconsequential, will be studied. Two different techniques are exposed, including the classical Gram Schmidt orthonormalization process. Their computational complexities and their impacts on the FSD computational complexity are studied. In the LTE context, the overall computational complexities of the two detection techniques are quantified and are shown to be dependent on the constellation size

Software Defined Radio Platform for Cognitive Radio: Design and Hierarchical Management

ISBN 978-953-307-274-6Cognitive radio (CR) and/or Software Defined Radio (SDR) inherently require multiband and multi-standard wireless circuit. A SDR is a communications device whose functionality is defined in software. Defining the radio behaviour in software removes the need for hardware alterations during a technology upgrade. A promised open architecture platform for SDR is proposed in this chapter. The platform consists of reconfigurable and reprogrammable hardware platform which provide different standards with a common platform, the SDR software framework which control and manage the whole systems, and the protocol processing software modules which is built on reusable protocol libraries. The main idea here is to have a very flexible platform that enables us to test the validity of the following design approaches: FPGA dynamic partial reconfiguration techniques, parameterization design approach using common operators, hierarchical distributed reconfiguration management

A Review to Massive MIMO Detection Algorithms: Theory and Implementation

Multiple-input multiple-output (MIMO) systems entered most major standards in the past decades, including IEEE 802.11n (Wi-Fi) and long-term evolution (LTE). Moreover, MIMO techniques will be used for 5G by increasing the number of antennas at the base station end. MIMO systems enable spatial multiplexing, which has the potential of increasing the capacity of the communication channel linearly with the minimum of the number of antennas installed at both sides without sacrificing any additional bandwidth or power. To handle the space-division multiplexing (SDM), receivers have to implement new algorithms to exploit the spatial information in order to distinguish the transmitted data streams. This chapter provides an overview of the most well-known and promising MIMO detectors, as well as some unusual-yet-interesting ones. We focus on the description of the different paradigms to highlight the different approaches that have been studied. For each paradigm, we describe the mathematical framework and give the underlying philosophy. When hardware implementations are available in the literature, we provide the results reported and give the according references

Software Defined Radio Equipment: What's the Best Design Approach to Reduce Power Consumption and Increase Reconfigurability ?

International audienc

Software Defined Radio & MIMO Signal Processing: From Theoretical to Practical Results

The research and contributions presented focus on intelligent radio and signal processing techniques applied to MIMO systems. The HDR thesis focuses on the following points: (1) ergodic capacity of the MIMO channel (wireless, optical), (2) analysis and improvement of suboptimal techniques for MIMO detection through geometric interpretation of the detection problem and bio-inspired methods, (3) free spectrum band sensing techniques in the context of smart radio using cyclostationarity or eigenvalues of the covariance matrix of received signals, (4) analysis, development, and hardware implementation of sample rate conversion techniques (SRC), (5) analysis and optimization of the FPGA partial dynamic reconfiguration technique, (6) some results of experimental studies of free band detection techniques using USRPs platforms.The author also presents his future research perspectives related to securing mixed-signal electronic circuits (SOCs) (e.g., RFSOCs) against screaming channels, identification of transmitters through their radio frequency fingerprints, and securing future smart radio-based Internet of Things (CR-IoT) networks. The developed topics have been described in about 20 international journals and more than 60 papers in international conferences

Standard Condition Number Based Spectrum Sensing Under Asynchronous Primary User Activity

International audienc

A geometrical approach detector for solving the combinatorial optimisation problem: Application to wireless communication systems.

The demand for mobile communication systems with high data rates and improved link quality for a variety of applications has dramatically increased in recent years. New concepts and methods are necessary in order to cover this huge demand, which counteract or take advantage of the impairments of the mobile communication channel and optimally exploit the limited resources such as bandwidth and power.The problem of finding the least-squares solution to a system of linear equations where the unknown vector is comprised of integers, but the matrix coefficients and given vector are comprised of real numbers, arise in many applications: communications, cryptography, MCCDMA, MIMO, to name a few.The Maximum Likelihood (ML) decoding is equivalent to finding the closest lattice point in an n-dimensional real space. In general, this problem is known to be non deterministic NP hard. In this thesis, a polynomial-time approximation method called Geometrical Intersection and Selection Detector (GISD) is applied to the MLD problem. Moreover, the proposed approach is based on two complementary "real time" operational research methods: intensification and diversification.Our approach has three important characteristics that make it very attractive for for VLSI implementation. First, It will be shown that the performance of GISD receiver is superior as compared to other sub-optimal detection methods and it provides a good approximation to the optimal detector. Second, the inherent parallel structure of the proposed method leads to a very suitable hardware implementation. Finaly, The GISD allows a near optimal performance with constant polynomial-time, O(n3), computational complexity (unlike the sphere decoding that has exponential-time complexity for low SNR). The proposed Detector can be efficiently employed in most wireless communications systems: MIMO, MC-CDMA, MIMO-CDMA etc...Cette thèse s'intéresse à la résolution du problème classique de décodage d'un mélange linéaire entaché d'un bruit additif gaussien. A partir d'une observationbruitée: y = Hx+b, d'un signal x ∈ {±1}n mélangé linéairement par une matrice H connue, b étant un vecteur de bruit, on cherche le vecteur x minimisant la distance Euclidienne entre y et le vecteur Hx. Ce problème est réputé NP-complet. Il intervient dans un grand nombre de systèmes de télécommunications (CDMA,MIMO, MC-CDMA, etc.). Nous proposons dans cette thèse un algorithme de résolution quasi optimal de ce problème et bien adapté à une implémentationmatérielle.Notre démarche s'appuie sur l'utilisation des méthodes classiques de recherche opérationnelle : trouver des points initiaux répartis sur l'espace des solutionspossibles et potentiellement proches de la solution optimale (diversification) et effectuer une recherche locale au voisinage des ces points (intensification). Dansce travail, la diversification est basée sur une approche géométrique utilisant les axes dominants de concentration du bruit (vecteurs singuliers associés auxvaleurs singulires minimales de la matrice H). Les performances en terme de taux d'erreur par bit de la méthode proposée sont proches de l'optimum tout engardant une complexité constante et un degré de parallélisme important (même pour des matrices H de taille très importantes, de l'ordre de 100). Nous avonsétendu cette méthode à la constellation MAQ-16 d'une part, et à la génération d'une décision souple d'autre part.Nous avons étudié l'algorithme proposé du point de vue implémentation matérielle.La sensibilité à l'utilisation de la précision finie et des normes sous optimales est décrite. Une étude de complexité de l'algorithme est présentée ainsi que les effets d'une mauvaise estimation de la matrice H.L'algorithme proposé présente d'une part une nouvelle alternative pour le 11 décodage quasi optimal du mélange linéaire bruité et d'autre part un importantdegré de parallélisme permettant une implémentation matérielle efficace et rapide

Near Maximum Likelihood Detection Algorithm Based on 1-flip Local Search over Uniformly Distributed Codes

International audienceThe maximum likelihood (ML) detection is the process to find the nearest lattice point to a given one in an N-dimensional search space. The ML problem is well known to be NP-hard. In this paper, we propose a near-maximum likelihood detection algorithm based on an intensification strategy over an initially efficient and uniformly distributed subset . This subset is given by a diversification step based on powerful uniformly distributed codes. The proposed algorithm has three characteristics that make it attractive for several practical wireless communication systems. First, the simulated bit error rate performance shows that this algorithm provides a good approximation to the ML detector. Second, it has a constant polynomial-time computational complexity. Finally, the inherent parallel structure of this algorithm leads to a suitable hardware implementation

Software Defined Radio & MIMO Signal Processing: From Theoretical to Practical Results

The research and contributions presented focus on intelligent radio and signal processing techniques applied to MIMO systems. The HDR thesis focuses on the following points: (1) ergodic capacity of the MIMO channel (wireless, optical), (2) analysis and improvement of suboptimal techniques for MIMO detection through geometric interpretation of the detection problem and bio-inspired methods, (3) free spectrum band sensing techniques in the context of smart radio using cyclostationarity or eigenvalues of the covariance matrix of received signals, (4) analysis, development, and hardware implementation of sample rate conversion techniques (SRC), (5) analysis and optimization of the FPGA partial dynamic reconfiguration technique, (6) some results of experimental studies of free band detection techniques using USRPs platforms.The author also presents his future research perspectives related to securing mixed-signal electronic circuits (SOCs) (e.g., RFSOCs) against screaming channels, identification of transmitters through their radio frequency fingerprints, and securing future smart radio-based Internet of Things (CR-IoT) networks. The developed topics have been described in about 20 international journals and more than 60 papers in international conferences