Two vertical handcover metrics toward an IEEE 802.11N network

International audienceThis paper deals with two metrics for vertical handover toward an IEEE 802.11n network, estimated from the physical layer instead of the MAC layer. For this reason we dont need to be connected to the network to estimate them. The first metric is related to the channel occupancy rate, and is estimated by the mean of a likelihood function of the observed samples. The second one is related to the collision rate. Using an information theoretic criterion and taking advantage of the OFDMstructure of the signal, we avoid the channel length estimation and decide if a collision occured or not

Exploiting the pilot pattern orthogonality of ofdma signals for the estimation of base stations number of antennas

International audienceIn a recent work, we proposed a GLR test dedicated to the identification of OFDM systems. In the present paper, we show that the proposed technique can be extended for the estimation of the number of antennas used by a base station. This extension is made possible thanks to the orthogonality property that exhibit the pilot pattern associated to the different antennas. Thanks to a multihypothesis testing we show that the number of transmitting antennas is estimated using only one antenna at the receiver and without any knowledge of the pilot sequence

Identification de Systèmes OFDM et Estimation de la QoS : Application à la Radio Opportuniste

The OFDM modulation scheme is being very widespread nowadays (WiFi, WiMAX, \dots) but also advocated as the best modulation candidate for future physical layer networks (3GPP/LTE, IEEE 802.22). This coexistence of OFDM networks makes the radio environment heterogeneous. To take befits from this heterogeneity one can imagine multi-mode terminals able to switch smartly from one standard to another seeking to satisfy the concept of "\textit{always best connected}". This switching process is known as a "\textit{vertical handover}". Before triggering a \textit{vertical handover}, the terminal has first to identify the active surrounding networks and then to evaluate the available quality of service in each detected network. Within this framework, in this thesis, we propose firstly some OFDM systems identification algorithms. Secondly, we focus on the quality of service estimation for CSMA/CA and OFDMA multiple access based networks. Some of the proposed metrics have been evaluated experimentally on the RAMMUS testbed of TELECOM Beretagne. All the proposed algorithms in this thesis are passive, with a low computational cost and do not require any connection to the access point which allow an economy of time and energy resources.Le schéma de modulation OFDM est très répandu de nos jours (WiFi, WiMAX, \dots) et préconisé comme couche physique pour de nombreux réseaux futurs (3GPP/LTE, IEEE 802.22). Ainsi cette coexistence de réseaux OFDM fait que l'environnement radio est de nos jours hétérogène. Afin de tirer partie de cette hétérogénéité et de satisfaire le concept de ''\textit{Always Best connected}'', il a été imaginé des terminaux multistandards capables de basculer de manière transparente d'un réseau à un autre à la recherche du réseau offrant la qualité de service la plus satisfaisante. Ce processus de basculement entre standards est appelé ''\textit{vertical handover}''. Avant de déclencher un \textit{vertical handover} le terminal se doit d'identifier les réseaux actifs qui l'entourent et estimer la qualité de service disponible sur chaque réseau. Ainsi, dans le cadre de cette thèse nous proposons dans un premier temps des algorithmes d'identification de systèmes OFDM. Dans un second temps, nous nous intéressons à la qualité de service disponible sur les réseaux détectés, nous avons ainsi proposé des estimateurs de métriques de qualité de service dédiés à des réseaux basés sur les schémas d'accès multiples OFDMA et CSMA/CA. Certaines de ces métriques ont été validées expérimentalement sur la plate-forme RAMMUS de TELECOM Bretagne. Toutes les techniques proposées dans le cadre de cette thèse, sont des approches passives à faible coût de calcul qui ne nécessitent aucune connexion au point d'accès, permettant ainsi une économie en temps et en énergie

An Adaptive Multi-User Multi-Antenna Receiver for Satellite-Based AIS Detection

International audienceIn the field of maritime surveillance, the space-based detection of Automatic Identification System (AIS) communications enables ship tracking and fleet monitoring with a global coverage. SAT-AIS is a joint initiative from theEuropean Space Agency (ESA) and the European Maritime Safety Agency (EMSA) to define a sustainable space-based system that will provide AIS data to institutional organisations and other entities. The AIS communication system was not originally designed for a capture from space. As a consequence, aspace-based AIS receiver faces severe technical issues, in particular a drastic amount of co-channel interferences. Astrium is working under ESA contract on an affordable SAT-AIS solution with a strong emphasis on a high-performance AIS payload and processing chain. We propose a multi-antenna AIS receiver coupled with an adaptive multi-user processing solution suited to maximize the detection of AIS messages. The proposed algorithm implements a number of diversity techniques to take advantage of the variability of received signal characteristics, especially the Direction of Arrival (DOA), incident polarization, Doppler spread, signal strength and path delay

Physical layer IEEE 802.11 channel occupancy rate estimation

International audienceWith the rapid growth of wireless communication networks, we are facing the challenge of integration of diverse wireless networks such as WLAN and WWAN. Therefore, it becomes important to think at vertical handoff solution where the user can move seamlessly among various type of networks, to provide the best QoS to the higher layers applications. In this paper, we propose a method to estimate the channel occupancy rate metric of an IEEE 802.11 network from the physical layer. This method can be applied for any network that use the CSMA/CA protocol. Our theorical results are validated using experimental measurements captured by RAMMUS RF Plateform

Introducing Pilot Cyclostationarity for LTE Base Station Number of Antennas Estimation

International audienceThis paper deals with a new challenge for cognitive opportunistic receivers : base station number of antennas estimation. This knowledge allows to get a better understanding of the Signal to Noise Ratio and of the achievable bit-rate with the BS. This task is achieved by taking benefits of the orthogonality between the pilots patterns used by the base station antennas and making use of a the Pilot Induced Cyclo-stationarity detector proposed by Sochelau et al. To the best of our knowledge our proposed algorithm is the first technique that can estimate any number of antennas using only one antenna at reception and without any knowledge of the pilot sequence

Two vertical handcover metrics toward an IEEE 802.11N network

International audienceThis paper deals with two metrics for vertical handover toward an IEEE 802.11n network, estimated from the physical layer instead of the MAC layer. For this reason we dont need to be connected to the network to estimate them. The first metric is related to the channel occupancy rate, and is estimated by the mean of a likelihood function of the observed samples. The second one is related to the collision rate. Using an information theoretic criterion and taking advantage of the OFDMstructure of the signal, we avoid the channel length estimation and decide if a collision occured or not

Enumeration of base station antennas in a cognitive receiver by exploiting pilot patterns

International audienceThis letter deals with the identification of the number of transmitting antennas at a base station. This estimation is achieved by exploiting the orthogonality between the pilot patterns from each transmitting antenna. This orthogonality allows us to use multi-hypothesis testing in order to enumerate the number of transmitting antennas using only one antenna at the receiver. As a side product, the proposed algorithm allows us to estimate the channel gains from all transmitting antennas and the noise variance

Identification de systèmes OFDM à partir de la signature des pilotes

National audienceCet article traite la problématique de l'identification de systèmes basés sur une couche physique OFDM. Dans une récente publication nous avons proposé un test GLR exploitant seulement la position des pilotes. Dans le présent document, nous proposons d'exploiter la corrélation souvent introduite entre paires de pilotes afin d'améliorer les performances de notre détecteur. Les résultats de simulations montrent que l'algorithme proposé est plus performant que notre première approche ainsi que les techniques existantes dans la littérature. Bien plus qu'une détection de système, l'algorithme que nous proposons effectue aussi une estimation de canal et de la puissance du bruit et ce moyennant un faible coût de calcul

OFDM system identification using pilot tone signature

International audienceThis paper deals with the challenge of OFDM system identification. In a recent paper, we developed a Generalized Likelihood Ratio Test approach that exploits only the pilot positions to detect the presence of a given system. In this paper, we propose to exploit the redundancy often induced between the pilot symbols as a side information to improve the detector performance. Computer simulations show that the proposed algorithm outperforms the first proposed method and the existing techniques in the literature. More than system detection, the proposed algorithm performs channel estimation as well as estimation of the noise variance and is computationally inexpensive