Acknowledgment procedures at radio link control level in GPRS

In this paper, we investigate the acknowledgment procedures used at radio link control level in General Packet Radio Service (GPRS). The GPRS is a new GSM service, which is currently being standardized by ETSI for GSM Phase 2+ and it provides packet switched data services over GSM network resources. The role of acknowledgment procedures is to assure the delivery of packets on GPRS radio interface. This paper gives a brief description of GPRS radio interface with a special attention to the Radio Link Control and Medium Access Control (RLC/MAC) layer procedures. Particularly, the acknowledgment parameters and operations are described and their performance is evaluated. The delay introduced by acknowledgment procedures is studied analytically. In order to ameliorate the performance of RLC acknowledgment mechanism, we propose and describe a new additional hybrid FEC/ARQ mechanism, which can operate with the current one. The purpose of new mechanism is to decrease the number of control blocks used for RLC acknowledgment mechanism and thus reduces the delay requested for a packet delivery. After presenting the channel models used, we evaluate by simulation the performance of acknowledgment procedures presented in ETSI specifications and the proposed one over a stationary channel model and over a noisy wireless channel model affected by burst of errors

Complexity of error correction devices

Estimating the complexity of implementation for a coding/decoding system is a delicate question. There is usually no unique answer. We can make a rought distinction between : - algorithmic complexity ; — hardware complexity, corresponding to the number of logical gates and binary memories contained in a codin g or decoding device. For the first notion in the case of block codes, one deals mostly with arithmetic complexity . We survey the mai n existing estimations "practical" and asymptotical while trying to distinguish between the operations in an extensio n field and those on the ground field. We illustrate the second notion with an example showing the limitations o f some evaluations .Apprécier la complexité de la mise en oeuvre d'un système de codage/décodage est une question délicate qui ne reçoit généralement pas de réponse unique . On peut sommairement distinguer : — une complexité algorithmique; — une complexité matérielle qui correspond au nombre de portes logiques et de mémoires binaires que compren d un codeur ou un décodeur . Pour la première notion et dans le cas des codes en blocs, il s'agit principalement d'une complexité arithmétique . Nous passons en revue les principales estimations existantes, « pratiques » ou asymptotiques, en tentant d e distinguer les opérations sur un corps extension de celles sur le corps de base. Nous illustrons la seconde notio n sur un exemple qui met en valeur les limitations de certaines évaluations

Achieving Frequency Reuse 1 in WiMAX Networks with Beamforming

In this chapter, we examine the performance of adaptive beamforming in connection with three different subcarrier permutation schemes (PUSC, FUSC and AMC) in WiMAX cellularnetwork with frequency reuse 1. Performance is evaluated in terms of radio quality parameters and system throughput. We show that organization of pilot subcarriers in PUSC Majorgroups has a pronounced effect on system performance while considering adaptive beamforming. Adaptive beamforming per PUSC group offers full resource utilization without need of coordination among base stations. Though FUSC is also a type of distributed subcarrier permutation, its performance in terms of outage probability is somewhat less than that of PUSC. We also show that because of lack of diversity, adjacent subcarrier permutation AMC has theleast performance as far as outage probability is concerned. Results in this chapter are based on Monte Carlo simulations performed in downlink.</p

Exhaustive testing of combinatorial circuits

We present a method for the construction of s-surjective arrays, which allows exhaustive testing of any set of s inputs in a combinatorial device . The method is based upon the use of linear codes, which implies simplicity of implementation. The size (number of tests) of the obtained arrays is close to the minimum f (n, s) for values of th e parameters n (total number of inputs) and s useful in practice .Nous présentons une méthode de construction de tableaux dits s-surjectifs qui permettent de tester exhaustivement tout ensemble de s entrées d'un circuit combinatoire . La méthode est basée sur l'emploi de codes linéaires, c e qui assure la simplicité de sa mise en œuvre. La taille (nombre de tests) des tableaux obtenus se rapproche d u minimum f(n, s) pour certaines valeurs des paramètres n (nombre total d'entrées du circuit) et s utiles en pratique

Outage probability formulas for cellular networks (contributions for MIMO, CoMP and time reversal features)

L étude de dimensionnement d un réseau cellulaire est une phase de conception qui doit permettre de déterminer les performances d un système dans une configuration donnée. Elle inclut l étude de couverture et l analyse de trafic. De complexes simulations sont possibles pour connaître les paramètres de performances d un réseau mais seules les études analytiques fournissent des résultats rapides. Par ailleurs, pour faire face à la demande de hauts débits, à la rareté du spectre fréquentiel et à l impossibilité d émettre à de plus fortes puissances, de nouvelles techniques de transmissions sont apparues. Nous sommes ainsi passés d un système classique à une seule antenne à des systèmes à multiple antennes et même à des scénarios de coopération entre stations de base. Dans cette thèse, nous proposons des modèles analytiques pour l étude des performances, notamment en termes de probabilités de coupure, de ces évolutions des réseaux cellulaires. Dans une première phase, nous considérons des systèmes multicellulaires à une antenne émettrice et une antenne réceptrice (SISO). Nous proposons deux méthodes d étude de l impact conjoint de l affaiblissement de parcours, de l effet de masque et des évanouissements rapides. Nous étudions, par la suite, un système à large bande utilisant le retournement temporel comme technique de transmission. Dans une deuxième phase, nous considérons des systèmes multicellulaires à antennes multiple à l émission ou à la réception (MISO/MIMO) implémentant les schémas de diversité Alamouti et de combinaison par rapport maximal (MRC). Ensuite, nous considérons un système multicellulaire multi-utilisateurs à précodage de forçage à zéro (ZFBF).The implementation of cellular systems have aroused issues related to the design of cellular networks termed to as network dimensioning. It includes the coverage estimation and thetraffic analysis. Simple models and methods are required to reduce the time consumption of these two analysis. At the same time, the growing demand for higher data rates constrained by the scarcity of frequency spectrum, and the requirements in terms of power consumption reduction make the telecommunication community think about new transmission techniques moving from the classical single antenna systems to multiple antenna systems and even the newly envisaged cooperative systems. In this thesis, we provide analytical models to assess the performance of these different cellular network evolutions in terms of outage probabilities. In a first study, we consider multicellular single input single output (SISO) systems. First, we propose two accurate methods to study the joint impact of path-loss, shadowing and fast fading. This system has so far been studied either considering the only impact of path-loss and Rayleigh fading, or considering the same channel model as in our case but providing very complex outage probability expressions. Then, we provide an outage probability expression in a wideband communication context implementing the Time Reversal (TR) transmission technique considering the impact of fast fading. In a second study, we focus on multiple antenna systems. We study the performance of a Multiple Input Multiple Output (MIMO) system implementing a transmit and a receivediversity schemes namely the Alamouti code and the Maximum Ratio Combining (MRC).PARIS-Télécom ParisTech (751132302) / SudocSudocFranceF

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements