In this paper, we propose a discrete time transfer function approximation for the reduced complexity parallel least mean square (RC-pLMS) adaptive beamforming algorithm. The RC-pLMS is built using a single least mean square (LMS) stage whose inputs are obtained as a linear combination of the present and past sample. Thus, in order to numerically assess the RC-pLMS stability and to determine the approximate maximum parametric value of the step size for which it remains stable, we derive its discrete time transfer function approximate. In this approximation, the input uniform linear antenna array is remodeled as a finite impulse response (FIR) fractional delay Farrow filter. Computer simulations, presented by the mean square error and beam radiation pattern, demonstrates the validity of the transfer function approximate. Additionally, the RC-pLMS stability is evaluated, with respect to the pole-zero plot, for different step sizes and the approximate upper bound value of the step size is determined.

Digital beamsteering (DBS) is an appealing technique to overcome the severe millimeter-wave path loss, with less complexity and less channel feedback. In multi-user systems, DBS generates a beam toward each user. However, in congested cells, such a system suffers from high inter-user interference causing by the neighboring beams. In this paper, a new approach of space division multiple access (SDMA) with power-domain non-orthogonal multiple access (PD-NOMA) is considered for millimeter-wave channel to significantly reduce the inter-user interference and thus enhance the overall throughput. The proposed scheme is designed by selecting the users located at the same direction to share one beam, in which PD-NOMA multiplexes the users in power domain. The proposed user clustering method built upon an interference metric, and followed by a fixed power allocation method based on the received power, makes possible the design of a low-feedback NOMA-DBS scheme. Simulation results, based on the New York university mm-wave simulator, show that the multi-user MIMO system can achieve higher sum-rate with our proposed joint SDMA and PD-NOMA scheme, with respect to only SDMA (e.g., up to 20 bps/Hz rate gain for 45 users in the cell).

We study in this work the quality of experience of live mobile TV users in the presence of a playout buffer at the receiver side. We specifically consider an LTE network delivering both unicast and broadcast services, and study two cases: i. lossless channels where interruptions in mobile TV delivery are due to the absence of resources at the base station because they are totally consumed by higher priority real-time voice services, and ii. lossy channels, where we propose to exploit the existence of feedback channels to request, if possible, retransmission of the lost video frame. We derive in both cases several QoS metrics pertaining to mobile TV performance, such as interruption frequency and duration as well as video frame loss probability. Our results show the trends of these metrics as a function of several system parameters and yield design rules for network planning as well as for the playout buffer so as to enhance efficiently the live TV watching experience.

We propose in this paper, some practical algorithms to deliver Mobile TV in a hybrid network where coexist both LTE and DVB-NGH technologies and two types of demanded video qualities: a basic single definition and another high definition. Those algorithms aim to manage the continuous reception of Mobile TV by using both infrastructures and taking decisions of TV scheduling on those operators. Two decisions policies are explored: one based on instantaneous actions and a second based on predictive actions. Results shows that the latter, which uses the Kalman filter, decreases the ping-pong between the HD reception delivered by LTE and the SD one offered by DVB-NGH, if compared to the former policy.

The LTE/DVB convergence to offer users a seamless Mobile TV service is at the heart of the emerging DVB-NGH standard. Most of the works addressing this issue focused solely on the impact of such convergence in terms of capacity gains brought by LTE and coverage gains brought by DVB. To the best of our knowledge, the impact of such convergence on the Mobile TV users' QoS has not been addressed yet and is the focus of our present work. We specifically evaluate the users' QoS in terms of quantifiable metrics, notably the probability of service degradation due to non availability of LTE bearers, its frequency and duration, and show how these metrics evolve with varying traffic load and in different network configurations.

Our aim in this work is to develop profit sharing strategies for coooperative 4G Long Term Evolution (LTE) and Digital Video Broadcasting - Next Generation Handheld (DVB-NGH) systems offering mobile TV service. We first study the capacity of the hybrid system for offering such a service and derive the associated cost for each network. We then focus on the sharing of profit between LTE and DVB operators as well as TV channels providers, taking into account the subscription revenues as well as the infrastructure and operation costs. We consider two cases: one in which both LTE and DVB networks are managed by a single operator and one in which the operators are separate. In both cases, we derive closed-form expressions for each player profit share using coalition game concept Shapley value. We further obtain the players optimal strategies, at the Nash equilibrium, where each player tries to maximize its own profit.

Dual carrier is a feature introduced in HSPA+ that allows scheduling a user on two carriers simultaneously. While this feature has been largely studied, and deployed, in the downlink and it has been proved that it provides significant capacity gains, its performance in the uplink is still to be investigated. This paper fills this gap by estimating the radio capacity improvement provided by dual-carrier feature in the uplink. The proposed method combines link budget simulations to assess the throughputs for a fixed number of users in the cell, and a queuing theory-based statistical capacity model, thereby providing a reliable estimate of the network radio capacity. Simulation results show that dual carrier significantly increases uplink radio capacity.

Extensive research addressing IEEE 802.11 Distributed Coordination Function (DCF) and 802.11e Enhanced Distributed Channel Access (EDCA) performance analysis, by means of analytical models, exists in the literature. It started mainly with the famous Bianchi's model and still continues today as several aspects have not been yet covered. Indeed, the ultimate goal is to obtain the model that provides the most accurate prediction of the performance metrics such as throughputs and delays. Unfortunately, the currently proposed models, even if there are numerous, do not reach this accuracy and are still not sufficiently complete, in the sense that they omit some important EDCA features. In this paper, we propose a complete analytical model for EDCA under saturation conditions. Based on the proposed model, saturated throughput and access delay of each EDCA Access category are given. Simulation is also performed to demonstrate that the proposed model has better accuracy than others.

Anonymous authentication is a means of authorizing a user without revealing his/her identification. Mobile technologies such as Radio Frequency Identification (RFID) Tags, PDAs and mobile phone systems are increasingly being deployed in pervasive computing. These mobile devices have raised public concern regarding violation of privacy, anonymity and information confidentiality. Considering these concerns, there is a growing need to discover and develop techniques and methods to overcome the threats described above. In this paper we propose an architecture which enhances the privacy and anonymity of users in ubiquitous computing and yet preserves the security requirements of the system. Our proposed architecture is based on Elliptic Curve techniques, on MaptoCurve or MapToPoint function, on Weil Pairing techniques and finally on elliptic curve based Okamoto Identification Scheme. In addition, we present a formal validation of our protocol by using the AVISPA tool. The main comparative study of our proposed architecture is to provide privacy and Anonymity for mobile users. Our proposed architecture achieves many of desirable security requirements

Several protocols have been proposed to provide robust mutual authentication and key establishment for wireless local area network (WLAN). In this paper we present a new secure authenticated key agreement (SAKA) protocol that provides secure mutual authentication, key establishment and key confirmation over an untrusted network. The new protocol achieves many of the required security and performance properties. It can resist dictionary attacks mounted by either passive or active networks intruders. It can resist Man-In-The Middle attack, and Impersonate attack. It also offers perfect forward secrecy which protects past sessions and passwords against future compromise. In addition, it can resist known-key and resilience to server attack. Our proposed protocol combines techniques of challenge- response protocols with symmetric key agreement protocols and offers significantly improved performance in computational and communication load over comparably many authenticated key agreement protocols such as B-SPEKE, SRP, AMP, PAK-RY, PAK-X, SKA and LR-AKE.

To provide secure communication for mobile devices, authenticated key agreement protocol is an important primitive for establishing session key. So far, several protocols have been proposed to provide robust mutual authentication and key establishment for wireless local area network (WLAN). In this paper we present a secure authenticated key agreement (EC-SAKA) protocol based on elliptic curve cryptography. Our proposed protocol provides secure mutual authentication, key establishment and key confirmation over an untrusted network. The new protocol achieves many of the required security and performance properties. It can resist dictionary attacks mounted by either passive or active networks intruders. It can resist man-in-the middle attack. It also offers perfect forward secrecy which protects past sessions and passwords against future compromise. In addition, it can resist known-key and resilience to server attack. Our proposed protocol uses the signature techniques of ECDSA and the authentication protocol SKA concept. We show that our protocol meets the above security attributes under the assumption that the elliptic curve discrete logarithm problem is secure. Our proposed protocol offers significantly improved performance in computational and communication load over comparably many authenticated key agreement protocols such as B-SPEKE, SRP, AMP, PAK-RY, PAK-X, SKA, LR-AKE and EC-SRP.

The cellular iterative computation model bears upon three broad-ranging application domains: pixel-level image processing, finite-difference approximation of continuum problems (boundary value PDEs) in computational physics, and cellular automata as discrete models of complex locally-interacting systems, aimed at probing their emergent collective properties. The common underlying idea is to compute the global dynamics of a lattice-structured state-space through the iterative propagation of purely local computational dependencies between state-components. A past generation of mesh-connected SIMD array-processors, among which the MPP [Bat 80], CLIP [Pre 84] and CAM [Tof 87] machines, were canonical architectural mappings of this fruitful concept. All were fine-grain synchronous solutions. The new generation of MIMD RISC-based parallel computers that superseded them are essentially coarse-grain and asynchronous; They can simulate a cellular iterative model in a parallel pseudo-synchronous SPMD mode with global coordination mechanisms. A fine-grain asynchronous architectural model departs in a somewhat paradoxical way from these two mainstream approaches. The idea is to match an architecture with a functional concept of a synchronism, specific to cellular relaxation algorithms. As we show in the following, benefits accrue at both levels from this matching.

New asynchronous adder structures with high performances and low cost have been designed. Previous work has only reported the design of carry-save and carry-ripple asynchronous adders. In this study, we have developed new asynchronous adders, Carry Select Adders, Carry Skip Adders, Carry Look Ahead Adders and we compare their potentialities in terms of speed and complexity. First, the functional properties of the conventional asynchronous carry ripple addition scheme are described so as to introduce the capabilities of asynchronous adders and to show how asynchronous operators can be far more efficient than synchronous ones. Then, starting from the well known architectures previously developed to accelerate the addition operation, we first describe their asynchronous equivalents and then show how they can be optimized to fully exploit the functional and electrical dependencies of the computation process with respect to the data.>