Sara Riahi

Bio: Sara Riahi is an academic researcher. The author has contributed to research in topics: UMTS frequency bands & WiMAX. The author has an hindex of 1, co-authored 2 publications receiving 7 citations.

Estimation of QoS in 4th generation wireless systems

Abstract: Before proposing new schedulers, our work began with an in-depth reflection on the objectives to be targeted in the allocation of OFDM resources and on the optimal way of checking to what extent they are eventually achieved. This paper deals in particular with the question of the criteria of performance evaluation to be retained for a fair and efficient classification of modern schedulers. Our study has highlighted that many schedulers are evaluated on unsuitable criteria that make their comparison difficult. To solve this problem, we have chosen to clearly define, for our future work, the relevant performance criteria for correctly judging the value of the schedulers. In this context we will present a new way to measure QoS effectively.

Approaches and Algorithms for Resource Management in OFDMA Access Mode: Application to Mobile Networks of New Generation

Abstract: The increased need for speed and mobility is the cause of the rapid evolution of mobile radio systems during the last decade. In mobile radio communication systems for broadband (e.g. UMTS, HSDPA, WiMax, LTE, … etc.), an intense research activity on optimization and radio resource management techniques (RRM Radio Resource Management) is conducted. Management and resource optimization are two themes dealt with separately. This study achieves two goals: achieving an overview of different methods and approaches for allocation of radio resources and focus on the optimization algorithms dedicated to the allocation of resources in the single cell case by deploying one of the most promising access technologies in terms of speed called OFDMA.

Optimal performance of the opportunistic scheduling in new generation mobile systems

Abstract: These algorithms come to make up for the deficit encountered by their predecessors in terms of equity of radio resources, bandwidth management, taking into account differentiations of services, etc. Scientific work has been undertaken to correct this state of affairs which led to the conclusion that a new MAC / PHY cross-layer approach is a particularly suitable solution for achieving optimal use of radio resources. The results of this approach proved to be effective and gave birth to: more robust opportunistic schedulers. Two classes of algorithms have emerged: the maximum signal-to-noise ratio (MaxSNR) and the Proportional Fair). Taking advantage of frequency and multi-user diversity to allocate priority resources to mobiles that have the most favorable transmission / reception conditions (the best signal-to-noise ratio). This type of algorithm uses infinite queues, these queues are used in the case of non real-time traffic. The main purpose of this type of algorithm is to maximize the overall system throughput.

The non-cooperative game theory applied to telecommunication systems

Abstract: In this paper, we outline various tools from the theory of non-cooperative games for studying competitive situations in telecommunication networks. We describe the mathematical tools while providing examples of various fields of telecommunication systems. In this paper, we study wireless systems in which mobile devices are autonomous in the choice of their communication configurations. This independence decision may involve, in particular the choice of the network access technology, the selection of the access point, the signal modulation, the frequency bands occupied, the power of the transmitted signal, etc. Typically, these configuration choices are made in order to maximize performance metrics specific to each terminal. Assuming that the terminals take their rational decisions to maximize their performance, game theory applies naturally to model the interactions between the decisions of different terminals. Specifically, the main objective of this article is to study emission power control equilibrium strategies to satisfy energy efficiency considerations. The framework of stochastic games is particularly suited to this problem and allows us in particular to characterize the region of performance achievable for all power control strategies that lead to a state of equilibrium. When the number of game terminals is large, we use the theory of mean field games to simplify the study of the system. This theory allows us to study not the individual interactions between the terminals, but the interaction of each terminal with an average field representing the overall state of the other terminals. Finally, for a power control game, the convergence of dynamics of better responses to equilibrium points has been studied.

Optimal resource allocation in wireless systems under quality of service constraint

Abstract: Optimal exploitation of available resources is one of the most important aspects of modern communication systems. Resource allocation algorithms are used to allocate bits and powers to the subcarriers of a multi-carrier communication system from the knowledge of the channel. The OFDM (Orthogonal Frequency Division Multiplexing) is the combination of OFDM and precoding. The idea is to group subcarriers into subsets using precoding matrices. Each subset uses the energy of its sub-carriers for transmitting a total number of bits greater than the sum of bits that can be transmitted on each subcarrier individually. The role of resource allocation in multi-carrier systems is to optimize either the throughput or robustness of the system. Under the PSD (Power Spectral Density) constraint and for a given error rate, the resource allocation typically gives either the maximum bit rate for a given system margin or the maximum system margin for a target bit rate.

Application of game theory to the optimization of wireless systems Algorithmic solutions

Abstract: This paper is primarily based on a study of some research that addressed resource management in wireless systems. The study presents a classification of schedulers in the uplink and is interested in the class of schedulers based QoS because of the importance of delay parameters and rate in optimizing the management of resources by the formalism of game theory. Then, some scheduling algorithms in the ascending link are exposed to make a complete analysis of the different aspects adopted in the scheduling. Second, the courtesy algorithm resource optimization in the uplink in fixed wireless systems is presented. The algorithm defines a priority management policy to improve the low-priority traffic service without affecting the high priority traffic QoS. Finally, a critical assessment of existing solutions is carried out to a design of a robust scheduling mechanism.

Power Control in Wireless Systems: Algorithmic Approaches and Dynamic Modeling

Abstract: This paper introduces the necessary basics for understanding of wireless networks. We will present the different types of wireless networks, such as the cellular network, the WLAN, the WSN sensor network and give a brief overview of the associated communication standards such as LTE, WiFi and ZigBee. We will then describe the OSI model that is common to all these networks. We will then detail the classical communication chain, with particular emphasis on the physical layer and the transmission channel. We will also look at QoS indicators at the physical layer level. Finally, we will present the issues specific to wireless networks such as energy efficiency and improvement of QoS by power control.