Bruno Baynat - Academia.edu (original) (raw)

Papers by Bruno Baynat

Computing Research Repository, 2006

LiTGen is an easy to use and tune open-loop trac genera- tor that statistically models wireless t... more LiTGen is an easy to use and tune open-loop trac genera- tor that statistically models wireless trac on a per user and application basis. We first show how to calibrate the underlying hierarchical model, from packet level capture originating in an ISP wireless network. Using wavelet and semi-experiments analysis, we then prove LiTGen's abil- ity to reproduce accurately the captured

This paper is a contribution to the generic problem of having simple and accurate models to dimen... more This paper is a contribution to the generic problem of having simple and accurate models to dimension radio cells with data traffic on a GPRS or EDGE network. It addresses the issue of capacity limitation in a given cell due to coupling with other cells because of a central equipment or transmission link of limited capacity. A mobile can't access the cell although it is alone, because the capacity limit is reached due to traffic on other cells. Our purpose is to extend our previously published Erlang-like law for data traffic to the constrained multiple-cell system and to derive asymptotic developments for all the average performance parameters that are necessary for the dimensioning of the multiple-cell system.

This paper applies to cross traffic estimation, a new methodology for analyzing and interpreting ... more This paper applies to cross traffic estimation, a new methodology for analyzing and interpreting measurement collected over Internet. This new approach is based on inferring cross traffic characteristics that lead to the observed losses by using an associated a priori constructive model.

TDMA based MAC protocols can provide a very good utilization of the shared radio resources, espec... more TDMA based MAC protocols can provide a very good utilization of the shared radio resources, especially at high input loads, in syn-chronized mobile ad hoc networks (MANETs). Global positioning systems like GPS or GALLILEO should provide a very good tim-ing accuracy for synchronization of nodes. This paper presents a medium access protocol for mobile ad hoc networks, called CRO-MA (Collision-free Receiver-Oriented MAC). It operates in a slot-ted environment, in a dynamic and distributed way. In this proto-col, receivers act as local base stations and can manage one or sev-eral communications on a single slot. Moreover, the hidden termi-nal as well as the exposed terminal problems are handled by CRO-MA. This paper gives a protocol description and provides an ana-lytical study of CROMA in a fully-connected network. Moreover, a special insight on the multislot communications feature of CRO-MA is given through simulations in a challenging multi-hop situa-tion.

Ad hoc and multi-hop networks will probably be part of the fourth generation of wireless networks... more Ad hoc and multi-hop networks will probably be part of the fourth generation of wireless networks, which will integrate networks of several size and capacities with heterogeneous coverage: cellular networks (3G), WLAN hot spots, Wireless Personal Area Networks (WPAN) and Wireless Body Area Networks (WBAN). In this context, MAC protocols play a deciding role for a high utilization of the wireless channel. In this paper, several issues of the MAC layer and concepts for the definition of a new MAC protocol are presented. These concepts include synchronization, multi-user diversity, and multi-packet reception. It is shown that all these techniques can drastically increase the capacity of the MAC layer for multi-hop networks.

A crucial step in the modeling of a system is to determine the values of the parameters to use in... more A crucial step in the modeling of a system is to determine the values of the parameters to use in the model. In this paper we assume that we have a set of measurements collected from an operational system, and that an appropriate model of the system (e.g., based on queueing theory) has been developed. Not infrequently proper values for certain parameters of this model may be difficult to estimate from available data (because the corresponding parameters have unclear physical meaning or because they cannot be directly obtained from available measurements, etc.). Hence, we need a technique to determine the missing parameter values, i.e., to calibrate the model. As an alternative to unscalable "brute force" technique, we propose to view model calibration as a nonlinear optimization problem with constraints. The resulting method is conceptually simple and easy to implement. Our contribution is twofold. First, we propose improved definitions of the "objective function" to quantify the "distance" between performance indices produced by the model and the values obtained from measurements. Second, we develop a customized derivative-free optimization (DFO) technique whose original feature is the ability to allow temporary constraint violations. This technique allows us to solve this optimization problem accurately, thereby providing the "right" parameter values. We illustrate our method using two simple real-life case studies.

In this paper, we present a sim pIe and accurate analytical model for performance evaluation of W... more In this paper, we present a sim pIe and accurate analytical model for performance evaluation of WiMAX networks with multiple traffic profiles. This very promising access technology has been designed to support numerous kinds of applications having different traffic characteristics. One of the QoS parameters considered by the standard for traffic classes is the maxim urn sustained traffic rate (MSTR), which is an upper bound for user throughput. Taking into account MSTR implies the implementation of a throttling scheduling policy that regulates the user peak rate. Our models take into account this policy and provides closed-form expressions giving all the required performance parameters for each traffic profile at a click speed. The model is compared with extensive simulations that show its accuracy and robustness.

Proceedings of the 11th annual international conference on Mobile computing and networking - MobiCom '05, 2005

This paper is a contribution to the generic problem of having simple and accurate models to dimen... more This paper is a contribution to the generic problem of having simple and accurate models to dimension radio cells with data traffic on a GPRS or EDGE network. It addresses the issue of capacity limitation in a given cell due to coupling with other cells because of a central equipment or transmission link of limited capacity. A mobile station can't access the requested resource although it is alone in a cell. The traffic on other coupled cells leads to reach the global capacity limit. Our objective is to avoid the derivation of any multi-dimensional Markovian (or semi-Markovian) model, where each dimension corresponds to a given cell of the system. Such direct extensions would be of non-manageable complexity. Instead we derive an analytical model that captures in an aggregate way the coupling between cells. We show that the performance parameters of the GPRS/EDGE network can be derived quickly and with a very good accuracy. Finally, as our modeling framework allows very fast computations, we show how to use it to perform complex iterative dimensioning studies.

MASCOTS '95. Proceedings of the Third International Workshop on Modeling, Analysis, and Simulation of Computer and Telecommunication Systems, 1995

ABSTRACT Queueing networks with synchronization mechanisms are encountered in the modeling and an... more ABSTRACT Queueing networks with synchronization mechanisms are encountered in the modeling and analysis of parallel computer systems and computer/communication networks. Exact analytical solutions of such networks are not available. In particular, due to the synchronization mechanisms. These networks do not have a product-form solution. As a result approximation methods that can provide accurate estimates of the performance parameters are of high interest. The purpose of this paper is to propose such an approximation method that applies to a fairly general class of multi-class closed queueing networks with synchronization mechanisms. The method is based on the use of a product-form approximation technique. Numerical results that show that the accuracy of the method is fairly good are provided.

2009 IEEE International Symposium on Modeling, Analysis & Simulation of Computer and Telecommunication Systems, 2009

In this paper, we explore a way to find the right scheduling policy for WiMAX networks, that achi... more In this paper, we explore a way to find the right scheduling policy for WiMAX networks, that achieves the best compromise between an efficient use of the resource and a relative fairness among users. This problem is of primary importance as no scheduling policy has been recommended in the WiMAX standard. To do so, we develop an extension of our previous analytical model for WiMAX networks, that takes into account a more general scheduling policy than those previously studied (i.e., instantaneous throughput fairness, slot sharing fairness and opportunistic scheduling). We show that this general policy covers the two extreme cases, namely the instantaneous throughput fairness policy and the opportunistic policy, and offers intermediate policies that are good candidates for finding the right trade-off. In order to formulate the decision criterion, we introduce a new performance parameter, the mean throughput obtained by a user depending on his efficiency to use the resource. The model has a closed-form solution, and all performance parameters can be obtained at a click speed. This allows us to carry on dimensioning studies that require several thousands of evaluations, which would not be tractable with any simulation tool.

2009 7th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks, 2009

In this paper, we present a simple and accurate analytical model for performance evaluation of Wi... more In this paper, we present a simple and accurate analytical model for performance evaluation of WiMAX networks with multiple traffic profiles. This very promising access technology has been designed to support numerous kinds of applications having different traffic characteristics. One of the QoS parameters considered by the standard for traffic classes is the maximum sustained traffic rate (MSTR), which is

Proceedings of the 2006 ACM CoNEXT conference on - CoNEXT '06, 2006

Where distributed agents must share voluminous set membership information, Bloom filters provide ... more Where distributed agents must share voluminous set membership information, Bloom filters provide a compact, though lossy, way for them to do so. Numerous recent networking papers have examined the trade-offs between the bandwidth consumed by the transmission of Bloom filters, and the error rate, which takes the form of false positives, and which rises the more the filters are compressed. In this paper, we introduce the retouched Bloom filter (RBF), an extension that makes the Bloom filter more flexible by permitting the removal of selected false positives at the expense of generating random false negatives. We analytically show that RBFs created through a random process maintain an overall error rate, expressed as a combination of the false positive rate and the false negative rate, that is equal to the false positive rate of the corresponding Bloom filters. We further provide some simple heuristics that decrease the false positive rate more than than the corresponding increase in the false negative rate, when creating RBFs. Finally, we demonstrate the advantages of an RBF over a Bloom filter in a distributed network topology measurement application, where information about large stop sets must be shared among route tracing monitors.

2005 IEEE 16th International Symposium on Personal, Indoor and Mobile Radio Communications, 2005

In this paper, we derive a simple and accurate Erlang-like law for the dimensioning of radio reso... more In this paper, we derive a simple and accurate Erlang-like law for the dimensioning of radio resources in GSM/GPRS/EDGE networks taking into account the voice and data traffic mix in a cell. Resources are assumed to be shared according to the so-called Partial Partitioning scheme whereby some circuits are dedicated to voice, others to data, and the remaining are shared but voice traffic can preempt them.

2004 IEEE International Conference on Communications (IEEE Cat. No.04CH37577), 2004

Abstract A model for GPRS/EDGE network engineering is developed in order to obtain an Erlang-lik... more Abstract A model for GPRS/EDGE network engineering is developed in order to obtain an Erlang-like law. It is based on a discrete-time Markov chain. It captures the main features of the GPRS/EDGE radio resource allocation and assumes an ON/OFF traffic (infinite sessions ...

Lecture Notes in Computer Science, 2007

This paper presents LiTGen, an easy to use and tune openloop traffic generator that statistically... more This paper presents LiTGen, an easy to use and tune openloop traffic generator that statistically models IP traffic on a per user and application basis. From a packet level capture originating in an ISP wireless network 1 , and taking the example of Web traffic, we show that the simple underlying structure of LiTGen is sufficient to reproduce the traffic burstiness accurately. In addition, the flexibility of LiTGen enables us to investigate the sensitivity of the traffic structure with respect to the distributions of the random variables involved in the model, and their possible dependencies.

Lecture Notes in Computer Science, 2007

LiTGen is an easy to use and tune open-loop traffic generator that statistically models wireless ... more LiTGen is an easy to use and tune open-loop traffic generator that statistically models wireless traffic on a per user and application basis. We first show how to calibrate the underlying hierarchical model, from packet level capture originating in an ISP wireless network. Using wavelet and semi-experiments analysis, we then prove LiTGen's ability to reproduce accurately the captured traffic burstiness and internal properties over a wide range of timescales. In addition the flexibility of LiTGen enables us to investigate the sensitivity of the traffic structure with respect to the possible distributions of the random variables involved in the model. Finally this study helps understanding the traffic scaling behaviors and their corresponding internal structure.

Lecture Notes in Computer Science, 2007

Current computer systems and communication networks tend to be highly complex, and they typically... more Current computer systems and communication networks tend to be highly complex, and they typically hide their internal structure from their users. Thus, for selected aspects of capacity planning, overload control and related applications, it is useful to have a method allowing one to find good and relatively simple approximations for the observed system behavior. This paper investigates one such approach where we attempt to represent the latter by adequately selecting the parameters of a set of queueing models. We identify a limited number of queueing models that we use as Building Blocks in our procedure. The selected Building Blocks allow us to accurately approximate the measured behavior of a range of different systems. We propose an approach for selecting and combining suitable Building Blocks, as well as for their calibration. We are able to successfully validate our methodology for a number of case studies. Finally, we discuss the potential and the limitations of the proposed approach.