Samuel Ouya

A PEG-like LDPC code design avoiding short trapping sets

In this paper, we propose a predictive method to construct regular column-weight-three LDPC codes with girth g = 8 so that their Tanner graphs contain a minimum number of small trapping sets. Our construction is based on improvements of the Progressive Edge-Growth (PEG) algorithm. We first show how to detect the smallest trapping sets (5; 3) and (6; 4) in the computation tree spread from variable nodes during the edge assignment. A precise and rigorous characterization of trapping sets (5; 3) and (6; 4) are given, and we then derive a modification of the Randomized Progressive Edge-Growth (RandPEG) algorithm [1] to take into account a new cost function that allows to build regular column-weight dv = 3, girth 8 LDPC codes free of (5,3) and with a minimization of (6,4). We present the construction and the performance results in the context of quasi-cyclic LDPC (QC-LDPC) codes.

WebRTC platform proposition as a support to the educational system of universities in a limited Internet connection context

This paper proposes a collaborative system based on WebRTC technology to improve digital universities e-Learning environment. It allows teachers and students, through a web browser, to communicate via chat, audio and camera. It also supports file transfer and screen sharing for computer connected lab equipment. All these features are functional in an IP environment without need for Internet access. For its design and realization, we had to implement a WebRTC signalisation server to manage real-time applications, using the three WebRTC APIs: MediaStream for the acquisition and synchronization of audio and video, Peer Connection for communication between users browsers and RTCDataChannel for file transfer, Chat and Screen Sharing.

Dynamic publishing and availability management of virtual machines in Virtual Organization

Nowadays, universities and research institutes are more and more feeling the need to establish collaboration networks for sharing skills, as well as material, human, software and virtualized resources. This refers to the idea of Virtual Organizations (VOs) which allow any user of a member organization to access technological and pedagogical resources available in another partner organization. However, this collaboration, most of the time, raises some concern for member organizations. Indeed, they are afraid not to be able to use their own resources when they need to. Information on resources availability is generally static, provided at a given moment. The presence management of virtual machines with the XMPP (Extensible Messaging and Presence Protocol) protocol presents limitations in the context of a collaborative network. So, the constraints identified in terms of resource sharing, instant availability and restrictions are the main obstacles to setting up such a virtual organization. This paper aims to propose and implement an application that manages dynamic discovery and availability of shared virtual machines. The proposed system manages in real time the presence of a resource and its availability in terms of its occupation or use. The system will also allow a member organization to make its resources available and enjoy priority on its resources in case it needs to use them.

New Centrality Measure in Social Networks Based on Independent Cascade (IC) Model

In this paper, we consider the influence maximization problem in social networks. There are various works to maximize the influence spread. The aim is to find a k - nodes subset to maximize the influence spread in a network. We propose a new algorithm (BRST-algorithm) to determine a particular spanning tree. We also propose a new centrality measure. This heuristic is based on the diffusion probability and on the contribution of the th neighbors to maximize the influence spread. Our heuristic uses the Independent Cascade Model (ICM). The two proposed algorithms are effective and their complexity is O(nm). The simulation of our model is done with R software and igraph package. To demonstrate the performance of our heuristic, we implement one benchmark algorithm, the diffusion degree, and we compare it with ours.

Spanning graph for maximizing the influence spread in Social Networks

In this paper, we consider the influence maximization problem in social networks. The aim is to find a subset of k - nodes called seeds, which maximizes the influence spread. We propose a new approach based on the Independent Cascade Model (ICM) which extracts an acyclic spanning graph from the social network. The extraction method used to build the acyclic spanning graph is based on the existing centrality measures to determine the firsts nodes. We implement two extraction algorithms: SCG-algorithm for a connected graph and SDG-algorithm for a digraph. Both proposed algorithms are effective and their complexity is O(nm). So we use the same centrality measures to determine the seeds in the extracted graph. To show the pertinence of our approach, the results showed that the seeds given by the acyclic spanning graph give better results than the seeds given by the initial graph. This seeds will be determined by using the same heuristic like degree heuristic, degree discount heuristic, degree diffusion heuristic. The performances of this approach are very perceptible through the simulation carried out by the R software and the igraph package.

Improved PEG construction of large girth QC-LDPC codes

In this paper, we present an improvement of the PEG algorithm for constructing quasi-cyclic low-density parity-check (QC-LDPC) codes with large girth. We introduce the concept of PEG-undetectable cycles on the computation tree in the PEG algorithm for QC-LDPC codes and give a predictive method to avoid these undetected cycles. The aim is to select only the candidates that ensure the maximization of local girth for a code of girth g ≥ 10 and thus avoid a posteriori verification after the creation of a new edge i.e. keep the predictive philosophy of the PEG algorithm. The proposed method is applicable to both regular and irregular codes and also protograph type-I codes. Simulation results are presented to demonstrate the efficiency of our method in terms of minimum circulant permutation matrix pmin and error performance.

Proposal of cloud-based online laboratory model for practical training in the telecoms and networking fields

The acquisition of practical skills has been recognized for a long time ago as a crucial point in the STEM (Science Technology Engineering and Mathematics). In case of e-learning, it becomes even more difficult because the learners are physically distant from the laboratories that they must use to get these skills. This paper presents a cloud-based laboratory model that provides learners a way to achieve practical work in the telecoms and networking fields in e-Learning context. This cloud technology offers many advantages exploitable by virtual laboratories. The proposed type of laboratory is mainly based on the virtual machines. It is also dynamic which means that the laboratory instances are created on demand, and destroyed at the end of the lab. To offer remote access we use the SPICE protocol. For implementation of the laboratory, in this paper we use Open Source technologies such as OpenStack, SPICE, asterisk, OpenIMScore. The laboratory was named TLaaS (Telecom Laboratory as a Service).

A quantification model of internal control impact on banking risks using FMECA

In this paper, we propose an optimal assessment of internal control impact on banking risks by making automatic the residual risk estimation step of FMECA which is based on an inductive reasoning to study causes, effects of failures and their criticality. For this we defined three equations based on maturity and type of controls then we have obtain a mathematical model which is applied on 333 risks and 491 controls. This model is a new approach which reduce time for obtaining residuals risks likelihood and severity and decrease estimation error rate of residual criticality by harmonizing the evaluation method. Test results are satisfactory for all banking processes and types of risk.

Contribution to SMS management over 4G network in distance education context

In parallel to the using of resources implemented for distance learning, learners appreciate send and receive SMS. Although 4G offers very high data rates and adaptable quality of service, it does not support the SMS legacy service of GSM. 3GPP is currently specifying two architectures for SMS transmission: SMS over SGs, and SMS over IMS. However, when the learner uses a 4G service, to send or receive a SMS, he is first switched to 3G, which interrupts the current service on 4G. It is in this context that we propose a solution that permits to learner to send or receive SMS while continuing to use his service on the 4G network.

Modeling the Effect of Security Measures on Electronic Payment Risks

Nowadays Banking is very digitized but electronic payment products are vulnerable to different types of attacks. Banks implement many security measures to manage fraud related to the use of debit, credit or prepaid cards. Also, they assess the impact of implemented security measures using a manual method which has some limits including many work sessions, significant level of expertise and estimation error. In this paper, we propose to quantify the impact of security measures on electronic payment risks by defining a mathematical model which is based on FMECA. For testing, the values obtained with the model were compared to reference values given by assessors during different working sessions and the correlation rate is satisfactory. The findings of the study help to assess maturity of implemented security measures and improve security of electronic payment transactions.