Homero Toral-Cruz

Accurate modeling of VoIP traffic QoS parameters in current and future networks with multifractal and Markov Models

Abstract In this paper, we analyze the jitter and packet loss behavior of Voice over Internet Protocol (VoIP) traffic by means of network measurements and simulations results. As result of these analyses, we provide a detailed characterization and accurate modeling of these Quality of Service (QoS) parameters. Our studies have revealed that VoIP jitter can be modeled by self-similar processes with short range dependence (SRD) or long range dependence (LRD). The discovery of LRD (a kind of asymptotic fractal scaling) in VoIP jitter was followed by a further work that shows the evidence of multifractal behavior. The implication of these behaviors for VoIP and other interactive multimedia services is that receiver de-jitter buffer may not be large enough to mask the jitter with LRD and multifractal characteristics. On the other hand, we use a description of VoIP packet loss based on microscopic and macroscopic packet loss behaviors, where these behaviors can be modeled by 2-state and 4-state Markov chains, respectively. Based on the above mentioned points, we present a methodology for simulating packet loss. Besides, we found relationships between Hurst parameter (H) with the packet loss rate (PLR); these relationships are based on voice traffic measurements and can be modeled by means of a power-law function, characterized by three fitted parameters. The proposed models can be used to: (i) design a de-jitter buffer, (ii) implement a synthetic generator of VoIP jitter data traces, where the synthetic jitter data traces can be used as test vectors to carry out the performance evaluation of a de-jitter buffer of VoIP system, and (iii) design effective schemes for packet loss recovery.

Traffic analysis for IP telephony

There is a great interest today in voice communication over the Internet (VoIP) with a high level quality of service (QoS). Our objective in this paper is to assess to what extent todays Internet is meeting this expectation. This work presents H.323 traffic analysis in the scenario where two LANs are connected through the Internet. For tests, series of H.323 calls between two endpoints were established, employing IP commercial cards and an Ethereal protocol analyzer for the packet reception. During the tests were taken into account a set of parameters such as: coded type, packet size (ms), and the voice activity detection. Relationships between the metrics: delay, jitter and packet loss were proved; considering real VoIP scenarios, and different types of codecs.

SDAW: secure data aggregation watermarking-based scheme in homogeneous WSNs

Redundant data retransmission problem in wireless sensor networks (WSNs) can be eliminated using the data aggregation process which combines similar data to reduce the resource-consumption and consequently, saves energy during data transmission. In the recent days, many researchers have focused on securing this paradigm despite the constraints it imposes such as the limited resources. Most of the solutions proposed to secure the data aggregation process in WSNs are essentially based on the use of encryption keys to protect data during their transmission in the network. Indeed, the key generation and distribution mechanisms involve additional computation costs and consume more of energy. Considering this, in this paper, we propose a new security mechanism to secure data aggregation in WSNs called SDAW (secure data aggregation watermarking-based scheme in homogeneous WSNs). Our mechanism aims to secure the data aggregation process while saving energy. For this, the mechanism uses a lightweight fragile watermarking technique without encryption to insure the authentication and the integrity of the sensed data while saving the energy. The links between the sensor nodes and the aggregation nodes, and also the links between the aggregation nodes and the base station are secured by using the watermarking mechanism.

An Outline of Data Aggregation Security in Heterogeneous Wireless Sensor Networks

Data aggregation processes aim to reduce the amount of exchanged data in wireless sensor networks and consequently minimize the packet overhead and optimize energy efficiency. Securing the data aggregation process is a real challenge since the aggregation nodes must access the relayed data to apply the aggregation functions. The data aggregation security problem has been widely addressed in classical homogeneous wireless sensor networks, however, most of the proposed security protocols cannot guarantee a high level of security since the sensor node resources are limited. Heterogeneous wireless sensor networks have recently emerged as a new wireless sensor network category which expands the sensor nodes’ resources and capabilities. These new kinds of WSNs have opened new research opportunities where security represents a most attractive area. Indeed, robust and high security level algorithms can be used to secure the data aggregation at the heterogeneous aggregation nodes which is impossible in classical homogeneous WSNs. Contrary to the homogeneous sensor networks, the data aggregation security problem is still not sufficiently covered and the proposed data aggregation security protocols are numberless. To address this recent research area, this paper describes the data aggregation security problem in heterogeneous wireless sensor networks and surveys a few proposed security protocols. A classification and evaluation of the existing protocols is also introduced based on the adopted data aggregation security approach.

P2PM-pay: Person to Person Mobile Payment Scheme Controlled by Expiration Date

Abstract In this paper, we propose P2PM-pay scheme which provides two key points. The first key point is related with the mobile cash. In P2PM-pay scheme, the mobile cash is controlled by the expiration date. The expiration date is embedded into the mobile cash by partial blind signature during the withdrawal date, and the bank does not hold information about the operation. Moreover, we have considered the effective date and deposit date for administrative purposes. The effective date is when customers use their mobile cash to pay for products, and the deposit date is when merchants receive the funds in their bank account. The other key point is related with the authentication process among participants. Although P2PM-pay uses WTLS protocol, we propose a wireless public key infrastructure with an efficient certificate path validation. Furthermore, the design of the proposed scheme achieves successfully the security requirements described in previous works. Consequently, P2PM-pay is secure against well-known attacks and efficient in terms of processing time.

Generalized Wavelet Fisher’s Information of Signals

This paper defines the generalized wavelet Fisher information of parameter . This information measure is obtained by generalizing the time-domain definition of Fisher’s information of Furuichi to the wavelet domain and allows to quantify smoothness and correlation, among other signals characteristics. Closed-form expressions of generalized wavelet Fisher information for signals are determined and a detailed discussion of their properties, characteristics and their relationship with wavelet -Fisher information are given. Information planes of signals Fisher information are obtained and, based on these, potential applications are highlighted. Finally, generalized wavelet Fisher information is applied to the problem of detecting and locating weak structural breaks in stationary signals, particularly for fractional Gaussian noise series. It is shown that by using a joint Fisher/F-Statistic procedure, significant improvements in time and accuracy are achieved in comparison with the sole application of the F-statistic.

Modeling QoS parameters of VoIP traffic with multifractal and Markov models

In this paper, we analyze the jitter and packet loss behavior of voice over Internet protocol (VoIP) traffic by means of networks measurements and simulations results. As result of these analyses, we provide a detailed characterization and accurate modeling of these Quality of Service (QoS) parameters. Our studies have revealed that VoIP jitter can be modeled by selfsimilar and multifractal models. We present a methodology for simulating packet loss. Besides, we found relationships between Hurst parameter (H) with packet loss rate (PLR).

An Introduction to VoIP: End-to-End Elements and QoS Parameters

In this chapter, two of the existing communication networks are studied: voice and data networks. Each network was created with the simple goal of transporting a specific type of information. For instance, the Public Switched Telephone Network (PSTN) was designed to carry voice and the IP network was designed to carry data. In the PSTN, the main terminal device is a simple telephone set, while in the network, it is more complex, and it is provided with most of the intelligence necessary for providing various types for voice services. On the other hand, in the IP network the most of intelligence was placed in the terminal device, which is typically a host computer and the network only offers the best effort service (Park, 2005). In mid 1990’s, the two separate networks started to merge. A buzz word around this time is voice and data convergence. The idea is to create a single network to carry both voice and data. However, with this convergence, a new technical challenge has emerged. In the converged network, the best effort services that are offered by the IP network is no longer good enough to meet requirements of real-time applications, such as Voice over Internet Protocol (VoIP). VoIP refers to the transmission of voice using IP technologies over packet switched networks. It consists of a set of end-to-end elements, recommendations and protocols for managing the transmission of voice packets using IP. A basic VoIP system consists of three main elements: the sender, the IP network and the receiver. VoIP is one of the most attractive and important service nowadays in communication networks and it demands strict QoS levels and real-time voice packet delivery. The QoS level of VoIP applications depends on many parameters, such as: bandwidth, One Way Delay (OWD), jitter, Packet Loss Rate (PLR), codec type, voice data length, and de-jitter buffer size. In particular, OWD, jitter, and PLR have an important impact. This chapter presents an introduction to the main concepts and mathematical background relating to communications networks, VoIP networks and QoS parameters.

IP telephony: an overview

One of the highest demand applications is the transmission of voice over IP networks with a high level quality of service and efficient bandwidth use. This paper shows some recommendations and protocols that lead to convergence communications networks for voice and data transmission over of the same structure. We focus on International Telecommunication Union Recommendation H.323 for voice over IP, which uses IP/UDP/RTP encapsulation for audio. Some metrics that make possible the IP telephony are also analyzed and H.323 architecture is presented for this technology. The main aspects of the problematic of voice and data transmission are analyzed.

A Survey on Quality of Service in the Voice Over IP Technology

In Mexico, the society in general lacks the habit and ethics of properly disposing garbage or in taking care of the environment. This paper focuses on analyzing and disposing garbage in an automated way. The present study also seeks to create and promote care for the planet. The minicomputer (GreenScanProcess) is an automated system whose process is based on an algorithm that stands out for its functionality. GreenScanProcess has sensors that allow the analysis and scanning of garbage. It also measures the weight and humidity of the garbage. The minicomputer also examines the garbage to know its composition. Likewise, GreenScanProcess takes the garbage to the container according to the garbage. The benefits obtained when conducting the research were: environmental, economic, technological, and educational.