Does the assumption of exponential arrival distributions in wireless sensor networks hold?

Wireless Sensor Networks have seen a tremendous growth in various application areas despite prominent performance and availability challenges. One of the common configurations to prolong the lifetime and deal with the path loss phenomena having a multi-hop set-up with clusters and cluster heads to relay the information. Although researchers continue to address these challenges, the type of distribution for arrivals at the cluster head and intermediary routing nodes is still an interesting area of investigation. The general practice in published works is to compare an empirical exponential arrival distribution of wireless sensor networks with a theoretical exponential distribution in a Q-Q plot diagram. In this paper, we show that such comparisons based on simple eye checks are not sufficient since, in many cases, incorrect conclusions may be drawn from such plots. After estimating the Maximum Likelihood parameters of empirical distributions, we generate theoretical distributions based on the estimated parameters. By conducting Kolmogorov-Smirnov Test Statistics for each generated inter-arrival time distributions, we find out, if it is possible to represent the traffic into the cluster head by using theoretical distribution. Empirical exponential arrival distribution assumption of wireless sensor networks holds only for a few cases. There are both theoretically known such as Gamma, Log-normal and Mixed Log-Normal of arrival distributions and theoretically unknown such as non-Exponential and Mixed cases of arrival in wireless sensor networks. The work is further extended to understand the effect of delay on inter-arrival time distributions based on the type of medium access control used in wireless sensor networks

A MAC protocol for quality of service provisioning in adaptive biomedical wireless sensor networks

Doctorate program on Electronics and Computer EngineeringNew healthcare solutions are being explored to improve the quality of care and the quality of life of patients, as well as the sustainability and efficiency of the healthcare services. In this context, wireless sensor networks (WSNs) constitute a key technology for closing the loop between patients and healthcare providers, as WSNs provide sensing ability, as well as mobility and portability, essential characteristics for wide acceptance of wireless healthcare technology. Despite the recent advances in the field, the wide adoption of healthcare WSNs is still conditioned by quality of service (QoS) issues, namely at the medium access control (MAC) level. MAC protocols currently available for WSNs are not able to provide the required QoS to healthcare applications in scenarios of medical emergency or intensive medical care. To cover this shortage, the present work introduces a MAC protocol with novel concepts to assure the required QoS regarding the data transmission robustness, packet delivery deadline, bandwidth efficiency, and energy preservation. The proposed MAC protocol provides a new and efficient dynamic reconfiguration mechanism, so that relevant operational parameters may be redefined dynamically in accordance with the patients’ clinical state. The protocol also provides a channel switching mechanism and the capacity of forwarding frames in two-tier network structures. To test the performance of the proposed MAC protocol and compare it with other MAC protocols, a simulation platform was implemented. In order to validate the simulation results, a physical testbed was implemented to replicate the tests and verify the results. Sensor nodes were specifically designed and assembled to implement this physical testbed. New healthcare solutions are being explored to improve the quality of care and the quality of life of patients, as well as the sustainability and efficiency of the healthcare services. In this context, wireless sensor networks (WSNs) constitute a key technology for closing the loop between patients and healthcare providers, as WSNs provide sensing ability, as well as mobility and portability, essential characteristics for wide acceptance of wireless healthcare technology. Despite the recent advances in the field, the wide adoption of healthcare WSNs is still conditioned by quality of service (QoS) issues, namely at the medium access control (MAC) level. MAC protocols currently available for WSNs are not able to provide the required QoS to healthcare applications in scenarios of medical emergency or intensive medical care. To cover this shortage, the present work introduces a MAC protocol with novel concepts to assure the required QoS regarding the data transmission robustness, packet delivery deadline, bandwidth efficiency, and energy preservation. The proposed MAC protocol provides a new and efficient dynamic reconfiguration mechanism, so that relevant operational parameters may be redefined dynamically in accordance with the patients’ clinical state. The protocol also provides a channel switching mechanism and the capacity of forwarding frames in two-tier network structures. To test the performance of the proposed MAC protocol and compare it with other MAC protocols, a simulation platform was implemented. In order to validate the simulation results, a physical testbed was implemented to replicate the tests and verify the results. Sensor nodes were specifically designed and assembled to implement this physical testbed. Preliminary tests using the simulation and physical platforms showed that simulation results diverge significantly from reality, if the performance of the WSN software components is not considered. Therefore, a parametric model was developed to reflect the impact of this aspect on a physical WSN. Simulation tests using the parametric model revealed that the results match satisfactorily those obtained in reality. After validating the simulation platform, comparative tests against IEEE 802.15.4, a prominent standard used in many wireless healthcare systems, showed that the proposed MAC protocol leads to a performance increase regarding diverse QoS metrics, such as packet loss and bandwidth efficiency, as well as scalability, adaptability, and power consumption. In this way, AR-MAC is a valuable contribution to the deployment of wireless e-health technology and related applications.Novas soluções de cuidados de saúde estão a ser exploradas para melhorar a qualidade de tratamento e a qualidade de vida dos pacientes, assim como a sustentabilidade e eficiência dos serviços de cuidado de saúde. Neste contexto, as redes de sensores sem fios (wireless sensor networks - WSN) são uma tecnologia chave para fecharem o ciclo entre os pacientes e os prestadores de cuidados de saúde, uma vez que as WSNs proporcionam não só capacidade sensorial mas também mobilidade e portabilidade, caracteristicas essenciais para a aceitação à larga escala da tecnologia dos cuidados de saúde sem fios. Apesar dos avanços recentes na área, a aceitação genérica das WSNs de cuidados de saúde ainda está condicionada por aspectos relacionados com a qualidade de serviço (quality of service - QoS), nomeadamente ao nível do controlo de acesso ao meio (medium access control - MAC). Os protocolos MAC actualmente disponíveis para WSNs são incapazes de fornecer a QoS desejada pelas aplicações médicas em cenários de emergência ou cuidados médicos intensivos. Para suprimir esta carência, o presente trabalho apresenta um protocolo MAC com novos conceitos a fim de assegurar a QoS respeitante à robustez de transmissão de dados, ao limite temporal da entrega de pacotes, à utilização da largura de banda e à preservação da energia eléctrica. O protocolo MAC proposto dispõe de um novo e eficiente mecanismo de reconfiguração para que os parâmetros operacionais relevantes possam ser redefinidos dinamicamente de acordo com o estado de saúde do paciente. O protocolo também oferece um mecanismo autónomo de comutação de canal, bem como a capacidade de encaminhar pacotes em redes de duas camadas. Para testar o desempenho do protocolo MAC proposto e compará-lo com outros protocolos MAC foi implementada uma plataforma de simulação. A fim de validar os resultados da simulação foi também implementada uma plataforma física para permitir replicar os testes e verificar os resultados. Esta plataforma física inclui nós sensoriais concebidos e construídos de raiz para o efeito. Testes preliminares usando as plataformas de simulação e física mostraram que os resultados de simulação divergem significativamente da realidade, caso o desempenho dos componentes do software presentes nos componentes da WSN não seja considerado. Por conseguinte, desenvolveu-se um modelo paramétrico para reflectir o impacto deste aspecto numa WSN real. Testes de simulação efectuados com o modelo paramétrico apresentaram resultados muito satisfatórios quando comparados com os obtidos na realidade. Uma vez validada a plataforma de simulação, efectuaram-se testes comparativos com a norma IEEE 802.15.4, proeminentemente usada em projectos académicos de cuidados de saúde sem fios. Os resultados mostraram que o protocolo MAC conduz a um desempenho superior no tocante a diversas métricas QoS, tais como perdas de pacotes e utilização de largura de banda, bem como no respeitante à escalabilidade, adaptabilidade e consumo de energia eléctrica. Assim sendo, o protocolo MAC proposto representa um valioso contributo para a concretização efectiva dos cuidados de saúde sem fios e suas aplicações

A Multi-Hop 6LoWPAN Wireless Sensor Network for Waste Management Optimization

In the first part of this Thesis several Wireless Sensor Network technologies, including the ones based on the IEEE 802.15.4 Protocol Standard like ZigBee, 6LoWPAN and Ultra Wide Band, as well as other technologies based on other protocol standards like Z-Wave, Bluetooth and Dash7, are analyzed with respect to relevance and suitability with the Waste Management Outsmart European FP7 Project. A particular attention is given to the parameters which characterize a Large Scale WSN for Smart Cities, due to the amount of sensors involved and to the practical application requested by the project. Secondly, a prototype of sensor network is proposed: an Operative System named Contiki is chosen for its portability on different hardware platforms, its Open Source license, for the use of the 6LoW-PAN protocol and for the implementation of the new RPL routing protocol. The Operative System is described in detail, with a special focus on the uIPv6 TCP/IP stack and RPL implementation. With regard to this innovative routing proto col designed specifically for Low Power Lossy Networks, chapter 4 describes in detail how the network topology is organized as a Directed Acyclic Graph, what is an RPL Instance and how downward and upward routes are constructed and maintained. With the use of several AVR Atmel modules mounting the Contiki OS a real WSN is created and, with an Ultrasonic Sensor, the filling level of a waste basket prototype is periodically detected and transmitted through a multi-hop wireless network to a sink nodeope

Integrated Architecture for Configuration and Service Management in MANET Environments

Esta tesis nos ha permitido trasladar algunos conceptos teóricos de la computación ubicua a escenarios reales, identificando las necesidades específicas de diferentes tipos de aplicaciones. Con el fin de alcanzar este objetivo, proponemos dos prototipos que proporcionan servicios sensibles al contexto en diferentes entornos, tales como conferencias o salas de recuperación en hospitales. Estos prototipos experimentales explotan la tecnología Bluetooth para ofrecer información basada en las preferencias del usuario. En ambos casos, hemos llevado a cabo algunos experimentos con el fin de evaluar el comportamiento de los sistemas y su rendimento. También abordamos en esta tesis el problema de la autoconfiguración de redes MANET basadas en el estándar 802.11 a través de dos soluciones novedosas. La primera es una solución centralizada que se basa en la tecnología Bluetooth, mientras la segunda es una solución distribuida que no necesita recurrir a ninguna tecnología adicional, ya que se basa en el uso del parámetro SSID. Ambos métodos se han diseñado para permitir que usuarios no expertos puedan unirse a una red MANET de forma transparente, proporcionando una configuración automática, rápida, y fiable de los terminales. Los resultados experimentales en implementaciones reales nos han permitido evaluar el rendimiento de las soluciones propuestas y demostrar que las estaciones cercanas se pueden configurar en pocos segundos. Además, hemos comparado ambas soluciones entre sí para poner de manifiesto las diferentes ventajas y desventajas en cuanto a rendimento. La principal contribución de esta tesis es EasyMANET, una plataforma ampliable y configurable cuyo objetivo es automatizar lo máximo posible las tareas que afectan a la configuración y puesta en marcha de redes MANET, de modo que su uso sea más simple y accesible.Cano Reyes, J. (2012). Integrated Architecture for Configuration and Service Management in MANET Environments [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/14675Palanci

Quality of service differentiation for multimedia delivery in wireless LANs

Delivering multimedia content to heterogeneous devices over a variable networking environment while maintaining high quality levels involves many technical challenges. The research reported in this thesis presents a solution for Quality of Service (QoS)-based service differentiation when delivering multimedia content over the wireless LANs. This thesis has three major contributions outlined below: 1. A Model-based Bandwidth Estimation algorithm (MBE), which estimates the available bandwidth based on novel TCP and UDP throughput models over IEEE 802.11 WLANs. MBE has been modelled, implemented, and tested through simulations and real life testing. In comparison with other bandwidth estimation techniques, MBE shows better performance in terms of error rate, overhead, and loss. 2. An intelligent Prioritized Adaptive Scheme (iPAS), which provides QoS service differentiation for multimedia delivery in wireless networks. iPAS assigns dynamic priorities to various streams and determines their bandwidth share by employing a probabilistic approach-which makes use of stereotypes. The total bandwidth to be allocated is estimated using MBE. The priority level of individual stream is variable and dependent on stream-related characteristics and delivery QoS parameters. iPAS can be deployed seamlessly over the original IEEE 802.11 protocols and can be included in the IEEE 802.21 framework in order to optimize the control signal communication. iPAS has been modelled, implemented, and evaluated via simulations. The results demonstrate that iPAS achieves better performance than the equal channel access mechanism over IEEE 802.11 DCF and a service differentiation scheme on top of IEEE 802.11e EDCA, in terms of fairness, throughput, delay, loss, and estimated PSNR. Additionally, both objective and subjective video quality assessment have been performed using a prototype system. 3. A QoS-based Downlink/Uplink Fairness Scheme, which uses the stereotypes-based structure to balance the QoS parameters (i.e. throughput, delay, and loss) between downlink and uplink VoIP traffic. The proposed scheme has been modelled and tested through simulations. The results show that, in comparison with other downlink/uplink fairness-oriented solutions, the proposed scheme performs better in terms of VoIP capacity and fairness level between downlink and uplink traffic