ABSTRACT: The IEEE 802.15.4 standard has been widely adopted in the communication community in the last years. It defines the PHY and MAC layer for Low Rate Personal Area Network (LR- WPAN) and therefore, it provides the technology for embedded networks, which have recently gained in popularity. The aim of this talk is to quantify the behavior of key networking metrics of IEEE 802.15.4 beacon-enabled nodes under typical operating conditions, with the inclusion of packet retransmissions. The behavior of the slotted CSMA/CA in an IEEE 802.15.4 network has often been investigated using the approach introduced by Bianchi for the IEEE 802.11 CSMA/CA, based on modeling a single node's behavior with a discrete-time Markov chain. In these models the state of each node evolves through its corresponding Markov chain independently of other nodes' states except for when it is sensing the channel As such, the assumptions that underlie the traditional Markov chain analysis available to date will be scrutinized during the seminar. Such an unprecedented analysis allows to identify some shortcomings of prior art and subsequently helps pave the way for a novel approach. In particular, it will be shown that - contrary to what is assumed in previous analysis - the probability of sensing the channel free can vary widely from one backoff stage to another. Likewise, the probability of sensing the channel free is not independent of the number of nodes that are sensing the channel. The implications of these assumptions will be discussed, and their impact on the characterization of various networking metrics will be assessed in the talk. Circumventing these assumptions, more accurate results have been obtained at the expense of a more computationally intensive approach (part analytical, part simulation). Additionally, a comprehensive event-driven simulator has been assembled in order to validate the analytical derivations and to aid in the computation of some of the metrics of interest.
SPEAKER: Maria Rita Palattella (Conversano, BA, Italy, 1982) received the Bachelor Degree in Telecommunication Engineering in 2004 and the Master's Degree in Telecommunication Engineering in 2007, both with honor, from Polytechnic of Bari, Italy. Between May 2007 and December 2007, she was a Research Assistant at the "Electrical and Electronics Department", DEE, of the Polytechnic of Bari. She received a number of research grants including: a CNIT grant on the project SITEMAT ("Sistemi e Tecnologie per il Monitoraggio dell'Ambiente e del Territorio") in June 2007, and a SIPD ("Scuola Interpolitecnica di Dottorato") grant in the area "Information and Communication Technologies" (ICT) in 2008. Since January 2008 she is a Ph.D. student in Electronic Engineering at the Polytechnic of Bari. In April 2009 she joined CTTC, as a visitor PhD student, where she is currently pursuing her research activities on MAC protocols for wireless sensor network, under the supervion of Dr. Mischa Dohler. She has also worked in collaboration with the Department of Information and Communication Technologies of Universitat Pompeu Fabra (UPF), in Barcelona (Spain). Her main research interest involves the study of wireless sensor networks (WSNs), power-efficient protocols and algorithms for data collection and management in WSNs, MAC protocols for WSNs and embedded systems.
