Events - Colloquia & Seminars

CCIS Colloquium Spring 2005

Low-Power Wireless Links Properties:
    Modeling and Applications in Sensor Networks

Speaker: Alberto Cerpa (UCLA)

Date: April 8, 2005

Talk: 2:00 pm, 366 WVH

Abstract

Advances in low-cost, low-power micro-sensor and radio design have led to active research in large-scale networks of small, wireless, low-power sensors and actuators. Radio communication is one of the critical components in any wireless distributed systems, but wireless sensor networks make extensive use of communications in order to perform the coordinated sensing tasks. These systems will be deployed in many environments the present very harsh conditions for wireless communication using low-power radios, including multipath/fading effects, reflections from obstacles, and attenuation from foliage. Moreover, recently several landmark wireless sensor network deployment studies clearly demonstrated a large discrepancy between experimentally observed communication properties and properties produced by widely used simulation models.

New approaches and models are required to deal with vagaries of the communication channel. In the first part of this talk, I motivate the need for precise wireless link characterization and describe the methodology used to collect extensive experimental data traces, using different hardware, in different environment, under systematic varied conditions. I perform statistical analysis on the data and provide sound foundations for our conclusions by extracting relationships between location (e.g distance) and communication properties (e.g. reception rate) using non-parametric statistical techniques. The objective is to provide a probability density function that completely characterizes the relationship. Furthermore, I study individual link properties and their correlation with respect to common transmitters, receivers and geometrical location. Using the modeled communication properties, we develop a series of wireless network models that produce networks of arbitrary sizes with realistic properties. I use an iterative improvement-based optimization procedure to generate network instances that are statistically similar to empirically observed networks. I evaluate the accuracy of the conclusions using our models on a set of standard communication tasks, like connectivity maintenance and routing.

In the second part of this talk, I describe more deeply the temporal properties of links in low power wireless communications. I investigate short term temporal issues, like lagged autocorrelation of individual links, lagged correlation of reverse links, and consecutive same path links. I also study long term temporal aspects, gaining insight on the length of time the channel needs to be measured and how often we should update our models. In addition, I explore how statistical temporal properties impact routing protocols. I analyze one-to-one routing schemes and develop new routing algorithms that consider autocorrelation, and reverse link and consecutive same path link lagged correlations. I have developed two new routing algorithms for the cost link model: (i) a generalized Dijkstra algorithm with centralized execution, and (ii) a localized distributed probabilistic algorithm.

Finally, I describe all the insight obtained by analyzing all these data, and propose new research direction for network protocol and system designers of sensor networks.

Biography

Alberto Cerpa is a Ph.D. candidate in Computer Science at the University of California, Los Angeles (UCLA), working under the supervision of Professor Deborah Estrin. Since Fall of 2000 he has been working in the Center for Embedded Networked Sensing (CENS) and the Laboratory for Embedded Collaborative Systems (LECS) at UCLA. Cerpa received his M.Sc. in Computer Science from the University of Southern California (USC) in 2000, his M.Sc. in Electrical Engineering from the University of Southern California (USC) in 1998, and his Engineer Degree in Electrical Engineer from the Buenos Aires Institute of Technology, Argentina in 1995.

Alberto Cerpa interests lie broadly in the computer networking and distributed systems areas. His recent focus has been systems research in wireless sensor networks, with emphasis in wireless radio channel measurement and characterization, network self-configuration, topology control, routing algorithms, programming models, and development of wireless testbeds. He is also interested in Internet protocols and operating systems issues. In the past, he has been involved in active networking, mobile IP, and protocol design and verification research.

Link to Alberto Cerpa home page http://www.lecs.cs.ucla.edu/~cerpa/.