% $Id: abstract.tex,v 1.6 2005/03/01 10:06:58 gokhale Exp $

\begin{abstract}
Performance of wireless sensor networks (WSNs) is dictated by their
parameters, such as number of sensor nodes, sensor mobility and the
network protocol used for routing. This paper provides two
contributions to the study of data dissemination protocols in
WSNs. First, we describe results investigating the performance of two
data dissemination 
protocols -- Directed Diffusion (DD) and Two-tier Data
Dissemination (TTDD) -- under varying WSN parameters and application
properties. We compare their performance along two dimensions
including (1) observed application latency and routing overhead, and
(2) sensor network efficiency in terms of packet transmission ratio
and energy consumption. Second, we describe our improvements
to these protocols and illustrate the performance gains achieved by
our changes.  

Our experiments analyzing network performance indicate that increasing
the number of nodes per unit sensing area does not make the network
more redundant. At increased network densities and sink sizes the
energy consumption starts increasing very rapidly on account of the
added traffic. This argues for a better energy utilization mechanism,
which scales the network as network density, while maintaining other
performance parameters, such as delivery fraction and average delay,
within acceptable limits.  Our proposed protocol modifications call
for local broadcast in DD and dynamically changing the flooding area
in TTDD without changing the cell size.

\noindent {\bf Keywords:}
Wireless sensor networks, Data dissemination protocols, performance.
\end{abstract}

