
% $Id: comparison.tex,v 1.4 2005/04/08 21:21:45 gokhale Exp $

\subsection{Comparison of EASM Performance}
\label{sec:compare}

We compare EASM with TTDD and DD in this section. The same
metrices described in Section~\ref{sec:methodology} are
used in these comparisons. TTDD alpha size is set to 50, for the same
experimental setup used for EASM.  We study the impact of network size
and sink mobility (in terms of sink speed) on each of the schemes.

Figure~\ref{fig:comp_routing_load} shows the routing load for each of
the protocols as network size is increased.  TTDD has the highest
load, followed by DD and EASM.  Each source in TTDD has to construct
and maintain a grid for dissemination of data, which is a costly
operation~\cite{Bokareva:04}.  

\begin{figure}[!ht]
\begin{center}
\includegraphics[width=2.3in]{eps/comparison_routing.ps}
\bfcaption{Comparison of Routing Load}
\label{fig:comp_routing_load}
\end{center}
\end{figure}


Variation of average delay against network size is shown in
Figure~\ref{fig:comp_delay_nw_size}.  The delays experienced by all
the schemes are comparable.  We also observe the average delay for
different sink speeds for TTDD and EASM as shown in
Figure~\ref{fig:comp_delay_sink_speed}.  Note that TTDD and EASM 
performance is similar for smaller sink speeds ( \textless 10 m/sec).
However, TTDD delay starts increasing when sink speed was increased
beyond 10 m/sec.  Recall that TTDD is suitable for localized sink
mobility patterns and hence experiences increased delays as speed is
increased. 

\begin{figure}[htb]
\begin{center}
\subfloat[Network Size]
{\includegraphics[width=2.3in]{eps/comparison_avg_delay_network_size.ps}
\label{fig:comp_delay_nw_size}}
\subfloat[Sink Speeds]
{\includegraphics[width=2.3in]{eps/comparison_avg_delay_sink_speed.ps}
\label{fig:comp_delay_sink_speed}}
\bfcaption{Comparison of Average Delay}
\end{center}
\end{figure}

Aggregate energy consumption is plotted for various network sizes in
Figure~\ref{fig:comp_en_cons_nw_size}.  EASM and TTDD graphs are
comparable, while DD has slightly higher consumption than each EASM
and TTDD.  However, note that when sink speed is increased TTDD
localized flooding (which is done when a sink enters a new cell)
increases leading to more energy consumption at higher speeds.  This
can be observed in Figure~\ref{fig:comp_en_cons_sink_speed}. 

\begin{figure}[htb]
\begin{center}
\subfloat[Network Size]
{\includegraphics[width=2.3in]{eps/comparison_engy_cons_nw_size.ps}
\label{fig:comp_en_cons_nw_size}}
\subfloat[Sink Speeds]
{\includegraphics[width=2.3in]{eps/comparison_engy_cons_snk_speed.ps}
\label{fig:comp_en_cons_sink_speed}}
\bfcaption{Comparison of Average Energy Consumption}
\end{center}
\end{figure}

