
% $Id: initial_results.tex,v 1.5 2005/04/08 21:25:58 gokhale Exp $

\subsection{Performance Results}
\label{sec:normal_results}

The scheme we proposed mainly addresss the sink mobility issue. As such 
in the first set of experiments we study EASM behavior varying the 
following parameters:
\begin{enumerate}
\item {\bf pause time:} In the sensor network, each mobile node remains
      initially stationary for a fixed period of time, known as the
      pause time. A destination is then selected from the flat
      simulation space defined and then the node starts moving towards
      the destination and the process is repeated for simulation time. 
      Pause time is thus a measure of sink mobility, since lower pause 
      time indicates highly mobile sinks and vice versa.
      stationary for longer periods. 
\item {\bf Maximum sink speed:} The maximum speed at which a sink may move.
      This is another measure of sink mobility.
\end{enumerate}

Aggregate Energy Depletion variation against sink speeds and pause times is
shown in Figures~\ref{fig:init_energy_depl} and
~\ref{fig:init_energy_depl_pause} respectively.  As the sink speed
increases the energy consumption increases.  Increased sink movement
means sink crosses and moves out of its current cell frequently.  The
queries for outstanding sink requests consume more energy as the
distance between the sink and the home grid center increases.  Similarly
for sink speed 10 m/sec energy consumption reduces as pause times
increase, as shown in Figure~\ref{fig:init_energy_depl_pause}.

\begin{figure}[htb]
\begin{center}
\subfloat[Sink Speeds]
{\includegraphics[width=2.3in]{eps/initial_energy_depletion.ps}
\label{fig:init_energy_depl}}
\subfloat[Pause Times]
{\includegraphics[width=2.3in]{eps/initial_energy_depletion_pause_time.ps}
\label{fig:init_energy_depl_pause}}
\bfcaption{Energy Depletion}
\end{center}
\end{figure}

Figures~\ref{fig:init_routing_load} and
~\ref{fig:init_routing_load_pause} plots the routing load variation
with sink speed, for a network size of 200 nodes.  In line with the
intution from EASM design, routing load increases with sink speed
since faster sinks lead to more nodes participating in routing.  EASM
scales well as the sink speed, since there is only a 10\% increase in
the routing load when the sink speed is increased from 1 m/sec to 30
m/sec.

\begin{figure}[htb]
\begin{center}
\subfloat[Sink Speeds]
{\includegraphics[width=2.3in]{eps/initial_routing_load.ps}
\label{fig:init_routing_load}}
\subfloat[Pause Times]
{\includegraphics[width=2.3in]{eps/initial_routing_load_pause_time.ps}
\label{fig:init_routing_load_pause}}
\bfcaption{Routing Load}
\end{center}
\end{figure}

For the same increase in speed, the latency increases by almost 33\%
as shown in Figures~\ref{fig:init_avg_delay} and
~\ref{fig:init_avg_delay_pause}.  A sink has to indicate its current
location to a grid center before data response can be sent to it.  As
the distance between grid center and sink increases (since sink is
faster, it changes cells frequently), the time to indicate its
location and get data response also increases thereby adding to the
delay perceived by sink node. 

\begin{figure}[htb]
\begin{center}
\subfloat[Sink Speeds]
{\includegraphics[width=2.3in]{eps/initial_avg_delay.ps}
\label{fig:init_avg_delay}}
\subfloat[Pause Times]
{\includegraphics[width=2.3in]{eps/initial_avg_delay_pause_time.ps}
\label{fig:init_avg_delay_pause}}
\bfcaption{Average Delay}
\end{center}
\end{figure}

Figures~\ref{fig:init_packet_frac} and
~\ref{fig:init_packet_frac_pause} inllustrate that packet delivery
fraction more or less remains constant.  Thus, increased sink speed
does not affect the success ratio in EASM.

\begin{figure}[!h]
\begin{center}
\subfloat[Sink Speeds]
{\includegraphics[width=2.3in]{eps/initial_packet_delivery_fraction.ps}
\label{fig:init_packet_frac}}
\subfloat[Pause Times]
{\includegraphics[width=2.3in]{eps/initial_packet_delivery_fraction_pause_time.ps}
\label{fig:init_packet_frac_pause}}
\bfcaption{Packet Delivery Fraction}
\end{center}
\end{figure}

