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<html><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><!--Converted with jLaTeX2HTML 2002 (1.62) JA patch-1.4patched version by: Kenshi Muto, Debian Project.LaTeX2HTML 2002 (1.62),original version by: Nikos Drakos, CBLU, University of Leeds* revised and updated by: Marcus Hennecke, Ross Moore, Herb Swan* with significant contributions from: Jens Lippmann, Marek Rouchal, Martin Wilck and others --><HTML><HEAD><TITLE>18.1 Free space model</TITLE><META NAME="description" CONTENT="18.1 Free space model"><META NAME="keywords" CONTENT="everything"><META NAME="resource-type" CONTENT="document"><META NAME="distribution" CONTENT="global"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"><META NAME="Generator" CONTENT="jLaTeX2HTML v2002 JA patch-1.4"><META HTTP-EQUIV="Content-Style-Type" CONTENT="text/css"><LINK REL="STYLESHEET" HREF="everything.css" tppabs="http://www.isi.edu/nsnam/ns/doc/everything.css"><LINK REL="next" HREF="node217.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node217.html"><LINK REL="previous" HREF="node215.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node215.html"><LINK REL="up" HREF="node215.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node215.html"><LINK REL="next" HREF="node217.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node217.html"></HEAD><BODY ><!--Navigation Panel--><A NAME="tex2html4590" HREF="node217.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node217.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html4584" HREF="node215.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node215.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html4578" HREF="node215.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node215.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html4586" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html"><IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="file:/usr/share/latex2html/icons/contents.png"></A> <A NAME="tex2html4588" HREF="node590.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node590.html"><IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index" SRC="file:/usr/share/latex2html/icons/index.png"></A> <BR><B> Next:</B> <A NAME="tex2html4591" HREF="node217.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node217.html">18.2 Two-ray ground reflection</A><B> Up:</B> <A NAME="tex2html4585" HREF="node215.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node215.html">18. Radio Propagation Models</A><B> Previous:</B> <A NAME="tex2html4579" HREF="node215.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node215.html">18. Radio Propagation Models</A>   <B> <A NAME="tex2html4587" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html4589" HREF="node590.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node590.html">Index</A></B> <BR><BR><!--End of Navigation Panel--><H1><A NAME="SECTION031510000000000000000"></A><A NAME="sec:freespace"></A><BR>18.1 Free space model</H1><P>The free space propagation model assumes the ideal propagation conditionthat there is only one clear line-of-sight path between the transmitter andreceiver. H. T. Friis presented the following equation tocalculate the received signal power in free space at distance from thetransmitter [<A HREF="node589.html#Friis46" tppabs="http://www.isi.edu/nsnam/ns/doc/node589.html#Friis46">14</A>].<P><BR><DIV ALIGN="RIGHT"><!-- MATH \begin{equation}P_r (d) = \frac{P_t G_t G_r \lambda^2}{(4\pi)^2 d^2 L}\end{equation} --><TABLE WIDTH="100%" ALIGN="CENTER"><TR VALIGN="MIDDLE"><TD ALIGN="CENTER" NOWRAP><A NAME="eqn:freespace"></A></TD><TD WIDTH=10 ALIGN="RIGHT">(18.1)</TD></TR></TABLE><BR CLEAR="ALL"></DIV><P></P><P>where is the transmitted signal power. and are the antennagains of the transmitter and the receiver respectively. is thesystem loss, and is the wavelength. It is common to select and in simulations.<P>The free space model basically represents the communication range as a circlearound the transmitter. If a receiver is within the circle, it receives allpackets. Otherwise, it loses all packets<P>The OTcl interface for utilizing a propagation model is the <TT>node-config</TT>command. One way to use it here is<P><PRE>$ns_ node-config -propType Propagation/FreeSpace</PRE><P>Another way is<P><PRE>set prop [new Propagation/FreeSpace]$ns_ node-config -propInstance $prop</PRE><P><HR><!--Navigation Panel--><A NAME="tex2html4590" HREF="node217.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node217.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html4584" HREF="node215.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node215.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html4578" HREF="node215.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node215.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html4586" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html"><IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="file:/usr/share/latex2html/icons/contents.png"></A> <A NAME="tex2html4588" HREF="node590.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node590.html"><IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index" SRC="file:/usr/share/latex2html/icons/index.png"></A> <BR><B> Next:</B> <A NAME="tex2html4591" HREF="node217.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node217.html">18.2 Two-ray ground reflection</A><B> Up:</B> <A NAME="tex2html4585" HREF="node215.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node215.html">18. Radio Propagation Models</A><B> Previous:</B> <A NAME="tex2html4579" HREF="node215.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node215.html">18. Radio Propagation Models</A>   <B> <A NAME="tex2html4587" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html4589" HREF="node590.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node590.html">Index</A></B> <!--End of Navigation Panel--><ADDRESS>2003-09-23</ADDRESS></BODY></HTML>⌨️ 快捷键说明
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