Bug 1064

Summary:	Correct Friis propagation loss equation in spectrum module
Product:	ns-3	Reporter:	Dean Armstrong <deanarm>
Component:	wifi	Assignee:	Dean Armstrong <deanarm>
Status:	RESOLVED FIXED
Severity:	minor	CC:	deanarm, nicola, ns-bugs
Priority:	P5	Keywords:	bug
Version:	ns-3-dev
Hardware:	All
OS:	All

Description Dean Armstrong 2011-02-28 06:26:46 UTC

The implementation of Friis' propagation loss equation in the spectrum
module is incorrect. Currently, the comment in
friis-spectrum-propagation-loss.h agrees with the implementation in
friis-spectrum-propagation-loss.cc in indicating that the free space
path loss is computed thus:

/* L = (4 * pi * d * f^2) / C^2 */
double loss = ( d * f * f) / ((3e8 * 3e8) / (4 * M_PI)) ;

These are both wrong - the entire numerator in the comment above should be
squared, rather than just the frequency term.

The fix I propose can be seen as changeset 6814:d5863a7ab817 in
http://code.nsnam.org/deanarm/ns-3-dev-wifi-spectrum

Comment 1 Nicola Baldo 2011-03-01 11:40:16 UTC

whoops... I wonder how I could write that... what a shame!
Thanks for catching it, I am fine with your proposed changeset:
http://code.nsnam.org/deanarm/ns-3-dev-wifi-spectrum/rev/d5863a7ab817

Comment 2 Dean Armstrong 2011-03-01 12:02:22 UTC

Fixed in changeset 6846:8cbf95884984 on ns-3-dev.