Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

Bronze

use of Feriis transmission equation for ptp wireless link

Hi everybody.

The equation only takes into consideration free path loss.

In its simplest form, the Friis transmission equation is as follows.  Given two antennas, the ratio of power available at the input of the  receiving antenna, P_r, to output power to the transmitting antenna, P_t, is given by

\frac{P_r}{P_t} = G_t G_r \left( \frac{\lambda}{4 \pi R} \right)^2

If we use  Pr = sensitivity of a receiver, the equation help us determine how far transmitter and receiver can be from each other.

1)Do we use this equation a lot  specially when establishing a wireless ptp link?

2) How about broadcast transmission say FM radio?  Can  we use the same equation to estimate the coverage area for r broadcast  radio transmission?

thanks and have a nice weekend.

Everyone's tags (5)
1 ACCEPTED SOLUTION

Accepted Solutions

use of Feriis transmission equation for ptp wireless link

Hi,

Well, I think this equation is being used more by telecommunication engineers that establish communication towers. Not usually used with Wi-Fi networks (but still can be used though).

In my practical experience I've never used this equation (maybe because I never established a PTP link). But anyway the equation is not mentioned in any Cisco doc. (not even Aruba docs AFAIK).

There are too many factors that affects the wireless installation. This equation is too ideal to fit in place because it considers ideal situation for communication (clear line of site, no interference, no nose..etc). So a it can give an idea about the maximum distance but in normal situations the distance is much more less than the ideal value calculated by this equation.

In my opinion it does not fit for broadcast communication because simply there is usually a big difference between sender and receiver gains besides the obstacles and interference/noise that may be exist.

This link should be useful to read:

http://www.moxa.com/newsletter/connection/2008/03/Figure_out_transmission_distance_from_wireless_device_specs.htm

HTH

Amjad

Rating useful replies is more useful than saying "Thank you"
1 REPLY

use of Feriis transmission equation for ptp wireless link

Hi,

Well, I think this equation is being used more by telecommunication engineers that establish communication towers. Not usually used with Wi-Fi networks (but still can be used though).

In my practical experience I've never used this equation (maybe because I never established a PTP link). But anyway the equation is not mentioned in any Cisco doc. (not even Aruba docs AFAIK).

There are too many factors that affects the wireless installation. This equation is too ideal to fit in place because it considers ideal situation for communication (clear line of site, no interference, no nose..etc). So a it can give an idea about the maximum distance but in normal situations the distance is much more less than the ideal value calculated by this equation.

In my opinion it does not fit for broadcast communication because simply there is usually a big difference between sender and receiver gains besides the obstacles and interference/noise that may be exist.

This link should be useful to read:

http://www.moxa.com/newsletter/connection/2008/03/Figure_out_transmission_distance_from_wireless_device_specs.htm

HTH

Amjad

Rating useful replies is more useful than saying "Thank you"
430
Views
0
Helpful
1
Replies
CreatePlease to create content