Calculating Maximum Distance

[WhyFi?]

http://www.afar.net/solution/howfar.htm

The site above discusses how to calculate the maximum distance of your wireless network. I'm not sure but I don't think the receivers transmission power is taken into consideration (unless that is the 15dB link margin), I wonder why not?

http://www.wi-foo.com/phorum//read.php?1,641,642#msg-642

This site also discusses the calculation, again it only discusses transmission power from one perspective and assumes the receiving sensitity of AP to wireless client is the same, what if it's not? The calc includes one AP output power, are we to assume that the receiving AP has the same output power? and if not what is the calculation?

I'm sure I'm missing something obvious here.

[M/Q]

Great questions.

I first do not like to use these types of calculations to determine distances as they assume perfect conditions. I prefer to use them as a basis to determine what parameters will be required to obtain the design link speed and link margin (ie link budget or system operating margin.) for a predetermined distance. The reason being is that the predicted distance is totally dependent on what you consider a viable link margin. I just look at the calculations differently and IMO in the real world it is a much safer approach as link margin is crucial for the success of a link. Especially when many of the physical and RF parameters along the link are not in your control.

Next, your observation about the fact that most publications on this subject make several assumptions that are not accurate are correct. Again, if you are in the real world, you need to be much more granular with your research as your reputation will depend on it. Hence my concern about link margin is again IMO justified.

If you are considering a point to point link, you would need to determine the link margin both ways and arrange parameters so that the path with the weakest link margin is still within what you consider an acceptable range.

If you are considering a point to multipoint link, you really need to focus on the multipoint sites as they have the weaker link budget typically. I am somewhat anal so I run the calculations both ways. It is quite easy due to all of the web sites that do all of the work for you. I use this site as it has several important calculations as well as the link budget or what they call the System Operating Margin.

http://www.terabeam.com/support/calculations/index.php