WiFi transmit and receive range

[adam young]

We are working on WiFi wireless transmit and receive products specification.
Can you tell me how best to understand :
1. the RF output transmit frequency vs power vs range
2. the receive frequency vs sensitivity vs range
What is the typical range estimates in outdoor open area and indoor offices?
Thank you.

 

[Joel Kolstad]

We are working on WiFi wireless transmit and receive products specification.
Can you tell me how best to understand :
1. the RF output transmit frequency vs power vs range
2. the receive frequency vs sensitivity vs range
What is the typical range estimates in outdoor open area and indoor offices?

Google "Friis equation." It's actually just a bit of algebraic manipulation
starting with the idea that power radiating into free space must fall off (in
density, W/m^2) with the square of distance... in free space. In The Real
World, you can demonstrate that there are worst case scenarions where power
falls off with the _cube_ of distance (ouch!); people doing link calculations
pick there favorite power, with 2.5 not being uncommon.

The way to think of free space attenuation is that each oscillation or
wavelength of a signal gets attenuated by a certain, constant amounts. Hence,
if you double the frequency, you halve the wavelength and double the
attenuation over a given distancedoubles as well.

---Joel Kolstad

 

[Jeroen Belleman]

Google "Friis equation." [...]

The way to think of free space attenuation is that each oscillation or
wavelength of a signal gets attenuated by a certain, constant amounts. Hence,
if you double the frequency, you halve the wavelength and double the
attenuation over a given distancedoubles as well.

That's NOT what happens! The equation assumes a receiving antenna
with a fixed size in wavelengths. Higher frequency means a smaller
antenna that intercepts less energy. _That_ is why the equation
gives higher path loss for higher frequencies. Path loss is a
misnomer, in fact.

Jeroen Belleman

 

[adam young]

Please help me to calculate.
The frequency for 802.11b is 2.4GHz, and 802.11g is 5.2GHz,
The maximum FCC allow unlicensed power is 0.5watts = 500mWatts.
So what is the range in distance? Thank you.

 

[Joel Kolstad]

Please help me to calculate.
The frequency for 802.11b is 2.4GHz, and 802.11g is 5.2GHz,
The maximum FCC allow unlicensed power is 0.5watts = 500mWatts.
So what is the range in distance? Thank you.

This is impossible to calculate without knowing the gain of your antennas (and
if you're indoors or outdoors). For point-to-point links, with 500mW you can
go tens of miles... for a roughly omnidirectional antenna, you most likely
won't even get one mile.

 

[James Douglas]

Please help me to calculate.
The frequency for 802.11b is 2.4GHz, and 802.11g is 5.2GHz,
The maximum FCC allow unlicensed power is 0.5watts = 500mWatts.
So what is the range in distance? Thank you.

A bunch of nerds went over 70 miles in the desert in Nevada, I copied
the article and gave it to the company wireless guy's as I can't connect
to the access point 20' away! At home my signal is good in the house and
two houses on both sides of me........

 

[Keith]

A bunch of nerds went over 70 miles in the desert in Nevada, I copied
the article and gave it to the company wireless guy's as I can't connect
to the access point 20' away! At home my signal is good in the house and
two houses on both sides of me........

I like these guy's approach:

http://www.usbwifi.orcon.net.nz/

 

[adam young]

OK, for both external indoor and outdoor operating in urban and rural
spaces,
using typical 2.4GHz 24 dB Gain grid antenna,
how do I calculate the range?

 

[Donald]

OK, for both external indoor and outdoor operating in urban and rural
spaces,
using typical 2.4GHz 24 dB Gain grid antenna,
how do I calculate the range?

"Calculate" range ????

You may be able to "Calculate" signal strength in an ideal environmet.

But Range ???

If you can model every foot of ground and air space between the
transmitter and receiver, well maybe not.

Good Luck

Donald

 

[Michael A. Terrell]

OK, for both external indoor and outdoor operating in urban and rural
spaces,
using typical 2.4GHz 24 dB Gain grid antenna,
how do I calculate the range?

Does the transmitter put out the full 500 mw? How many Microvolts are
required at the receiver's antenna to get an acceptable error rate? Is
there anything along the path that can cause multi-path reception? How
well made are the antennas? Is there any chance the receiver will be
desensed from another source? How accurately are the antennas aimed?
You don't give anywhere near enough data to give a valid answer.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[[email protected]]

Guys- propagation of 2.4GHz WiFi is so influenced by diverse
reflections & obstructions that it's near impossible to factor exact
range into calculations. Additionally local spectrum noise ( from
microwave ovens, cordless phones, APs, BlueTooth etc ) can mask weak
signals. Weather & even season can be a factor too- very dry air in
winter can sustain longer links that moist summer air. Hence it's
STRONGLY suggested that you grab a WiFi laptop or PDA & run
NetStumbler or WiFiFoFum( WFFF) while doing a site audit, perhaps with
one of our cookware parabolas. This is usually THE very first thing to
do - see a ~1km LOS ( line of sight) proof of concept trial we ran in
Wellington NZ => www.usbwifi.orcon.net.nz/wifi1km.jpg

 

[Carl Smith]

I like these guy's approach:

http://www.usbwifi.orcon.net.nz/

There's just something cool about the term "chinese parabolic
cookware."

 

[adam young]

Similiar situation, how does cellular telephone operator estimate cover a
city or an area?
So since WiFi is higher in frequency, how do they estimate how to cover an
area?

 

[Michael A. Terrell]

Similiar situation, how does cellular telephone operator estimate cover a
city or an area?
So since WiFi is higher in frequency, how do they estimate how to cover an
area?

Its right there in the name: Cell, or small areas covered by a single
base station that are connected to provide wider coverage.

This kind of question belongs in

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Iwo Mergler]

Similiar situation, how does cellular telephone operator estimate cover a
city or an area?
So since WiFi is higher in frequency, how do they estimate how to cover an
area?

Computer models for the rough geography, guru experience for the
rest. Then measurements and adjustments to antenna patterns and
power as needed.

The situation is slightly different in that they are not looking
for maximum range for a given setup, but adjust the setup to
get the needed range.

Kind regards,

Iwo

 

[adam young]

So how do you estimate WiFi and Cellular phone antenna coverage?
For rough estimate, how to design antenna coverage area pattern for typical
suburban areas?

 

[Iwo Mergler]

So how do you estimate WiFi and Cellular phone antenna coverage?
For rough estimate, how to design antenna coverage area pattern for
typical suburban areas?

You look at the place, make an educated guess about the
absorption and reflection properties of the landscape,
buildings and other stuff and go by gut feeling.

It's about as accurate as forecasting the weather. In
theory, it can be calculated exactly, but in reality
you never have sufficient information to do it.

It's not an exact science. In free space, you can calculate
exactly, after that people tend to use rules of thumb.


Kind regards,

Iwo

 

[Joel Kolstad]

It's about as accurate as forecasting the weather. In
theory, it can be calculated exactly, but in reality
you never have sufficient information to do it.

Yeah, although for big cities it seems that, e.g., the cell phone guys are
willing to pay for some pretty fancy software to try to get their estimates
correct. See: http://www.softwright.com/tap6.html or
http://www.cwins.wpi.edu/projects/scripts/new_york.html

 

[Iwo Mergler]

Yeah, although for big cities it seems that, e.g., the cell phone guys are
willing to pay for some pretty fancy software to try to get their
estimates
correct. See: http://www.softwright.com/tap6.html or
http://www.cwins.wpi.edu/projects/scripts/new_york.html

Have you seen the computers the weather guys are using? ;-)

Iwo

 

[adam young]

So, rough design estimest, would you say every 1 square mile per antenna
point, or 2 or 3 or 5 square mile?

I know, nobody want Cell or WiFi antenna tower in front of their house.