Go Premium for a chance to win a PS4. Enter to Win

x
Solved

# Ap Coverage

Posted on 2013-01-29
Medium Priority
327 Views
Does anyone know how to determine coverage (feet) of an AP in free space.  The information I have currently is:

23dbm = transmit power
3 dbi = antenna gain
0
Question by:simonphoenix10
• 5
• 3

LVL 37

Expert Comment

ID: 38833674
in free space, you need to apply cube law

to calculate the range, you also need the receiving unit antenna gain and both units minimum signal level.
0

LVL 21

Expert Comment

ID: 38835344
The maximum distance is going to vary depending on the radio band and connection speed. Check the web for tables relating to wireless distance for details.
0

LVL 37

Expert Comment

ID: 38835620
@Rick_O_Shay in free space as per the original question) , the frequency (band)  is irrelevant for RF propogation.
0

LVL 21

Expert Comment

ID: 38837287
But for the coverage of an AP in a real world situation the band and the speed the device connects at do matter.
0

LVL 37

Expert Comment

ID: 38837476
I would agree, but the original question was for "free space"...
0

Author Comment

ID: 38837499
Thanks, but really interested in general guidelines and not absolute math or is anyone aware of an online calculator
0

LVL 37

Accepted Solution

ArneLovius earned 2000 total points
ID: 38837845
RF propagation at 2.4 and 5Ghz, is affected by much smaller objects than for GSM., it gets attenuated by some things, and bounces off others, this can create "interesting" interference patterns.

There is modeling software available for several vendors, this "hides" some of the mathematics (physics), however it is always worthwhile doing a site survey, as site drawings are never "complete", things like people changing from wooden desks to metal topped desks, desk dividers that change from being foam covered MDF, to sheet aluminium with or without holes, changing glass walls from clear single thickness, to reflective coated (very thin layer of aluminium) double glazed, changing ceiling tiles from punched metal, to fibreboard, etc etc

The other aspect is the antenna, dbi is measured relative to "i", an isotropic radiator, it has gain by reducing the directions that it works in, presuming that a vertical antenna is used, it would in simple terms, "flatten" the sphere of radiation of an isotropic radiator, so would have more gain sideways and less gain upwards or downwards.than an isotropic radiator.

I have put APs into some building where to combat the internal structures we needed an AP every ~30 feet (on very low power), others where one was needed for each conference room but only two to cover the rest of the floor, the quantity of users can also affect usable bandwidth.

tl:dr no simple calculator can be accurate
0

LVL 21

Expert Comment

ID: 38839278
Attached is a table from an AP manufacturer from before 802.11n and 80211.ac (because I couldn't find a newer version) with maximum distances. You'll want to look at the ones for "outside" as they are for free space.
max-dist-a-b-g.pdf
0

LVL 37

Expert Comment

ID: 38839310
just love their use of the word "obstruction"...
0

## Featured Post

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Multi-source agreements are important because they set standards that all manufacturers should follow to ensure that devices are compatible with multiple vendors. The multi-source agreement (MSA) is an agreement that establishes how multiple vendors…
For Sennheiser, comfort, quality and security are high priority areas. This paper addresses the security of Bluetooth technology and the supplementary security that Sennheiser’s Contact Center and Office (CC&O) headsets provide.
This Micro Tutorial will show you how to maximize your wireless card to its maximum capability. This will be demonstrated using Intel(R) Centrino(R) Wireless-N 2230 wireless card on Windows 8 operating system.
Viewers will learn how to connect to a wireless network using the network security key. They will also learn how to access the IP address and DNS server for connections that must be done manually. After setting up a router, find the network security…
###### Suggested Courses
Course of the Month12 days, left to enroll