Wireless Site Survey : The process of planning and designing a wireless network, in particular an 802.11 Wi-Fi wireless network, to provide a wireless solution that will deliver the required wireless coverage, data rates, network capacity, roaming capability and Quality of Service (QoS).

There are a number of factors that determine the final placement of access points (AP) throughout a facility including:

1. Required throughput - What sort of data will be transmitted between the access points and the client devices? A cutoff point in kilobytes per second should be determined prior to the actual survey.
2. Number of clients - How many end users would be connected to a single access point (AP) at a time? If you're installing a wireless network in a 500 seat lecture hall filled with users demanding high bandwidth you can easily criple a single AP. What sort of load can a single AP handle, and how many will be needed in highly dense client environments.
3. Facility Environment - Into what sort of environment will the APs be installed? Will there be materials that will absorb signal (large rolls of paper, dense products), which may require more APs? Is there high metal racking that may limit the horizontal reach of the signal?
4. Indoors or outdoors - Will you need to use certain weatherproof enclosures or antennas to battle harsh weather conditions? Will you need to put the hardware in a heated enclosure?
5. Geographic location - What country are you testing in? Different countries have different allowable frequencies in which the network can occupy.
6. Neighboring networks - Is there a large amount of interference coming from nearby 802.11 networks? If so, is this interference on the 802.11 b/g (2.4ghz) spectrum, or the 802.11a (5ghz) spectrum?

There is no amount of research that can substitute for a physical site survey. Performing a physical site survey involves setting up an access point and taking real time readings of throughput between the temporary network, and the client device. Throughput will be affected during the tests just as it will be affected when the network is in place.

Wireless Site Survey Steps:

1. Obtain facility blueprints - It is important that you have an accurate blueprint of the facility you are surveying so you can diagram coverage zones and access point locations as the survey is performed.
2. Perform an initial walk thru of facility - More often than not, the person performing the survey has been contracted, and has no familiarity with the area being surveyed. Doing an initial site walk thru will familiarize the surveyor of the facility. It will also let any on site IT or management point out areas that may not need coverage.
3. Visually determine a starting point - An experienced surveyor will be able to analyze a facility and determine a starting point. This starting point is in no way set in stone, but provides for the first zone to be tested for data throughput between the temporarily installed network, and the client PC. It is best to start in a corner of the building and work to the other side.
4. Install first zone's access point - Using a lift, you will now temporarily install the access point and chosen antenna to the ceiling. Depending on the environment, you will choose either a Dipole, Directional, or Omni-Directional antenna. Other considerations would be the Peak Gain (dBi) of the antenna.
5. Determine data transfer rates between AP and client PC - Using software to send data back and forth between the installed network and the client PC, you will now walk through the facility and monitor actual throughput. Measuring actual throughput will give you the best representation of what to expect when your completed network is in place.
6. Determine first coverage zone - As you walk further from the AP you will see the throughput rates begin to drop. As soon as they have dropped to your allowable throughput cutoff rate you have found the end of your zone. You should try to test the entire zone and determine the exact perimeter in which to use as a cut off area. The throughput rates should be determined prior to the site survey and depend on what sort of data is being transferred on your network.
7. Repeat process for next zone - With zone one completed you should have a good idea of the coverage to expect. Take down the installed access point & antenna, and reinstall in a neighboring zone. Repeat the steps to determine coverage area. Continue this process until the entire building is covered. Keep in mind that all zones will not necessarily require the same antenna type, or dBi.
8. Determine channel selection for APs - Each AP can be configured on a different frequency - or channel. The available channels on the B/G spectrum (at least in the US) are 1 - 11. The only non-overlapping channels would be 1, 6, 11. To minimize interference between your access points it is important to develop an AP layout that uses only these channels, and keeps the same channels as far away from one another as possible.