The initial placement of an access point is based on an estimate of the signal loss that will occur between the access point and the users of the access point.
The starting point for an estimate depends on how much loss in power a signal would experience in the vacuum of space, without any obstructions or other interference. This is called the free space path loss and is specified in decibels (dB)
The estimate is tuned with an understanding that the actual expected signal loss depends on the medium through which the signal will travel, which is undoubtedly not a vacuum. An RF singal can be affected by
- Reflection(steel, metal door)
- Absorption(water,tree,thick wood)
- Refraction(signal is bent when going through a medium with one density to a medium with another density.eg.water tank)
- Diffraction(signal which is bent while going through a region where reflective obstruction exits can interfere with that part of RF signal that is not bent
Wireless installation site survey
A site survey can be as simple as walking around with a wireless notebook computer and using the utility to measure signal strength.Signal strength can also be determined with a protocol analyzer. The WildPackets AiroPeek analyzer, for example, presents the signal strength for each frame received.
An access point typically sends a beacon frame every 100 milliseconds(ms).When evaluating the various metrics that are provided by wireless utilities, be sure to measure frame corruption and not just signal strength. With a protocol analyzer, capture frames and check for cyclic redundancy check (CRC) errors.
Wireless utility such as the Cisco ACU, WildPackets, OmniPeek, or NetStumbler to check signal strength
