Site survey concepts
The greatest goal of a wireless site survey is to figure out the number and positioning of access points (or mesh nodes) that provides sufficient signal coverage throughout a facility or city area. With most implementations, “adequate coverage” means support of a minimum data rate or throughput. In order to perform a successful survey, you'll need to associate the required performance to a value that survey tools measure, such as SNR. A wireless site survey also detects the existence of RF interference coming from other resources that could degrade the performance of the wireless LAN.
1. Understand the wireless requirements -
In order to recognize the best possible locations for access points or mesh nodes, you must have a good comprehension of particular requirements for the network that impacts signal coverage. For example, maximum range between a client device and the access point reduces as data rate and resulting performance increases. Thus, you need to know the target data rates (and throughput) to correctly interpret survey results. Also, client devices may have relatively low transmit power, which must be taken into consideration when using most site survey tools.
2. Obtain a facility diagram -
Before getting too far with the site survey, locate a set of building blueprints or city maps. If none are available, prepare a drawing that depicts the location of walls, walkways, etc. Site survey tools import diagrams in various image formats. Of course mapping software is a good source for outdoor city surveys. If all else fails for in-building surveys, consider taking a digital photograph of the fire escape diagram, which is usually present on hallway walls.
3. Visually inspect the facility -
4. Assess existing network infrastructure -
Determine the capacity of any existing wired networks that can interface the access points or mesh nodes. Most buildings have Ethernet and in some cases optical fiber networks. Check on how much of the existing networks can be made available for supporting the wireless network. This will aid designers later on in the deployment when defining the architecture and bill of materials for the wireless network.
5. Identify coverage areas -
On the facility diagram or city map, indicate all areas where coverage is needed, such as offices, hallways, stairwells, utility rooms, bathrooms, break rooms, patios, parking garages, and elevators. Also, identifying where users will not wireless coverage is important to avoid wasting time surveying unnecessary areas. Keep in mind that you might get by with fewer access points and lower equipment costs if you can limit the roaming areas.
6. Determine preliminary access point locations -
7. Verify access point locations -
Take note of performance or signal readings at different points as you move to the outer bounds of the access point coverage. In a multi-floor facility, perform tests on the floor above and below the access point. Keep in mind that a poor signal quality reading could indicate that RF interference is affecting the wireless LAN. This would warrant the use of a spectrum analyzer to characterize the interference, especially if there are no other indications of its source. Based on the results of the testing, you might need to reconsider the location of some access points and redo testing for the affected locations.
8. Document findings -
These steps will point you in the right direction, but experience really pays off. If you're new to wireless LANs, you'll begin to build an odd intuition about the propagation of radio waves after accomplishing several wireless site surveys.
AirMagnet Survey goes beyond just verifying RF coverage, by plotting actual end-user network performance in terms of connection speed, throughput and packet statistics. The end result is a complete Wi-Fi “weather map” of all critical RF and end-user performance metrics.
Advanced features allow users to integrate with professional spectrum analyzers, model pre-deployment scenarios, generate customized survey reports, perform outdoor surveys, conduct voice surveys, verify end-user network requirements, and do detailed end-user capacity planning.
AirMagnet Survey is available in “Express” and “PRO” versions. AirMagnet Survey Express offers a lighter version of the solution that allows users to perform the basics of Wi-Fi site surveying with ability to map out signal, noise and even user performance. AirMagnet Survey PRO extends those capabilities found in the Express version and adds powerful, industry-defining features including 802.11n deployments, multi-floor deployments, outdoor surveys, network design verification, voice readiness verification and surveys, RF spectrum analysis, and many more. Read more about our Wireless AirMagnet Survey here.