How to do a wireless site survey

A wireless site survey measures how Wi-Fi actually behaves in a building, so access points can be placed where they work rather than where they are easy to fix. Done properly, it answers four questions:

• Coverage: is there enough signal everywhere people and devices need it?
• Quality: is the signal clean, or drowned by noise and neighbouring networks?
• Capacity: can the network carry the number of people and devices at the busiest moment?
• Roaming: do devices hand over cleanly as people move, or do calls and scanners drop?

A phone app showing signal bars answers none of these properly. It shows what one device sees, in one spot, at one moment.

1. Agree the requirements first. Which areas, how many users and devices, what they do (email, video calls, scanners, voice), and the pass marks the network must meet. Without written requirements, there is nothing to measure against.
2. Get scaled floor plans. Every floor, with the scale set correctly in the survey software. A wrong scale makes every measurement and access point distance wrong.
3. Walk the site before measuring. Note ceiling types and heights, wall materials, racking, lifts, risers, comms rooms and where cable can and can't go.
4. Choose the survey types. Usually a passive survey, plus active and AP-on-a-stick where needed (see the table below).
5. Calibrate and set up the kit. We use Ekahau Sidekick with Ekahau AI Pro, so measurements are consistent whoever carries the kit and comparable between visits.
6. Walk the survey route. A steady pace, close to every wall and into every room, clicking position on the plan as you go. Gaps in the route become gaps in the heatmap.
7. Measure at working height. Where devices are used: desk height in offices, scanner height in warehouses.
8. Record what you see. Photos of mounting positions, ceilings, cabinets and cable routes, tied to the plan.
9. Analyse against the requirements. Signal, signal-to-noise, channel overlap, secondary coverage for roaming, and capacity. Many designs use about -67 dBm signal and 25 dB signal-to-noise as a starting point for voice and real-time apps, but the right figures depend on the devices and what they do.
10. Design and report. Access point positions, channel and power plan, cabling and containment needs, and a costed kit list. See what a report includes.
11. Validate after installation. Survey again once the network is live, against the same requirements, and fix anything that falls short.

• Surveying an empty building. Furniture, people and loaded racking all absorb signal. Survey as close to real conditions as possible, or allow for the difference. See why racking changes everything.
• Only checking signal strength. Strong signal with heavy channel overlap or noise still performs badly.
• Ignoring the devices. The weakest device on the network, often an old scanner or a phone, decides what "good" means, not the laptop used for the survey.
• Designing for coverage, not capacity. A meeting room or classroom can have perfect signal and still fail when 30 people connect at once.
• Forgetting the cabling. An access point position nobody can cable, power or reach later isn't a real position.
• No validation. Without a survey after installation, nobody knows whether the design was delivered.

For a small office or a home, a free app and some common sense will often find an obvious dead spot. For a business that relies on its Wi-Fi, an Ekahau survey by a trained surveyor is the difference between knowing and guessing: calibrated measurements, a design to written pass marks, and evidence you can hold the installer to.

SEGwifi is an Ekahau partner. We survey across London, Hertfordshire and the UK, including multi-site programmes, and our own teams can carry out the business Wi-Fi installation afterwards.