WN Podcast 051 – Validation Survey


Validation Survey, next to the Predictive Survey & Design, is the most popular type of the engagement we do in the WiFi consultancy world. We won’t exaggerate when we say we do it at least weekly and that validating / troubleshooting WiFi is a totally crucial skill.

Here is the video version of the Podcast – you can peek at our Ekahau Validation Survey template:



And here is what we have discussed:

  • Multiple names for the same thing
    • RF Assessment
    • Validation Survey
    • Troubleshooting Survey
    • It’s actually very similar to Post Deployment survey 
  • Targeting brownfield sites
    • Capture ‘as-is’ state of WiFi
    • Data captured is used to produce an easy to read ‘summary’ followed by simple ‘recommendations’
  • Why do clients ask us to perform a Validation Survey
    • Documentation purposes
    • Having issues that are most likely related to RF (physical side of WiFi) and must be identified and rectified
    • Building business case for re-design
    • Often sold together with Configuration Assessment
    • Often leads to more business
      • Be honest and don’t exaggerate
  • How and what do we capture on-site
    • Go on site
    • Perform full, detailed, passive survey with a survey tool of your choice
      • Active vs passive – why Ekahau is not best for active
      • Best active survey test – check if WiFi works for what it was designed for
        • Voice & video – can you have a good quality call? If not – why?
        • Basic data – can you browse, scan barcodes etc.?
      • If you must do throughput test, do them locally (ePerf, WLANpi throughput test) 
      • Ping is a poor test in WiFi due to the nature of how WiFi works – DCF aka ‘The Game’
    • Grab results of your fav WiFi Scanning tool
      • Capture what Ekahau can’t capture
        • Info from QBSS data like number of associated stations, AP reported channel utilisation
        • Amendments used
        • Authentication type used
        • SS info and more
      • On top of helping understanding RF better, quick WiFi scan can identify tons of common configuration issues without having to review the configuration
    • Be accurate
      • Click where you are
      • Don’t walk on water
      • Use good quality floor plans and measure with laser tool if required
  • What do we include in the Ekahau template – quick template demo
    • Ekahau captures tons of data and gives us access to tons of different heatmaps
    • Don’t include everything, include only what is relevant for your project
    • Here are the heatmaps and other info from Ekahau that we include in our Validation Survey documents:
      • Generic (band agnostic)
        • Requirements & Areas
        • Access Points
        • Survey Routes
        • Associates APs (make sure to use ‘measured’)
        • Capacity Health
        • Data Rates
        • Throughput (only if done local tests)
        • RTT (very infrequently)
      • Per band (same heatmaps for 2.4 and 5)
        • Coverage per AP
        • Primary Signal Strength
        • Secondary Signal Strength
        • Interference / noise
        • SNR
        • CCI
        • Network Health
        • Network Issues
        • Spectrum Utilization
        • Channel Width
    • What we don’t include 
      • Capacity: Clients per AP – predicted, no value
      • Channel Coverage – can’t see a use case
      • Channel Interference – predicted, no value
      • Jitter – not best metric
      • Number of APs – use secondary coverage instead
      • Packet loss – exaggerated in Ekahau, not great metric
      • RTT – not best metric
      • Spectrum Channel Power – can’t see use case
      • Difference in Signal Strength – can be valuable to compare surveys, but never used it
  • What do we include in the Summary
    • A sentence or two about all heatmaps
    • DFS condition check
    • Types of APs / Antennas used, their suitability against env they’re in and requirements, mounting
  • Typical issues
    • Incorrect type of APs/Antennas used
      • Tendency to be scared of directional antennas
    • Dual band operation
      • Band select used
      • Some devices on terribly bad 2.4GHz
    • Coverage and SNR
      • Not sufficient coverage
      • High non-WiFi interference
      • Low SNR
    • Tons of rogue APs on site
      • Old overlays, hotspots, click shares
    • Excessive CCI 
      • Not unusual to see 30+ in central London on 5GHz
    • Not enough APs
      • Capacity requirements not met 
      • Sometimes a 100 or more associated stations
    • Insufficient secondary coverage
    • Poor WLAN config
      • No amendments used
      • Low data rates enabled
      • APs covering too much – 15m high omnis in WH?
    • High spectrum utilisation
      • More devices using WiFi than scoped
      • WiFi and non-WiFi interference
      • Too many SSIDs – seen 16 more than once
    • High packet loss
      • High airtime utilisation = tons of retransmissions = packet loss
    • Site heavily affected by DFS
  • Typical recommendations (just an example, can vary vastly)
    • Re-design of physical WiFi
      • Different APs, different antennas types, different mounting
    • Disable 2.4GHz
    • Set 5GHz statically to 20MHz
      • Channel width set to best is sometimes crazy
      • Use 40MHz until you can’t
    • Enable some amendments
      • 802.11r
      • 802.11k
    • Disable low data rates
      • 12 or 24 mandatory is typically OK with all lower disabled and all higher supported
    • Limit min and max Tx power levels in RRM
      • 5GHz should be ‘louder’ than 2.4GHz – at least 6dBm difference
      • Typical Tx levels for 5GHz – around 14-17dBm

Cheers and tons of love,

Your Ninjas.

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This WiFi Ninjas Podcast archive consists of all the podcasts we have ever recorded!