Wi-Fi issues: site-surveys and troubleshooting

Wi-Fi site surveys

Recently, we did numerous site surveys and verification of Wi-Fi deployments at the customers’ sites with more than 50 APs (access points) per office in a managed setup (i.e., a setup in which APs are under the supervision of a wireless controller). In this post, I’d like to sketch the encountered issues and improvement suggestions, which may be useful in general to Wi-Fi networks.

Fig. 1. Work-in-progress on post-processing the measurements

Wi-Fi networks deployment verification

The verification process we conducted included the following items:

• Active and passive site survey (separate measurements for 2.4 GHz and 5 GHz band) at the customer’s site, using Wi-Fi site survey tools, including:
  • signal strength measurements (coverage),
  • SNR,
  • channel overlap (number of APs on the same channel in a particular location),
  • active measurements: throughput and delay – using an actual download/upload of the files from the measuring device;
• Physical AP location checks to verify installation;
• Performance troubleshooting in problematic areas using Wi-Fi site-survey tools;
• Configuration and performance verification in the wireless controller dashboard.

Fig. 2. Photo from site-survey

Found issues

The key issues we found during those site-surveys included:

• Many networks “on-air” interfering with the customer’s Wi-Fi network (especially at 2.4 GHz, but in some places, 5 GHz was also very poisoned);
• Using 2.4GHz band for a dense network, which, in such a setup, performs poorly;
• RRM (radio resource management) algorithms (like transmit power control, automatic channel setup, load balancing) instabilities – resulted in a frequent channel and transmit power changes;
• AP mounting and location issues – placing APs, e.g. above metal lampshades, close to obstacles (like concrete poles or metal covers), or close to room edges/walls;
• Load imbalance – some APs have a very large load (many users connected to them), while at the same time other APs have a very small load (meaning, they are underutilized: e.g., having 0 or 1 users connected);
• Too few APs in open spaces – yielding low network capacity.

Those issues caused low throughput, dropped connections and problems with attaching to the network for the end-users.

Suggestions for improvements

Having such problems identified, the recommendations for improvements are the following:

• Switch-off 2.4 GHz band (in general), and use it only where/when needed;
• Change the location of the APs – move them to central locations and close to where the users are;
• Change mounting of the APs – to decrease disturbance from the metal elements;
• Avoid mounting APs close to windows and main walls – to decrease the signal dissipation thus waste of the radio energy towards the areas where there are no users;
• Decrease transmit power – to decrease overshooting;
• Increase the configured minimum bit-rate – not to allow users to “stay longer” connected to a particular AP – to save the “air time”;
• Use dedicated APs for conference rooms and separate for open spaces;
• Increase the channel bandwidth at 5 GHz band to 40 MHz (if channels are available) – to increase the capacity of an individual AP;
• Decrease the number of SSIDs to the minimum – to save the “air-time”;
• Name the APs properly in the controller dashboard/portal and locate them on a map within the dashboard/portal – to make the troubleshooting easier.

Fig. 3. Example report

Resources and services related to Enterprise Wireless

• To read our blogs on Wi-Fi, click here.
• To download a white paper on Wi-Fi, measurements, and troubleshooting, click here.
• To check out and sign up for our dedicated training on Wi-Fi systems, click here.
• To check out our Wi-Fi site survey, planning, and troubleshooting services, click here.
• If you are interested in hiring us to perform such a survey and troubleshoot issues in your Wi-Fi network please write to info@grandmetric.com