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Wi-Fi issues: site-surveys and troubleshooting



24.01.2020

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.

Site survey

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.

GM-SS

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.

GM Site survey report

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, 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

 

Author

Marcin Dryjanski, Ph.D.

Marcin Dryjanski received his M.Sc. degree in telecommunications from the Poznan University of Technology in Poland in June 2008 and Ph.D. in September 2019. During the past 8 years, Marcin has served as R&D Engineer, Lead Researcher, R&D Consultant, Technical Trainer and Technical Leader. He has been providing expert level courses in the area of LTE/LTE-Advanced for leading mobile operators and vendors. Marcin provides consulting services to business projects in the area of 5G related topics. In addition to that, Marcin was a workpackage leader in EU-funded research projects aiming at radio interface design for 5G including FP-7 5GNOW and FP-7 SOLDER. He co-authored a number of research papers targeting 5G radio interface design. To contact Marcin please write to: marcin.dryjanski@grandmetric.com

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