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  • Wi-Fi issues: site-surveys and troubleshooting

    Wi-Fi issues: site-surveys and troubleshooting

    Date: 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, 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

    Author

    Marcin Dryjanski, Ph.D.

    Marcin Dryjanski received his Ph.D. in telecommunications from the Poznan University of Technology in September 2019. During the past 15 years, Marcin has served as R&D Engineer, Lead Researcher, R&D Consultant, Technical Trainer, Technical Leader and Board Member. He has been providing expert-level courses in the area of 5G/LTE/LTE-Advanced for leading mobile operators and vendors. In addition to that, Marcin was a work-package 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 and a book "From LTE to LTE-Advanced Pro and 5G" published by Artech House. Marcin is co-founder of Grandmetric and co-founder and CEO at Rimedo Labs, currently focusing on Open RAN systems.

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