Post-WiFi part3

Wi-Fi’s problems, part 3

Hello all,

In my last posts, I talked about the uses of the “Scan“, “Spectral-history” and “Spectral-scan” tools.

Now let’s see how we can use them to troubleshoot our wireless network issues.

Note: This article assumes that we are working in a site with many Wi-Fi routers.

First off, the worst thing we can do is to increase the power of our APs. This will cause interference between the routers and it can generate “hidden node” issues. A “hidden node” is a client which is far away (and on the opposite side) from the AP with respect to other clients. It hears its AP (barely, usually), but does not hear other clients. So it will transmit believing it’s alone on the network. This results in collisions, retransmissions and network delays.

When we do our troubleshooting, we have several steps to do.

• The “Spectral-history” tool allows you to see, over time, the use of the spectrum.
• The “Spectral-scan” tool will identify sources of interference, if any.
• The “Scan” tool is used to see what is happening at a specific moment in time. A small mAP connected to a laptop (and powered by the USB connector) allows us to walk and take precise measures. Tip: get help from someone who will record your measurements.

Once you have done the three steps, you have all the required data to analyze your network’s behavior.

Experts often say that the cells (coverage area of ​​a router) should intersect each other by 15% to 30%. If the cells’ shape was perfectly round, it would be easy. In real life, coverage will vary according to the obstacles. If you have taken enough readings during the site survey, you will have a good idea of ​​the cells’ shapes.

With this data, you can now adjust the power of your routers so that they are not too strong. If you find that a channel disappears sporadically, perhaps it’s a bad router? If after the power adjustments some places have insufficient Wi-Fi cover, you may need to add routers. Wi-Fi is simple beast to understand; it is better to put more at lower power than the opposite.

Tip: To simplify my life, rather than going through the various power adjustment parameters, I simply modify the “antenna gain” value (in dBi) in the card’s main parameters. I find this to be an easier approach.

Caution: There are specialized tools for site surveys. Although they are expensive, they take more accurate readings and can even record the results and overlay them on a digitized site plan. This provides accurate results and color coded Wi-Fi coverage.

If you have any comments, please let me know. Writing posts can be is a solitary task. I would like to hear your experiences in the world of Wi-Fi.

Best regards,