February 23, 2015

Wi-Fi Doctor Will Keep Your WLAN Healthy


Wi-fi proliferation and the impact on our ux



Over the last 10 years WLAN has evolved from a best effort, “nice–to–have” mobile LAN connection to a technology that competes with wired LAN interfaces - such as Ethernet – for delivering bandwidth hungry multimedia services seamlessly.

This battle for more bandwidth and true mobility is reflected in the evolution of the WLAN IEEE 802.11 standard. Whereas 802.11 supported not more than 1Mbps in the late 90s, 802.11ac now aims at supporting between 1.4Gbps and 7.8Gbps. Needless to say that the overall goal of the standard is to replace fixed wired connections and enable the same set of services (e.g. communication, LAN, IPTV, audio streaming) on mobile devices, while effectively reducing installation costs and improving ease of use.

Although WLAN technology is evolving at an exponential rate, the actual user experience isn’t. Analysis of operator helpdesk logs and technical blogs show that the more users join the wireless highway, the worse the user experience becomes. Home Wi-Fi® issues have quickly become and remain the number one helpdesk item for every ISP, despite all evolutions in IEEE WLAN standards. Moreover, they lead to higher churn rates for subscribers.


Existing troubleshooting tools not living up to expectations


In general, home Wi-Fi issues can be split into two distinct categories: unable to set up a connection and bad or degraded connection speeds. Nowadays most helpdesks can handle the first problem area, since they have well documented guidelines to help end users (re)configure their mobile devices. Although these Wi-Fi® network setup issues also drive OpEx up considerably, it is mainly the second problem area that is boosting service providers’ operational costs. These poor connectivity issues are still a grey zone for both operators and WLAN savvy people.[subscribe_reminder]

While connection issues can be solved with a deterministic multi-step approach (e.g. a flow chart), stability or performance issues are variable by nature and require in-depth knowledge of both the 802.11 protocol as well as RF (radio frequency) in order to devise a solution.

As this is not an easy task, we see a wide variety of attempts to come up with a solution for diagnosing such problems. Over the years, a lot of “tools” and “methods” have been developed with the aim to detect and solve WLAN performance issues. Common examples are heatmappers, signal bars on a device, scanning tools that visualize the presence of networks in a channel, and even remote monitoring tools using e.g. TR-069.

Sadly all of these tools fail to address the actual issue at hand, because they lack a structured approach. If we compare them with how common medicine tackles a health problem, we see the following flow: A doctor looks for a set of symptoms that gives him a clinical picture, which he can then link to a certain disease. This procedure is necessary for him to propose a treatment that will then hopefully lead to a cure. Most existing WLAN fixing tools, however, simply capture and store data, mostly gathered by an external device that is not the one the user complains about. As a consequence, skilled technicians have to dig into the dataset in order to find the actual problem or simply conclude that the required data was not captured.

Other tools out there focus on only one parameter, rather than the full clinical picture. For example, an RSSI measurement is supposed to be an indication for the WLAN link quality. In reality it doesn’t indicate more than the signal strength, i.e. not the SNR (signal-to-noise ratio) and definitely not the availability of the medium.

The following test results serve as practical examples:

  • The STA (station, client) is fairly close to the AP (access point); the RSSI indicated by the STA is - 40dBm, which should be an indication for excellent WLAN performance
  • The STA indicates -90dBm of noise measured, again a very good result suggesting that excellent performance should be reached
  • A background channel scan of both the AP and the STA results in a list of one detected AP. The signal strength at which this AP is observed is -85dBm – perfect! The other network is pretty well attenuated, so the in-home performance should be good
  • The WLAN link speed indicates 130Mbps, which is the maximum for a 2x2 802.11n setup

All conditions reported by these common tools are excellent. Yet when the end user launches a speed test(1), the result sometimes indicates not more than 2.5Mbps throughput - exactly what the end user is complaining about.

How is this possible, one could ask, given the fact that all tools indicate that the performance of the measured WLAN link should be good? In reality, there can be points in time where your neighbor’s network is saturated with prioritized Wi-Fi® traffic, using up the complete medium. It is also possible that another device is using the – unlicensed – ISM (industrial, scientific and medical) band, blocking the user’s network devices from accessing the medium. Such conditions are undetectable by classical tools that can only record signal strength and link speed.

Since helpdesk operators are typically not WLAN experts, they are unable to address reported issues of “the grey kind” in a quick and accurate way. In order for them to react swiftly and accurately, a more advanced tool is required.

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