In this period of pandemics employees, students and pupils rely on doing their work from home. Home schooling and home offices are becoming the vivid experience of the digital transformation, with notebooks and tablets as its essential utensils.
As professional and educational activities move to the home, the home network grows in importance to become an indispensable component of professional practice. In consequence it must face the much higher demands of mission-critical business applications on the quality of network service.
Quality deficiencies at this point lead to stressful situations and hinder the efficient work, especially in larger teams. Almost everyone who has participated in video conferences with a notebook or tablet is familiar with such situations. Lack of speech intelligibility, delayed transmission of the presentation, and stuttering on the screen can drastically reduce the value and efficiency of online meetings.
But often home networks are not designed to meet such requirements:
- Houses and apartments are not wired like offices; WLAN is the dominant networking technology. But in WLAN, all stations share the medium and all applications compete to be able to transmit.
- Residential networks are often connected asymmetrically with low “upstream” data rates. This was originally not so problematic, but because home working and home-schooling applications often generate bidirectional data traffic, for example during a video conference, a sufficient upstream data rate is becoming increasingly important.
In this article, we address the aspect of quality in WLAN and show how home working or home schooling can benefit from it. We will concentrate on WLAN according to the IEEE 802.11n and IEEE 802.11ac standards in the frequency bands at 2.4 GHz and 5 GHz, as is currently predominantly found in the home sector.
The toolbox for WLAN QoS contains a whole range of instruments that can be used to ensure good WLAN quality and thus enhance user experience (UX):
- Channel selection
- Band steering
- Router placement
- WIFI-QoS with Airtime Fairness and Airtime Policy Enforcement
- 4G/5G failover
In this series of blog articles, we will deal with most of this instruments and will start with selecting a proper WLAN-channel.
In a home environment overlapping of the reception ranges often occurs due to the proximity of WLAN systems. This can be particularly annoying in the 2.4GHz frequency band, if the radio channels of the neighbors and the own channel overlap due to the channel width of 20MHz. In 5Ghz band this is less a problem because the base channels there are defined with non-overlapping frequency bands.
Overlapping radio channels causes interference, disturbed reception and in consequence mor retransmissions at the receiver when transmitting simultaneously. The modus operandi is to select a channel with less interference which is usually a task of the access point. This should have an opportunity to automatically select the best channel, a functionality which can be activated in the configuration settings. Many modern home-based routers have this functionality, but its execution is by no means uniform. In some systems, channel selection is performed only once, usually when the router is (re-) started. In other systems, available channels are checked regularly and the channel in use is adjusted if necessary.
In this context, our investigation in the lab shows that devices react quite differently in the same environment at the same time. For example, the device from one manufacturer changed its channel about 2-3 times a day, while devices from another manufacturer adjusted the channel several times an hour.
However, the latter in particular can easily intensify an undesired adverse effect if the channel change causes the devices to disconnect and reconnect to the WLAN only after a longer period of time. This results in repeated connection interruptions, which significantly impair a good user experience especially during online conferences.
In our tests with common home routers, we found that the WLAN signal was usually restored within 10 seconds after a channel change, but it took up to 90 seconds for some PC to reconnect to the WLAN.
The picture below demonstrates this effect of a channel switch between a WIFI Access Point and two types of end devices..
Although a functionality that initiates a channel change in a controlled manner has been available since the standard extension 802.11h and has been further improved in IEEE 802.11y, a number of factors that lie in the interaction between the end device and the access point influence the scheduled sequence of a controlled channel change.
Because of that, technical skilled users may want to select a custom channel by himself and for those we want to give some hints for best practices. There are now several tools available that can display the usage of the various WLAN channels, and modern home routers often have a display that provides information about the WLAN usage of the individual channels. From such displays, you can identify the channels that are used less than others.
However, especially in the 2.4GHz range, it is not recommended to select a channel that is itself less used but is the nearest or next but one neighbor of frequently used channels. This is due to the effects of interference from overlapping bands from adjacent channels. Because interference of overlapping bands from neighboring channels can interfere with WLAN reception much more than some alien WLAN systems on the same channel will do.
This is due to the procedure that regulates access to the air interface. This so-called CSMA/CA procedure ensures that only one WLAN system transmits on a channel and prevents multiple WLAN systems from transmitting on the same channel simultaneously. So, they do not interfere each other.
It is therefore advisable to select one of the so-called overlap-free channels. In addition, this also allows channel bundling of 40 MHz in the 2.4GHz range to be implemented with less interference. In Europe, channels 1, 5, 9 and 13 could be used at 2.4 GHz, but the recommendation is to use channels 1, 6 and 11 to ensure greater compatibility with devices on the international market. For example, a major German network provider restricts automatic channel selection in its home router to the latter combination.
However, one must abandon the idea that one measure alone can eliminate WLAN problems. Instead, a comprehensive approach is required, as already mentioned at the beginning and as will be further elaborated in coming articles.