The spread of enterprise-grade laptops, tablets and smartphones combined with the deployment of broadband-intensive applications such as video calls, softphones, etc. has led to greater requirements being placed on enterprise and campus networks. This is often accompanied by problems with stability, speed and reliability in the WLAN. Most of these problems can be solved by optimised signal coverage of the WLAN and can be detected by means of coverage planning. Good coverage will give you more capacity for mobile clients and will future-proof your network.
A WLAN essentially comprises communication between access point and client – the endpoint. Communication takes place on the level of radio waves in the 2.4 GHZ or 5 GHZ spectrum. Just like other radio waves, WLAN waves are prone to interference and lose speed and connection stability when signal strength drops.
The greatest interference factors for WLAN are materials like water, metals and solid walls. Depending on their composition, the various materials either reflect or absorb the WLAN signal to varying degrees, thus impacting the coverage of the surrounding access points.
Settings on the access points – such as channel assignment – same SSIDs or signal overlaps from other floors or buildings can also impair connection quality. However this can be avoided when planning WLAN coverage.
Positioning is the key
Even the thinnest of glass partitions or slightly too long distancing to the access point can impair the quality of WLAN signals. That’s why access points should always be positioned in direct line of sight to the devices using the signal. Put simply, this means that access points should be planned in rooms with high levels of usage in places where they are visible to as many users as possible. Positioning in corridors weakens the WLAN on the way to the client and also restricts coverage within the rooms.
Buildings that have solid walls and are full of little nooks and crannies can impair coverage in places where this is the case. If a signal is needed in these places, it should be supplied by installing additional access points.
In most cases, these access points should be installed high up on walls or on the ceiling. However, due to the signal range, the right height must be found in large halls with high ceilings to optimise coverage at floor-level for most of the clients.
Good positioning also allows users to make subsequent modifications to the WLAN by only changing the settings on the access points and also creates a basis for perfect functionality for solutions such as artificial intelligence.
Targeted deployment of 5 GHz and 2.4 GHz
As the two WLAN frequency bands each cover different ranges, the deployed frequencies and channels should be included in the coverage planning as well as the rule of thumb regarding line of sight. While frequencies need to overlap for the transition between access points at signal strengths of approx. -50 dB, the channels must not overlap under any circumstance at the transition points. This is the only way to ensure that clients can clearly differentiate between signals and maintain the connection to the stronger signal – regardless of whether it is 5 GHz or 2.4 GHz.
2.4 GHz provides a good 200 m of range but only a few channels that can be used without overlap. Channels 1 to 14 are available for selection, whereby only channels 1, 6 and 11 can be used without overlap. That is why optimal coverage must be achieved with just three channels in the 2.4 GHz spectrum. If a lot of access points are required for optimal coverage in a building full of nooks and crannies, the low level of flexibility with channel assignment in the 2.4 GHz spectrum can lead to problems with overlaps or sub-optimal coverage.
5 GHz provides a range of approx. 100 m and up to 16 channels that can be used without overlap. In addition to the greater speed, even more precise coverage can be achieved with 5 GHz thanks to the larger number of channels. Due to the greater bandwidth, 5 GHz can take on more clients and reduce the strain on the 2.4 GHz frequency band when deployed in parallel. The result is that not only devices with 5 GHz capability benefit from deployment of the technology but clients in the 2.4 GHz frequency band too.
Due to the shorter range of 5 GHz, the access points must be positioned nearer to one other to achieve optimal coverage. This can lead to overlaps in the 2.4 GHz spectrum if all the access points transmit both signals. To avoid channel overlaps of the 2.4 GHz signal, it may be useful to reduce the signal strength at the access points or to switch it off at some APs and only use the 5 GHz signal there.
To achieve the best possible client compatibility, both frequency bands should be operated with different SSIDs. In order to optimise coverage, it is usually worth using a commonly available software – such as the professional site survey suite from Ekahau or free tools like the one provided by Ubiquity – to carry out a site survey and WLAN planning based on the floor plan.
In your channel planning for optimal coverage, the floors above or below the planned floor as well as surrounding buildings can constitute a source of interference. Here too it is important to consider the residual signals and assign the channels differently for each floor.
Using directionality to fine tune optimal coverage
Depending on the model deployed and its features, modern access points can not only give support when setting the signal strength but also when setting the signal’s directionality. Due to their length, particularly narrow rooms may need multiple access points, which in turn can interfere with surrounding signal sources. If reducing the signal strength at multiple access points makes no sense in such a case – and if the positioning of the access points allows – a narrower rather than a wider signal distribution may be more effective.
Due to their smaller beam angle, signals concentrated on one position may give stronger coverage in the direction of their orientation, thus causing overlaps with other surrounding signals. This means it is also important to consider how the signal changes in response to directionality.
Hands-off into the future
In some cases, well-equipped access points with up-to-date technologies can detect themselves whether signal overlaps occur and can automatically circumvent this problem by adjusting the directionality or the strength of the signal. Such features should be taken into account when planning coverage as such technologies do not necessarily require very detailed planning, and individual settings in the access points can even cause the signal to deteriorate.
If you would like to learn more about the topic of AI and future-proof WLAN, you should take a look at the Mist AI WLAN products in our portfolio. We will be glad to advise you based on your requirements and find a WLAN that suits your needs.