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When someone is going to implement a Wireless Network, it is sometimes not possible to plan the deployment properly, thinking that the Access Point can be installed under any environment available.
The FortiAP can be installed at any place, but the wireless network is not going to have the same performance under different sites. Before installing any Access Point is always mandatory to accomplish the following points, in order to know how to provide the best installation possible:
Site Survey:
This is an important factor to consider before implementing the FortiAPs, the first stage is to plan the survey analysis which will give the ability to identify where FortiAP placements will be. The benefit is that it will provide quality wireless connections.
There are some types of site surveys like predictive site surveys, passive site surveys, and active site surveys.
Passive site survey:
Determines where to place the Access points to provide the best performance possible, the information gathered tells if there are more Access points and their Signal strength, SNR, and some interference, also one important thing is to identify no Wi-Fi interference with a dedicated spectrum analysis.
Active site survey:
This should be done once the wireless network is under production, the purpose is to validate the information in relation to traffic.
If there have been some changes to the building or site, the furniture, structures all interior layout can affect how the network will be behaving. It is possible to test the Wi-Fi network during and after business hours and the result will be different.
Sometimes, it is necessary to determine if more FortiAPs are needed or if some of them should be moved to a different position or place.
Predictive site survey:
Is focused on where to place the access points using different tools dedicated to designing and predicting how wireless signals will be propagating through the space loading some maps with all its materials including walls, furniture, and ceiling.
As a result, the wireless designer can estimate how many Access points will be needed, the model and the potential positions, is a good guides but is not advisable to follow 100% of these types of surveys because cannot provide a stable wireless network, because this predictive survey is not able to know if the site has some Wi-Fi or non-Wi-Fi interference.
When doing a wireless implementation is good to know some information beforehand:
- How many users will be using the 2.4GHz band.
- How many users will be using the 5GHz band.
- In order to avoid low performance, can I disable the 2.4GHz band?
- Check the requirements that the application needs when using a Wi-Fi connection like voice, video, RTLS, and data.
- What type of client devices does the environment have.
- Keep 3 SSIDs at the most* to avoid management frame congestion. More than 3 SSIDs can cause the frame congestion.
- The data rates supported by each device are different, considering that the design can be done using the weakest user´s wireless card.
- Validate a secondary coverage FortiAP with the same level as the primary FortiAP, this is a good method of backup for applications like voice and video.
- Consider the -65dBm or -67dBm RSSI (Receive Signal Strength Indicator) with its own SNR of 25-30dBm for voice applications, resulting in less air time per user consumption, and higher data rates.
- Some specific wireless cards have different capabilities like channels, authentication, and encryption methods, and receive sensitivity.
- Design the wireless network for future growth, probably now the requirement has 50 clients, but in the future will be 400 clients, to see further, it is possible to avoid interruptions in the network and several maintenance windows.
- Validate how to save air time when an application is used considering the band in use, device performance, and channel width, devices transferring with faster speeds can free the medium and allow other devices to start transferring as soon as possible.
- Use DARRP if there is a high level of channel utilization, it helps to have a better performance when the RF environment is heavy.
- Use 20MHz channel width to avoid interference in high-density deployments in comparison with 40 or 80MHz.
- Try to isolate lower data rates like 802.11b in order to avoid low performance in the wireless network.
- Sometimes more FortiAPs are needed because while the enterprise is growing the FortiAP has more traffic to handle and it cannot cope with all the users. But before adding more FortiAps, consider some factors like CCI, transmit power, data rates, and frequency bands.
- Validate the building structure by checking the floor attenuation factors.
- Validate that the correct regulatory domain and channels are used.
- Keep in mind that one design dedicated to capacity and another for coverage is not the same.
- Consider some attenuation factors:
Material | Attenuation under 2.4GHz | Attenuation under 5GHz
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Glass/window 2–3 dB 6–8 dB
Fabric, blinds, ceiling tiles 1 dB 1.5 dB
Cubicle wall 2–5 dB 4–9 dB
Interior drywall 3–4 dB 3–5 dB
Steel/fire exit door 13–19 dB 25–32 dB
Wood door (Hollow –Solid) 3–4 dB 6–7 dB
Double-pane coated glass 13 dB 20 dB
Brick/concrete wall 6–18 dB 10–30 dB
In the end, the wireless network design is not the same as a wired network, it has a different challenge, and after the deployment, the work continues because it needs constant maintenance. Tunning, performing regular surveys in order to avoid some coverage issues, capacity issues, and security threats.
Related document:
https://wlanprofessionals.com/wireless-design-principles-and-best-practices/
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