Radio planning
- It is best to perform radio measurements before radio planning. Without measurements, radio planning will be based on theoretical calculations, which may differ from the real environment.
When performing radio measurements, it is necessary to take into account the SNR (signal-to-noise ratio) parameter. A high SNR means that the signal is significantly higher than the noise, which, in turn, ensures reliable and high-quality communication.
SNR (dB) Signal quality Commentary 40+ Excellent High-speed stable connection. 25-40 Good Provides smooth operation of VoIP, video conferencing and cloud services. Suitable for processing large amounts of data. Ideal for enterprise tasks with high requirements for connection stability. 15-25 Low Sufficient for working with email and small files. HD video playback (1080p) may be unstable. Suitable for everyday tasks with moderate bandwidth requirements. 10-15 Very low Connection is extremely unstable. This signal level is only adequate for basic tasks, such as receiving text emails without attachments. However, the connection will be virtually unusable for streaming, video conferencing, or downloading large files due to high latency and frequent disconnections. Less than 10 Unusable The connection is unreliable, the noise level is too high, and it is difficult to distinguish the signal from the noise. The SNR value is displayed in the GUI of the WLC controller:
The RSSI parameter is also important, but it should be remembered that an access point usually has a more powerful transmitter and a more sensitive receiver than client devices.- It is recommended to perform radio planning using specialized software such as Ekahau Pro Site Survey Tool, Tamograph Site Survey Pro and similar programs. To achieve maximum compliance with the actual operating conditions of the wireless network, select Client Mode during measurements in Ekahau.
- It is necessary to consider the frequency at which client devices can operate. Some devices only operate in the 2.4 GHz band, in which case only three non-overlapping 20 MHz channels can be used.
For compatibility with a large number of client devices in the 5 GHz band, it is recommended to use 17 non-overlapping 20 MHz channels: 36, 40, 44, 48, 52, 56, 60, 64, 132, 136, 140, 144, 149, 153, 157, 161.
If there are enough free channels available on the air to eliminate interference, it is recommended to increase the channel width to 40 MHz. This will increase the throughput of the wireless connection by increasing the available bandwidth. However, it is important to remember that using 40 MHz channel width is only justified in very clear airwaves, as this channel width is more susceptible to interference.
Radio survey (survey of the characteristics of the object and penetration of obstacles)
The optimal number of access points depends on the coverage area and the type of obstacles (concrete/brick walls, partitions, etc.).
Table showing Wi-Fi signal loss when passing through different media:
| Obstacle | Additional loss (dB) | Effective range1 |
|---|---|---|
| Open space | 0 | 100 % |
| Window without tinting (no metallic coating) | 3 | 70 % |
| Window with tinting (metallic coating) | 5-8 | 50 % |
| Wooden wall | 10 | 30 % |
| Interior wall (15.2 cm) | 15-20 | 15 % |
| Load-bearing wall (30.5 cm) | 20-25 | 10 % |
| Concrete floor/ceiling | 15-25 | 10-15 % |
| Monolithic reinforced concrete slab | 20-25 | 10 % |
1 Effective range is the distance by which the range of a Wi-Fi signal is reduced after passing through an obstacle compared to open space. For example, if the Wi-Fi range in open space is 400 meters, after passing through one interior wall, it will be reduced to 15% of the original value, i.e., to 60 meters. After the second wall, the range will again decrease by 15% from 60 meters to 9 meters, and after the third wall, to 1.35 meters. Thus, it is unlikely that a stable wireless connection can be established through three interior walls.
It is also recommended to consider the number of users who will connect to the access point simultaneously and the estimated amount of traffic usage (e.g., browsing pages, streaming videos, downloading files, etc.). This parameter can be predicted during planning using specialized tools, such as the Ekahau Pro Site Survey Tool. The number of access points should be selected based on the performance of the equipment.
Installation of access points
- Access points should be installed on ceilings no higher than 5 meters. If installed too high, signal quality will deteriorate.
- Ensure that the front of the access point (the main lobe of the antenna's directional pattern) is facing the target coverage area.
- It is not recommended to install access points behind any kind of obstruction, such as suspended ceilings, household appliances, etc. This reduces the signal level and, accordingly, the coverage radius.
- The minimum distance from the access point to any metal structures should be 10-15 cm.
- To ensure high-quality coverage, the access point should be installed below all metal structures in the service area, including those located in adjacent rooms.
- Place access points away from sources of interference such as cordless phones, microwave ovens, etc.
- When installing, keep a distance of half a meter from alarm/fire extinguishing devices and one and a half meters from LTE signal amplifiers.
- If roaming between access points is necessary, ensure that the coverage areas of neighboring access points overlap by 10-15% to ensure smooth roaming.
- When installing access points in a lobby/large conference room or other room where two access points need to be placed, it is recommended to install them diagonally.
Radio survey after installation
After installing and configuring the equipment, it is recommended to check the signal levels using a dual-band Wi-Fi client device and, if necessary, perform additional configuration. It is recommended to use specialized equipment, such as Ekahau Sidekick in client mode, as a Wi-Fi client for testing.
When scanning an access point (Rogue AP Detection), the signal level from neighboring access points should not exceed the following thresholds:
- No more than -85 dBm for a neighboring point operating on the same channel;
- No more than -55 dBm for a neighboring point operating on an adjacent channel (e.g., Ch1 and Ch6 or Ch40 and Ch44).
If the thresholds are exceeded, increase the distance between the points and/or reduce the transmitter power on them.
At this stage, a full network test should be performed to ensure that its performance and coverage area meet the requirements defined in the planning stage.