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Ask The Experts: Wi-Fi Tips About Pre-Deployment

By boundless team in · Experts · September 22, 2016
The job of managing or deploying Wi-Fi can raise many questions, and we have set out to answer some that are common. In this series of posts, we have therefore compiled a collection of Wi-Fi tips from experts, which have been gathered over time. In our first post, the expert tips are Aerohive-specific. Today we answer general pre-deployment questions about WLANs.
The "Wi-Fi Tips" series is a project in motion, so if you you have anything to add, please tweet @Aerohive and let us know! 
Mesh Islands

Avoid creating mesh islands. Do not set radios in backhaul or dual mode on any nearby portal APs that might disrupt a point-to-point or point-to-multipoint mesh topology. Set the radios on the portal APs that are only serving clients to access mode. This helps avoid the situation where a mesh point might choose a sub-optimal path off the mesh or a path that does not have access to the necessary VLANs that a mesh connection might need.

Interference Sources

Know the sources of interference, both Wi-Fi and non-Wi-Fi. 2.4GHz band is universally used by Wi-Fi and non-Wi-Fi devices. This could include cordless phones, baby monitors, microwave ovens, security cameras, and projectors, among other devices. While there is much less interference in the 5GHz bands, you’ll have to be aware of the DFS regulations for your country.

PCI Compliance Tip

If you need your network to be PCI compliant, do not enable DFS on some of the APs distributed throughout the site so that they can scan all channels in the 5 GHz band. APs on DFS channels do not do background scanning because they must always remain vigilant for radar transmissions whereas APs on non-DFS channels scan all channels.

Site Survey Required

Do a site survey. Basic, inexpensive site-survey tools are available. By validating wireless requirements and performing an RF site survey, you can make informed decisions about how to design your wireless LAN network to provide the network access in the desired coverage area. 

Site Survey Before Overbuild
If you have existing Wi-Fi: Import the information into the tool (if supported). If the tool allows the live site survey, perform at least a passive survey (passive will record ALL Wi-Fi signals, not only your APs). If you do not have the Wi-Fi yet, use a predictive survey (unless you are a hospital, warehouse or a similar challenging environment). It does take some practice to do it right. The Airmagnet and Ekahau websites are great resources for tips and tricks.
Coverage Requirements

–70 dBM primary coverage is needed for high data rate connectivity. –75 dBM coverage is needed for roaming. Depending of the VoWiFi client vendor, –65/–67 dBM primary coverage is needed for quality voice communications over the WLAN.

Point to Point Tips

When building a point-to-point Wi-Fi bridge, you should set the channel for the bridge link on both APs to the same channel and not use the auto setting. Ideally, this would be a 5GHz non-DFS channel. 

Also, make sure you select Directional for the antenna type instead of the default Omni. And create a radio profile specifically for the mesh connection with settings to help optimize the connection, as these settings may be different than those of your regular radio profile(s). Make sure your Eth0 Operation Mode is set properly on each AP for how your network is setup on each end of the bridge.

Disable Lower Data Rates

Disable the lower data rate. Deny 802.11b clients. Pick 24 Mbps to be the basic data rate for 2.4GHz & 5GHz for Management Frames. One thing to remember is that many older client devices may still require lower data rates, 1 &2 Mbps, to connect and to maintain the connection. So it’s also important to know your client requirements

Don't Bond 2.4Ghz
Don't ever bond channels in 2.4Ghz. Don't ever use anything but channels 1, 6, and 11 in the US. Do create a channel plan. Do remember that 2.4Ghz will propagate further than 5GHz, so take that into account when setting your TX power. In very high density environments, you can even turn off some of the 2.4GHz radios to avoid too much cell overlap.

Don't ever bond channels in 2.4. Don't ever use anything but channels 1, 6, and 11 in the US. Do create a channel plan. Do remember that 2.4 will propagate further than 5, so take that into account when setting your TX power.
Metka adds: In very high density environments, you can even turn off some of the 2.4 GHz radios to avoid too much cell overlap.

20 MHz in 5Ghz
Use 20MHz channels in 5GHz for the best wireless range! The technical reason: MCS 0 requires 8dB of SNR when using 80MHz channels. Conversely, MCS 0 requires only 2dB of SNR when deploying 20MHz channels. To put another spin on this, using 80MHz channels requires -85dBm of signal strength to achieve some sort of data transfer. 20MHz channels on the other hand requires only -91dBm – that’s 200% less power! In short, using 20MHz is less demanding and will allow for data transfer at extended ranges. Also use the 20 MHz channel width in any High Density High Capacity situation to maximize the spectrum use.



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