Tip 2: Minimize AP Power
As cell size decreases, you must reduce the AP power so that cells on the same channel don’t overlap. Overlapping channels cause co-channel interference that reduces available Wi-Fi capacity. Co-channel interference occurs when APs on the same channel interfere with each other and have to take turns using it. Imagine having a super-sized cell in which more clients have access to limited bandwidth.
You can eliminate channel overlap by reducing AP power levels to make the cells smaller. Note that consumer-level products often have crude power controls, if any—making it difficult to size the cells properly. The 2.4GHz band has only three non-overlapping channels: 1, 6 and 11, which makes it hard to avoid co-channel interference. The 5GHz band offers more channels and naturally smaller cells that help minimize interference. In either case, a site survey and solid design will avoid problems.
Tip 3: Migrate Endpoints to Higher Bandwidths
Where possible, migrate clients to Wi-Fi generation five (802.11ac), which uses both 2.4GHz and 5GHz bands to achieve high speeds with good coverage. This tip is a variation of the previous article’s
Tip 5: Disable Slow Speed Channels.
Your Wi-Fi AP refresh plan should include upcoming support for Wi-Fi generation six (802.11ax). Very few devices currently support Wi-Fi six, but the 6GHz bands will offer better performance and will attract clients as the new standard gains hardware support. The timing of the transition will depend mostly on when endpoints support it.
Don’t forget to include wireless controller upgrades in your Wi-Fi hardware refresh plan. And stay current with the software releases, which fix bugs and provide new capabilities.
Tip 4: Design for Mobility
Design the Wi-Fi network with mobility in mind. This step is critical for continuity of voice calls, as described in the article, “
Lack of Wi-Fi Mobility Can Cripple UC.” A Layer 3 (network layer) design using different subnets is a better long-term solution than extending a Layer 2 (data-link layer) network (a single subnet broadcast domain) across the physical infrastructure. The Layer 3 design, while more tedious to set up, avoids spanning tree loops, which can take down the entire network and are difficult to diagnose.
Tip 5: - QoS and Applicability to UC
Wi-Fi supports a simplified form of quality-of-service (QoS) called Wi-Fi multimedia (WMM), based on IEEE 802.11e. It provides four QoS profiles:
- Platinum – For voice applications
- Gold – For real-time, interactive video applications
- Silver – For best-effort traffic, such as typical data applications
- Bronze – For background traffic that doesn’t have strict performance requirements (email, file transfer)
The traffic classification and marking mechanisms typically used on wired networks aren’t available for wireless clients. Instead, applications within the endpoints must perform the marking. Wi-Fi-based phones are designed with this in mind. General-purpose computers (laptop and desktop) must be configured for their applications to do the necessary marking. Configuration of WMM varies according to the vendor, so you should plan for some extra work to make this happen consistently across the wireless infrastructure.
Tip 6: Employ Directional Antennas Where Necessary
Directional antennas are necessary for covering large outdoor areas where it’s not possible to install smaller cells. Be careful, however, that the client counts, and data rates won’t exceed the system’s ability to support them. You can also extend a network between buildings with wireless bridges and directional antennas. Careful design and installation are required.
You may not even need directional antennas if you use modern APs that incorporate multi-input, multi-output (
MIMO) technology that use beamforming and antenna diversity. These systems use multiple antenna systems to concentrate transmit RF power and to increase receiver sensitivity.
Up Next: Monitoring
You can’t manage what you can’t monitor, so my next article in this series will explore Wi-Fi monitoring tips that will help you proactively identify problems.
