Wireless Networking
Wi-Fi is a shared radio medium. A strong signal alone does not guarantee a good network. Capacity, interference, channel reuse, client behavior, roaming, wired uplinks, and authentication all affect the user experience.
Radio-Frequency Basics
- Signal strength: How strongly a client receives the access point.
- Noise floor: Background RF energy.
- Signal-to-noise ratio: The difference between useful signal and noise.
- Interference: Competing Wi-Fi or non-Wi-Fi transmissions.
- Airtime: The limited shared time available for clients to transmit.
Frequency Bands
| Band | Strengths | Tradeoffs |
|---|---|---|
| 2.4 GHz | Longer reach and broad client compatibility | Few nonoverlapping channels and frequent interference |
| 5 GHz | More channels and higher capacity | Shorter effective range through walls |
| 6 GHz | Large clean spectrum for compatible clients | Requires newer clients and generally denser AP placement |
Channel Width
Wider channels can provide higher peak throughput, but they consume more spectrum and reduce channel reuse. In dense deployments, multiple well-planned 20 or 40 MHz channels often provide better total capacity than a few very wide channels.
Access Point Placement
Place access points according to the space and expected client density, not just maximum coverage. Avoid mounting APs inside metal cabinets, above dense obstructions, or at one end of a long building. Warehouses, hotels, offices, outdoor spaces, and event venues require different antenna and placement strategies.
Capacity Versus Coverage
A single access point may cover a large area but still lack airtime for all clients. Design for the number of active users, application demand, and client capabilities. High-density spaces may need lower transmit power and more access points to create smaller cells.
Roaming
The client normally decides when to roam. A wireless system can assist by advertising neighbor information and reducing authentication delay, but poor AP placement, excessive transmit power, or inconsistent security settings can still cause sticky clients and dropped sessions.
SSID and VLAN Design
Keep the number of SSIDs reasonable because each SSID creates management overhead on every channel. Map SSIDs to clear trust zones such as employee, voice, guest, and managed devices. Apply routing and firewall policy after traffic enters the wired network.
Wireless Security
- Use WPA2 or WPA3 with strong authentication.
- Prefer enterprise authentication for organizational networks.
- Isolate guest clients and restrict access to internal networks.
- Protect management interfaces through dedicated networks.
- Disable obsolete ciphers and protocols.
- Monitor for rogue access points and unexpected SSIDs.
Wired Infrastructure Still Matters
An access point can only perform as well as its switch port, uplink, power, DHCP, DNS, routing, and internet path. Verify PoE budget, port speed, VLAN trunking, MTU, and controller reachability.
Wireless Troubleshooting
- Determine whether association, authentication, addressing, DNS, or application access is failing.
- Compare affected and unaffected clients.
- Check signal, noise, channel utilization, retries, and data rates.
- Verify the client is using the intended AP, band, SSID, and VLAN.
- Confirm DHCP and gateway reachability.
- Test the AP’s wired uplink for errors and congestion.
- Review roaming and authentication logs.
Survey and Validation
A predictive design should be validated after installation. Walk the space with representative client devices and measure signal, SNR, channel use, roaming behavior, and application performance. Revalidate after major layout or occupancy changes.
Common Design Mistakes
- Using maximum transmit power everywhere
- Deploying too few APs for client capacity
- Using channels that overlap unnecessarily
- Creating too many SSIDs
- Ignoring 2.4 GHz interference
- Assuming every client supports the newest standard
- Failing to test roaming and voice applications