Utilizing the existing wireless infrastructure to allow mobile phones to make phone calls.

Benefits of WIFI calling

  • In areas where cellular coverage is inadequate WIFI calls can be placed
  • Employees do not have to use their data plan
  • Utilize existing wireless LAN (WLAN)


  1. Existing WLAN must be designed, configured and optimized for voice over WIFI (VoWIFI), specifically in the 5GHz range
  2. Be aware of E911 standards
  3. Perform a wireless site survey
  4. Firewall policy allowing ESP traffic outbound

Wireless Site Survey

As with all things WIFI a wireless site survey is essential for successfully designing, implementing and optimizing the wireless network. The wireless life cycle involves continuous monitoring and troubleshooting and optimization.

Sample wireless network designed for primary coverage at -65 RSSI and 25 SNR. Site surveys can be predictive in nature, followed by an onsite AP on a stick survey and finally an onsite validation survey.

Received Signal Strength Indicator (RSSI) of -65

Signal to noise ration (SNR) of 25dB

Enhanced 911 – Wireless Services (E911)

The FCC’s wireless Enhanced 911 (E911) rules seek to improve the effectiveness and reliability of wireless 911 services by providing 911 dispatchers with additional information on wireless 911 calls. The FCC’s wireless E911 rules apply to all wireless licensees, broadband Personal Communications Service (PCS) licensees, and certain Specialized Mobile Radio (SMR) licensees. More information on E911 can be found here… or here…

Firewall policy for E911.

Ensure that the firewall is configured to allow the following ports:

Base Controller config:

Enable iPhone for WIFI calling

Connect iPhone to WLAN

Find out what channel(s) the access point is on – configure analysis tool to capture packets on the respective channels.

Place a call from the iPhone

WIFI calling ports blocked outbound

no ESP traffic in the capture

WIFI calling allowed a call to be placed to mobile phone – QoS to be covered in another blog post. ESP traffic in capture

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