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Cellular Calls on your nearest Wi-Fi AP

- September 9, 2015 - 3 Comments

Can you place phone calls over Wi-Fi to save roaming costs when you travel abroad? Is there an easy solution for making phone calls despite poor indoor cellular coverage?

The answer is Yes! You can do all of the above using a new solution adopted by service providers and cell phone vendors known as Wi-Fi calling. The most compelling aspect of the solution is its non-intrusive nature. You don’t need to install any apps or change your directory; it’s all tightly integrated and built into the phone itself.


Mobile Service Providers (MSP’s) are extensively using Wi-Fi to offload data to meet the ever-increasing demands of mobile device users. In the next phase of Mobile-Offloading MSP’s are now supporting Voice over Wi-Fi (and refer to it as Wi-Fi calling).

iOS and Android devices support it today. Apple’s supports Wi-Fi calling with newer phones along with iOS8, whereas on the Android front, Wi-Fi source code is publicly available, and is being supported on almost 30+ phones.

Services providers are embracing Wi-Fi calling throughout the world. As Sprint and T-Mobile are leading the way in the US; EE in UK and 3, SmarTone are early adopters in Asia. Wi-Fi calling is expected to be supported by larger variety of mobile devices and offered on more MSPs by the end of 2015. AT&T has already enabled this service in the latest version of iOS 9 beta.

Challenges in enabling Wi-Fi calling on IT managed Enterprise Wi-Fi Networks

One of the major challenges in enabling Wi-Fi calling on enterprise Wi-Fi networks is moving from MSP carrier grade cellular network to IT-managed enterprise Wi-Fi networks with different service level agreements (SLA). This translates to the burden of maintaining call quality and SLAs from SPs to IT network engineers.

An Enterprise Wi-Fi infrastructure handles more than just carrier voice traffic, and this limited spectrum is shared by other applications and services like Video streaming & Web Conferencing. The stringent requirement for voice in terms of latency and jitter warrants a network with proper end-to-end QoS design & Voice optimizations that would optimize delivery of Wi-Fi calling packets in the presence of other applications.

How does Cisco infrastructure optimize Wi-Fi Calling?

By using Cisco’s Wi-Fi Access Points and Wireless LAN Controllers as the infrastructure to handle Voice over Wi-Fi calls, IT managers are leveraging technology that is Application aware and designed to deliver a High Definition Voice Experience (HDVX).

  • Visibility: Cisco Application Visibility and Control (AVC) will classify and prioritize Wi-Fi calling voice packets. AVC uses NBAR2 library that uses Deep Packet Inspection (DPI) to classify up to 1050 applications. Wi-Fi calling is one of the new applications that will be classified in Protocol Pack 15. In addition, Wi-Fi calling packets can be classified today in Cisco Router using Custom AVC.
  • Coverage and Capacity: 802.11ac with 4×4 MIMO and 3 Spatial Streams provides the highest data rate and coverage area in the industry. ClientLink 3.0: increase Wi-Fi performance and range by up to 60% and also significantly improves link stability for better call quality and reliability.
  • RF Turbo Performance: supports a high density of Wi-Fi devices with no performance degradation. CleanAir now available on 80MHz provides RF interference detection and mitigation that are optimized for 802.11ac’s wider channel bandwidths. BandSelect steers dual bands Wi-Fi enabled phones from the 2.4 GHz band toward the 5GHz band with wider channels and typically less congested.
  • Optimized Roaming:  enables to intelligently assist a device to roam between access points or from Wi-Fi to the cellular network to ensure good user experience
  • Enhanced Roaming 802.11 Standards
    • 802.11r: fast BSS transition to permit fast and secure handoffs from one access point to the other in a seamless manner
    • 802.11k: assisted roaming allows clients to request neighbor reports for intelligent roaming across access points.
    • 802.11v: BSS transition management enables network assisted roaming for a better client connectivity performanc
  • Reporting & Troubleshooting: Cisco Prime provides powerful tools to resolve and troubleshoot application performance issues across the network. In addition, Reporting on Prime Infrastructure can be used to monitor the current as well as historical Wi-Fi calling traffic across the network.

With Wi-Fi calling, MSPs will start off-loading voice calls from carrier grade cellular to IT managed Wi-Fi networks. Take advantage of the value added services provided by existing Cisco infrastructure to deliver unparalleled High Definition Voice Experience.

Learn more about Best Practices for Apple Mobile Devices on Cisco Wi-Fi network.


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  1. AVC is only able to classify from WLC meaning upstream traffis is not prioritized by WMM unless clients classifies the RTPs. Coverage area of 802.11ac is if anything same as 802.11a some would say less due to higher modulation needed for the new data rates. ClientLink does not extend range but optimizies SNR in midrange opting for better modulation.

      Thanks Thomas for the comments. I am glad you bought up client WMM classification. WiFi calling is one of the applications which marks traffic priority upstream on the client itself, and AVC helps prioritize client traffic downstream resulting in accurate bidirectional QoS marking and prioritization for Wi-Fi calling traffic.

    HDVX is a game changer, it adds a lot of workload traffic but worth it