IPX providers – The nucleus of VoWiFi roaming

by Isabelle Paradis, President at Hot Telecom


Making Voice over WiFi calls while roaming is essentially invisible to either the visited network or the IPX provider handling normal roaming signalling and call handling. This is due to the fact that once the WiFi roaming connection is set-up, the voice call is handled in an IPsec tunnel over the public internet between the handset and the various servers in the home network. The call is then either terminated in the home network or onward routed to its destination (the visited network or internationally).

One of the issues here is that voice calls to the visited network (which could be significant for business travellers) are routed around the world. In addition, the quality of the call is potentially compromised, as it is dependent on unmanaged internet access.

I therefore believe that major wholesalers and IPX providers are perfectly positioned to help mobile operators deal with these routing and quality issues. They will be able to support the growth of the VoWiFi roaming ecosystem by playing a central role in simplifying interactions between carriers around the world.

Partly based on specifications developed by the Wireless Broadband Alliance and 3GPP, which define the different processes to facilitate a successful WiFi connection and then a VoWiFi roaming call, I think that IPX providers, who want to play a key hubbing role in VoWiFi roaming, should aim to support the 6 following functions:


Here, the VoWiFi roaming hub is involved in enabling the authentication and authorization of the user by terminating the IPsec tunnel and then confirming the ability of this user to make VoWiFi calls with the home network.


This activity encompasses the validation, processing and rating of the call records, together with the wholesale invoicing and settlement between carriers. The same records can be used for retail billing by the home network.


As distinct from data WiFi roaming, the media for a VoWiFi call will be routed back to the VoWiFi roaming hub in the IPX for a routing decision. This enables regional breakout where calls to the visited network are routed there from a regional point close to that destination, and calls back to the home network are onward routed over the IPX. Other international calls are routed as appropriate.

Therefore, a natural role to be played here by the IPX provider involved in VoWiFi roaming will be to transport and terminate this traffic at the highest quality and the lowest cost possible. Different potential business models to be used by IPX providers to achieve this are possible and detailed in the following section of this article.


IPX providers at the centre of the authentication, clearing, billing and media transport, will have visibility of all the key elements constituting the VoWiFi flow. From there, they can easily monitor and report in real-time on customer usage, fraud and network quality. In some cases, they could also take the necessary actions based on the information gathered (in the case of fraud for example).

IPX providers could also monitor the voice quality (MOS and R-Factor) of these VoWiFi calls and help determine (in real-time), whether it would be most optimal to move the call (without disruption) to a cellular network or to another WiFi network.

In addition, up to date information on each of the WiFi networks (provider information, location information and SSID) could be kept by the IPX provider on its secure IPX cloud application to be tapped at any time to manage policy around which Access Point to connect to.


In addition, as quality and security have now become an integral part of each of the VoWiFi constituents, IPX providers will need to support each of these functions over high quality and secure networks and systems. Fraud and quality monitoring (as mentioned earlier) are therefore crucial capabilities to add to the mix.

Here again, IPX providers’ central location within the VoWiFi roaming environment and the visibility they have of all parts of the communication flow, puts them in a perfect position to achieve this.


Finally, a further function that IPX providers could play in the WiFi roaming environment is the role of a trusted hub and deal maker. By nature, IPX providers are connected to a large number of mobile operators globally, and if they could add to these relationships key global hot spots providers, they could easily bring the two together and enable WiFi roaming (with managed VoWiFi) as a service.

In this case, the IPX providers would be the trusted party in the middle and would enable the commercial and technical side of this type of agreement using a one stop shop business model. Through this proposition, mobile operators could rapidly deploy WiFi and VoWiFi roaming globally at low risk and low cost. On the other hand, hot spots could then benefit from an expanded pool of customers, almost overnight.

Lastly, IPX providers could use this proposition to add incremental services that are not dependent on the per minute model, helping transition them to the future.

The diagram below summarises the possible functions IPX providers could support in VoWiFi roaming, with some of the capabilities they will require to do so.

VoWiFi - 360 vision - Article 3 - Chart1


In order to enable the functions outlined above, and offer what we call VoWiFi roaming hubbing services, IPX providers will need to play a central role in the whole call flow, not only for authentication, monitoring and accounting, but more importantly for voice hubbing. VoWiFi normally transits directly from handset to home network and so fulfilling a roaming hub service requires the tunnel to be terminated and the voice calls handled and routed.

In this scenario, the IPX provider is in charge of not only coordinating the Authentication, Monitoring and Clearing / settlement of the WiFi roaming session, they are also more importantly in charge of managing the VoWiFi session itself, routing all the traffic, whether it is terminating in the home network, in the visited network or internationally.

In this case, the traffic is directly routed over the internet from the WiFi hot spot to a regional hub of the IPX provider. From there, the IPX provider terminates the IPsec tunnel, gains authorization and policy from the home network and takes the necessary voice routing decisions to optimise call quality, without the need to route all the traffic back to the home network.

This does require a new network component – which we have called the hybrid SBC/PSCF – which is in the process of becoming available from some vendors. This device’s main functions are to establish policy for the call (by signaling to the home network) and then handle the SIP signaling and routing decisions necessary to route the call itself.

Therefore, in this case, the traffic destined to the visited network would be routed back (using regional break-out) and the international traffic would be sent from that hub via the IPX itself or other wholesalers. The traffic destined for the home network would be sent over the IPX to the home network’s mobile operator.

The benefits of this scenario for mobile operators, compared with the bilateral option discussed in the previous article include:

  • Simplification of some of the operational and commercial functions
  • A more regionally appropriate routing of the voice traffic
  • Involvement in the rating and settlement of voice calls with other carriers simplifies that function for the home operator
  • Potential use of the IPX provider as a trusted deal broker, minimizing the risk, cost and time of implementing VoWiFi roaming globally

From the IPX providers’ point of view, it brings in new traffic that it would not have otherwise transported VoWiFi roaming traffic (including the home traffic) that would otherwise have simply been routed out of the home network.

We estimate that on average 30-35% of the roaming traffic is terminated in the visited network, between 50-55% is terminated in the home network and between 10-20% is terminated internationally, this depending on the origin of the roamer and the countries visited.

It would therefore be highly beneficial for IPX providers to be in a position where they would transport 100% of the roaming traffic, instead of only 40-55%, if option 1 was implemented.

In addition, with this option, the IPX provider could actually offer a VoWiFi roaming turn-key solutions supporting all the functions a mobile operator needs to offer VoWiFi roaming to its customer, including the relationships with the WiFi hot spots and the intelligent traffic routing.

VoWiFi - 360 vision - Article 3 - Chart2


For IPX providers, playing the role of a VoWiFi roaming hub, would be highly beneficial for a number of reasons.

  • Increase the voice roaming traffic it transports (by as much as 50% in some cases)
  • Help mobile operators stimulate voice roaming traffic as a whole and fight OTTs
  • Enable wholesalers to move above and beyond connectivity / transport towards value added services such as of authentication, clearing, billing and real-time monitoring / reporting
  • May generate new sources of revenue (as a deal broker), if offering WiFi and VoWiFi roaming as a service

Nevertheless, this comes with challenges, as to achieve this IPX providers will have to:

  • Sustain a global high quality and secure network
  • Interconnect with a large number of mobile operators, cablecos and WiFi hot spots to establish a comprehensive global network of WiFi access
  • Develop a number of intelligence and big data tools to provide real-time monitoring and reporting functions to help optimise the quality of service over these diverse access networks
  • Provide fraud management tools
  • Offer clearing and settlement services

Not all wholesalers or IPX providers will be able to provide such a service, however those who will, will become an integral part of their customers’ roaming success and will therefore be one step closer to future proofing their business.