In both the core and access portions of the communications network, virtualization is becoming a fundamental building block for use of all network assets, owned and borrowed. Both the coming 5G mobile networks and core networks using Network Functions Virtualization are examples. 

Such sharing has been informal for some time, as exemplified by smartphone Wi-Fi access. But sharing mechanisms are becoming more formalized and integrated, as exemplified by Wi-Fi calling.

In many cases, Wi-Fi calling is a way to overcome mobile network signal issues indoors, with sessions maintained even when a connection switches from mobile to Wi-Fi, for example.  

There are, in fact, a growing number of ways to  virtualize spectrum and access assets, both formal and informal. Several methods for bonding licensed and unlicensed spectrum assets are available, including LTE-U, license assisted access and license shared access.

In a growing number of instances, both direct and indirect revenue models might be involved, with a growing amount of integration of owned and third party access assets.

Of course, in other cases, Wi-Fi is a feature of a service the buyer actually does pay for directly. The best example is consumer fixed network internet access, where Wi-Fi typically is the physical mechanism used to connect devices. In that sense, Wi-Fi replaces physical cables and outlets.

Wi-Fi calling also represents an early and informal method of spectrum sharing, in this case treating licensed mobile operator assets and owned or third-party Wi-Fi assets as interchangeable parts of the physical network access infrastructure.

That virtualization of the details of network access already is a building block for service providers

Such as Republic Wireless and Google’s Project Fi, and is different from Wi-Fi-only calling offered by over-the-top apps such as Skype, Google Hangouts, Facebook Messenger and WhatsApp.

In the future, MulteFire, a method for creating Long Term Evolution 4G networks entirely using unlicensed spectrum, might be an important platform.