Femtocells and Fixed-Mobile Substitution (FMS)

Fixed-Mobile Substitution (FMS) – the use of a mobile phone instead of a fixed, wired telephone – has long been a desire of mobile operators, a way to increase addressable market and revenue. One mechanism to facilitate FMS is Fixed-Mobile Convergence (FMC) – the use of dual-mode handsets with both cellular and WiFi connectivity, and handoff between the two. When WiFi is available, FMC uses it to route the voice traffic between the handset and the core of the cellular network, without loading the scarce radio spectrum resource of the macrocell radio access network (RAN). The standard technology for FMC is the Generic Access Network (GAN), originally called Unlicesed Mobile Access (UMA).

A key barrier to the adoption of UMA is the small selection of handset models it can work with. UMA/GAN only works with UMA-enabled dual-mode handsets. There is currently a range of only around 30 UMA-enabled handset models. This is a very small number, compared for example to the 726 HSPA^[&#8224] handset models that exist today accroding to the Global mobile Suppliers Association (GSA).

And this is where femtocells come into play. They provide the same functionality as UMA/GAN, of offloading traffic from the macrocell RAN, but with the critical advantage of working with any handset an operator supports. Consequently, femtocells create a new promising opportunity for mobile operators to launch and succeed with repackaged FMS offerings.