Comcast’s Xfinity Mobile venture was viewed by many industry observers as an unassuming entrant into the mobile arena, providing minimal threat to existing US mobile network operators. Almost one year on since Xfinity Mobile made its debut, Comcast is bulking up its mobile back end operations through a partnership deal with Charter – to accelerate Xfinity Mobile services as well as Charter’s soon-to-launch Spectrum Mobile MVNO venture. A common platform for operations such as mobile billing between the two US cable operators has been public knowledge since Comcast unveiled Xfinity Mobile, yet this week’s joint announcement reveals the collaboration is even closer than initially assumed – potentially preparing for a mega merger following Comcast’s rejected pursuit of Sky in the…