A system, method, and computer readable medium for provisioning radio access via a femtocell system that includes integrated BTS and BSC functions are provided. The femtocell system is coupled with a packet switched backhaul and provides an IP-accessible radio access network. The femtocell system includes a session initiation protocol adapter that supports a SIP client pool and provides conversion of call set-up functions to SIP client set-up functions for provisioning of radio access to a user equipment. The user equipment may have a session initiation protocol client associated with the user equipment. The session initiation protocol client is hosted and registered with a registrar service by the femtocell system. Accordingly, telecommunication services may be directed to and from the user equipment over the packet-switched backhaul to the user equipment via the femtocell system.