Femtocells promise improved indoor coverage and increased throughput for mobile data services while off-loading traffic from expensive macro radio access networks onto the low cost public Internet. While the mobile industry holds high hopes for femtocells, a number of key technical challenges must first be addressed before the femtocell market can see significant commercial success. One such challenge is to define and standardize an approach for integrating femtocells back into mobile core service networks, i.e. deviceto- core network connectivity. The Radio Access Network (RAN) in use today comprises hundreds of base stations connected to a single Radio Network or Base Station Controller (RNC/BSC).
The interface is Iub running the Asynchronous Transfer Mode (ATM) protocol over dedicated leased lines. Unlike macro 3G RAN, femtocell access networks require operators to integrate hundreds of thousands of low-capacity home base stations that can be moved, added, and changed by end users at any time, all connected over the unsecured and untrusted public Internet. This raises a number of important issues: Is it scalable, secure and standardized? Because the latest technological progress allows powerful processing capabilities to be applied to low-cost home base stations, the network protocol stacks can now be substantially collapsed. In addition, the standard Internet Protocol (IP) has rapidly replaced hierarchic telecom-specific transmission protocols. The combination of the collapsed protocol stacks and IP transport enables femtocells to utilize flat networks – such as the Internet – as a backhaul transport to operator core networks, as illustrated.
