Eliminating rouge femtocells based on distance bounding protocol and geographic information

Recently, femtocell solutions have been attracting increasing attention since coverage for broadband radios can effectively eliminate wireless notspots. To restrict malicious subscribers from accessing femtocells, 3G/WiMAX standards introduce an access control strategy, called Closed Subscriber Group (CSG). However, CSG only prevents malicious clients, but not rouge femtocells. In 2009, Han et al. proposed the first mutual authentication mechanism. This mechanism does not consider the case that an attacker can locate femtocells in an unregistered area even these femtocells are legitimate. In this paper, we first define two attacks, sinkhole and wormhole attacks, in femtocell-enabled mobile networks. Then, we design two approaches based on distance bounding protocols and geographic information to defend against these two attacks. In our design, a subscriber can confirm whether or not the femtocell he connected with is physically-present. Experiment results demonstrate that the distance bounding protocol can estimate an approximate distance between a subscriber's device and the deployed femtocell. Moreover, femtocells that are deployed inside or outside can both be identified and distinguished without the bias of signal strength based on our design.