Physical Layer Development Framework for OsmocomBB

The open source GSM protocol stack of the OsmocomBB project offers a versatile development environment regarding the data link and network layer. There is no solution available for developing physical layer baseband algorithms in combination with the data link and network layer. In this paper, a baseband development framework architecture with a suitable interface to the protocol stack of OsmocomBB is presented. With the proposed framework, a complete GSM protocol stack can be run and baseband algorithms can be evaluated in a closed system. It closes the gap between physical layer signal processing implementations in Matlab and the upper layers of the OsmocomBB GSM protocol stack. An embedded version of the system has been realized with FPGA and PowerPC to enable real-time operation. The functionality of the system has been verified with a testbed comprising an OpenBTS base-station emulator, a receiver board with RF transceiver and our developed physical layer signal processing syste

Shadow Phone and Ghost SIM: A Step Toward Geolocation Anonymous Calling

abstract: Mobile telephony is a critical aspect of our modern society: through telephone calls, it is possible to reach almost anyone around the globe. However, every mobile telephone call placed implicitly leaks the user's location to the telephony service provider (TSP). This privacy leakage is due to the fundamental nature of mobile telephony calls that must connect to a local base station to receive service and place calls. Thus, the TSP can track the physical location of the user for every call that they place. While the The Internet is similar in this regard, privacy-preserving technologies such as Tor allow users to connect to websites anonymously (without revealing to their ISP the site that they are visiting). In this thesis, the scheme presented, called shadow calling, to allow geolocation anonymous calling from legacy mobile devices. In this way, the call is placed from the same number, however, the TSP will not know the user's physical location. The scheme does not require any change on the network side and can be used on current mobile networks. The scheme implemented is for the GSM (commonly referred to as 2G) network, as it is the most widely used mode of mobile telephony communication. The feasibility of our scheme is demonstrated through the prototype. Shadow calling, which renders the users geolocation anonymous, will be beneficial for users such as journalists, human rights activists in hostile nations, or other privacy-demanding users.Dissertation/ThesisMasters Thesis Computer Science 201