Security of Mobile Networks

Routing Trees in WiMAX Mesh

NC.D.SecurityMobNets NC.D.RoutingTrees
After Edward Snowden revealed secrets of NSA global surveillance programs, security of telecommunication networks is again a hot topic. Questions regarding privacy in the digital world and threats of interception of calls and sensitive data by governments spying on their own citizens have become a serious problem. The most popular device used to hack mobile networks is the so called IMSI Catcher – a device enabling easy deployment of Fake Base Stations (FBS). FBSs pose a major threat to privacy of mobile networks users. The mutual authentication introduced in LTE only partially solves the problem; in practice it just limits the range of possible attacks but does not eliminate them. A solution to this problem, proposed in the thesis, is based on adding two additional components to the mobile network architecture (4G/5G): Connectivity Manager, located at the core network side and Connectivity Agent, located at the user side. Connectivity Agent acquires information about topology of the network and credentials from the Connectivity Manager. Communication between Connectivity Agent and Connectivity Manager uses the LWM2M protocol, where LWM2M Server and Client are located in the Manager and Agent, respectively. Exchange of data is performed by LWM2M Object update, which also triggers corresponding connectivity procedures. Connectivity Manager informs the user about the legitimate, trusted base stations. In order to eliminate threat of FBSs, data needed to identify and connect to the trusted base station are delivered from the core network by LWM2M Object Transfer. Apart from keeping users safe from FBSs, the components can also serve as a way to manage all connections with the network. Implementation of the ideas presented in the thesis is a part of the Fraunhofer FOKUS Open5GCore project.

Title: Design & Implementation of a Secure Device Management Solution for Trusted Base Stations
Author: J. Siemiątkowski
Supervisor: Th. Magedanz (TU Berlin), M. Średniawa
Defended: September 2018

In wireless mesh networks, data is transmitted over a subset of available links. In case of WiMAX, this subset forms a tree rooted in a Base Station. The choice of links that form such a tree has impact on the usage of transmission resources, and so on the network throughput. There are many ways of optimizing the routing tree for a given network load. This thesis however tries to answer the question if there are any measurable topological properties of the routing tree (such as the averages related to node degree, distance to root, link SNR, tree balance, etc.) that are independent on the load, and yet strongly correlated with network efficiency. Finding such descriptors might for example allow improving the routing tree construction algorithms based on various heuristic approaches. To investigate this, a fast, modular WiMAX network simulator has been created, and used to test thousands of scenarios during the research phase.

Title: Routing Tree Construction in WiMAX Mesh Networks
Author: J. Nowiński
Supervisor: P. Gajowniczek
Defended: October 2012