ε-WiFi: Embedded Position Determination and Security in Wireless Fidelity Networks

The goal of ε-WiFi (Embedded Position Determination and Security in Wireless Fidelity Networks) is to detect the position of COTS wireless 802.11a/b/g client hardware by evaluating differential propa­gation delays, thereby enhancing security in WiFi networks. Typical applications for that are location based access rights for office networks and wireless industrial electronics applications. In the latter case safety for the operating of industrial machines can only be guaranteed by the restriction that a machine may only be operated by wireless control if the command is issued from a certain area (e.g., a crane may only be operated from a position with direct sight to the load rather than from outside of the production building.
The proposed solution foresees using one Access Point (AP) and multiple so-called smart timing repeaters (STRs) located at distinct positions within the area of interest. Ultimately, these STRs will be battery powered, which can be done by keeping them passive with the only exception that they send their timing information if queried by the Access Point.. The actual position calculation will be done for the three dimensional case by evaluating the signal propagation delay differences between the Access Point and the smart antennas. The high accurate clock synchronization needed to measure the delays will be reached by hardware timestamping. Although the techniques will be based on principles well known from Ethernet, significant adaptations must be introduced to cope with the challenges of the wireless environment, in particular with multi-path transmissions. Contrary to conventional wireless systems, therefore, the first occurrence of the preamble of a frame has to be detected. Determining the signal with the highest reception power is not sufficient. In order to meet this requirement the analogue baseband signal will be digitized and evaluated with the help of a high performance digital signal processing. The overall vision of the proposed project is to accurately determine the position of a sender as a basis for new techniques for access control and system security. The proposed security architecture will offer services such as spatial access policies, VLANs or Internet connections defining precise spatial coverage.