Analysis and augmentation of timing advance-based geolocation in LTE Cellular Networks

Abstract

The ubiquity of cellular technology has woven a variety of services, now axiomatic, into modern social fabric. Among those services is the ability to provide mobile user location. Applications of these location-based services include providing directions, emergency services, fraud protection, and direct marketing. This work provides in-depth analysis of cellular positioning, which leverages the Long Term Evolution (LTE) signaling plane timing advance (TA) parameter for the end of user geolocation. Additionally, we propose a novel method of augmenting TA-based positioning, Cellular Synchronization Assisted Refinement (CeSAR). We simultaneously show CeSAR to be a network performance multiplier and security vulnerability vis-a-vis the method's electromagnetically passive nature. Furthermore, we demonstrate how CeSAR improves positioning by adding system information and mitigating the effects of poor network infrastructure geometry. Through robust statistical analysis, we derive a theoretical lower bound on TA-based positioning and demonstrate that a statistically efficient estimator is possible in this context. Furthermore, numerical studies are conducted with synthetic and empirical data. The real-world data are observed in actual network deployments found in geographically diverse environments, such as Maryland and California. The results not only demonstrate the efficiency of the estimator but show that accuracy on the order of tens of meters is possible. Indeed, TA-based positioning is shown to be accurate on the order of 40 m in some scenarios. Additionally, we demonstrate that CeSAR is able to passively provide improvements ranging from 10 to 254 m over TA-only positioning.