The GEOCOM Mobile Positioning System

D. Weigand, E. Soto, M. Volpe, J. Koss

Abstract:	Summary and Objectives This paper describes Argon ST’s GEOCOM Mobile Positioning System, which is being developed to generate and report accurate positions of users (e.g., first responders) in all environments (e.g., urban canyon, indoor, underground). The system addresses the challenges associated with estimating user position in an environment where few, if any, GPS signals can penetrate and where received RF ranging signals are corrupted by multipath. SWAP constraints prevent the use of phased arrays to mitigate multipath, and existing inertial systems drift too quickly to maintain accurate position locations over extended periods of time, so the GEOCOM leverages synthetic aperture-based multipath mitigation and sensor fusion to provide accurate user position estimates. Operational CONOPs require that the user locator units can scale from a few to hundreds of units and that the system can be integrated with existing systems. System Architecture & Capabilities The GEOCOM Mobile Positioning System does not require any existing communication or navigation infrastructure (e.g., beacons, Wi-Fi, cellular). Instead, it incorporates a robust, self-forming and self-healing network that provides connectivity between the locator units and to the central command, where the user positions are reported and observed. Each user is provided with a host locator node, and these nodes automatically form clusters with their neighbors. Position information and peer-to-peer range estimates are shared between the nodes in each cluster, and this position data is reported back to the command base station via one or more hops through the system. As each host locator node moves throughout the environment, it can automatically change association with clusters to ensure the best link quality within its current cluster. Each locator node provides accurate user positions in GPS-denied or degraded environments by integrating navigation sensors including GPS, IMU, peer-to-peer ranging, barometer, and magnetometer. The modular RF design of the locator node accommodates multiple frequency bands for peer-to-peer ranging or other RF ranging and communication functions. The locator node is a software defined radio that supports advanced and customized positioning algorithms, deployment scenarios, and user applications and provides interfaces for 3rd party integration, including TCP/IP networking and Bluetooth interfaces for connection of personal area networks to the GEOCOM. Key Innovative Elements The GEOCOM system provides robust communications between the locator nodes and the command base station using the Hybrid Mobile Ad-hoc Network (HyNet™), a self-forming and self-healing mesh network protocol for peer-to-peer communications. HyNet is a hybrid between a base-to-mobile (cellular-like) network and a mobile-to-mobile (MANET) network, which enables it to provide robust connectivity with a high degree of mobility. The protocol is configurable and adaptable to a variety of applications—including large-scale test and training (supporting 10,000+ nodes) and the GEOCOM mobile positioning system. HyNet’s multi-hop relay feature extends the range of user nodes and reduces the occurrence of network “dead spots.” The same waveform used for peer-to-peer ranging is used in the primary inter-node data link used by HyNet. The units provide optional cellular and Wi-Fi communications links which can be used by HyNet to enhance network reliability where this communications infrastructure is available. The use of Synthetic Aperture Line of Sight Assessment (SALSA) is a key innovative aspect of the GEOCOM system that enables it to mitigate the impact of multipath effects on the RF ranging. Multipath propagation is one of the major error sources for radio navigation systems. While many new applications require ever more precise user positioning in urban and indoor settings, existing receivers are especially vulnerable to severe multipath, which is often present in such environments. This paper will include a description of the synthetic aperture navigation and ranging techniques that are used by the GEOCOM user locator nodes to combat the adverse effects of multipath. Performance Results This paper will present the latest performance results from a GEOCOM demonstration system. These results will emphasize the positioning performance and communications connectivity in multiple challenged environments. Conclusions & Significance of Work The GEOCOM Mobile Positioning System is designed to provide accurate user position reporting in challenged environments. It solves for user position and maintains connectivity between user nodes without requiring any external infrastructure or a priori knowledge of the environment, and it scales autonomously as the number of users increases. Multiple user communities, including military test and training, first responders, law enforcement, and tactical military users, are in need of this type of position reporting technology and will benefit from the GEOCOM’s capability. Copyright ©2013 Boeing. All rights reserved.
Published in:	Proceedings of the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2013) September 16 - 20, 2013 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	439 - 447
Cite this article:	Weigand, D., Soto, E., Volpe, M., Koss, J., "The GEOCOM Mobile Positioning System," Proceedings of the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2013), Nashville, TN, September 2013, pp. 439-447.
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