Roland Gierlich

Local Positioning for Wireless Sensor Networks

This workshop paper gives an overview of local positioning and tracking principles for wireless sensor networks including recent results of the European project RESOLUTION (reconfigurable systems for mobile local communication and positioning). Measurements of a first demonstrator applying a frequency modulated continuous wave (FMCW) radar principle are presented. The unlicensed ISM band around 5.8 GHz, 150 MHz bandwidth and less than 25 mW effective isotropic radiated transmit power are used. Excellent 3-D positioning accuracies in the order of 4 cm in an anechoic chamber and 18 cm in a conference hall with strong multipath and area of 800 m2 are measured. Furthermore, the results of optimized radio frequency integrated circuits and a suitable compact flash card are outlined.

Integrated Active Pulsed Reflector for an Indoor Local Positioning System

This paper presents an indoor localization system based on a frequency modulated continuous wave radar in the industrial-scientific-medical band at 5.8 GHz. An integrated active pulsed reflector behaves as a backscatter by regenerating the incoming phase with phase coherent startup at a constant frequency. The base station (BS) determines the distance to this reflector with a round-trip time-of-flight measurement. The active pulsed reflector is built around a switchable and tunable oscillator. The circuit has been fully integrated in a 0.18-¿m CMOS technology. Outdoor measurements revealed a positioning accuracy of 15 cm, while in a harsh multipath environment with omnidirectional antennas a positioning accuracy of 32.88 cm was measured. The localization system is capable of detecting multiple reflectors at the same time, and no synchronization between BSs is needed.

Performance Analysis of FMCW Synchronization Techniques for Indoor Radiolocation

A high precision localization system (HPLS) operating in the 5.8 GHz ISM band is presented. The system principle is based on the sequential exchange of frequency modulated continuous wave (FMCW) signals between identical radar stations. The round-trip time-of-flight (RToF) localization method requires exact synchronization of all involved stations. Consequently, accurate compensation of clock frequency drift is indispensible. We analyze the impact of clock deviation on synchronization accuracy and present a precise compensation method. The synchronization technique has been tested on a prototype system. Measurements showed a 3D-position accuracy of 2.8 cm under laboratory conditions.

A Reconfigurable MIMO System for High-Precision FMCW Local Positioning

In this paper, a highly accurate local positioning system is presented that is based on linear frequency-modulated continuous-wave signals in the 5.8-GHz industrial-scientific-medical band. The developed system allows for much higher operating distances than leading ultra-wideband local positioning systems, while it provides the same or even better accuracy. This is achieved by a novel multiple-input multiple-output (MIMO) measurement concept that enables the receiving unit to control the beam patterns of the receiving and the transmitting antenna arrays by a coherent combination of the received signals. In this way, interfering multipath components are suppressed, leading to a significantly reduced ranging error. Furthermore, the angle of arrival and the angle of departure are determined from the MIMO datasets using super-resolution direction-finding techniques. For position determination, both range and angle information are exploited. Extensive measurements with the MIMO system in different indoor environments show that the position error can be reduced by up to 80% compared to an equivalent single-antenna setup.

A 5.8 GHz Local Positioning and Communication System

In this paper, we present a hybrid local positioning and communication system under development within the scope of the EU funded RESOLUTION project. Very stringent requirements to positioning accuracy combined with tight bandwidth limitations demand innovative approaches to combat channel multipath effects. Closely spaced multipath components are the dominant cause of error in the system. Results of system simulations utilizing indoor channel scenarios and measurements using a discrete prototype are presented to prove the possibility of achieving the design goals in spite of limiting spectral regulations.

A Wireless Sensor Network with Radiolocation Subsystem

In this paper, the suitability of 5.8 GHz FMCW localisation schemes using chip-integrated radio transmitters is shown for the application of wireless sensor networks and one possible implementation is proposed. The synthesizer concept is based on a fractional-n PLL and was partly realized in an integrated circuit within the RESOLUTION EC-funded project. The basics of FMCW-TDOA radiolocation are described and the most important principles and parameters are described. Furthermore, the advantages of an active radiolocation system in combination with wireless data connectivity are outlined. The proposed system hence consists of the RESOLUTION chip in combination with a ZigBee meshed wireless network interface.