RF Ranging for Indoor Tracking and Positioning

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Ambrose Norton
8 years ago
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1 WPI Technology Workshop: Precision Indoor Personnel Location and Tracking for Emergency Responders Dennis McCrady Robert Goldberg Tim Pfister August 7, 2006

2 Agenda Background RF Ranging System Description Keys to Accurate RF Ranging RF Ranging Performance Laboratory Field (Over the Air) ITT Software Defined Radios (SDR) Conclusions Tracking for Emergency Responders l August 7, 2006 l 2

Field (Over the Air) ITT Software Defined Radios (SDR)

3 Background GPS provides excellent accuracy in areas where it can be received Satellite navigation improvements are on the horizon GPS III and Galileo When? What improvements will finally be implemented? In the meantime, GPS restricted environments require multiple technologies in a blended solution Use GPS when available Inertial sensors (MEMS are feasible) RF ranging systems (TOA, DTOA, AOA) Focus on RF ranging (TOA) technology developed at ITT Implemented within a direct sequence spread spectrum communication system Utilizes waveforms, modem, and networking protocol to facilitate the RF ranging application Tracking for Emergency Responders l August 7, 2006 l 3

In the meantime, GPS restricted environments require multiple technologies in a blended solution Use GPS when available Inertial sensors (MEMS are feasible) RF ranging

4 RF Ranging System Description System is comprised of mobile (M) and reference (R) wireless units (WU) RWUs can be mobile FIXED REFERENCE BUILDING MOBILE FIXED REFERENCE MWU uses a minimum of 3 RWUs for 3D location Range based on two way TOA Can vary update rate Additional RWUs improve solution MOBILE Carrier Sense Multiple Access Collision Avoidance protocol controls media access for ranging as it does for communications FIXED REFERENCE FIXED REFERENCE FIXED REFERENCE Solution can be relative to local coordinate system or absolute if RWUs have GPS Good RF Ranging Accuracy is Achieved in All Environments by Establishing an Error Budget and Attention to Key Details Tracking for Emergency Responders l August 7, 2006 l 4

controls media access for ranging as it does for communications FIXED REFERENCE FIXED REFERENCE FIXED REFERENCE Solution can be relative to local coordinate system or absolute if

5 Keys to Accurate RF Ranging No permanent infrastructure Two-way ranging eliminates need for synchronized clocks 1 ppm clocks are sufficient Internal delay calibration Use optimum carrier frequency for propagation in buildings and urban areas: MHz Use the highest achievable bandwidth supported by the frequency allocation (Crammer Rao Bound): CRB = 1/(BW x SNR 1/2 ) Use a two part TOA ranging waveform: acquisition then TOA synchronization symbols Leading edge curve fitting to minimize multipath (MP) effects Quadrature Multi-Frequency Ranging (QMFR) for multipath mitigation ITT patented technique Mod Turn-On & AGC Setting Times (N1 Symbols, 128 Chips per Symbol) Acquisition Sequence (16 Symbols, 128 Chips per Symbol) Multipath Window (N2 Chips) Note: 1) 1 <= N1 <= 128 2) 384 <= N2 <= 511 TOA Ranging Waveform TOA Synchronization 2 Symbols (1023 Chips per Symbol) Mod Turn-Off Time (10 Symbols, 128 Chips per Symbol) NIJ-005 Two Part Ranging Waveform Reduces Required Processing Main Path Distorted Correlation Leading Edge Function of Correlation Function (Main Path + Multipath Correlation Multipath) Function NIJ_003 MP Distorts the Correlation Function Used for TOA Tracking for Emergency Responders l August 7, 2006 l 5

ranging waveform: acquisition then TOA synchronization symbols Leading edge curve fitting to minimize multipath (MP) effects Quadrature Multi-Frequency Ranging (QMFR) for multipath mitigation ITT

6 Performance - Laboratory PC 1 WU 1 ADC OUT 2 db Splitter ATT 0-20 AT 0-20 db 2 WU db PC 2 2 Combiner Time Delay 1 ADC Or TD1+TD2 OUT Or TD1+TD3 Or TD4 MULTIPATH CONDITION Direct path only 15ns 0dB NON- QMFR (ns) QMFR (ns) Logic Analyzer Floppy Disc Transfer Logic Analyzer Floppy Disc Transfer 30ns 0dB 60ns 0dB 15ns 8dB QMFR was not running in WU hardware for lab measurements QMFR TOA data captured by Logic Analyzer and processed off line Different length cables to emulate direct path and multipath QMFR versus single frequency non-qmfr compared using 10 trials QMFR TOA (Mean + σ) approximately twice as accurate as non-qmfr TOA Tracking for Emergency Responders l August 7, 2006 l 6

5 QMFR was not running in WU hardware for lab measurements QMFR TOA data captured by Logic Analyzer and processed off line Different length cables to emulate direct path and

7 Metric Horizontal Position Accuracy Open Terrain Horizontal Position Accuracy Urban Terrain Horizontal Position Accuracy In Building Terrain Horizontal Position Accuracy Forest Terrain Vertical Position Accuracy In Building Terrain Performance Field (Over the Air) Phase 2 Measured Performance (m) Circular Error Probable Phase 3 Measured Performance (m) Circular Error Probable Phase 3 Measured Performance (m) 95 % Testing conducted at McKenna MOUT area of Fort Benning, Georgia 1 MWU and 5-8 RWUs that included GPS coordinates QMFR not used RWUs were 1-750m from the MWU and the TOA update rate was 1/second TOA integrated with IMU and baro results were driven by TOA accuracy Goal (m) 95% Not Measured Phase 3 waveform improvements resulted in establishing a.5m CEP accuracy limit and greatly improved accuracy in the harsh environments Tracking for Emergency Responders l August 7, 2006 l 7

Measured Performance (m) 95 % Testing conducted at McKenna MOUT area of Fort Benning, Georgia 1 MWU and 5-8 RWUs that included GPS coordinates QMFR not used RWUs were 1-750m from the MWU and the TOA

8 ITT Software Defined Radios Tracking for Emergency Responders l August 7, 2006 l 8

9 ITT Sensor Radio 3.3 x 3 x 1 Prototypes Available SDR for Unattended Sensors ITT Actively Working on Design for Low Cost Sensor Radio with Production Goal of $500 Tracking for Emergency Responders l August 7, 2006 l 9

10 ITT Wearable Soldier Radio Technical Description 1 Mbps and 2.6 Mbps at 1.2 MHz BW SCA 2.2 Compliant Supports Voice, Data, Video traffic UHF MHz; Up to 5 W Xmit power Range: 2 Km open field, 1 km Urban Type III COMSEC, Type 1 Upgradeable Internal Commercial GPS Receiver Interfaces: Ethernet, USB, RS-232, Headset SWAP: 24 Cu In, 1.2 lbs, < 5W avg power Includes adaptive power management Prototype Available Now EDM Available Fall 2006 Operational Description Radio (Wearable and Handheld) for Dismounted Soldiers Provides CNR voice for dismounted units Radio automatically generates position report without the need for attached PDA Demonstrated integration with FBCB2 for SA data collection and display Demonstrated Tactical Internet interoperation Simple HMI minimizes training and operator interaction during mission Tracking for Emergency Responders l August 7, 2006 l 10

Interfaces: Ethernet, USB, RS-232, Headset SWAP: 24 Cu In, 1.

11 Conclusions Two-way RF ranging with real time delay calibration (loop back) Synchronization of mobile and reference WU clocks not required Infrastructure not required Two part waveform reduces real time processing requirements and improves mobility and multipath performance QMFR provides orthogonal multipath and direct path Enables more accurate leading edge curve fit of the correlation function resulting in a more accurate TOA estimate Over the air past performance at Fort Benning, Georgia without QMFR.5m horizontal CEP in open terrain 3-5m horizontal CEP in harsh environments Future performance estimate with QMFR m horizontal CEP in harsh environments Future: Integrate RF ranging into ITT SDR and Field Test Tracking for Emergency Responders l August 7, 2006 l 11

correlation function resulting in a more accurate TOA estimate Over the air past performance at Fort Benning, Georgia without QMFR.

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