Tightly-Coupled Opportunistic Navigation for Deep Urban and Indoor Positioning Ken Pesyna, Zak...

Tightly-Coupled Opportunistic Navigation for Deep Urban and Indoor Positioning

Ken Pesyna, Zak Kassas, Jahshan Bhatti, and Todd Humphreys

Presentation at ION 2011|September 23, 2011

Outline

I. Motivate & define Tightly-Coupled Opportunistic Navigation (TCON)

II. Explore “signals of opportunity” for TCON

III. Discuss the central estimator to optimally fuse signals together

IV. Present experimental results

Goal

Optimally extract navigation and timing information from ambient radio signals

Tightly-Coupled Opportunistic Navigation is a framework to achieve this goal

TCON is an optimal generalization of specific hybrid navigation technologies

Generalize Optimize

Tightly-Coupled Opportunistic Navigation

Cellular [1]

HDTV [2]

GNSS

Iridium [3]

TCON

[1] R. Rowe, P. Duffett-Smith, et. al., “Enhanced GPS: The tight integration of received cellular timing signals and GNSS receivers for ubiquitous positioning,” in Position, Location, and Navigation Symposium, IEEE/ION, 2008.

[2] J. Do, M. Rabinowitz, and P. Enge, “Performance of hybrid positioning system combining GPS and television signals,” in Position, Location, And Navigation Symposium, IEEE/ION, 2006.

[3] M. Joerger, et. al., “Iridium/gps carrier phase positioning and fault detection over wide areas,” ION GNSS 2009.

TCON: Breaking it Down

Tightly-Coupled

Signals downmixed and sampled with the same clock

Absolute time correspondence at the nanosecond level

Opportunistic Navigation

Receiver continuously searches for signals from which to extract navigation and timing information

Receiver employs on-the-fly signal characterization: Clock stability Clock offset Carrier-to-noise ratio Transmitter location

Tightly-Coupled Opportunistic Navigation

Signals of Opportunity

TCON treats all RF signals as potential signals of opportunity GNSS signals: GPS, Galileo, Glonass Cellular signals: CDMA, GSM, 4G LTE, & WiMAX Other satellite signals: Iridium Other ground-based signals: HDTV, Wi-Fi

What SOP characteristics are desirable?

1. High received carrier-to-noise ratio

2. Good frequency stability

3. Known location/timing offset

Unfortunately, we almost never get all three properties if we are not working with dedicated

navigation signals

Freestyle Navigation CDMA Cellular

Carrier-to-noise is high, penetrates well Towers do not move Only roughly synchronized to GPS Carrier stability varies from provider to provider

Iridium Carrier-to-noise ratio is higher than GNSS Global coverage Not continuous – “Bursty” TDMA structure Ambiguous in carrier phase from burst to burst

Centralized Estimator

Optimally combines observables from all SOPs

Our preferred implementation is an extended Kalman filter:

Base State: SOP state:

Full State:

Centralized Estimator

GPS carrier phase measurement model:

CDMA carrier phase measurement model:

Iridium carrier phase measurement model:

Carrier Phase Measurement Models

Dynamics dependent on current state and process noise:

Process noise covariance formed by models of clock dynamics:

Dynamics Model

Adaptive Dynamics Model

Run Kalman FilterUpdate SOP Clock Model

old new

Iterate

Output *

* Can only be done when is observable (to within a constant offset)

Simple TCON Demo: Experiment Setup

GRID Software Receiver

MATLAB EKFNational Instruments RFSA

Storage

Simple TCON Demo: SOP Wardriving

A Simple Demonstration of TCON

Run Kalman Filter

old new

Iterate

Update SOP Clock Model

6x 2x

(1) Obtaining Truth

(2) Characterizing CDMA SOP (3) Demonstrate post-characterization CDMA SOP only estimate of

Truth Estimate CDMA-based estimate vs.

So What?

Achieve our estimate error of by differencing the CDMA-only estimate from the truth variations:

The stability of will affect the length of achievable GNSS coherent integration in weak signal conditions

In this experiment, CDMA-only TCON (after-characterization) could supply coherent integration times beyond 100 seconds

100+ sec. coherent integration allows GNSS acquisition of signals below 0 dB-Hz assuming all else ideal

-

Mean squared coherence of

Conclusions

TCON is a framework to optimally extract navigation and timing information from ambient radio signals

Tight-coupling at the carrier-phase level and SOP characterization are essential to TCON

A simple TCON demonstration on timing showed a TCON-enabled receiver can coherently integrate beyond 100 seconds using characterized CDMA signals

Questions?