May 2004 Correal, Motorola, Inc. Slide 1 doc.: IEEE 802.15- 04/XXX Submiss ion Project: IEEE P802.15 Working Group for Wireless Personal Area Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Networks (WPANs) Submission Title: IEEE 802.15.4 Relative Location Date Submitted: May 2004 Source: Neiyer Correal, Frederick Martin, Motorola, Inc. Contact: F. Martin, Motorola, Inc., 8000 W. Sunrise Blvd. Plantation, FL 33322 Voice: +1 954-723-6395, FAX: +1 954-723-3712, E-Mail: [email protected]Re: Technical Contribution to TG4A Abstract: Relative location based on received signal strength ranging can be used for 2 dimensional location in personal area networks. Purpose: To provide information on potential location performance of networks based on IEEE 802.15.4. Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15.
Transcript
May 2004
Correal, Motorola, Inc.Slide 1
doc.: IEEE 802.15-04/XXX
Submission
Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: IEEE 802.15.4 Relative LocationDate Submitted: May 2004Source: Neiyer Correal, Frederick Martin, Motorola, Inc.Contact: F. Martin, Motorola, Inc., 8000 W. Sunrise Blvd. Plantation, FL 33322Voice: +1 954-723-6395, FAX: +1 954-723-3712, E-Mail: [email protected]
Re: Technical Contribution to TG4A
Abstract: Relative location based on received signal strength ranging can be used for 2 dimensional location in personal area networks.
Purpose: To provide information on potential location performance of networks based on IEEE 802.15.4.
Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.
Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15.
May 2004
Correal, Motorola, Inc.Slide 2
doc.: IEEE 802.15-04/XXX
Submission
Motivation for Relative Location Techniques
• Device data must be accompanied by its location– Actuator must know where to act– Alarm must be localized to be useful to a human operator
• Placing & locating every device is labor-intensive• Cost of device location must be considered
– GPS cost, power consumption can be prohibitive• Only an outdoor solution
– Local Positioning Systems (LPS) need intensive installation• High Cost of wiring• Labor intensive
May 2004
Correal, Motorola, Inc.Slide 3
doc.: IEEE 802.15-04/XXX
Submission
Relative Location
• Goal: Self-location with few known-location nodes
– Without wired infrastructure
– Applicable to any environment
datalink
central computer
1
2
4
5
6
8
9
AB
C
7
‘Blindfolded’
Wireless Sensors
‘Reference’
3
• Difficulties
– Ad hoc connectivity
• Advantages
– Reference devices are the ‘infrastructure’
– Peer-to-peer range measurement possible
– Accuracy/range extension
May 2004
Correal, Motorola, Inc.Slide 4
doc.: IEEE 802.15-04/XXX
Submission
Relative Location• Conventional Location
– Devices are located only with respect to fixed base stations
• Relative Location– All devices calculate the distance
• Relative location analogy:– Nails represent absolute location information– Springs’ natural lengths are the estimated range between nodes
– Spools are nodes
Lo
cati
on
Map
pin
g A
lgo
rith
mRelative Range Data
Reference and Blind NeuRFons
Spools will move in the direction of force until sum of forces equals zero
May 2004
Correal, Motorola, Inc.Slide 7
doc.: IEEE 802.15-04/XXX
Submission
Range Estimation Techniques
• Time Difference of Arrival (TDOA) relies on time synch– (ns) time-synch unlikely
• Time-of-Arrival (TOA) can be measured via round-trip
• At 1 meter range resolution for 3 ns time resolution (RF signal), wide bandwidth signal is needed.
• Received Signal Strength (RSS) is considered coarse due to the multipath channel
• Range estimate variance increases with range
• WE WILL FOCUS ON RSS ON RF SIGNALS
• Various media are possible
RF Infrared Ultrasound Acoustic
Time-Based Techniques
Signal Strength Techniques
May 2004
Correal, Motorola, Inc.Slide 8
doc.: IEEE 802.15-04/XXX
Submission
Relative Location Simulation
Path Loss Errors of = 6 dBSingle room, 20 m by 10 m3, 4, or 6 Reference devices1 to 10 Blindfolded devicesReference devices located in cornersOther devices placed at random
• Simulation of Indoor Relative Location
– Signal Strength as a Ranging Technology
• Location Accuracy improves with either
– More Reference devices– More Blindfolded
devices.
May 2004
Correal, Motorola, Inc.Slide 9
doc.: IEEE 802.15-04/XXX
Submission
Relative Location Experiment Set-up
• Measurements– Mot. Labs Plantation FL, office
environment– 13 by 15 m area– 44 devices (0.2 /m2)– 4 reference devices in corners of area– Nodes at 1m height– Multipoint to multipoint– 44*43*5 = 9460 measurements– 2.4 GHz signal, 40 MHz BW
Figure: Area Map, Device # and Location
May 2004
Correal, Motorola, Inc.Slide 10
doc.: IEEE 802.15-04/XXX
Submission
Relative Location Experiment Set-up
• RMS Location Error of 2.14 m
• Histogram of Errors
#T #RTrue Location Relative Location EstimateKey:
RMS is 15% of Ref. device separation
May 2004
Correal, Motorola, Inc.Slide 11
doc.: IEEE 802.15-04/XXX
Submission
Relative Location Radio Testbed• Testbed Device
– 900 MHz, 50 kbit/s FM – 8 channels– Sensor Suite
• RSS Ranging
May 2004
Correal, Motorola, Inc.Slide 12
doc.: IEEE 802.15-04/XXX
Submission
Relative Location Measurement Results
• Environments
– Outdoor Parking Lot
– Residential Home
• 9m x 9m area, 4 by 4 grid– Reference nodes at corners
• RMS location errors
– 1.0m in parking lot
– 2.1m in house
Above: Map of the Perkins home and grid of 16 device locations.
Side: Parking lot experiment. Devices are located on top of blue upside-down recycling bins.
May 2004
Correal, Motorola, Inc.Slide 13
doc.: IEEE 802.15-04/XXX
Submission
Summary
802.15.4 can be used for location under some conditions
RSSI appears to be a viable method for location resolution
Cooperative location can enhance location estimation
-- higher density of nodes results in improved location estimation
For reference node separation on order of 10m, 2D location with RMS errors on order of 2m is possible
For more information, see
N. Patwari, A. O. Hero, III, M. Perkins, N. Correal, R. J. O’Dea, “Relative location estimation in wireless sensor networks,” IEEE Trans. On Signal Processing, vol. 51, no. 8, August, 2003, pp. 2137-2148.
