1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: Sub-GHz_Overview
Date Submitted: July 18th, 2005
Source: Mark Jamtgaard (1)
Companies:
(1) Æther Wire & Location, Inc., 520 E. Weddell Drive, Suite 5, Sunnyvale, CA , USA
Voice: (1)
(1)
Abstract: An overview of sub-GHz UWB technology for a alt-PHY
Purpose: To present an overview of sub-GHz UWB
Notice: This document has been prepared to assist the IEEE P 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 contributors acknowledge and accept that this contribution becomes the property of IEEE and may be made publicly available by P802.15

2. Sub-GHz UWB Baseband Pulse Sequences Doublets
Pairs of pulses with opposite polarity
Spectrum has lobes and notches with a Gaussian envelope

3. Advantages Ranging Relies On First Arrival Detection
The estimation performance is degraded considerably when the energy of the first arriving component is not dominant among multipath components of a received signal
Material Propagation Is Important
Low Frequencies Have Better Propagation Characteristics Than High Frequencies
Low Frequencies Experience Less Shadowing
Results In High Accuracy First Arrival Detection

4. 1.2cm Wallboard Attenuation
Attenuation at 620 MHz = 0.4 dB
Attenuation at 4.12GHz = 0.45 dB
R. Buehrer, W. Davis, A. Safaai-Jazi, and D. Sweeney, “Ultra wideband propagation measurements and modeling - Final report to Darpa NETEX program,” tech. rep., Virginia Tech, 2004.

5. 4.5cm Door Attenuation Attenuation at 1.01GHz = 0.51 dB

6. 5.9cm Cloth Office Partition Attenuation
Attenuation at 520 MHz = 0 dB
Attenuation at GHz = 1.91 dB

7. 5.8cm Brick Attenuation Attenuation at 1.01 GHz = 2.06 dB

8. Suburban Home Propagation
Sub-GHz band propagation advantage over 3-5 GHz band
4 x 0.05dB
0.2dB
1 x 2dB
2dB
1 x 3dB
3dB
5.2dB

9. Office Building Propagation
Link through 5 partitions.
Sub-GHz band has a 10dB propagation advantage over 3-5 GHz band

10. Disadvantages More Interference In The Sub-GHz Band
Non-coherent detection not possible
Longer code lengths
Larger dynamic range

11. Applications
Numerous applications require 3D position tracking in buildings.
These applications require 5 links per node to compute 3D position.
To robustly maintain 5 links in real applications requires:
Penetration through multiple walls / objects
30 meter range

12. Track Firefighter Status
A network of locators determine their location relative to each other and transmit their location to a command center
Can penetrate Buildings, Metal containers, Fire and smoke

13. Military Operations in Urban Terrain
MOUT
Penetrates Interior Walls
1-meter
accuracy
50-200m
range
UWB
Localizer
Wearable
Computer
Low
power
LPI/LPD
Light weight
GPS
Receiver

14. Regulator Status
FCC: “In the frequency band below 960 MHz these devices are permitted to emit at or below the limits” [First order and report, 2002]
15.209
Measured With Quasi-Peak Detector (CISPR 16-1) with 120-kHz resolution filter
Charge time is 1ms
Discharge time is 550ms

15. FCC Mask

17. System Block Diagram Time- Integrating Correlator A/D Converter LargeRF
Amplifier
Time-
Integrating
Correlator
Time-Integrating
Correlator
A/D
Converter
Large
Current
Radiator
Crystal
Oscillator
Real Time
Clock
Code
Sequence
Generator
Transmitter
Antenna
Driver
Processor
and Memory

18. Large Current Radiator
Baseband impulses (<1GHz) can be effectively radiated from small (<4 cm) Large Current Radiator (LCR) antenna (FDTD simulation)

19. Antennas Large Current Radiator
Preserves impulse shape
Frequency response varies <6 dB from <100 MHz to >2.5 GHz
Requires low (1W) source impedance
Direct drive from CMOS
No transmission line
6 cm Electric Dipole (for comparison, 4 cm LCR fits within 6cm sphere)
Differentiates impulse shape
Gain varies 40 dB from 100 MHz to 2.2 GHz
Other UWB antennas with comparable low-frequency response (e.g. TEM horn) are physically large (> 1 meter)

20. Reception Coherent Reception via Correlation
Time Integrating Correlator is a Matched Filter
Analog input signal is multiplied by Reference code & integrated
Each of 32 correlator phases represents a different time alignment of input signal & reference code
Each correlator is offset ¼ chip
Tolerant of clock jitter and drift
30 dB Process Gain with families of orthogonal 1023-chip codes
Each reception starts with zero integrated noise

21. Sub-GHz UWB Correlator Snapshots

22. First Detection Window
Rapid Acquisition
Received correlator output of Beacon signal plus noise.
Peaks exist every tm = 310 nanoseconds.
Receptions are spaced
tc = ms plus offset shown on Timeline.
20 ms
10 ms
10 ms
10 ms
First Detection Window
Scan Window
(Scan 320 ns, then jump 10 ms)
20 ns overlap
Five Receptions
Per Scan
Correlator window
Size tw = 80 ns
80 ns
First Detection
320 ns Scan Window

23. Link Budget

24. Conclusion
The Sub-GHz band propagation characteristics make it attractive for applications requiring 3D location in industrial environments.