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 94089, USA Voice: (1) 408 400 0785 E-Mail: (1) mark@aetherwire.com Abstract: An overview of sub-GHz UWB technology for 802.15.4a alt-PHY Purpose: To present an overview of sub-GHz UWB 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 contributors acknowledge and accept that this contribution becomes the property of IEEE and may be made publicly available by P802.15

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

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

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.

4.5cm Door Attenuation Attenuation at 1.01GHz = 0.51 dB

5.9cm Cloth Office Partition Attenuation Attenuation at 520 MHz = 0 dB Attenuation at 4.02 GHz = 1.91 dB

5.8cm Brick Attenuation Attenuation at 1.01 GHz = 2.06 dB

Suburban Home Propagation Sub-GHz band propagation advantage over 3-5 GHz band 4 x Drywall @ 0.05dB 0.2dB 1 x Door @ 2dB 2dB 1 x Brick @ 3dB 3dB 5.2dB

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

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

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

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

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

Regulator Status FCC: “In the frequency band below 960 MHz these devices are permitted to emit at or below the 15.209 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

FCC Mask

System Block Diagram Time- Integrating Correlator A/D Converter Large RF 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

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

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)

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

Sub-GHz UWB Correlator Snapshots

First Detection Window Rapid Acquisition Received correlator output of Beacon signal plus noise. Peaks exist every tm = 310 nanoseconds. Receptions are spaced tc = 1.024 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

Link Budget

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