CSP

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Project IEEE 802.15 Study Group for Wireless
Personal Area Networks (WPANs) Submission Title
On Sensitivity of Location Estimates to
SNR Date Submitted 10 September,
2004 Source Shahriar Emami, Celestino A.
Corral, Gregg Rasor Company1 Freescale
Semiconductor, Address 8000 W. Sunrise Blvd.,
Plantation, FL 33322, Voice(954) 723-3854,
FAX [phone], Re Accuracy of Location
Estimates Abstract The relationship between
SNR and location accuracy is explored. A region
with reasonable location accuracy is
found. Purpose To gain an understanding of
parameters that impact location accuracy of
802.15 TG4a. This work should assist designers
in predicting the location accuracy of their
system. 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.
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On Sensitivity of Location Estimates to SNR
Shahriar Emami, Celestino A. Corral and Gregg
Rasor Freescale Semiconductor
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Outline

• Introduction
• Prior Art
• Open Issues
• Proposed Approach
• Root Raised Cosine (RRC) Pulse Shape
• Raised Cosine (RC) Pulse Shape
• Error Statistics Achievable Accuracy
• Conclusions

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Introduction

• The impact of AWGN on the accuracy of measurement
  was previously investigated
• - R. Enns, The Effect of AWGN on Accuracy of
  Time of Arrival Detection, IEEE802.15-04-0335-00-
  004a, July 2004.
• Outstanding questions
• What is the desirable SNR in AWGN channels?
• Does pulse shaping impact the location estimates?

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Approach

• Pulse shapes
• - Root raised cosine
• - Raised cosine
• Various roll-off factors (0.15-0.85)
• A length 31 PN sequence was utilized
• Peak detector at the receiver

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RRC Pulse Shape -1
Mean location estimate does not vary with
roll-off factor
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RRC Pulse Shape - 2

• There are three distinct regions

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RRC Pulse Shape - 3
omni antenna above house
omni antenna near ground
Variance of the location estimate does not vary
with roll-off factor
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RC Pulse Shape - 1
Dry soil
Wet soil and wet roof
200 m
200 m
Mean location estimate does not vary with
roll-off factor
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RC Pulse Shape - 2
Dry soil
Wet soil
Variance of the location estimate does not vary
with roll-off factor
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Error Statistics
Dry soil
Dry soil
Mean and variance of estimation error when SNR
-5 dB
TX antenna placed at 1.5m height and at the side
of the house
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Achievable Location Accuracy

• Consider a UWB
• transmitter with
• - RRC pulse shaping
• - Rc 10 Mc/s
• - 100 samples/chip
• Sub meter accuracy with SNRgt0 dB

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Conclusions

• There are three regions in terms of location
  estimate accuracy.
• To have a good accuracy you need to operate in
  region 1.
• Location accuracy appears to be independent of
  pulse shape and roll-off factor.
• Sub-meter accuracy can be achieved if
• SNR gt 0 dB.