Sensitivity of Location Estimates to SNR

1. 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: [(954) 723-3883], 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. Shahriar Emami, Freescale Semiconductor

2. On Sensitivity of Location Estimates to SNR Shahriar Emami, Celestino A. Corral and Gregg Rasor Freescale Semiconductor Shahriar Emami, Freescale Semiconductor

3. Outline • Introduction • Prior Art • Open Issues • Proposed Approach • Root Raised Cosine (RRC) Pulse Shape • Raised Cosine (RC) Pulse Shape • Error Statistics & Achievable Accuracy • Conclusions Shahriar Emami, Freescale Semiconductor

4. 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? Shahriar Emami, Freescale Semiconductor

5. 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 Shahriar Emami, Freescale Semiconductor

6. RRC Pulse Shape -1 Mean location estimate does not vary with roll-off factor Shahriar Emami, Freescale Semiconductor

7. RRC Pulse Shape - 2 • There are three distinct regions: Shahriar Emami, Freescale Semiconductor

8. RRC Pulse Shape - 3 omni antenna above house omni antenna near ground Variance of the location estimate does not vary with roll-off factor Shahriar Emami, Freescale Semiconductor

9. 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 Shahriar Emami, Freescale Semiconductor

10. RC Pulse Shape - 2 Dry soil Wet soil Variance of the location estimate does not vary with roll-off factor Shahriar Emami, Freescale Semiconductor

11. 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 Shahriar Emami, Freescale Semiconductor

12. Achievable Location Accuracy • Consider a UWB transmitter with: - RRC pulse shaping - Rc = 10 Mc/s - 100 samples/chip • Sub meter accuracy with SNR>0 dB Shahriar Emami, Freescale Semiconductor

13. 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 > 0 dB. Shahriar Emami, Freescale Semiconductor