Performance Evaluation of U-TDOA Positioning for IEEE 802.16m (15.8.2)
IEEE 802.16 Presentation Submission Template (Rev. 9)
Document Number: IEEE C802.16m-09/2294
Date submitted: Nov. 6, 2009
Source: Chien-Hwa Hwang, Pei-Kai Liao, Yih-Shen Chen MediaTek Inc.
Venue: Session #64: 16-20 November 2009 Atlanta, USA
Re: Letter Ballot #30a on the Draft Amendment (IEEE P802.16m/D2)
Base Contribution: IEEE C80216m-09_2294
Purpose: Discussion and approval
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Introduction
• Performance of D-TDOA positioning was evaluated in [1] in Hawaii, USA
(IEEE Session #63.5).
• This document defines some specific assumptions required for U-TDOA
based positioning evaluation and presents simulation results for U-TDOA
positioning that were obtained with specified assumptions
• This contribution is compliant with the latest version of IEEE 802.16m/D2
[2]
Motivation
• One of the most powerful ways to personalize mobile services is based on
location. One of the most obvious technologies behind location based
service (LBS) is positioning
• Strict requirements on user positioning accuracy are imposed on existing
location services such as wireless Enhanced 911 and new upcoming
services
• It is imperative to verify whether IEEE 802.16m network is able to meet
the positioning accuracy requirements
IEEE 802.16m SRD - LBS Performance Requirements
• According to IEEE 802.16m SRD [3], IEEE 802.16m systems should
provide support for LBS. IEEE 802.16m systems should satisfy the
requirements in the following table
LBS Requirements
Feature
Requirement
Location determination
latency
< 30 s
Handset-based position
accuracy (in meters)
50 meters (67%-tile of the CDF
of the position accuracy)
150 meters (95%-tile of the
CDF of the position accuracy)
Network-based position
accuracy (in meters)
100 meters (67%-tile of the
CDF of the position accuracy)
300 meters (95%-tile of the
CDF of the position accuracy)
Comments
Need to meet E911
Phase II Requirements
Description of TOA Estimation Algorithm
• A format 0 non-synchronized ranging signal is used by the AMS
• The code index of the Zadoff-Chu sequence adopted by the AMS is known
to the serving and neighbor ABS’s
• The block diagram of TOA estimation is shown in the figure below
Rx Signal
LPF
RCP
Removal
RCP: Ranging Cyclic Prefix
FFT
Extraction of
Ranging Code
Zero
Padding
Ranging Code
IFFT
Peak
Test
Obtain
Timing
Timing
Simulation Assumptions
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
3 ABS’s (1 serving ABS + 2 neighbor ABS’s) form an equilateral triangle with a
side length of 1.5 kilometers
Carrier frequency: 2.5 GHz
Carrier bandwidth: 10 MHz
FFT size: 1024
CP ratio: 1/8
Number of OFDM symbols per subframe: 6
P802.16m/D2 non-synchronized ranging channel, format 0
1 Tx antenna, 2 Rx antennas
Modified ITU Pedestrian B Channel, velocity: 3km/hr
One other user is doing ranging in the same subband with probabilities 1, 0.333, 0.1
Other subcarriers (besides subcarriers for ranging) are transmitting data
Positioning algorithm: TDOA
Distance-dependent pathloss: L (in dB) = 128.1+37.6 log10 R (R in km)
The power of AWGN is 10dB less than the power of intercell interference
Frequency reuse factor = 1
Frames of serving and neighbor ABS’s are synchronized
Sources of Interference
Neighbor
ABS
Neighbor
ABS
Serving
ABS
• The serving and neighbor ABS’s suffer
from
– AWGN
– Intracell interference: interference
exists because subcarrier
orthogonality cannot be maintained
when non-synchronized ranging
signal is used
– Intercell interference
– Another user in the serving cell is
doing periodic/aperiodic ranging
with a certain probability
Simulation Results
• Collision probability is defined as the probability that another user in the
serving cell is doing periodic/aperiodic ranging
• One or two times TOA estimates are executed to perform U-TDOA
positioning
• SIR is fixed as 5dB; AWGN power is 10dB less than interference power
Simulation Results: 1 TOA Estimate
Simulation Results: 2 TOA Estimates
Conclusion
• During the execution of LBS, there may be other users in the same cell
doing periodic/aperiodic ranging. This degrades the performance of
positioning
• Intracell interference due to loss of orthogonality when sending ranging
signals and intercell interference from neighboring cells also deteriorate the
performance
• The ranging channel based U-TDOA positioning is NOT able to meet strict
Enhanced 911 Phase II requirements in above-mentioned interference
limited multipath environment
References
[1] IEEE C80216m-09/2086, “Evaluation of D-TDOA Positioning”
[2] IEEE P802.16m/D2. “DRAFT Amendment to IEEE Standard for Local and
metropolitan area networks—Part 16: Air Interface for Broadband Wireless
Access Systems—Advanced Air Interface” / 2009-10-14
[3] IEEE 802.16m-07/002r9, “IEEE 802.16m System Requirement Document
(SRD)”/ 2009-09-24