1. Date Submitted: October 24, 2005]
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Numerical results on the new ranging packet structure]
Date Submitted: October 24, 2005]
Source: [Yihong Qi, Huan-Bang Li, Shinsuke Hara, Bin Zhen and Ryuji Kohno, Company: National Institute of Information and Communications Technology ]
Contact: Yihong Qi
Voice: ,
Abstract: [Numerical results using a new ranging packet structure are presented. These results include extra energy consumption, ranging accuracy improvement and carrier sense probability.]
Purpose: [To propose a new ranging packet structure]
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 contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P
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2. Numerical results on the new ranging packet structure
Yihong Qi, Huan-Bang Li, Shinsuke Hara, Bin Zhen and Ryuji Kohno National Institute of Information and Communications Technology (NICT)
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3. Outlines Problems with the current data packet
Low throughput with CSMA or ALOHA
No flexibility for a variety of ranging applications
Review of the proposed packet structure
Numerical results with the proposed packet structure
Carrier sense (CS) probability
Ranging accuracy improvement
Extra energy consumption
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4. Current ranging packet
Preamble
Header
Payload
Data on timing, crystal offset, etc
Acquisition; channel sounding
Control information
contents
modulation
length
preamble
Acquisition; channel sounding
Ternary code
three lengths: 500us, 1ms, 4ms
header
Control information
TBD
payload
Data on timing, crystal offset, etc
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5. Problem with ranging
A variety of conflicting factors imposed by various (potential) ranging applications,
Mobility
Update rate
On-air time
Ranging accuracy
VS.
Current solution (?):
three preamble lengths, 500us, 1ms and 4ms.
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6. Problem with CSMA or ALOHA10 -1 1
0.05
0.1
0.15
0.2
offered load
normalized payload throughput
preamble-only CS
whole packet CS
pure aloha
Low throughput
From Bin Zhen’s
Doc 619r0
1ms preamble, 0.25ms data(1Mbps, 32 bytes data)
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7. The proposed ranging packet
Preamble
+ (multiplexing)
Preamble
Header
Payload
Preamble is superimposed in the header and payload section.
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8. An Illustration of the proposed data packet
Energy level
Data s s s s s s t
preamble sec.
header and payload sec
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9. Observation 1.
Pulses in the superimposed preambles are much denser than those data pulses.
The superimposed preamble consists of repeated ternary codes.
The symbol duration of data pulses is 1us or 2us with modulation schemes 2PPM or 8PPM. Yet the time duration of the pulse burst is rather short, e.g., the duration of the code sequence with length 8 is 8*2ns=16ns=1% of symbol duration.
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10. Observation 2
The pulse energy of the multiplexed preamble is much lower than that of a data pulse. 7~15dB reduction is examined in the numerical results.
For minimizing the resulting interference to data detection and SOP.
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11. Advantages Extra preambles for channel sounding/ranging are available
An application can use preamble with a flexible length based on tradeoff among mobility, update rate, ranging accuracy, etc
CS (carrier sense) in the payload section is possible by using the embedded regular data structure.
Throughput performance will improve.
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12. Concerns with the new structure
Interference to data detection and SOP
Extra energy consumption
Performance improvement in ranging
Performance improvement in CSMA
On non-coherent issues
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13. Reduction of interference to data detection and SOP
Quasi-orthogonality between the data code sequence and the multiplexed preamble sequence
The pulse energy of the multiplexed preamble is about 7~13dB lower than that of a data pulse
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14. Parameters and assumptions in numerical results
Preamble: ternary code with length 31
Data
Modulation: 2 PPM, peak PRF=494MHz
Symbol length: 1us
Data length (256 bits): 256us
Assumptions:
Pulse energy in preamble section and payload section is same
Pulse energy of the multiplexed preamble is 7~13dB lower than that of a data pulse (reduce the interference to data detection and SOP)
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15. Ratio of energy consumption of the superimposed preamble
Observation:
Extra energy consumption is low, around 5% for longer preamble section (>=500us) and high pulse ratio (>10dB).
Pulse ratio = pulse energy of data / pulse energy of the multiplexed preamble.
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16. How to approximate the accuracy improvement in ranging
Assumption: the variance of a ranging estimate is proportional to 1/SNR.
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17. Improvement in ranging accuracy
L= number of symbols used for channel sounding/ranging in preamble section.
Observation:
Significant accuracy improvement (>80%) due to small number of symbols actually used for channel sounding in the regular preamble section.
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18. Successful CS probability with Eb/N0=10dB and false alarm around 5%
CS window=1us
Observation:
Successful CS probability is almost over 90% when pulse ratio is less than 13dB.
Pulse ratio = pulse energy of data / pulse energy of the multiplexed preamble.
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19. Successful CS probability with Eb/N0=10dB and false alarm around 5%
CS window=10us
Observation:
Successful CS probability is over 95% when pulse ratio is less than 13dB.
Pulse ratio = pulse energy of data / pulse energy of the multiplexed preamble.
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20. On non-coherent issues
Non-coherent receivers may not need to use the payload section to do ranging and CS due to the cost-effective concern.
The proposed packet structure has little interference on the current non-coherent ranging and data detection because of
Quasi-orthogonal between the payload and the superimposed preamble codes
Pulse energy of the superimposed preamble is sufficiently reduced.
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21. Conclusions The proposed packet structure has
Low extra energy consumption
Low interference to data detection and SOP
High ranging accuracy improvement
Effective CS performance
No confliction with the non-coherent reception
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