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New Ranging Packet Structure: Numerical Results

This submission presents numerical results on a new ranging packet structure, including energy consumption, ranging accuracy improvement, and carrier sense probability.

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New Ranging Packet Structure: Numerical Results

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  1. Project: IEEE P802.15 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:+81 46 847 5092, E-Mail: yhqi@nict.go.jp] 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 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.

  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)

  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

  4. Current ranging packet Preamble Header Payload Data on timing, crystal offset, etc Acquisition; channel sounding Control information

  5. Problem with ranging A variety of conflicting factorsimposed by various (potential) ranging applications, • Mobility • Update rate • On-air time • Ranging accuracy VS. Current solution (?): three preamble lengths, 500us, 1ms and 4ms.

  6. 0.2 preamble-only CS whole packet CS 0.15 pure aloha normalized payload throughput 0.1 0.05 0 -1 0 1 10 10 10 offered load Problem with CSMA or ALOHA • Low throughput From Bin Zhen’s Doc 619r0 1ms preamble, 0.25ms data(1Mbps, 32 bytes data)

  7. The proposed ranging packet Preamble + (multiplexing) Preamble Header Payload Preamble is superimposed in the header and payload section.

  8. An Illustration of the proposed data packet Energy level Data s s s s s s t preamble sec. header and payload sec

  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.

  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.

  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.

  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

  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

  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)

  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.

  16. How to approximate the accuracy improvement in ranging • Assumption: the variance of a ranging estimate is proportional to 1/SNR.

  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.

  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.

  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.

  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.

  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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