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Low Data Rate in CSS: Realization and Modification Techniques

This document discusses different ideas for lowering the data rate in Chirp Spread Spectrum (CSS) communication system. It includes mapping schemes and modulation techniques to achieve lower data rates.

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Low Data Rate in CSS: Realization and Modification Techniques

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title:How to realize the low data rate in CSS Date Submitted: June 7, 2005 Source:Rainer Hach Company: Nanotron Technologies Address:Alt-Moabit 61, 10555 Berlin, Germany Voice: +49 30 399 954 207 E-Mail:r.hach@nanotron.com Re: [] Abstract: different ideas for lowering the data rate Purpose: material to be discussed 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. Hach, Nanotron

  2. The actual 1Mb/s mode 2 x 3 information bits are mapped onto 2 x 4 code bits. 2 x 4 code bits are modulated onto 1 chirp symbol by using DQPSK Modulator (1 Mb/s) Data-rate: 1 Mb/s S/P Symbol Mapper P/S Mapper QPSK 3 3 4 1 1 Binary Data S/P 2 1 1 2 S/P Symbol Mapper P/S 3 3 4 1 1 DBO-QCSS Signal CSK Gen. 2450 MHz PHY modulation 8-ary Differentially Bi-Orthogonal Quaternary-Chirp-Spread-Spectrum (DBO-QCSS) Modulator for 1 Mb/s Data-rate Hach, Nanotron

  3. Actual mapping scheme ham_dist = 0 2 2 2 4 2 2 2 2 0 2 2 2 4 2 2 2 2 0 2 2 2 4 2 2 2 2 0 2 2 2 4 4 2 2 2 0 2 2 2 2 4 2 2 2 0 2 2 2 2 4 2 2 2 0 2 2 2 2 4 2 2 2 0 avg_dist = 2.2857 8-ary Bi-Orthogonal Symbol Mapping Table 0 000 1 001 2 010 3 011 4 100 5 101 6 110 7 111 1 1 1 1 1 -1 1 -1 1 1 -1 -1 1 -1 -1 1 -1 -1 -1 -1 -1 1 -1 1 -1 -1 1 1 -1 1 1 -1 Hach, Nanotron

  4. The actual proposal for lower data rate 1 x 3 information bits are Mapped onto the 4 code bits. 4 code bits are modulated onto 1 chirp symbol by using DBPSK Modulator (250 Kb/s) Data-rate: 250 kb/s Binary Data FEC Encoder r=1/2 S/P Symbol Mapper P/S 1 1 1 1 1 3 3 4 1 DBO-BCSS Signal CSK Gen. 2450 MHz PHY modulation 8-ary Differentially Bi-Orthogonal Binary-Chirp-Spread-Spectrum (DBO-QCSS) Modulator for 250 Kb/s Data-rate Hach, Nanotron

  5. Lower data rate by modified mapping scheme (1) 4-ary Symbol Mapping Table ham_dist = 0 3 2 3 3 0 3 2 2 3 0 3 3 2 3 0 avg_dist = 2.6667 0 00 1 01 2 10 3 11 1, 1,-1,-1 1,-1, 1, 1 -1, 1,-1, 1 -1,-1, 1,-1 Effective Data rate: 2 bits /6us = 330 kBit/s Hach, Nanotron

  6. Lower data rate by modified mapping scheme (2) 4-ary Symbol Mapping Table ham_dist = 0 4 4 0 avg_dist = 4 0 00 1 01 1, 1, 1, 1 -1,-1,-1,-1 Effective Data rate: 1 bits /6us = 165 kBit/s Con Doesn‘t meet the 250 kBit Pro Original code words We achieve lower rate by taking something away Hach, Nanotron

  7. Comparison convolutional code R=0.5, K=6, dfree=8 vs. block biorthogonal(1,4) over AWGN Hach, Nanotron

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