Chirp Spread Spectrum (CSS) PHY Submission

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_at_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.
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
2
1
1
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
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
Decimal (m) Binary (b0,b1,b2) Bi-Orthogonal Code (01,02,03,04)








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
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
S/P
Symbol Mapper
FEC Encoder r1/2
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
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
Decimal (m) Binary (b0,b1) Bi-Orthogonal Code (01,02,03,04)




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
6
Lower data rate by modified mapping scheme (2)
4-ary Symbol Mapping Table
Decimal (m) Binary (b0,b1) Bi-Orthogonal Code (01,02,03,04)


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 Doesnt meet the 250 kBit
Pro Original code words We achieve lower rate by
taking something away
7
Comparison convolutional code R0.5, K6, dfree8
vs. block biorthogonal(1,4) over AWGN