IEEE 802.15 <PHY Proposal>

1
Project IEEE P802.15 Working Group for Wireless
Personal Area Networks (WPANs) Submission Title
Impulse Radio Signaling for Communication and
Ranging Date Submitted 12 May 2005 Source
Francois Chin, Lei Zhongding, Yuen-Sam Kwok,
Xiaoming Peng Company Institute for Infocomm
Research, Singapore Address 21 Heng Mui Keng
Terrace, Singapore 119613 Voice 65-68745687
FAX [phone] E-Mail chinfrancois_at_i2r.a-
star.edu.sg Re Abstract Presents
signaling options to achieve precision ranging
with both coherent and non-coherent
receivers Purpose To discuss which signal
waveform would be the most feasible in terms of
performance and implementation trade-offs 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
Objectives

• PRF definition
• Impulse Radio Signaling Proposal
• System Parameters (500 MHz and 1500 MHz Bands)
• Transmit Signaling for Synchronisation, Ranging
  and Data Communications
• Receiver Code Sequences

3
PRF Definition

• Pulse repetition frequency (PRF) Number of
  pulses occurring in 1 s.
• Pulse repetition interval (PRI) Time from the
  beginning of one pulse to the beginning of the
  next.

4
PRF Definition Example
Pulse Repetition Interval
1
2
3
N
4
5
6
7
8
N-1

Non0inverted pulses are blue, Inverted pulses are
green.
Pulse Width, Tc 4ns _at_ 500MHz BW
.................

Quiet time
Active time
Symbol Interval
5
Minimum PRF Requirements
BW 528 MHz BW 528 MHz BW 528 MHz
Technology CMOS 90nm 0.7 Vpp CMOS 90nm 0.7 Vpp
TChip (nsec) 1.9 1.9
Sequence Bipolar Ternary (equal 1 0)
VPeak (v) 0.35 0.35
PAve (dBm) -14 -14
PPeak (dBm) 1 -2
PRF (MHz) _at_ VPeak 16.5 33
BW 1584 MHz BW 1584 MHz BW 1584 MHz
Technology CMOS 90nm 0.7 Vpp CMOS 90nm 0.7 Vpp
TChip (nsec) 0.54 0.54
BW (MHz) Bipolar Ternary (equal 1 0)
VPeak (v) 0.35 0.35
PAve (dBm) -9.3 -9.3
PPeak (dBm) 1.5 -1.5
PRF (MHz) _at_ VPeak 132 264
6
Frequency Plan
Band No. Bandwidth (MHz) Low Freq. (MHz) Center Freq. (MHz) High Freq. (MHz)
1 (optional) 528 3168 3432 3696
2 (Mandatory) 528 3696 3960 4224
3 (optional) 528 4224 4488 4752
4 (optional) 1584 3168 3960 4752
Band No. 4
1
2
3
3
4
5
GHz
3.5
4.5
3.25
3.75
4.25
4.75
7
Main Features of proposed system

• Proposal main features
• Impulse-radio based (pulse-shape independent)
• Common synchronisation / ranging preamble
  signaling for different classes of nodes / type
  of receivers (coherent / differential /
  noncoherent)
• Band Plan based on multiple 500 MHz bands (center
  band mandatory) and optional wider bandwidth (1.5
  GHz) concentric with center band
• Robustness against SOP interference
• Robustness against other in-band interference
• Scalability to trade-off complexity/performance

8
Types of Receivers Supported

• Coherent Detection The phase of the received
  carrier waveform is known, and utilized for
  demodulation
• Differential Chip Detection The carrier phase of
  the previous signaling interval is used as phase
  reference for demodulation
• Non-coherent Detection The carrier phase
  information (e.g.pulse polarity) is unknown at
  the receiver

9
Proposed System Parameters (528 MHz)
Bandwidth 528MHz
Pulse Rep. Freq. 33 MHz
Chip / symbol (Code length) 31 9 zero padding
Channel coding e.g. Conv code K 4, r2/3
Symbol Rate 33/40 MHz 0.825 MSps
coded bit / sym (Mandatory Mode) 2 coded bit / symbol
Mandatory bit rate 2/3 x 2 bit/sym x 0.825 MSps 1.1 Mbps
Code Sequences for Orthogonal Keying 4 (2 bit/symbol)
Lower bit rate scalability Symbol Repetition
Modulation 1,-1 bipolar and 1,-1, 0 ternary pulse train
Total simultaneous piconets supported 6 per FDM band
Multple access for piconets CDM (fixed code) FDM (fixed band)
10
Frame Format
2
1
0/4/8
2
n
Octets
Data Payload
Frame Cont.
MAC Sublayer
Seq.
Address
CRC
MHR
MSDU
MFR
Data 32 (n23)
??
1
1
For ACK 5 (n0)
Octets
PHY Layer
Frame Length
Preamble
SFD
MPDU
SHR
PHR
PSDU
PPDU
11
Criteria of Code Sequence Design

• The sequence Set should have orthogonal (or near
  orthogonal) cross correlation properties to
  minimise symbol decision error for all the below
  receivers
• For coherent receiver
• For differential chip receiver
• For non-coherent symbol detection receiver
• Energy detection receiver
• Each sequence should have good auto-correlation
  properties for synchronisation and ranging

12
Base Sequence Set
Seq 1 - - 0 0 0 - 0 0 0 - 0 0 0 0 0 0 - 0 - 0 0 - -
Seq 2 - 0 - - 0 0 0 0 0 - 0 0 0 0 0 - 0 0 0 0 - - -
Seq 3 - 0 - - - 0 0 0 0 - 0 0 - 0 0 0 0 0 0 - - 0 0
Seq 4 0 0 - - 0 - - 0 0 0 - - 0 0 0 - 0 0 0 0 0 0 -
Seq 5 - - 0 0 - 0 0 0 0 0 0 0 - - 0 - 0 0 0 0 - - 0
Seq 6 0 0 - - 0 0 0 0 0 0 - 0 0 - 0 0 0 0 - - - 0 -

• 31-chip Ternary Sequence set are chosen
• Only one sequence and one fixed band (no hopping)
  will be used by all devices in a piconet
• Logical channels for support of multiple piconets
• 6 sequences 6 logical channels (e.g.
  overlapping piconets) for each FDM Band
• The same base sequence will be used to construct
  the symbol-to-chip mapping table

13
Good Properties of the Mapping Sequence

1. Cyclic nature, leads to simple implementation
2. Zero DC for each sequence
3. No need for carrier phase tracking (i.e. coherent
   receiver)
4. The same code sequence will be used for
   synchronisation, ranging, data communications
   SOP interference suppression

14
Ternary Bipolar Unipolar Conversion
Seq 1 - - 0 0 0 - 0 0 0 - 0 0 0 0 0 0 - 0 - 0 0 - -
Seq 2 - 0 - - 0 0 0 0 0 - 0 0 0 0 0 - 0 0 0 0 - - -
Seq 3 - 0 - - - 0 0 0 0 - 0 0 - 0 0 0 0 0 0 - - 0 0
Seq 4 0 0 - - 0 - - 0 0 0 - - 0 0 0 - 0 0 0 0 0 0 -
Seq 5 - - 0 0 - 0 0 0 0 0 0 0 - - 0 - 0 0 0 0 - - 0
Seq 6 0 0 - - 0 0 0 0 0 0 - 0 0 - 0 0 0 0 - - - 0 -
Ternary
? 0 ? -
Seq 1 - - - - - - - - - - - - - - -
Seq 2 - - - - - - - - - - - - - - -
Seq 3 - - - - - - - - - - - - - - -
Seq 4 - - - - - - - - - - - - - - -
Seq 5 - - - - - - - - - - - - - - -
Seq 6 - - - - - - - - - - - - - - -
Bipolar
This is in fact m-Sequences!
? - ? 0
Seq 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Seq 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Seq 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Seq 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Seq 5 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Seq 6 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Unipolar
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Properties of M-Sequence
Transmit Unipolar M-Seq 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0
repeated 4x Receive Bipolar M-Seq - - -
- - - - - - - - - - - -

16
Properties of M-Sequence
Transmit Bipolar M-Seq - - - -
- - - - - - - - - - - repeated
4x Receive Unipolar M-Seq 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0
17
Properties of M-Sequence
Transmit Bipolar M-Seq - - - -
- - - - - - - - - - - repeated
4x Receive Bipolar M-Seq - - - -
- - - - - - - - - - -
18
How to make use of these properties?
Transmit signaling Unipolar Bipolar Bipolar
Receive signaling Bipolar Unipolar Bipolar
Tx PAR 2x 1x 1x
Corr O/P peka Signal Amp 16 x sqrt(2) 16 32
Corr O/P noise Pwr 32 s2 16 s2 32 s2
Corr O/P SNR 16 / s2 16 / s2 32 / s2
Despread Gain 16 16 32
Auto-corr 0 0 Low
Applications Energy Det - Ranging / Sync / Comm Coherent Det - Ranging Coherent Det - Sync / Comm
19
Ranging Code Sequences for different Receiver
Criteria/Target ZERO autocorrelation sidelobes
Receiver Type Ranging Signaling Sequence Receive Sequence
Coherent Binary Unipolar
Differential Chip Binary Unipolar(Differential(Binary))
Energy Detector Ternary Bipolar
20
Communication Code Sequences for different
Receiver
Criteria/Target Max SNR and min inter-sequence
interference after despreading
Transmit Signaling Receiver Type Receive Sequence
Ternary (Mode 1) Coherent Ternary
Ternary (Mode 1) Differential Chip Differential(Ternary)
Ternary (Mode 1) Energy Detector Bipolar
Binary (Mode 2) Coherent Bipolar
Binary (Mode 2) Differential Chip Differential(Bipolar)
Binary (Mode 2) Energy Detector N.A.
21
Snychronisation Code Sequences for different
Receiver
Criteria/Target balance max post-despreading
SNR and low auto-correlation sidelobes
Transmit Signaling Receiver Type Receive Sequence
Ternary (Mode 1) Coherent Ternary
Ternary (Mode 1) Differential Chip Differential(Ternary)
Ternary (Mode 1) Energy Detector Bipolar
Binary (Mode 2) Coherent Bipolar
Binary (Mode 2) Differential Chip Differential(Bipolar)
Binary (Mode 2) Energy Detector N.A.
22
Synchronisation Preamble

• M-sequences has excellent autocorrelation
  properties
• Synchronisation / Ranging Preamble is constructed
  by repeating the base sequence
• Ternary for Common Signaling e.g. Beacon Packet
• Ternary for Energy Detector
• Bipolar for Coherent and Differential Chip
  Detectors
• Long preamble for distant nodes is constructed by
  further symbol repetition

23
Bipolar Signaling for Synchronisation Ranging
Pulse Repetition Interval 30ns
1
2
3
31
4
5
6
7
8
30

Non0inverted pulses are blue, Inverted pulses are
green.
Synchronisation / Ranging preamble Binary Base
Sequence repeated For K times


.................
Symbol Interval 940ns
Symbol Interval 940ns
24
How Energy Detector despread?
Ternary Seq - - 0 0 0 - 0 0 0 - 0 0
0 0 0 0 - 0 - 0 0 - -
Unipolar M-Seq 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
Bipolar M-Seq - - - - - - -
- - - - - - - -
25
Synchronisation for Energy Detector in AWGN
Before Depreader Unipolar M-Seq 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0
repeated 4x Despread Sequence Bipolar M-Seq
- - - - - - - - - - - - -
- -
26
How Energy Detector handle inter- pulse
interference?
Pulse Repetition Interval 30ns
1
2
3
4
5
6
7
Ternary signaling Non-inverted pulses are
blue, Inverted pulses are green.
PRI
T8
T5
T6
T7
T1
T2
T3
T4
After Square Law
PRI
T8
T5
T6
T7
T1
T2
T3
T4
Integration in PRI
e1
e2
e3
1
2
3
4
5
6
7

More Noise
PRI
T1
T2
T3
T4
27
How Energy Detector handle inter- pulse
interference?

• Energy is spilled into adjacent PRI
• Each PRI contains partial energy from previous
  pulses

After square law Integration in PRI
e1
e2
e3
1
2
3
4
5
6
7

More Noise
PRI
T1
T2
T3
T4
Equivalent to
c5e1 c4e2c3e3

28
How Energy Detector handle inter- pulse
interference?

• RAKE fingers are used to combine energy across
  adjacent PRI

Despreading Period
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Data CommsTransmission Mode
Mode Data Rate (Mbps) Bit / symbol Sym. Rep. TX Sign-aling Receiver type
1a 3 2 1 Ternary - Short Preamble for all receivers - High Data Rate Mode (for Energy Collection receivers)
1b 0.75 2 4 Ternary - Long Preamble for all receivers - Low Data Rate Mode (for Energy Collection receivers)
2a 3 2 1 Bipolar - High Data Rate Mode (for Coherent / Differential Chip Receiver)
2b 0.75 2 4 Bipolar - Low Data Rate Mode (for Coherent / Differential Chip Receiver)
30
Modulation Coding (Mode 1)
Binary data From PPDU
Symbol- to-Chip
Bit-to- Symbol
Symbol Repetition
Zero Padding
Pulse Generator
0,1,-1 Ternary Sequence

• Bit to symbol mapping
• group every 2 bits into a symbol
• Symbol-to-chip mapping
• Each 2-bit symbol is mapped to one of 4 31-chip
  sequence, according to 4-ary Ternary Orthogonal
  Keying
• Zero Padding
• suggested 9 PRI for reducing inter-symbol
  interference
• Symbol Repetition
• for data rate and range scalability
• Pulse Genarator
• Transmit Ternary pulses at PRF 33MHz

31
Symbol-to-Chip Mapping Gray 4-ary Ternary
Orthogonal Keying
Symbol Cyclic shift to right by n chips, n 32-Chip value
00 0 - - 0 0 0 - 0 0 0 - 0 0 0 0 0 0 - 0 - 0 0 - -
01 8 - 0 - 0 0 - - - - 0 0 0 - 0 0 0 - 0 0 0 0 0 0
11 16 - 0 0 0 0 0 0 - 0 - 0 0 - - - - 0 0 0 - 0 0 0
10 24 - 0 0 0 - 0 0 0 0 0 0 - 0 - 0 0 - - - - 0 0 0
Base Sequence 1
32
Symbol Mapping for Mode 1 Ternary Orthogonal
Keying Zero Padding
Symbol Cyclic shift to right by n chips, n 319-Chip value
00 0 - - 0 0 0 - 0 0 0 - 0 0 0 0 0 0 - 0 - 0 0 - - 0 0 0 0 0 0 0 0 0
01 8 - 0 - 0 0 - - - - 0 0 0 - 0 0 0 - 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
11 16 - 0 0 0 0 0 0 - 0 - 0 0 - - - - 0 0 0 - 0 0 0 0 0 0 0 0 0 0 0 0
10 24 - 0 0 0 - 0 0 0 0 0 0 - 0 - 0 0 - - - - 0 0 0 0 0 0 0 0 0 0 0 0
Base Sequence 1
Zero Padding
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Modulation Coding (Mode 2)
Binary data From PPDU
Ternary- Bipolar
Symbol- to-Chip
Bit-to- Symbol
Symbol Repetition
Zero Padding
Pulse Generator
1,-1 Binary Sequence
0,1,-1 Ternary Sequence

• Bit to symbol mapping
• group every 2 bits into a symbol
• Symbol-to-chip mapping
• Each 2-bit symbol is mapped to one of 4 31-chip
  sequence, according to 4-ary Bipolar Orthogonal
  Keying
• Ternary to Binary conversion
• (-1/1 ? 1,0 ? -1)
• Zero Padding
• suggested 9 PRI for reducing inter-symbol
  interference
• Symbol Repetition
• for data rate and range scalability
• Pulse Genarator
• Transmit bipolar pulses at PRF 33MHz

34
Symbol Mapping for Mode 2 Bipolar Orthogonal
Keying Zero Padding (after Ternary Binary
Conversion)
Symbol Cyclic shift to right by n chips, n 319-Chip value
00 0 - - - - - - - - - - - - - - - 0 0 0 0 0 0 0 0 0
01 8 - - - - - - - - - - - - - - - 0 0 0 0 0 0 0 0 0
11 16 - - - - - - - - - - - - - - - 0 0 0 0 0 0 0 0 0
10 24 - - - - - - - - - - - - - - - 0 0 0 0 0 0 0 0 0
Binary Base Sequence 1
Zero Padding
35
Bipolar Signaling for Symbol 00
Pulse Repetition Interval 30ns
1
2
3
31
4
5
6
7
8
30

Non0inverted pulses are blue, Inverted pulses are
green.
.................

Quiet time 272ns
Active time 940ns
Symbol Interval 1.212us
36
Code Sequence Properties Performance

• AWGN Performance
• Multipath Performance
• For Coherent Symbol Detector
• For Non-coherent Symbol Detector
• For Differential Chip Detector
• For Energy Detector

To be included in future revision
37
Proposed Optional Wider Band System
Bandwidth 1584MHz
Pulse Rep. Freq. 264 MHz
Chip / symbol (Code length) 31 9 zero padding
Channel coding e.g. Conv code K 4, r2/3
Symbol Rate 264/40 MHz 6.6 MSps
coded bit / sym 2 coded bit / symbol
Max bit rate (in benign multipath channels) 2/3 x 2 bit/sym x 6.6 MSps 8.8 Mbps
Code Sequences for Orthogonal Keying 4 (2 bit/symbol)
Lower bit rate scalability TBD
Modulation 1,-1 bipolar and 1,-1, 0 ternary pulse train
Total simultaneous piconets supported 6
Multple access for piconets CDM (fixed code per piconet)
38
Summary

• The proposed Impulse-radio based system
• has common ternary signaling that
• Can be received simultaneously by different types
  of receivers, namely coherent, differential, and
  energy detectors
• Can be used for both synchronisation and ranging
  simultaneously
• Synchronisation Ranging Repeated Base
  Sequence (Ternary or Binary)
• Data Communications Orthogonal Keying Symbol
  (with cyclic shift version of base sequence
  zero padding)
• Is robust against SOP interference