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 18 July 2005 Source
Francois Chin, Yuen-Sam Kwok, Sai-Ho Wong,
Zander Lei, 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 values for Mandatory and optional wider band
  systems
• Impulse Radio Signaling Proposal
• Common Signaling for different receivers, for
  Synchronisation, Ranging and Data Communications
• Deterministic Pulse structures
• Optimal Receiver Code Sequences

3
Minimum PRF Requirements (BW500MHz)
BW 500 MHz BW 500 MHz BW 500 MHz
Technology CMOS 90nm 1.0 Vpp CMOS 90nm 1.0 Vpp
TChip (nsec) 2 2
Sequence Bipolar Ternary (equal 1 0)
VPeak (v) 0.5 0.5
PAve (dBm) -14.3 -14.3
PPeak (dBm) 3.8 3.8
Chip Rate (MHz) _at_ VPeak 7.75 15.5
PRF (MHz) _at_ VPeak 7.75 7.75

• Key Requirement is to meet CMOS Tx Vpp constraint
• For Ternary signaling
• 1.0Vpp _at_ 15.5MHz CRF without backoff perfect
  antenna
• 1.2Vpp _at_ 15.5MHz CRF without backoff 30 (or
  1.5dB) feed loss
• 1.0Vpp _at_ 15.5MHz CRF without 1.5dB backoff 30
  (or 1.5dB) feed loss

4
Minimum PRF Requirements (BW1.5GHz)
BW 1500 MHz BW 1500 MHz BW 1500 MHz
Technology CMOS 90nm 1.0 Vpp CMOS 90nm 1.0 Vpp
TChip (nsec) 0.66 0.66
BW (MHz) Bipolar Ternary (equal 1 0)
VPeak (v) 0.5 0.5
PAve (dBm) -9.6 -9.6
PPeak (dBm) 4.4 4.4
Chip Rate (MHz) _at_ VPeak 62 124
PRF (MHz) _at_ VPeak 62 62

• Key Requirement is to meet CMOS Tx Vpp constraint
• For Ternary signaling
• 1.0Vpp _at_ 124MHz CRF without backoff perfect
  antenna
• 1.2Vpp _at_ 124MHz CRF without backoff 30 (or
  1.5dB) feed loss
• 1.0Vpp _at_ 124MHz CRF without 1.5dB backoff 30
  (or 1.5dB) feed loss

5
124 MHz CRF Mode is logical

• 1.5GHz system, 3x larger bandwidth means
• 3x shorter pulse duration
• 3x higher average transmit power
• The keep the same peak transmit power, 1.5GHz
  system should have 9x higher CRF (or PRF),
  compared to 500MHz system
• 124MHz CRF 8 x 15.5 MHz CRF
• Or in terms of PRF, 62 MHz 8 x 7.75 MHz

6
Minimum numbers of Chip Rates

• After considering antenna feed loss and PSD
  backoff, we have min 2 CRFs
• 15.5MHz for 500MHz systems
• 124MHz for 1500MHz systems

7
Main Features of proposed Impulse Radio Signaling

• Proposal main features
• Impulse-radio based (pulse-shape independent)
• Ternary Codes for Common Preamble Data
  signaling for different classes of nodes / type
  of receivers (coherent / differential /
  noncoherent)
• Perfect balance ternary sequences for
  synchronisation ranging preambles Perfect
  Autocorrelation for coherent and energy detectors
• M-ary signaling for data transmission to achieve
  higher spreading gain - Robustness against SOP
  interference

8
Key Features of proposed System

• Impulse-radio based (pulse-shape independent)
• Chip Repetition Frequency 15.5MHz
  (corresponding to PRF of 7.75MHz)
• 1 Mbps mandatory and 10Mbps optional modes
• Ternary Codes for Common Preamble Data
  signaling for different classes of nodes / type
  of receivers (coherent / differential /
  noncoherent)
• 31-Chip Perfect Balance Ternary Sequences (PBTS)
  for synchronisation ranging preambles Perfect
  Autocorrelation for coherent and energy detectors
• 16-ary Ternary Orthogonal Keying (derived from
  31-chip sequence PBTS) for data transmission to
  achieve higher spreading gain - Robustness
  against SOP interference

9
Criteria of Code Sequence Design

• The code sequence should have perfect
  auto-correlation properties for synchronisation
  and ranging (leading edge detection) for all the
  below receivers
• Coherent receiver
• Energy detection receiver
• Differential chip receiver
• The sequence Set should have orthogonal (or near
  orthogonal) cross correlation properties to
  minimise symbol decision error

10
Base Sequence Set (31-chip Ternary)
Seq 1 0000--00000-0000-00--
Seq 2 -00000000---0-00-0000
Seq 3 0-0000-00-0000-00-00-
Seq 4 00000-00-0-00-000-00-
Seq 5 -0----000000000-00000
Seq 6 0-000000-0-00000--00-
These are Wideband Access-I2R proposed Perfect
Balance Ternary Sequences for Preambles for
Ranging

• 31-chip Ternary Sequence Set
• Only one base 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 500MHz Band
• The same base sequence will be used for
• acquisition / ranging and
• Data transmission via symbol-to-chip mapping

11
Base Sequence Properties (Auto-Corr.)

• Perfect balance ternary sequences for
  synchronisation ranging preambles
• Perfect Autocorrelation for coherent and energy
  detectors

12
Base Sequence Properties (Cross-Corr.)
First 3 sequences have lowest possible
cross-correlation values
13
Spectral PAR (PSD Backoff)
PSD Backoff 1.0dB _at_ 15.5 MHz
14
Synchronisation Preamble

• The Ternary Base Sequence has excellent
  autocorrelation properties
• Synchronisation / Ranging Preamble is constructed
  by repeating the preamble
• Noted that with this new improved ternary
  sequences, there is no need for Receiver-specific
  signaling

15
Ternary Signaling for Preambles
CHIP Repetition Interval 65ns
1
2
3
31
4
5
6
7
8
30

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


.................
Symbol Interval 2us
Symbol Interval 2us
16
Modulation Coding
Coded Bits
Zero Padding
Pulse Generator
Symbol Repetition
Symbol- to-Chip
Bit-to- Symbol
Scrambling
0,1,-1 Ternary Sequence

• Bit to symbol mapping
• group every 4 bits into a symbol
• Symbol-to-chip mapping
• Each 2-bit symbol is mapped to one of 16 31-chip
  sequence, according to 16-ary Ternary Orthogonal
  Keying
• Zero Padding
• suggested 1 PRI for reducing inter-symbol
  interference
• Symbol Repetition
• for data rate and range scalability
• Scrambling
• with bipolar sequence _at_ 15.5MHz, to suppress
  cross correlation sidelobes due to excessive
  delay spread
• Pulse Genarator
• Transmit Ternary pulses _at_ 15.5MHz

17
Symbol-to-Chip Mapping Gray coded 16-ary Ternary
Orthogonal Keying
Symbol Cyclic shift to right by n chips, n 32-Chip value
0000 0 0 0 0 0 - - 0 0 0 0 0 - 0 0 0 0 - 0 0 - - 0
0001 2 - - 0 0 0 0 - - 0 0 0 0 0 - 0 0 0 0 - 0 0 0
0011 4 0 - - 0 0 0 0 - - 0 0 0 0 0 - 0 0 0 0 0 0
0010 6 0 0 - - 0 0 0 0 - - 0 0 0 0 0 - 0 0 0 0 0
0110 8 0 0 - 0 0 - - 0 0 0 0 - - 0 0 0 0 0 - 0 0 0
0111 10 0 0 0 0 - 0 0 - - 0 0 0 0 - - 0 0 0 0 0 0
0101 12 0 - 0 0 0 0 - 0 0 - - 0 0 0 0 - - 0 0 0 0 0
0100 14 0 0 - 0 0 0 0 - 0 0 - - 0 0 0 0 - - 0 0 0 0
1100 16 0 0 0 - 0 0 0 0 - 0 0 - - 0 0 0 0 - - 0 0 0
1101 18 0 0 0 0 - 0 0 0 0 - 0 0 - - 0 0 0 0 - - 0 0
1111 20 0 0 0 0 0 - 0 0 0 0 - 0 0 - - 0 0 0 0 - - 0
1110 22 - 0 0 0 0 0 - 0 0 0 0 - 0 0 - - 0 0 0 0 - 0
1010 24 - - 0 0 0 0 0 - 0 0 0 0 - 0 0 - - 0 0 0 0 0
1011 26 0 0 - - 0 0 0 0 0 - 0 0 0 0 - 0 0 - - 0 0 0
1001 28 0 0 0 - - 0 0 0 0 0 - 0 0 0 0 - 0 0 - - 0 0
1000 30 0 0 0 0 - - 0 0 0 0 0 - 0 0 0 0 - 0 0 - - 0
Base Sequence 1
1 zero padding
18
Code Sequences for different Receivers
Receiver Type Preamble / Data Sequence Receive Sequence
Coherent Ternary Ternary
Differential Chip Ternary Differential(Ternary)
Energy Detector Ternary Bipolar

• For both Preamble and Data
• Ternary to Bipolar conversion

? 0 ? -
19
Cross Sequence Correlation Properties for
Coherent Receiver
For Coherent Detector, RX Mapping Matrix TX
Mapping Matrix
RX Mapping Matrix TX Mapping Matrix'
20
Rx Sequence for Energy Detector
Symbol Cyclic shift to right by n chips, n 32-Chip value
0000 0 - - - - - - - - - - - - - - - -
0001 2 - - - - - - - - - - - - - - - -
0011 4 - - - - - - - - - - - - - - - -
0010 6 - - - - - - - - - - - - - - - -
0110 8 - - - - - - - - - - - - - - - -
0111 10 - - - - - - - - - - - - - - - -
0101 12 - - - - - - - - - - - - - - - -
0100 14 - - - - - - - - - - - - - - - -
1100 16 - - - - - - - - - - - - - - - -
1101 18 - - - - - - - - - - - - - - - -
1111 20 - - - - - - - - - - - - - - - -
1110 22 - - - - - - - - - - - - - - - -
1010 24 - - - - - - - - - - - - - - - -
1011 26 - - - - - - - - - - - - - - - -
1001 28 - - - - - - - - - - - - - - - -
1000 30 - - - - - - - - - - - - - - - -
Ternary to Bipolar conversion of Base Sequence 1
21
Sync Ranging - Energy Detector operation
(example)
Ternary Seq - - 0 0 0 - 0 0 0 - 0 0
0 0 0 0 - 0 - 0 0 - -
After Square Law Integration in PRI
Unipolar M-Seq 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
In AWGN
Soft output
Noncoherent detection of OOK
Sliding Correlator
LPF / integrator
BPF
( )2
ADC
Sample Rate 1/Tc
1,-1 Binary Sequence
Bipolar M-Seq - - - - - - -
- - - - - - - -
22
Cross Sequence Correlation Properties for Energy
Detector
For Energy Detector, RX Mapping Matrix
Ternary2Bipolar(TX Mapping Matrix)
RX Mapping Matrix abs(TX Mapping Matrix)'
23
Why M-ary Orthogonal Keying ?

• Good coding gain as M-ary Orthogonal Keying is
  power-limited coding
• More coding gain is achieved with higher M values
• Marginal gain for M gt 16
• Robust against SOP interference inter-pulse
  interference due to high despreading gain per
  M-ary symbol

24
Simulation Results

• AWGN Performance Multipath Performance
• For Coherent Symbol Detector
• For Energy Detector
• For differential Chip Detector (to be provided
  later)

25
Proposed Mandatory System Parameters
Bandwidth 500MHz
Ternary Pulse Rep. Freq. 15.5 MHz
Chip / symbol (Preambles) 31
Chip / symbol (Comms.) 31 1 Zero padding 32
Channel coding e.g. Conv code K 3, r1/2 (Hard decoding)
Symbol Rate (Comms.) 15.5/32 MHz 0.484375 MSps
coded bit / sym 4 coded bit / symbol
Mandatory bit rate 1/2 x 4 bit/sym x 0.484375 MSps 0.96875 Mbps
Higher bit rate 10.33 Mbps (Details in following pages)
Code Sequences for Ternary Orthogonal Keying 16 (4 bit/symbol)
Lower bit rate scalability Symbol Repetition
Modulation 1,-1, 0 ternary pulses
Total simultaneous piconets supported 6 per FDM band
Multple access for piconets CDM (fixed code) FDM (fixed band)
26
Multipath Performance (1 Mbps, 500MHz BW)

• Random transmit scrambling seq.
• Coherent and energy detectors
• AWGN, CM1 CM8
• 1-Rake 4-Rake
• Ideal Channel acquisition timing estimation
• Benefit of ½ rate CC not obvious in isolated
  piconet operation advantage may be in SOP
  operation

27
SOP Multipath (1 Mbps, 500MHz BW)
To be provided later
28
Proposed Mandatory System Parameters (Max Bit
Rate Mode)
Bandwidth 500MHz
Pulse Rep. Freq. 15.5 MHz
Chip / symbol (Preamble) 31
Chip / symbol (Comms.) 1
Channel coding e.g. Conv code K 3, r2/3
Symbol Rate 15.5 MSps
coded bit / sym 1 coded bit / symbol
Max bit rate 2/3 x 1 bit/sym x 15.5 MSps 10.33 Mbps
Code Sequences for Orthogonal Keying Nil
Modulation 1,-1 bipolar pulses
Total simultaneous piconets supported -
Multple access for piconets CDM (fixed code per piconet)
29
Multipath Performance (10 Mbps, 500MHz BW)

• No Ternary Ortho.Keying
• Coherent detector only
• AWGN, CM1
• 1-Rake 4-Rake
• Ideal Channel acquisition timing estimation

30
Proposed Optional Wider Band
1.5GHz systems
31
Key Features of proposed wider band system

• Impulse-radio based (pulse-shape independent)
• Chip Repetition Frequency 124MHz
  (corresponding to PRF of 62MHz)
• 1 Mbps mandatory and 10Mbps optional modes
• Ternary Codes for Common Preamble Data
  signaling for different classes of nodes / type
  of receivers (coherent / differential /
  noncoherent)
• 127-Chip Perfect balance ternary sequences for
  synchronisation ranging preambles Perfect
  Autocorrelation for coherent and energy detectors
• 16-ary Ternary Orthogonal Keying (with 256-chip
  sequence) for data transmission to achieve higher
  spreading gain - Robustness against SOP
  interference, especially in 1.5GHz system
  (without FDMA for SOP)

32
Base Sequence Set (127-chip Ternary)
Seq 1 0000--000-0000-0--0-000000-0-0-0-0--0--0000 000-00000---0000--00--0000-00--000-0-00000000000
Seq 2 -000-0000000-000--000000-0-000000-000000-00--- -000-0-00-00-00-0000000-0000---0---00-0000-0-
Seq 3 -00-000-000-0--00000000-000000--0000000000----00-0-00-0000-0000-00-0000--0-0--0-00-0-000-00
Seq 4 000-0-0-0--0000000-0000----00000--000-0000 000000-000-00--000-0-0-0-0-00000-000-000--00-0-00
Seq 5 0-00000---0000-0000000000000-0--0-000-000--0 0000000000-00-0-000000-0--00---0----0-000-000-0
These are Wideband Access-I2R proposed Perfect
Balance Ternary Sequences for Preambles for
Ranging

• 127-chip Ternary Sequence Set
• Only one base sequence and one fixed band (no
  hopping) will be used by all devices in a piconet
• Logical channels for support of multiple piconets
• 5 sequences 5 logical channels (e.g.
  overlapping piconets) for 1500MHz Band
• The same base sequence will be used for
• acquisition / ranging and
• Data transmission via symbol-to-chip mapping

33
Ternary Signaling for Preambles
CHIP Repetition Interval 8.1ns
1
2
3
127
4
5
6
7
8
126

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


.................
Symbol Interval 1.03us
Symbol Interval 1.03us
34
Proposed Optional Wider Band System
Bandwidth 1488MHz
Ternary Pulse Rep. Freq. 124 MHz
Chip / symbol (Preamble) 127
Chip / symbol (Comms.) 256 (Details later)
Channel coding e.g. Conv code K 3, r1/2
Symbol Rate 124/256 MHz 0.484375 MSps
coded bit / sym 4 coded bit / symbol
Mandatory bit rate 1/2 x 4 bit/sym x 0.484375 MSps 0.96875 Mbps
Max bit rate 10.33 Mbps (see next page)
Code Sequences for Ternary Orthogonal Keying 16 (4 bit/symbol) (16k-chip cyclic right shift, across the 16 sequences)
Lower bit rate scalability Symbol Repetition
Modulation 1,-1, 0 ternary pulses
Total simultaneous piconets supported gt6
Multple access for piconets CDM (fixed code per piconet)
35
Multipath Performance (1 Mbps, 1500MHz BW)

• Random Transmit scrambling seq.
• Coherent and energy detectors
• AWGN, CM1 CM8
• 1-Rake 4-Rake
• Ideal Channel acquisition timing estimation
• Benefit of ½ rate CC not obvious in isolated
  piconet operation advantage may be in SOP
  operation

36
SOP Multipath (1 Mbps, 1500MHz BW)
To be provided later
37
Proposed Optional Wider Band System (Max Bit
Rate)
Bandwidth 1488 MHz
Pulse Rep. Freq. 124 MHz
Chip / symbol (Preamble) 127
Chip / symbol (Comms.) 32 (identical to that for 500MHz system)
Channel coding e.g. Conv code K 3, r2/3
Symbol Rate 124/32 MHz 3.875 MSps
coded bit / sym 4 coded bit / symbol
Max bit rate 2/3 x 4 bit/sym x 3.875 MSps 10.33 Mbps
Code Sequences for Ternary Orthogonal Keying 16 (4 bit/symbol) (identical to that for 500MHz system)
Modulation 1,-1, 0 ternary pulses
Total simultaneous piconets supported gt6
Multple access for piconets CDM (fixed code per piconet)
38
Multipath Performance (10 Mbps, 1500MHz BW)

• Random Transmit scrambling seq.
• Coherent and energy detectors
• AWGN, CM1 CM8
• 1-Rake 4-Rake
• Ideal Channel acquisition timing estimation
• Benefit of ½ rate CC not obvious in isolated
  piconet operation advantage may be in SOP
  operation

39
Summary

• The proposed Impulse-radio based system
• has ternary signaling only that
• Can be received simultaneously by different types
  of receivers, namely coherent, differential, and
  energy detectors
• Can be used for both Preamble and Comm.
  simultaneously
• Synchronisation Ranging Repeated Ternary Base
  Sequence for preambles
• Simple sliding correlator can be used for Ranging
  Sync
• Data Communications 4bit/symbol Ternary
  Orthogonal Keying Symbol (with cyclic shift
  version of base sequence zero padding)
• Good coding gain due to M-ary orthogonal keying
• Is robust against SOP interference due to high
  spreading gain per symbol