1. June 14th, 2005
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: TG4a Review of Proposed UWB-PHY Modulation Schemes and Selection Criteria
Date Submitted: June 14, 2005
Source: Gian Mario Maggio & Philippe Rouzet (STMicroelectronics)
Contact: Gian Mario Maggio
Voice: ,
Abstract: Review of modulations/waveforms for TG4a UWB-PHY standard and proposed selection criteria
Purpose: To provide information for further investigation on and selection of the modulation/waveforms for the UWB-PHY
Notice: This document has been prepared to assist the IEEE P 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 P
Gian Mario Maggio; Philippe Rouzet (STM)

2. IEEE 802.15.4a: UWB-PHY Modulation
June 14th, 2005
IEEE a: UWB-PHY Modulation
UWB-PHY Modulation Subgroup
Gian Mario Maggio & Philippe Rouzet
Gian Mario Maggio; Philippe Rouzet (STM)

3. List of Contributors/Documents
June 14th, 2005
List of Contributors/Documents
Gian Mario Maggio & Philippe Rouzet - STMicroelectronics ( a)
Matt Welborn – Freescale ( a)
Francois Chin et al. – I2R ( a)
Huang-Ban Li et al. – NICT ( a)
Ismail Lakkis & Saeid Safavi – Wideband Access ( a)
Phil Orlik, Andy Molisch et al. - MERL ( a)
Gian Mario Maggio; Philippe Rouzet (STM)

4. Topics for Discussion Pulse shaping Modulation formats Waveform design
June 14th, 2005
Topics for Discussion
Pulse shaping
Modulation formats
Waveform design
Design parameters
Adaptive modulation
& coding
Selection Criteria
Receiver Architecture
Simulation Results
ACTION LIST
UWB-PHY GROUP
Gian Mario Maggio; Philippe Rouzet (STM)

5. UWB-PHY: Introduction
June 14th, 2005
UWB-PHY: Introduction
Impulse-radio based (pulse-shape independent)
Support for different RX architectures:
Coherent
Differentially-coherent
Non-coherent
Support for multiple rates
Support for SOP
Gian Mario Maggio; Philippe Rouzet (STM)

6. June 14th, 2005
UWB Terminology (ITU)
Ultra-wideband (UWB) emission: Broadband emissions having B–10 (–10 dB bandwidth) of at least 500 MHz or greater than 0.2
Activity factor: Fraction of time during which an UWB device is actively transmitting
UWB pulse (or impulse): Signal with a time duration of 1/B–10
Pulse transmitter duty cycle: Ratio of the impulse duration to the time between the start of two adjacent impulses
Burst: Group of pulses (emitted signal with time duration greater than 1/B–10)
Proposed definitions:
Frame time (Tf): Time reference interval, comprising Nc chips
Chip time (Tc): Elementary time unit (in the frame)
Symbol: Group of pulses/bursts, spanning multiple (Nf) frames
Gian Mario Maggio; Philippe Rouzet (STM)

7. Pulse Shaping Pulse shape:
June 14th, 2005
Pulse Shaping
Pulse shape:
a) Gaussian
b) Raised cosine
c) Chaotic
d) Chirp ….
Optional: Variable pulse shapes with SSA (Soft Spectrum Adaptation)
Pulse duration: Lower bound set by bandwidth occupation (e.g. 500 MHz); Upper bound may be set according to design considerations
Pulse amplitude: Peak-to-peak voltage limited by CMOS technology
Gian Mario Maggio; Philippe Rouzet (STM)

8. June 14th, 2005
Definitions
Coherent RX: The phase of the received carrier waveform is known, and utilized for demodulation
Differentially-coherent RX: The carrier phase of the previous signaling interval is used as phase reference for demodulation
Non-coherent RX: The phase information (e.g. pulse polarity) is unknown at the receiver
- operates as an energy collector
- or as an amplitude detector
Gian Mario Maggio; Philippe Rouzet (STM)

9. Pros/Cons of RX Architectures
June 14th, 2005
Pros/Cons of RX Architectures
Coherent
+ : Sensitivity
+ : Use of polarity to carry data
+ : Optimal processing gain achievable
- : Complexity of channel estimation and RAKE receiver
Differentially-Coherent (or using Transmitted Reference)
+ : Gives a reference for faster channel estimation (coherent approach)
+ : No channel estimation (non-coherent approach)
- : Asymptotic loss of 3dB for transmitted reference (not for DPSK)
Non-coherent
+ : Low complexity
+ : Acquisition speed
- : Sensitivity, robustness to SOP and interferers
Gian Mario Maggio; Philippe Rouzet (STM)

10. Modulation Format(s) Simple, scalable modulation format
June 14th, 2005
Modulation Format(s)
Simple, scalable modulation format
One mandatory mode plus one or more optional modulation modes
Modulation compatible with multiple coherent/non-coherent receiver schemes  Flexibility for system designer
Time hopping (TH) for spectral smoothing and to permit multiple access
Gian Mario Maggio; Philippe Rouzet (STM)

11. Time Hopping-IR: Basics
June 14th, 2005
Time Hopping-IR: Basics Ts Tc Tf +1 -1
Each symbol represented by sequence of very short pulses
Each user uses different PN sequences (for multiple access)
Spectrum mostly determined by pulse shape
Gian Mario Maggio; Philippe Rouzet (STM)

12. June 14th, 2005
Waveform Design
Combination of (outer) TH and BPPM, combined with BPSK/DBPSK
Guarantee coexistence of coherent and non-coherent RX architectures:
Non-coherent receivers just look for energy in the early or late slots to decode the bit (BPPM); OOK receiver may be used to demodulate BPPM symbol as well
Coherent and differentially-coherent receivers, in addition, understand the fine symbol structure (BPSK or DBPSK)
Principle: Non-coherent and differentially-coherent modes should not penalize coherent-RX performance
Gian Mario Maggio; Philippe Rouzet (STM)

13. Central Timing Control
June 14th, 2005
RX Coexistence
Rake Receiver
Finger Np
Finger 2
Finger 1
Summer
Pulse Gen.
TH Seq
BPSK symbol mapper
Delay
Central Timing Control
Multiplexer
Coherent RX Td TX
Differentially-Coherent RX
( )2
Non-Coherent RX
Gian Mario Maggio; Philippe Rouzet (STM)

14. Mitigation of Peak-Voltage through Multi-Pulses
June 14th, 2005
Mitigation of Peak-Voltage through Multi-Pulses
Tf=PPI
ppV = peak-to-peak voltage
M = 1
IS « EQUIVALENT » TO
Tf=PPI
M = 4
ppV/2
Tf=PPI
M = 2
ppV/sqrt(2)
Gian Mario Maggio; Philippe Rouzet (STM)

15. BPPM Symbol Structure Doublet-based symbol Burst-based symbol
June 14th, 2005
BPPM Symbol Structure
Doublet-based symbol
Realization 1a: TH-IR + TR
(the whole TR symbol is BPPM modulated)
Realization 2a: TR + Inner TH
(apply TH code to each frame)
Realization 3a: Diff. encoding + Inner TH
(doublets with memory from previous bit)
Burst-based symbol
Realization 2a: Generalized TR
(one reference pulse, multiple information pulses)
Realization 2b: “CDMA-like” burst
(burst of pulses, modulated by a spreading code)
Gian Mario Maggio; Philippe Rouzet (STM)

16. (1) Transmitted-Reference: Basics
June 14th, 2005
(1) Transmitted-Reference: Basics Td
data Ts Tc Tf +1 -1
reference
First pulse serves as template for estimating channel distortions
Second pulse carries information
Drawback: Waste of 3dB energy on reference pulses
Gian Mario Maggio; Philippe Rouzet (STM)

17. (1a) Example - Signal Waveforms
June 14th, 2005
(1a) Example - Signal Waveforms Ts
« 11 »
« 01 »
2-PPM + TR base
M = 2
(with two bits/symbol)
« 10 »
« 00 »
(coherent decoding possible)
2-PPM + 16 chips 2-ary TH code
Time hopping code is (2,2) code of length 8/16, can be exploited by non-coherent RX
Effectively, 28 or 216 codes to select for channelization for non-coherent scheme
Gian Mario Maggio; Philippe Rouzet (STM)

18. (1a) Detailed Symbol Structure
June 14th, 2005
(1a) Detailed Symbol Structure Ts
« 0 » Td
negative
positive
Same polarity : bit = 0 Th
Inner time hop of Tdelta = 2 Th
Outer time hop of Tc = Tf/2 = n*Th Tc Tf
Tdelay
Gian Mario Maggio; Philippe Rouzet (STM)

19. (1b) Example - Signal Waveforms
June 14th, 2005
(1b) Example - Signal Waveforms Ts
« 11 »
2-PPM + TR base
M = 2
One bit/symbol
« 01 »
« 10 »
« 00 »
2-PPM + 16 chips 2-ary TH code
or 2-PPM + 8 chips 4-ary TH code
(coherent decoding possible)
Time hopping code is (2,2) code of length 8/16, can be exploited by non-coherent RX
Effectively, 28 or 216 codes to select for channelization for non-coherent scheme
Gian Mario Maggio; Philippe Rouzet (STM)

20. (1b) Detailed Symbol Structure
June 14th, 2005
(1b) Detailed Symbol Structure Ts
Outer time hop of Tc = Tf/2 = n*Th Tf
Same polarity : bit = 0
Same polarity : bit = 0
« 0 » Th
Inner time hop of Tdelta = 2 Th
+ inner polarity hop
negative
positive Td Tx Tx
Tdelay Tc
Gian Mario Maggio; Philippe Rouzet (STM)

21. (1c) Differential Encoding: Basics
June 14th, 2005
(1c) Differential Encoding: Basics
b-1 b0 b1 b2 b3 b4 b5
Tx Bits
Reference Polarity Ts
Gian Mario Maggio; Philippe Rouzet (STM)

22. (1c) Example - Signal Waveforms
June 14th, 2005
(1c) Example - Signal Waveforms
bi-1 = 1, bi = 1
bi-1 = 0, bi = 1
bi-1 = 0, bi = 0
bi-1 = 1, bi = 0
Use of doublets with memory from previous bit (encoding of reference pulse with previous bit)
Gian Mario Maggio; Philippe Rouzet (STM)

23. Pulse Shift, polarity invert
June 14th, 2005
(2a) Generalized TR
Basic Mode
(as seen by non-coherent)
« 1 »
τdelay +τΔ D
Enhanced Mode D
« 1 1 »
« 1 0 »
τdelay +τΔ
Pulse Shift, polarity invert
τΔ + τdelay
τΔ + τdelay τΔ
τdelay
τdelay τΔ
τΔ + τdelay
τΔ + τdelay
TH Pattern
TH Code , , , , , ,1
Data , , , , , ,0
Gian Mario Maggio; Philippe Rouzet (STM)

24. (2b) “CDMA-Like” Burst June 14th, 2005 One BPPM symbol
Similar signal using 31-pulse sequence
Can use coherent or non-coherent receiver
Can use PPM/OOK by sending pulse burst in
Either first or second bit location
One BPPM symbol
Gian Mario Maggio; Philippe Rouzet (STM)

25. (2b) Example: 31-Chip Code
November 18
doc.: IEEE /424r1
June 14th, 2005
(2b) Example: 31-Chip Code
Symbol
Cyclic shift to right by n chips, n=
31-Chip value 00 01 8 11 16 10 24
Can support both coherent and non-coherent pulse compression
Add 33 zero chips to get baseline mode for non-coherent receivers
Note: In general, careful code design is needed for spectral shaping
Gian Mario Maggio; Philippe Rouzet (STM)
Stuart J. Kerry - Philips Semiconductors, Inc.

26. Design Parameters (1/3) Pulse Repetition Period (PRP)
June 14th, 2005
Design Parameters (1/3)
Pulse Repetition Period (PRP)
Realization #1:
1a) PRP = 100 ns
1b) PRP = 40 ns
1c) PRP = 40 ns
Burst Repetition Period (BRP)
Realization #2:
2a) BRP ≥ 200 ns
2b) BRP = 436 ns
Inter-pulse interval:
Minimum: ~5 ns (technology constraint)
Realization #1: ~20 ns
Realization #2(b): ~4.5 ns
Note (TR): Max realizable analog delay ~10 ns
Gian Mario Maggio; Philippe Rouzet (STM)

27. Design Parameters (2/3) Time-hopping: Polarity hopping:
June 14th, 2005
Design Parameters (2/3)
Time-hopping:
TH code (outer): 2-ary (or M-ary in general, for better SOP support) of length 4-16; granularity level ~Tf/2 (or Tf/M)
Inner TH code (Realization #1b,c): Apply inner TH code (frame-by-frame) down to 2 ns (or multiples) granularity level
Polarity hopping:
May be applied on top, for spectral smoothing purposes and/or signals separation
Gian Mario Maggio; Philippe Rouzet (STM)

28. Design Parameters (3/3) Channelization Multi-access capabilities:
June 14th, 2005
Design Parameters (3/3)
Channelization
Coherent schemes: Use of TH codes and polarity codes
Non-coherent schemes: Use of TH codes (polarity codes for spectrum smoothing only)
Realization 2b): CDMA
Multi-access capabilities:
Max # of coexisting users within piconet
SOP support:
Up to 6 SOP/band
Gian Mario Maggio; Philippe Rouzet (STM)

29. Adaptive Modulation & Coding
June 14th, 2005
Adaptive Modulation & Coding
Adaptive modulation: Enhanced modes (available for coherent receiver)
Adaptive PRP: Two PRP values supported
Adaptive processing gain: Variable TH code length (variable number of pulses/bit)
Adaptive coding rate (e.g. by acting on the puncturing associated with a convolutional code)
Gian Mario Maggio; Philippe Rouzet (STM)

30. Optional: Encoding of “Extra”-Bits
June 14th, 2005
Optional: Encoding of “Extra”-Bits
x1=bk bk
Convolutional
Encoder x2
Example: Rate-½ convolutional encoder
Produce multiple coded bits from each data bit
Special case of convolutional code is a “systematic” code
First coded bit is same as input data bit
Second coded bit is computed by encoder
Mapping coded bits to waveform
Map first coded bit (systematic bit) into position for BPPM
Map second coded bit into TR symbol
Can be extended to more general (non-systematic) codes very easily
Gian Mario Maggio; Philippe Rouzet (STM)

31. Proposed Selection Criteria (Validated by Simulation)
June 14th, 2005
Proposed Selection Criteria (Validated by Simulation)
BER/PER performance with 15.4a channel (with rate ½ convolutional code) with/without SOP (up to 6)
Support #users/piconet; SOP isolation (max #SOP)
Resilience to multipath, ISI, and narrow-band interference
Receiver flexibility: Support for coherent, diff. coherent and non-coherent RX
Coherent vs. non-coherent performance (including OOK)
Time-domain: TPAR (temporal peak-to-average ratio)
Spectrum: SPAR (spectral peak-to-average ratio)
Scalability: Trade-off performance vs. complexity
 Goal: Select mandatory mode, optional modes and determine optimal symbol waveform, PRP, TH code/length, etc.
Cross sub-group considerations: Ranging performance, acquisition, pulse compression, band-plan compliance, etc.
Gian Mario Maggio; Philippe Rouzet (STM)

32. (Extra-Slides: Support for Discussion)
June 14th, 2005
ANNEX
(Extra-Slides: Support for Discussion)
Gian Mario Maggio; Philippe Rouzet (STM)

33. Coherent Receiver: RAKE Receiver
June 14th, 2005
Coherent Receiver: RAKE Receiver
Channel Estimation
Rake Receiver
Finger 1
Demultiplexer
Rake Receiver
Finger 2
Sequence
Detector
Convolutional
Decoder
Summer
Data
Sink
Rake Receiver
Finger Np
Addition of Sequence Detector – Proposed modulation may be viewed as having memory of length 2
Main component of Rake finger: pulse generator
A/D converter: 3-bit, operating at symbol rate
No adjustable delay elements required
Gian Mario Maggio; Philippe Rouzet (STM)

34. Differentially-Coherent Receiver (for Transmitted Reference)
June 14th, 2005
Differentially-Coherent Receiver (for Transmitted Reference)
Matched
Filter
Convolutional
Decoder Td
Note: Addition of Matched Filter prior to Delay & Correlation operations improves output SNR and reduces noise-noise cross terms
Gian Mario Maggio; Philippe Rouzet (STM)

35. Non-Coherent Receiver (Energy Collector)
June 14th, 2005
Non-Coherent Receiver (Energy Collector)
Band Matched
LNA
BPF
Tracking
Thresholds setting
Dump
Latch
RAZ
DUMP
Controlled
Integrator
ADC
BPPM Demodulation branch x2
r(t)
Gian Mario Maggio; Philippe Rouzet (STM)

36. De-Spreading TH Codes June 14th, 2005 Band Matched TH r(t)
Sequence Matched
Filter
r(t)
LNA
BPF
Bit Demodulation
ADC
Case I - Coherent TH de-spreading
Band Matched TH
Sequence Matched
Filter
r(t)
Bit Demodulation
b(t)
soft info
LNA
BPF
ADC
Case II – Non-coherent / differential TH despreading
Gian Mario Maggio; Philippe Rouzet (STM)

37. TR-BPSK  Non-Coherent Detection
June 14th, 2005
TR-BPSK  Non-Coherent Detection
Idea: Transmitted-reference BPSK symbol can be decoded by a non-coherent detector (like OOK symbol)
Advantages: Differential and non-coherent receiver may coexist
Concept can be generalized to N-ary TR-BPSK
Pulse Matched
f(t)
s(t)
r(t)
“0”
“1”
LNA
Delay D
BPF
Non-Coherent Detector
(Energy Collection) -
Synchro
Tracking
Thresholds setting
Gian Mario Maggio; Philippe Rouzet (STM)

38. TR-BPPM Schemes Comparison (1/2)
June 14th, 2005
TR-BPPM Schemes Comparison (1/2)
Notes:
Results are theoretical calculations
Assumes ideal ”impulse” UWB pulses in AWGN channel
Different TR-BBPM options are considered with different number of pulses per pulse train
Multipath fading simulations can be performed to back up theory
Gian Mario Maggio; Philippe Rouzet (STM)

39. TR-BPPM Schemes Comparison (2/2)
June 14th, 2005
TR-BPPM Schemes Comparison (2/2)
Parameters:
PPI slot - slot inside each TH chip containing a burst of pulses including reference pulses
Np represents the number of pulses in each PPI slot
The energy E per PPI slot is kept constant
The pulse energy Ep = E/Np
TW represent the time-bandwidth product
Gian Mario Maggio; Philippe Rouzet (STM)

40. Pulse Repetition Structures- Scheme 1 TR-BPPM with doublets
June 14th, 2005
Pulse Repetition Structures- Scheme 1 TR-BPPM with doublets
Gian Mario Maggio; Philippe Rouzet (STM)

41. Pulse Repetition Structures - Scheme 2 TR-BPPM single reference
June 14th, 2005
Pulse Repetition Structures - Scheme 2 TR-BPPM single reference
Gian Mario Maggio; Philippe Rouzet (STM)

42. June 14th, 2005
Pulse Repetition Structures - Scheme 3 Auto Correlation BPPM with doublets
Gian Mario Maggio; Philippe Rouzet (STM)

43. June 14th, 2005
Pulse Repetition Structures - Scheme 4 Auto Correlation BPPM single reference
Gian Mario Maggio; Philippe Rouzet (STM)

44. Pulse Repetition Structures - Scheme 5 Auto Correlation BPPM alternate
June 14th, 2005
Pulse Repetition Structures - Scheme 5 Auto Correlation BPPM alternate
Scheme 5: “AC Alternate” performs better then all the other pulse repetition structures
AC generally performs better than TR
“AC alternate” and “AC with doublets” require a single delay
Gian Mario Maggio; Philippe Rouzet (STM)