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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: TG4a UWB-PHY overview. Date Submitted: November 30, 2005 Source: Gian Mario Maggio (STMicroelectronics) Contact: Gian Mario Maggio

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Project ieee p802 15 working group for wireless personal area networks wpans

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

Submission Title: TG4a UWB-PHY overview.

Date Submitted: November 30, 2005

Source: Gian Mario Maggio (STMicroelectronics)

Contact: Gian Mario Maggio

Voice: +41-22-929-6917, E-Mail: [email protected]

Abstract: Review of the 802.15.4a UWB-PHY.

Purpose:To provide a summary of the current status of the 802.15.4a UWB-PHY and an outlook of the future TG4a work for this portion of the standard.

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.

Gian Mario Maggio (ST)


802 15 4a uwb phy

802.15.4a UWB-PHY

(http://www.ieee802.org/15/pub/TG4a.html)

Gian Mario Maggio

STMicroelectronics

November 30th, 2005

Gian Mario Maggio (ST)


Outline

Outline

  • IEEE 802.15.4a

  • UWB-PHY

  • Band-plan

  • Data rates

  • Preamble

  • Modulation

  • Spreading

  • Coding

  • Waveforms

Gian Mario Maggio (ST)


802 15 4a overview

802.15.4a Overview

Gian Mario Maggio (ST)


802 15 4a introduction

802.15.4a: Introduction

  • The IEEE 802.15 Low Rate Alternative PHY Task Group (TG4a) for Wireless Personal Area Networks (WPANs) has defined a project for an amendment to 802.15.4 for an alternative PHY

  • The main interest is in providing communications and high-precision ranging/localization capability (1 meter accuracy), high aggregate throughput; as well as adding scalability to data rates, longer range, and lower power consumption and cost

  • These additional capabilities over the existing 802.15.4 standard are expected to enable significant new applications and market opportunities

Gian Mario Maggio (ST)


802 15 4a short history

802.15.4a: Short History

  • 802.15.4a became an official TG in March 2004 (committee work tracing back to November 2002)

  • The committee is actively drafting an alternate PHY specification for the applications identified

  • In March 2005, the baseline specification was selected (without enacting down-selection procedures)  baseline with 100% approval

  • The baseline is two optional PHYs consisting of:

    • UWB Impulse Radio (operating in unlicensed UWB spectrum)

    • Chirp Spread Spectrum (operating in unlicensed 2.4GHz spectrum)

  • The UWB Impulse Radio will be able to deliver communications and high precision ranging

Gian Mario Maggio (ST)


802 15 4a schedule

802.15.4a: Schedule

Gian Mario Maggio (ST)


Tg4a working groups

TG4a Working Groups

UWB-PHY (P. Rouzet – ST)

 P. Orlik (MERL)/I. Lakkis (Novowave)

CSS-PHY (J. Lampe – Nanotron)

Sub-GHz (P. Houghton – AetherWire)

Ranging (V. Brethour – Time Domain)

Channel Modeling (A. Molisch – MERL)

MAC (J. Bain – Fearn Consulting )

Gian Mario Maggio (ST)


Uwb phy sub groups

UWB-PHY Sub-groups

Bandplan TSE: Saeid Safavi

Pulse modulation TSE: Phil Orlik

Pulse compression TSE: Ismail Lakkis

Simulation TSE: Matt Wellborn

Sub-GHz UWB-PHY TSE: Mark Jamtgaard

Liaison to IEEE 802.19 Patricia Martigne

Gian Mario Maggio (ST)


Uwb phy introduction

UWB-PHY: Introduction

  • Impulse-radio based (pulse-shape independent)

  • Support for different receiver architectures (coherent/non-coherent)

  • Flexible modulation format

  • Support for multiple rates

  • Support for SOP (simultaneously operating piconets)

Gian Mario Maggio (ST)


Operating frequency range band plan

Operating Frequency Range(Band-Plan)

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Band plan

Band-Plan

  • The UWB-PHY operates in the frequency range from 3211–4693 MHz (LFB) and, optionally, from 5931.9-10304.25 MHz (HFB)

  • LFB: A compliant device shall be capable of transmitting in the mandatory channel #2 (*) with a 3dB-bandwidth of 494MHz

  • HFB: Transmission in all other frequency band is optional

    • If transmission in HFB is desired then a transmitter shall be capable of transmitting in channel #8 (*)

(*) See next slide for channels assignment

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Channels assignment

Channels Assignment

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Lfb band plan

4

111 MHz

207 MHz

2

1

2

3

fGHz

3.00 3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00

LFB Band-Plan

Gian Mario Maggio (ST)


Hfb band plan

13

14

15

4

4

4

-41.3

5

6

7

8

9

10

11

12

PSD dBm/MHz

-70

fGHz

6.00 6.25 6.50 6.75 7.00 7.25 7.50 7.75 8.00 8.25 8.50 8.75 9.00 9.25 9.50 9.75 10.00 10.25 10.50 10.75

HFB Band-Plan

Gian Mario Maggio (ST)


Lfb pll reference diagram

Oscillator

Reference

Divider

÷ R

Phase

Detector

LPF

VCO

fcomp

fc

fX

÷ N

÷ M

fs = 494 MHz

LFB: PLL Reference Diagram

XTAL

Gian Mario Maggio (ST)


Hfb pll reference diagram

Oscillator

Reference

Divider

÷ R

Phase

Detector

LPF

VCO

fcomp

fX

fc, high band

XTAL

÷ N

÷ 2

fs = 1352 MHz via ÷ 3

÷ M

fs = 507 MHz

HFB: PLL Reference Diagram

fc, low band

Gian Mario Maggio (ST)


Hfb remarks

507MHz

15.84375MHz

7.921875MHz

253.5MHz

÷ 2

÷ 16

÷ 2

HFB: Remarks

  • Use of the “free spectrums” of both Japan and EU (OFCOM)

  • Integer product relationship between center frequencies and PRF

  • Harmonization with the accepted low frequency band plan (Use of the same PRF)

  • A single PLL can generate all necessary frequencies using direct synthesis

  • The supported PRFs range from 507 MHz to 3.9609375 MHz through simple division by a power of 2:

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Data rates

Data Rates

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Data rates1

Data Rates

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Optional 100 kb s data rate

Optional: ~100 kb/s Data Rate

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Ranging acquisition preamble

Ranging/Acquisition Preamble

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Preamble symbol

Preamble Symbol

  • The preamble field is used by the transceiver for:

    • Acquisition: to obtain chip and symbol synchronization with an incoming message

    • Ranging: to acquire/track signal leading edge

Gian Mario Maggio (ST)


Preamble length

Preamble Length

  • The adopted preamble lengths (symbols) are 64, 256, 1024, 4096:

    + Optional (short) length-16 preamble for improved energy efficiency in high data-rate communications

Gian Mario Maggio (ST)


Preamble codes length 31

Preamble Codes: Length-31

  • PBTS (Perfect Balanced Ternary Sequences) are adopted as ranging/acquisition codes, Si

  • The code can be selected from length-31 or length-127 PTBS

  • Length-31 ternary codes:

  • Note: These are the six codes with the best cross-correlation of the 12 possible codes with perfect periodic auto-correlation

Gian Mario Maggio (ST)


Preamble codes length 127

Preamble Codes: Length-127

  • Length-127 ternary codes:

  • Note: These are the 26 codes with perfect periodic autocorrelation and best cross-correlation properties

Gian Mario Maggio (ST)


Auto correlation cross correlation l 31

Auto-correlation & Cross-correlation (L = 31)

Gian Mario Maggio (ST)


Preamble structure

Preamble Structure

Preamble

Header

Payload

  • Two forms of preamble are supported:

    • Normal preamble

    • Preamble for ~100 kb/s

  • SYNC: Synchronization Field

  • SFD: Start Frame Delimiter Field

  • CE: Channel Estimation Field

SYNC/CE

SYNC

SFD

Si

Si

Si

Si

Si

Si

-Si

0

- Si

0

-Si

0

-Si

0

(a)

or

Si

Si

Si

Si

Si

Si

-Si

-Si

0

0

-Si

-Si

0

0

(b)

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Preamble parameters l 31

Preamble Parameters (L=31)

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Preamble parameters l 127

Preamble Parameters (L=127)

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Definitions

Definitions

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Project ieee p802 15 working group for wireless personal area networks wpans

PRF Definition

Pulse Repetition Interval

1

2

3

4

5

6

7

8

N-1

N

…………………………

Non-inverted pulses are blue,

Inverted pulses are green.

Pulse Width, Tc

~ 4ns @ 500MHz BW

……………………….................

……………

Quiet time

Active time

Symbol Interval

Gian Mario Maggio (ST)


Pulse repetition frequency

Pulse Repetition Frequency

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Minimum prf requirements

Minimum PRF Requirements

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Prf preamble data harmonization

Data

Preamble

Peak Preamble PRF = ~ 31 MHz

(actually 494/16)

Peak Preamble PRF = 494 MHz

PRF: Preamble & Data Harmonization

Average Preamble PRF

~ 16 MHz (actually 494/31)

 every 1uS, 16 pulses

Average Data PRF

~ 16 MHz

1uS 16 pulses

 This maintains same pulse amplitude for Preamble and Data!

Gian Mario Maggio (ST)


Modulation

Modulation

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Baseline modulation

Baseline Modulation

  • 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) to achieve multiple access

Gian Mario Maggio (ST)


Modulation format

Modulation Format

  • The UWB-PHY is required to support both coherent and non-coherent receivers

  • The modulation format is a combination of Pulse Position Modulation (PPM) and Binary Phase Shift Keying (BPSK)

  • A UWB PHY symbol is capable of carrying two bits of information: one bit is used to determine the position of a burst of pulses while an additional bit is used to modulate the phase (polarity) of this same burst

Gian Mario Maggio (ST)


Chip rate

Chip Rate

  • The UWB-PHY uses an IR-based signaling scheme in which each information-bearing symbol is represented by a sequence/burst of short time duration pluses

  • The duration of an individual pulse is nominally considered to be the length of a chip

  • Chip duration is equal to 2.02429 ns or a chipping rate of 494MHz

Gian Mario Maggio (ST)


Modulation1

47

47

47

47

48

48

48

48

0

0

0

0

1

1

1

1

31

31

31

31

32

32

32

32

33

33

33

33

63

63

63

63

15

15

15

15

16

16

16

16

burst

PPI

symbol duration

Modulation

PPM bit (seen by coherent and non coherent receiver)

BPSK bit (seen by coherent receiver only)

S

-S

S

-S

Gian Mario Maggio (ST)


Symbol structure

S = +--+-++-

=

S

1 chip ~ 2 ns

burst duration

symbol duration

Symbol Structure

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Reference modulator

Reference Modulator

Note: “Input Data” is after FEC coding

Gian Mario Maggio (ST)


Receiver architecture

Receiver Architecture

Gian Mario Maggio (ST)


Modulation parameters

Modulation Parameters

  • Mandatory data rate:

  • Optional data rates @PRF=15.94 MHz

  • Optional data rates @PRF=3.98 MHz

Gian Mario Maggio (ST)


Spreading

Spreading

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Spreading1

Spreading

  • In addition to the data modulation, the UWB-PHY symbol provides for some multi-user access interference rejection in the form of TH

  • Each symbol contains a single burst of pulses and the burst length is typically much shorter than the duration of the symbol

  • The location of the pulse within each burst can be varied on a symbol-to-symbol basis according to a TH code

  • This is part of the functionality provided by the “Scrambler and Burst Position Hopping”

Gian Mario Maggio (ST)


Scrambling

Scrambling

  • The constituent pulses in each burst are scrambled by applying a time varying scrambling sequence

  • This scrambler is a pseudo-random binary sequence (PRBS) defined by a polynomial generator.

  • The polynomial generator, g(D), for the pseudo-random binary sequence (PRBS) generator is g(D) = 1 + D14 + D15, where D is a single bit delay element.

  • The polynomial not only forms a maximal length sequence, but is also a primitive polynomial. Using this generator polynomial, the corresponding PRBS, sj, is generated as

    where “” denotes modulo-2 addition

Gian Mario Maggio (ST)


Scrambler

Scrambler

  • Scrambler linear feedback shift register:

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Time hopping

Time Hopping

  • The hopping sequence is derived from the same linear feedback shift registers by using the output of the first three registers

  • When each symbol, x(k)(t), is generated, the spreader is run for Nburst cycles  the Nburstconsecutive outputs of the spreader are the spreading sequence for the symbol (sj, j = 1,2, …, Nburst)

  • The current hopping position, h(k) is determined by the following equation:

  • The state variables are sampled at the start of the transmission of the current modulation symbol

Gian Mario Maggio (ST)


Spreading2

S

S

S

S

47

47

47

47

48

48

48

48

0

0

0

0

1

1

1

1

31

31

31

31

32

32

32

32

33

33

33

33

63

63

63

63

15

15

15

15

16

16

16

16

-S

-S

-S

-S

S

S

S

-S

-S

-S

Spreading

possible positions obtained through scrambling

Guard time for channel delay spread (260ns)

S

-S

S

-S

Note: S value is also changed at each symbol

Gian Mario Maggio (ST)


Project ieee p802 15 working group for wireless personal area networks wpans

FEC

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Project ieee p802 15 working group for wireless personal area networks wpans

FEC

  • The FEC used by the UWB PHY is a concatenated code consiting of an outer Reed-Solomon (RS) systematic block code and an inner systematic convolutional code

  • No interleaver is required

  • The outer RS code is a RS6(K+8,K) over Galois field GF(26)

  • The systematic Reed Solomon code uses the generator polynomial:

    where a= 010000 is a root of the binary primitive polynomial 1+x+x6 in GF(26)

  • Both RS encoding with default codeword operation (K = 55) and shortened codeword operation are required

Gian Mario Maggio (ST)


Modulation coding mandatory data rate

Modulation & Coding–Mandatory Data Rate

Gian Mario Maggio (ST)


Uwb phy symbol

UWB-PHY Symbol

  • The UWB-PHY supports two average Pulse Repetition Frequencies (PRF):

    • HPRF=15.4375MHz

    • LPRF=3.859375MHz

  • These PRFs in addition to the data rate, modulation and coding rate determines the overall timing of a UWB-PHY symbol

Gian Mario Maggio (ST)


Symbol mapping

Symbol Mapping

  • The UWB-PHY map groups two consecutive bits into modulation symbols, as follows:

Gian Mario Maggio (ST)


Project ieee p802 15 working group for wireless personal area networks wpans

Gian Mario Maggio (ST)


Project ieee p802 15 working group for wireless personal area networks wpans

Reed Solomon

Primitive polynomial:

Generator polynomial:

FEC

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Fec soft decisions

FEC: Soft Decisions

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Modulation coding optional data rates

Modulation & Coding–Optional Data Rates

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Uwb phy symbol1

UWB-PHY Symbol

  • The additional data rates require that the # of pulses/burst are modified; this in turn alters the burst duration and other symbol parameters:

HPRF = 15.94 MHz

LPRF = 3.98 MHz

Gian Mario Maggio (ST)


Modulation format1

Modulation Format

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Project ieee p802 15 working group for wireless personal area networks wpans

Reed Solomon

Primitive polynomial:

Generator polynomial:

FEC

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Modulation coding options

Modulation & Coding Options

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Waveforms

Waveforms

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Pulse shaping

Pulse Shaping

  • The reference pulse, r(t), used by the UWB-PHY is a root raised cosine pulse with roll-off factor of = 0.6

  • Mathematically this is:

  • In order for a UWB-PHY transmitter to be compliant with the standard, the transmitted pulse must have a cross- correlation with r(t) that is greater or equal to 0.7 (-3dB)

Gian Mario Maggio (ST)


Optional wafeforms

Optional Wafeforms

  • Weighted linear combination of pulses

  • Chirp pulses (CoU)

  • Continuous Spectrum (CS) pulses

  • Chaotic pulses

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Weighted linear pulses combination

Weighted Linear Pulses-Combination

  • This optional pulse shape is the sum of N weighted and delayed “fundamental” pulses, p(t):

  • The number of pulses N is set to a fixed value of 4 (although some of the weights may be set to zero)

  • The values of the pulse delays shall be limited

  • Features:

    • Adaptive determination of weight and delay

    • Adaptive spectral shaping

    • Can adjust to interferers at different distances (required nulldepth) and frequencies

Gian Mario Maggio (ST)


Chirp on uwb 1 2

Chirp on UWB (1/2)

  • Additional dimension to support SOP

    • Chirp slopes and chirp patterns

    • Better performance than DS codes

    • Combination with FDM and/or CDM

  • Additional link margins

    • Low peak-to-average ratio.

  • Robustness against interference and multipath

    • Excellent correlation characteristics

  • Potential high-precision ranging

    • Excellent correlation characteristics

Main features:

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Chirp on uwb 2 2

Chirp on UWB (2/2)

  • Mathematical expression:

    where P(t) denotes the mandatory pulse and μ=B/T the chirping rate (chirping slope); B and T are the bandwidth and time duration of the chirped pulse

  • Raised cosine pulse:

Gian Mario Maggio (ST)


Project ieee p802 15 working group for wireless personal area networks wpans

Transmitter

BW = 494 MHz

FEC

Spreading

Pulse

shaping

GA

modulation

CHIRP

D

Local oscillator

Receiver

Pre-Select

Filter

De-spreading

Decision/

FEC decoder

LPF

GA

1 to 2-bit ADC

LNA

GA

LPF

1 to 2-bit

ADC

DE-

CHIRP

I

Local

oscillator

Sync.

Q

Additional circuits to DS-UWB as an option

Block Diagram With Optional CS

Gian Mario Maggio (ST)


Cs pulse 1 2

CS Pulse (1/2)

  • Mathematical expression:

  • where (f) is the group delay and:

  •  Examples:

Gaussian without CS

1ns/1GHz CS

5ns/1GHz CS

10ns/1GHz CS

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Cs pulse 2 2

CS Pulse (2/2)

  • Main features:

    • SOP support: CS filtering provides additional anti-interference ability (additionally larger SIR) w.r.t. DS

      Interference scenarios:

      CS CS: Piconets with different CS filtering can reduce the interference against each other

      DS  CS: Piconet with CS filtering can reduce the interference from DS-only piconets

      CS  DS: DS-only piconet receivers smaller interference from piconets with CS filtering

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Chaotic pulse

PRI

VPeak

Ts

TC

Chaotic Pulse

TG4a

Draft

Ts =~ 2 nsec. => Chip duration ≈ 2 ns (2.024291 ns)

-PRF of Chaotic pulse length(Ts) can be changed flexibly without altering the spectral shape or Band Plan

Bit 1

Bit -1 => Bit 1

Bit 0 => 0

Chaotic

Option 1

Unipolar

Ts

Ts =~ 30 nsec.

Bit 1 => Ref & (+Ref)

Bit -1 => Ref & (-Ref)

Bit 0 => 0

Chaotic

Option 2

Ternary

Ts

Ts =~ 30 nsec.

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Block diagram with chaos option

Block Diagram With Chaos Option

4.5 GHz

LO

Preamble

Ternary

Scrambler

BPSK.

MOD

MUX

Preamble

Data

Impulse

S/W

S/W

RF

Chaotic

Data

FEC

Scrambler

Code1

Cross Correlator

S/W

Decision

BPSK .

DEMOD

LPF

S/W

Code2

Cross Correlator

S/W

RF

Non-coherent

Detector

Chaotic Detector

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