March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

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: Mitubishi Electric Proposal Time-Hopping Impulse RadioDate Submitted: March 3rd, 2003Source: Andreas F. Molisch et al., Mitsubishi Electric Research LaboratoriesAddress MERL Murray Hill 558 Central Avenue Murray Hill, NJ 07974, USA Voice: +1 908 363 0524, FAX: +1 908 363 0550 , E-Mail: Andreas.Molisch@ieee.org

Re: [Response to Call for Proposals]

Abstract: We present a standards proposal for a high-data-rate physical layer of a Personal Area Network, using ultrawideband transmission. The air interface is based on time-hopping impulse radio, using BPSK for the modulation, and in addition polarity randomization of the pulses within the symbol. Combinations of delayed and weighted pulses allow an efficient shaping of the spectrum. This provides good suppression of interference, and guarantees fulfillment of coexistence requirements. The system is designed to have A/D conversion and digital processing only at the symbol rate, not the chip rate. Costs are comparable to Bluetooth.

Purpose: [Proposing a PHY-layer interface for standardization by 802.15.3a]

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.

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Ultra WideBand

Mitsubishi Electric Proposal

Time-Hopping Impulse Radio

A. F. Molisch, Y.-P. Nakache, P. Orlik, J. ZhangMitsubishi Electric Research Lab

S. Y. Kung, Y. Wu, H. Kobayashi, S. Gezici, E. Fishler, V. PoorPrinceton University

Y. G. LiGeorgia Institute of Technology

H. Sheng, A. HaimovichNew Jersey Institute of Technology

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Contents

– System overview – Physical-layer details– Performance evaluation

– Signal robustness

– Coexistence

– Cost analysis

– Summary and conclusions

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Goals and Solutions

• Commonly used technology Time hopping impulse radio

• Fulfillment of spectral mask, but full exploitation of allowed power. Interference suppression Linear combination of basis pulses

• Cheap implementation, robustness to multipath Few Rake fingers, all A/D conversion and computation done at

200MHz

• Scalability Multi-code transmission

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Creation of Proposal

• Proposal based on

– Scientific experience of leading research groups (Princeton, Georgia Tech, MERL, MELCO)

– Practical experience of high-quality product development team of Mitsubishi in USA and Japan

– Experience in hardware (RF components, antennas, semiconductor, applications,…..) and applications design

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Data Source

Demultiplexer

Convolutional Code

Sync. & Training Sequence

Timing Logic

Timing Logic

Central Timing Control

Pulse Gen.TH Seq.-1

Pulse Gen.TH Seq.-N

PolarityScrambler

PolarityScrambler

Convolutional Code

Power Control

Multiplexer

Multiplexer

Transmitter Structure

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Receiver Structure

Synchronization

Rake ReceiverFinger Np

AGC

Demultiplexer Rake ReceiverFinger 2

Rake ReceiverFinger 1

Summer

Timing Control Channel Estimation

MMSEEqualizer

Convolutional Decoder Data

Sink

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Contents

– System overview – Physical-layer details– Performance evaluation

– Achievable coverage

– Coexistence

– Cost analysis

– Summary and conclusions

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Spectral Shaping & Interference Suppression

• Basis pulse: fifth derivative of Gaussian pulse

• Drawbacks:– Loses 3dB compared to FCC-allowed power

– Strong radiation at 2.45 and 5.2 GHz

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Linear Pulse Combination

• Solution: linear combination of delayed, weighted pulses– Adaptive determination of weight and delay

– Number of pulses and delay range restricted

– Can adjust to interferers at different distances

(required nulldepth) and frequencies

• Weight/delay adaptation in two-step procedure• Initialization as solution to quadratic optimization problem (closed-

form)

• Refinement by back-propagating neural network

• Matched filter at receiver good spectrum helps coexistence and interference suppression

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Modulation and Multiple Access

• Multiple access:– Combination of pulse-position-hopping and polarity hopping for multiple

access– More degrees of freedom for design of good hopping sequence than pure

pulse-position-hopping– Short hopping sequences, to make equalizer implementation easier

• Modulation: BPSK

• Channel coding: – rate ½ convolutional code; – requires 6dB SNR for 10^-5 BER– Improvement by 3dB possible by turbo codes

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Rake Receiver

• Main component of Rake finger: pulse generator

• A/D converter: 3-bit, operating at 220Msamples/s

• No adjustable delay elements required

adj.weight

low-passfilter

programmablepulse gen.

programmablepulse gen.

programmablepulse gen.

rake finger

low-passfilter

low-passfilter

adj.weight

adj.weight

sample& A/D

sample& A/D

sample& A/D

sample timingcontroller

pulse sequencecontroller

Demultiplexer

Demultiplexer

Demultiplexer

Summer

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Synchronization

• Combination of MAC-Layer and PHY-Layer approach

• Beacon provides rough timing estimation (within runtime of the piconet diameter)

• Fine acquisition by transmission of synch pulses

• Acceleration of acquisition by Block Search algorithms

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Block Search Algorithms

• Steps in acquisition:– Find delay region where signal is likely to exist

– After finding it, search in more detail for first significant path

• Block search algorithm– Serial block search (SBS): integrate output of detector

over delay region (block), search for block with significant energy

– Average block search (ABS): average over absolute values of detector output

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Channel Estimation

• Swept delay correlator

• Principle: estimating only one channel sample per symbol. Similar concept as STDCC channel sounder of Cox (1973).

• Sampler, AD converter operating at SYMBOL frequency

• Requires longer training sequence

• Three-step procedure for estimating coefficients:– With lower accuracy: estimate at which taps energy is significant

– With higher accuracy: determine tap weights

– Determine effective channel seen by equalizer

• “Silence periods”: for estimation of interference

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Channel Estimator – Block Diagram

Σ

Adj.Weight

ReceiverFront End

Programmable Training Waveform Gen.

Timing Controller

Programmable Training Waveform Gen.

Programmable Training Waveform GEN.

Multiplier & Low-Pass Filter

Multiplier &Low-Pass Filter

Multiplier &Low-Pass Filter

Adj.Weight

Adj.Weight

MMSE Equalizer

Equalizer Estimator

Channel Estimator

EQ TrainingSequence

Coefficients

EQ Output

Rake receiver OutputRake Finger 1

Rake Finger 2

Rake Finger N

Channel Estimation Output

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Contents

– System overview – Physical-layer details– Performance evaluation

– Signal robustness

– Coexistence

– Cost analysis

– Summary and conclusions

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Link BudgetParameter Value

Throughput (Rb) > 110 Mb/s

Average Tx power (TP ) -3.5 dBm

Tx antenna gain (TG ) 0 dBi

maxmin' fff c : geometric center frequency of

waveform (minf and maxf are the -10 dB edges

of the waveform spectrum)

5.73GHz

Path loss at 1 meter ( )/4(log20 '101 cfL c )

8103c m/s

47.6 dB

Path loss at d m ( )(log20 102 dL ) 20 dB at d=10 meters

Rx antenna gain (RG ) 0 dBi

Rx power (21 LLGGPP RTTR (dB)) -71.1 dBm

Average noise power per bit ( )(log*10174 10 bRN )

-93.6 dBm

Rx Noise Figure Referred to the Antenna Terminal (

FN )1 11 dB

Average noise power per bit ( FN NNP ) -82.6 dBm

Minimum Eb/N0 (S) 6 dB

Implementation Loss2 (I) 3 dB

Link Margin ( ISPPM NR ) 2.5 dB

Proposed Min. Rx Sensitivity Level3 -73 dBm

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

PER as Function of Distance

AWG N

d is tan ce / m

Pac

ket e

rror

rat

eP E R a s fu n c tio n o f d is tan ce

C M 1

C M 2

C M 3

C M 4

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Probability of Link Success

d is tan ce / m

Pac

ket e

rror

rat

e

P ro b ab ility o f lin k su ccess

C M 1

C M 2

C M 3

C M 4

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Outage vs. SNR

90%

out

age

PE

R

C M 1

C M 2

C M 3

C M 4

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Signal Acquisition Time

A cq u is itio n tim e [m ic ro seco n d s]0 5 1 0 1 5 2 0 2 5 3 0 3 5 4 0

Pro

babi

lity

of

acqu

istio

n

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Susceptibility to Interference

• Piconets– All channels AWGN– Desired user: 6dB above sensitivity

• admissible distance of interferer: 2.5m– Desired user: 10m distance

• Admissible distance: 6m

• 802.11a: influence only when interferer less than 0.4m distance, in CM2

• 802.11b: no noticeable influence (even at 0.3m distance of interferers) in all cases

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Coexistence (at 1m)

System

Desired

Achieved

FCC Mask

802.11a

- 88 dBm

- 90 dBm

- 75 dBm

802.11b

- 82 dBm

- 85 dBm

- 70 dBm

802.15.1

- 76 dBm

- 95 dBm

- 80 dBm

802.15.3

- 81 dBm

- 85 dBm

- 70 dBm

802.15.4

- 91 dBm

- 95 dBm

- 80 dBm

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Cost Estimates (for 110Mbit/s mode)

• TX– Digital:

• Coders 100k gates

• timing logic <100k gates

– RF

• Pulse generators (4): 0.6mm2

• Polarity scramblers 0.04mm2

• Summers 0.04mm2

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Cost Estimates (for 110Mbit/s mode)

• RX– Digital:

• Viterbi Decoder 100k gates

• timing logic <100k gates

• MMSE equalizer 50k gates

• Rake finger weighting and summing <50k gates

– RF

• LNA (11dB SNR) 0.05mm2

• Pulse generators (2*10): 3.2mm2

• Polarity descramblers 0.04mm2

• Low-pass filters 0.48mm2

• Summers 0.04mm2

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Cost Estimates - Summary

• RF part: – total die size <10mm2 – less than Bluetooth

– 0.18mu CMOS technology sufficient

• Digital part:– Less than 500k gates

– Operation at 220Mbit/s

• Antenna: cavity-backed spiral antenna• Total costs comparable to Bluetooth

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Self-Evaluation (I)

CRITERIA REF. IMPORTANCE

LEVEL PROPOSER RESPONSE

Unit Manufacturing Complexity (UMC)

3.1 B Comparable to Bluetooth

Signal Robustness

Interference And Susceptibility

3.2.2 A No noticeable impact by interferers

Coexistence 3.2.3 A Does not disturb at 1m distance

Technical Feasibility

Manufacturability 3.3.1 A Cost comparable to Bluetooth

Time To Market 3.3.2 A Uses technology that is available now

Regulatory Impact 3.3.3 A Fulfills FCC requirements

Built-in flexibility for future European and Japanese standards

Scalability (i.e. Payload Bit Rate/Data Throughput, Channelization – physical or coded, Complexity, Range, Frequencies of Operation, Bandwidth of Operation, Power Consumption)

3.4 A Scalability by variable spreading factor (for data rates 110Mbit/s)

Multicode transmission (for >110Mbit/s)

Location Awareness 3.5 C Could be added

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Self-Evaluation (II)CRITERIA REF.

IMPORTANCE LEVEL PROPOSER RESPONSE

Size And Form Factor 5.1 B Determined by antenna: 65*40mm

and battery

PHY-SAP Payload Bit Rate & Data Throughput

Payload Bit Rate 5.2.1 A 110Mbit/s (?)

PHY-SAP Data Throughput 5.2.2 A 80Mbit/s

Simultaneously Operating Piconets

5.3 A Minimum distance

Signal Acquisition 5.4 A <12 microseconds

Link Budget 5.5 A 3dB link margin in AWGN at 10m

Sensitivity 5.6 A -73dBm

Multi-Path Immunity 5.7 A Multipath penalty <7dB

Power Management Modes 5.8 B (i) active

(ii) standby

Power Consumption 5.9 A

Antenna Practicality 5.10 B Suggested antenna in use today

March 2003

Molisch et al., Time Hopping Impulse Radio

doc.: IEEE 802.15 03111r0_TG3a

Submission

Summary and Conclusions

• TH-IR based standards proposal– Meets targets of 802.15.3a for LOS

• Innovative way to manage spectrum– Meet FCC requirements

– Improve performance in interference environment

– Decrease interference to other systems

• Allows cheap implementation– All digital operations at symbol rate, not chip rate

• Scaleable– Multicode / multirate system.