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: [email protected]
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.