Post on 13-Dec-2015
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_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: May 5th, 2003Source: Andreas F. Molisch et al., Mitsubishi Electric Research LaboratoriesAddress MERL, 201 Broadway Cambridge, MA, 02139, USA Voice: +1 617 621 7558, FAX: +1 617 621 7550 , 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.
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_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
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_TG3a
Submission
Contents
– System overview – Physical-layer details– Performance evaluation
– Signal robustness
– Coexistence
– Cost analysis
– Summary and conclusions
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_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
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_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
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_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
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_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
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_TG3a
Submission
Contents
– System overview – Physical-layer details
– acquisition
– channel estimation
– polarity hopping
– spectral shaping
– Rake structure
– Performance evaluation– Summary and conclusions
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_TG3a
Submission
Fast acquisition
• template signal and received signal need to be aligned
• standard method: serial search (chip by chip)• but: chip duration very short in UWB, takes
long time• our solution:
– Beacon provides rough timing estimation (within runtime of the piconet diameter)
– new “block search” methods for actual acquisition
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_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– Sequantial block search (SBS): integrate output of
detector over delay region (block), search for block with significant energy. Best for LOS
– Average block search (ABS): average over absolute values of detector output. Best for NLOS
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_TG3a
Submission
Sequential Block Search
1) Check the bth block using the first template signal (t).
2) If the output of the bth block is not higher than a block threshold, τb, then, go to step 6.
3) If the output of the bth block is higher than the block threshold, τb, then search the block in more detail, i.e., cell-
by-cell serial search with a signal threshold τs, using the
second template signal (t).
4) If no signal cell is detected in the block, go to step 6.
5) If the signal cell is detected in the block, DONE.
6) Set b = (b mod B) + 1 and go to step 1.
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_TG3a
Submission
Average Block Search
1) Check difference between successive averages wi mod B - w(i-
1) mod B.2) If the difference is not higher than a first threshold go to
step 6.3) If the difference is higher than, check
z(i mod B)K+1, …, z(i mod B)+1)K serially, comparing to a second threshold, .
4) If no signal cells detected, go to step 6. 5) If signal cell(s) are detected, DONE. 6) Set i = (i + 1) mod B, and go to step 1.
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_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
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_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
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_TG3a
Submission
Estimator algorithm
510
0
1.
511c k t c f ck
h nT b y nT kN T
evaluation of one sample per 5ns interval, offset by Tc
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_TG3a
Submission
Estimator
• Multi-step procedure1. estimate which taps have significant weights
2. estimate tap weights for L significant taps
3. determine Rake receiver weights via minimum mean square error criterion
4. determine equivalent (symbol-spaced) channel from transmitter to output Rake receiver
5. find equalizer for this equivalent channel (MMSE)
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_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 4dB SNR for 10^-5 BER– Improvement by 3dB possible by turbo codes
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_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
Time (s) frequency (Hz)
Monocycle, 5th derivative of gaussian pulse Power spectral density of the monocycle
Ma
gn
itud
e o
f p
(t)
10
log
10|P
(f)|
2 d
B
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_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
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_TG3a
Submission
Initialization
• find “modified” mask that follows FCC and required interference suppression (e.g., 20dB for 802.11a
• approximate “optimum filling of mask” as
• solution of this in closed form (eigenvector belonging to largest eigenvalue)
2
[ , ]
| ( ) |min max , 1.
( )T
s
S jsubject to s Rs
M
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_TG3a
Submission
Iterative Refinement
• backpropagating neural network
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_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
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_TG3a
Submission
Contents
– System overview – Physical-layer details– Performance evaluation
– Signal robustness
– Coexistence
– Cost analysis
– Summary and conclusions
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_TG3a
Submission
Link BudgetParameter Value
Throughput (Rb) > 110 Mb/s 200Mb/s 480Mbit/s
Average Tx power ( TP ) -4.3 dBm -4.3 dBm -4.3 dBm
Tx antenna gain ( TG ) 0 dBi 0 dBi 0 dBi
maxmin' fff c : geometric center frequency of
waveform ( m inf and m axf are the -10 dB edges
of the waveform spectrum)
5.73GHz 5.73GHz 5.73GHz
Path loss at 1 meter ( )/4(log20 '101 cfL c )
8103c m/s
47.6 dB 47.6 dB 47.6 dB
Path loss at d m ( )(log20 102 dL ) 20 dB at d=10 meters
12 dB at d=4 meters
20 dB at d=4 meters
Rx antenna gain ( RG ) 0 dBi 0 dBi 0 dBi
Rx power ( 21 LLGGPP RTTR (dB)) -71.9 dBm -63.9 dBm -63.9 dBm
Average noise power per bit ( )(log*10174 10 bRN )
-93.6 dBm -91.0 dBm -87.2 dBm
Rx Noise Figure Referred to the Antenna Terminal ( FN )1
11 dB 11 dB 11 dB
Average noise power per bit ( FN NNP ) -82.6 dBm -80.0 dBm -76.2 dBm
Minimum Eb/N0 (S) 4 dB 4 dB 4 dB
Implementation Loss2 (I) 3 dB 3 dB 3 dB
Link Margin ( ISPPM NR ) 3.7 dB 9.1 dB 5.3 dB
Proposed Min. Rx Sensitivity Level3 -78.9 dBm -70.9 dBm -70.9 dBm
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_TG3a
Submission
PER as Function of Distance
0 2 4 6 8 10 12 14 16 18 200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Distance (m)
PE
R
AWGN
CM1
CM2
CM3
CM4
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_TG3a
Submission
0 2 4 6 8 10 12 14 16 18 200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Distance (m)
Pro
ba
bili
ty o
f Lin
k S
ucc
ess
CM1
CM2
CM3
CM4
Probability of Link Success
Sensitivities:
AWGN 13m
cm1 6.8
cm2 6.2
cm3 5.3
cm4 5.0
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_TG3a
Submission
Outage vs. SNR
0 5 10 15 200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
90% outage PER function of the Eb/No
Eb/N0 dB
90%
out
age
prob
abili
ty
CM1
CM2
CM3
CM4
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_TG3a
Submission
0.5 1 1.5 20
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Interfering Piconet Separation Distance (m)
PE
RAverage PER over 4 channel models with one interfering piconet from cm1
test link: 20 first realizations of cm120 first realizations of cm220 first realizations of cm320 first realizations of cm4
Specified PER = 8%
Single co-channel interferer separation distance
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_TG3a
Submission
Single co-channel interferer separation distance
0.5 1 1.5 20
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Interfering Piconet Seperation Distance (m)
PE
RAverage PER over 4 channel models With One Interfering Piconet Throught CM3
CM4
CM3
CM2
CM1
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_TG3a
Submission
Single co-channel interferer separation distance
0.5 1 1.5 20
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Interfering Piconet Seperation Distance (m)
PE
R
Average PER over 4 Channel Models With One Interfering Piconet Through CM4
CM1
CM3
CM4
CM2
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_TG3a
Submission
Test link uncoordinated piconet dint AWGN AWGN < 0.5 m
20 first realizations of cm1 21st realization of cm1 0.9 m 20 first realizations of cm2 21st realization of cm1 0.9 m 20 first realizations of cm3 21st realization of cm1 1.1 m 20 first realizations of cm4 21st realization of cm1 1.4 m 20 first realizations of cm1 21st realization of cm3 0.9 m 20 first realizations of cm2 21st realization of cm3 0.9 m 20 first realizations of cm3 21st realization of cm3 1.2 m 20 first realizations of cm4 21st realization of cm3 1.4 m 20 first realizations of cm1 21st realization of cm4 0.95 m 20 first realizations of cm2 21st realization of cm4 1.0 m 20 first realizations of cm3 21st realization of cm4 1.4 m 20 first realizations of cm4 21st realization of cm4 1.4 m
Single co-channel interferer separation distance
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_TG3a
Submission
Susceptibility to Interference
• Piconets– 20 first realizations of the 4 channel model and AWGN
– Desired user: 6dB above sensitivity
• admissible distance of interferer: between 0.5 and 1.5m
• 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
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_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
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_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
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_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
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_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
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_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
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_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
May 2003
Molisch et al., Time Hopping Impulse Radio
doc.: IEEE 802.15 03111r1_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.