Transcript 15-05-0028-01-004a-waveform-modulated-low-rate-uwb-system-proposal-15-4a-alt-phy.ppt

doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [WAVEFORM MODULATED LOW RATE UWB SYSTEM - Proposal for 15.4a alt PHY]
Date Submitted: [Jan., 2005]
Source: [Soo-Young Chang] Company [California State University, Sacramento]
Address [6000 J Street, Dept. EEE, Sacramento, CA 95819-6019 ]
Voice:[916 278 6568], FAX: [916 278 7215], E-Mail:[[email protected]]
Re: [This submission is in response to the IEEE P802.15.4a Alternate PHY Call for Proposal ]
Abstract: [This document describes the waveform modulated UWB proposal for IEEE 802.15 TG4a.]
Purpose: [For discussion by IEEE 802.15 TG4a.]
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.
Submission
Slide 1
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
WAVEFORM MODULATED
LOW RATE UWB SYSTEM
- Proposal for 15.4a alt PHY-
Soo-Young Chang
California State University, Sacramento
Submission
Slide 2
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
INTRODUCTION
• Use short duration impulses: purely processed in time
domain, not in frequency domain
– Simple concept
– Simple digital processing  Low complexity  Low cost
– No components for processing frequency information (e.g. filter,
osc., etc.)
– High locating accuracy and fast ranging with very short duration
pulses
– Stealth mode of operation possible with relatively small RF
signature by coding frequency subbands with orthogonal codes
– Excellent co-existence capability due to adaptive frequency band
usage – flexible to eliminate forbidden bands (e.g. UNII band)
Submission
Slide 3
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
PLAUSIBLE MYTHS
•
Myth 1
– ‘Low rate needs less power consumption.’
 With high rates, low power consumption can be achieved.
•
Myth 2
– ‘Digital implementation needs more complexity and is not easily realizable with
the state-of-the art technologies.’
 Digital implementation can be realized with less complexity and provide more
flexibility.
•
Myth 3
– ‘Higher frequency is not easy to manage or implement.’
 Unless high power is not considered, digital processing method can be applied for
higher frequency band.
•
Myth 4
– ‘Since this technology was not realizable yesterday, today also it is not easy to
realize.’
 Since technologies advances rapidly, more sophisticated and conceptual ideas
should be considered for future applications.
Submission
Slide 4
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
CONSIDERATIONS
FOR LOW RATE UWB (1)
• Frequency band
– Enjoy full frequency band assigned: 3.1 – 10.6 GHz in the US
– Only max power spectral density is limited: Transmitted power is
proportional to the bandwidth
– Pulse width is inversely proportional to bandwidth: more accurate ranging
possible for time based ranging
– Large bandwidth entails low fading
 High rate sampling is needed to process using digital methods
 To overcome this problem, new processing method should be devised
• Transmit power
– Enjoy full power transmitted under frequency mask if waveforms have the
spectrum similar to frequency mask
– Max power will be -41.3dBm/MHz*7500MHz = -2.54dBm = 0.5mW
– More transmit power needs more power consumption ???
 New waveform is needed to fit exactly to frequency mask
Submission
Slide 5
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
CONSIDERATIONS
FOR LOW RATE UWB (2)
• Data rate
– In TRD, “low rate” is suggested with expectation to reduce power
consumption and complexity/cost
– Power consumption is mainly proportional to the time of signal
transmission and processing
– No need to reduce data rates if higher rates possible with the same
cost/efforts
• with higher data rate, less probability of conflict with other transmissions for
CSMA and higher success rate with ack
– More pulses may be transmitted for the same information with higher
rates: more redundancy can be achieved
– The amount of information delivered is the key issue for any
communication systems
• The higher the data rate is, the less time it takes to deliver.
 More sophisticated signal processing for higher rate is inevitable.
Submission
Slide 6
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
CONSIDERATIONS
FOR LOW RATE UWB (3)
• Full digital processing
– Provide full flexibility for any change in signal environments, system
concepts and requirements
– May also be compatible with a variety of complex digital modulation
schemes
– Eliminate the cost and complexity of a down conversion stage
 Sophisticated digital signal processing technologies needed including high
speed ADCs and DACs with sampling rate > 1 Gsamples/sec
Submission
Slide 7
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
FREQUENCY PLAN
• Flexible enough to satisfy any frequency mask and
to avoid any forbidden bands
 pulse waveforms can be adaptively tailored to any
frequency mask applied
• With FCC mask, 3.1GHz to 10.6 GHz full
frequency band is used to enjoy more transmitted
power
 3.8 dB more power used than Gaussian pulse’s case in
the same frequency band
 3.8 dB more margin for link budget
Submission
Slide 8
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
FREQUENCY SUBBANDS
• Whole frequency band under FCC mask is divided into 4 groups
• Each group has 4 subbands
– BW of a subband = (10.6-3.1) GHz /16 = 469 MHz
– Each subband has its own waveform
group 1
group 2
group 3
group 4
f
3.1 GHz
10.6 GHz
subband 1
subband 2
subband 3
subband 4
f
base waveform
Submission
w21
w23
w22
Slide 9
w24
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
PULSE WAVEFORM OF SUBBAND
•
Pulse waveform shape
– Mathematical derivation/expression
– Shape: duration: 9 ns
– Spectrum: almost flat throughout whole band
•
How can pulses be generated
– Digital way? Overlapped with various delays
 can be generated with relatively lower sampling rate DACs
• 100 samples/waveform:
• 16 waveforms/group for binary representation
81 waveforms/group for ternary representation
• 1600 or 8100 sample information stored in ROM per group
 1.6 or 8.1 Kbytes ROM needed to store waveform information if 8 bits/sample is
adopted
• Generate waveforms using DACs which has a sampling rate of 1 Gsamples/sec
– Analog way?
• No idea
– 4 digital ways considered in this proposal
•
How can delay devices for TX and RX be implemented?
 Cost/accuracy/step size are the key issues
Submission
Slide 10
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
TYPICAL PULSE WAVEFORM AND
ITS SPECTRUM
•
•
•
For each subband, there is one waveform which has flat spectrum as shown in the above.
Group i has four base waveforms: wi1, wi2 , wi3 , and wi4
Group i has 16 waveforms: mi1, mi2, mi3, . . . , mi16
mij,=a* wi1 +b* wi2 +c* wi3 +d* wi4
where a, b, c, and d are determined by modulation method applied
Submission
Slide 11
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
POSSIBLE MODULATIONS
• OOK
– Two levels: +1, 0
• Anti-podal: BPSK
– Two levels: +1, -1
• OOK + Anti-podal
– Three levels: +1, 0, -1
• n level modulation
• nQAM
Submission
Slide 12
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
MODULATION/MA EFFICIENCY
•
Energy or power efficient?
joule/sec
– Energy=power*time
– Power limited by FCC mask
• Pmax=-41.3dBm/MHz*7500MHz=-2.54dBm=0.5mW






•
To use more energy, more time needs to be transmitted  totally related to time
for UWB, BW>500MHz or fractional BW>20% of fc  short duration pulses
use multiple pulses for one bit (or symbol)
need more power under frequency mask to have higher power
power constrained with frequency mask for UWB case
new waveform needed to have more transmitted power
Spectrally efficient?
bit/Hz
– Not important for UWB because of plenty of bandwidth
•
Time efficient?
bit/sec
– For higher rate, more important: for lower rate, less important  more room for
flexibility for LR-WPAN
– However, as bit duration increases, more power consumption may be required
Submission
Slide 13
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
WAVEFORMS FOR EACH GROUP
group 1
group 2
group 3
group 4
f
3.1 GHz
Submission
10.6 GHz
m1,1(t)
m2,1
1,1(t)
m3,1
1,1(t)
m4,1(t)
m1,2(t)
m2,2
1,2(t)
m3,2
1,2(t)
m4,2(t)
m1,16(t)
m2,16
1,16(t)
m3,16
1,16(t)
m4,16(t)
Slide 14
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
SUBGROUPS FOR EACH GROUP
group 1
group 2
group 3
group 4
f
3.1 GHz
10.6 GHz
SG1
m1,1(t) m1,6(t)
m1,11(t) m1,16(t)
m2,1(t) m2,6(t)
m2,11(t) m2,16(t)
m3,1(t) m3,6(t)
m3,11(t) m3,16(t)
m4,1(t) m4,6(t)
m4,11(t) m4,16(t)
SG2
m1,4(t) m1,7(t)
m1,10(t) m1,13(t)
m2,4(t) m2,7(t)
m2,10(t) m2,13(t)
m3,4(t) m3,7(t)
m3,10(t) m3,13(t)
m4,4(t) m4,7(t)
m4,10(t) m4,13(t)
SG3
m1,2(t) m1,8(t)
m1,9(t) m1,15(t)
m2,2(t) m2,8(t)
m2,9(t) m2,15(t)
m3,2(t) m3,8(t)
m3,9(t) m3,15(t)
m4,2(t) m4,8(t)
m4,9(t) m4,15(t)
SG4
m1,3(t) m1,5(t)
m1,12(t) m1,14(t)
m2,3(t) m2,5(t)
m2,12(t) m2,14(t)
m3,3(t) m3,5(t)
m3,12(t) m3,14(t)
m4,3(t) m4,5(t)
m4,12(t) m4,14(t)
Submission
Slide 15
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
BASE WAVEFORM FOR ONE GROUP
• For four subbands – assuming each
has 1 GHz BW
+
amplitude
– If smaller BW, larger pulse width
Submission
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
00
+
+
1
2
3
4
5 6 7 8 9
Frequency( GHz.)
t (ns)
10
0
Slide 16
4
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
BASE WAVEFORM FOR ONE GROUP
• For four subbands - for smaller BW, larger pulse width
For BW=469 MHz
subband 1
subband 2
subband 3
subband 4
Submission
Slide 17
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
EXAMPLES OF WAVEFORMS (OOK)
m1,5(t)
Submission
m1,12(t)
Slide 18
m1,16(t)
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
WAVEFORM FOR DATA STREAM (OOK)
Submission
Slide 19
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
EXAMPLES OF WAVEFORMS (BPSK)
m1,1(t)
Submission
m1,11(t)
Slide 20
m1,16(t)
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
MODULATION PROPOSED
• Proposed Mod (1)
– 8 frequency bins are coded with an 8 bit Walsh code and represent
one bit using BPSK
• Proposed Mod (2)
– 4 waveforms of a subgroup are mapped to 2 bit (quaternary)
information
ex)
m1,1(t)  00
m1,6(t)  01 m1,11(t)  10
m1,16(t)  11
– Each user sends information using one subgroup of each group
 at one time 8 bit information is delivered
– Each waveform is modulated by OOK or BPSK or OOK+BPSK
Submission
Slide 21
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
MAPPING FREQUENCY BINS TO WALSH
ENCODED SYMBOLS
Submission
Slide 22
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
DATA RATES
• 1 Mbps max with 100% overhead  Tb = 1/2 Mbps = 500 ns
• Pulse width = 9 ns  Duty cycle = 2 %
Mod type
# of waveforms
/subgroup
# of bits/symbol
duration
symbol duration
(ns)
Data rate w/100%
overhead
(Mbps)
Mod (1)
BPSK
4
2
500
2
Mod (2)
OOK or BPSK
16
8
500
8
500 ns
Submission
500 ns
Slide 23
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
MULTIPLE ACCESS (1)
• Possible MAs considered
– Frequency hopping (FH)
among groups
f
• Not efficient because of
uncertainty of FCC’s
ruling on FH so far and
less usage of power
Group 4
Group 3
– TDMA
Group 2
• Less time efficient
– Direct-sequence (DS)
CDMA
Group 1
t1
• Less time efficient and
more complex
t2
t3
t4
t5
t
16 frequency bins
time domain bins
Submission
Slide 24
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
MULTIPLE ACCESS (2)
• For each subband, one base waveform exists
– 16 base waveforms:
w11(t), w12(t), w13(t), w14(t), w21(t), . . . . , w43(t), w44(t)
– Each waveform is almost orthogonal to each other
• Each group has
– 16 waveforms for mod (1) or 81 waveforms for mod (2)
• m1,1=0, m1,2= w1, m1,3= w2, . . . . , m4,16= w13+ w14+ w15+ w16
Submission
Slide 25
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
MULTIPLE ACCESS (3)
•
Correlation
N
N
autocorrelation   si (k ) si (k )   si (k ) 2
*
k 1
k 1
where si (k ) : kth sample of ith waveform of a subband for N samples
N
crosscorre lation   si (k ) s j (k )
*
k 1
– Ratio of correlations = autocorrel/crosscorrel for various N values
– Orthogonality holds for sinusoidal waveforms with some conditions
(Orthogonality condition, refer to next slide), but the waveforms used here
are not sinusoidal with some envelope
– At receiver, a processing procedure can be used to make pure sinusoidal
for a period
• mij*mij=(a* wi1 +b* wi2 +c* wi3 +d* wi4 )(a* wi1 +b* wi2 +c* wi3 +d* wi4)
where mij is the waveform transmitted and mij is the waveform generated at RX
• After integrate for a one waveform duration, only autocorrelation terms remain
• Orthogonality can hold at RX during detection
– What is the best sampling frequency such that orthogonality can be
achievable?
Submission
Slide 26
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
CORRELATIONS
correlation
correlation ratio
w11
w11
0.020984
1/1
w12
0.0012155
17.264/9.7396
0.020984
1/1
w13
2.2562×10-5
930.05/3957.3
6.8651×10-6
305.66/106.69
w14
3.4173×10-6
6140.6/9681.8
0.0012155
2.2562×10-5
930.05/3957.3 17.264/9.7396
•
•
w12
w13
w14
0.0012155
2.2562×10-5 3.4173×10-6
17.264/9.7396 930.05/3957.3 6140.6/9681.8
6.8651×10-6 2.2562×10-5
305.66/106.69 930.05/3957.3
0.020984
1/1
0.0012155
17.264/9.7396
0.020984
1/1
# of samples = 180
# of samples = 90
Correlation ratio = autocorrelation/crosscorrelation
Submission
Slide 27
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
ORTHOGONALITY OF SINUSOIDS
•
A key property of sinusids is that they are orthogonal at different frequencies.
That is,
•
This is true whether they are complex or real, and whatever amplitude and
phase they may have. All that matters is that the frequencies be different. Note,
however, that the sinusoidal durations must be infinity.
For length sampled sinusoidal signal segments exact orthogonality holds only
for the hamonics of the sampling rate-divided-by- , i.e., only for the
frequencies
•
•
•
These are the only frequencies that have a whole number of periods in
samples
Ex. N=100 for 4 ns pulse duration, fs=25 GHz
– fk=k*25*10**9/100=2.5*10**8*k=0.25*k GHz
– For any integer k, fk can be determined  center frequencies of each subband can
be determined
http://ccrma.stanford.edu/~jos/r320/Orthogonality_Sinusoids.html
Submission
Slide 28
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
MAPPING FREQUENCY BINS TO WALSH
ENCODED SYMBOLS
Submission
Slide 29
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
MUTIPLE ACCESS (4)
•
A orthogonal set of 8 8-bit Walsh codes is used
– Max autocorrelation, min (or zero) crosscorrelation each other
– One code consists of 8 frequency domain bins
– Minimal Hamming distance of this code set is 4
• One frequency bin error can be corrected while three bin errors can be detected; works as
an ECC code; increases robustness
•
8 SOPs case
– For one user, one code is assigned
– One time domain bin is occupied by two codes
• Each code represents one bit; one time domain bin represents two bits; during one time
domain bin two bits are delivered
•
64 SOPs case
– For one user, two codes (16 bits) are assigned
– One time domain bin is occupied by two codes
• two codes represent one bit; one time domain bin represents one bit; one time domain bit
deliver one bit
Submission
Slide 30
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
TRANSMITTER STRUCTURE
• Simple structure with impulse radio concept
–
–
–
–
–
FEC encoder
Interleaver
Pulse generator
Modulator
Antenna
Data in
antenna
This part can be
realized using digital
processing
Data
manipulator
Source coding
Channel coding
interleaving
Submission
Slide 31
modulator
Pulse
generator
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
TRANSMITTER BLOCK DIAGRAM
S/P converter
data
manipulator
input data
encoding
interleaving
encryption
Submission
ROM, group 1
ROM, group 2
DAC
DAC
waveform transformer
waveform transformer
ROM, group 3
DAC
waveform transformer
ROM, group 4
DAC
waveform transformer
Slide 32
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
RECEIVER STRUCTURE
• Simple receiver structure
–
–
–
–
–
–
–
Antenna
LNA
Demodulator
Data detector
De-interleaver
Channel decoder
Synchronizer
- Pulse generator
- Location processor
Synch
Information
retriever
location
Pulse
generator
Data out
antenna
Submission
LNA
demodulator
detector
Slide 33
Data
De-manipulator
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
RECEIVING BLOCK
received
signal
correlation
pulse
generator
Time correlator concept
ROM
LNA
Submission
waveform
conditioner
Slide 34
ADC
correlator correlation
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
LINK BUDGET ANALYSIS
•
Submission
AWGN and 0 dBi gain at TX/RX antennas assumed. Fc=5.73GHz
Parameter
Value
Value
Value
Information Data Rate
1 Mb/s
2 Mb/s
1 Mb/s
Average TX Power
-2.54 dBm
-2.54 dBm
-2.54 dBm
Total Path Loss
(49.15dB@1m + L2)
77.14 dB
(@ 30 meters)
67.60 dB
(@ 10 meters)
67.60 dB
(@ 10 meters)
Average RX Power
-79.68 dBm
-70.14 dBm
-70.14 dBm
Noise Power Per Bit
-114 dBm
-111 dBm
-114 dBm
RX Noise Figure
8 dB
8 dB
8 dB
Total Noise Power
-106 dBm
-103 dBm
-106 dBm
Required Eb/N0
6.25 dB
6.25 dB
6.25 dB
Implementation Loss
2.5 dB
3.0 dB
2.5 dB
Link Margin
17.57 dB
23.11 dB
22.61 dB
RX Sensitivity Level
-97.25 dBm
-93.25 dBm
-92.75 dBm
Slide 35
Soo-Young Chang, CSUS
doc.: IEEE 802.15-05-0028-01-004a
Jan. 2005
WHY THIS PROPOSAL?
•
More transmit power used under frequency mask
–
More margin: at least 3 dB more by using full power under any frequency-power
constraints with waveforms adaptive to frequency mask
 Spectrally efficient / more received signal power
 More chance to intercept signals
•
Very simple architecture
–
–
Directly generated pulse waveforms using ROM
Processing in digital methods
•
No need to have analog devices (e.g., mixer, LO, integrator, etc)
 low cost / low power consumption
•
High location accuracy
– Wider bandwidth for each waveforms  narrower pulse width
 more accurate location information
•
High adaptability to frequency, data rate, transmit power requirements
 high scalability in frequency, data rate, system configuration, waveform, etc.
Submission
Slide 36
Soo-Young Chang, CSUS