Proposal for 15'4a altphy

1
doc. IEEE 802.15-05-0028-00-004a
doc. IEEE 802.15-05-0028-00-004a
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 Voice916 278 6568, FAX 916 278
7215, E-Mailsychang_at_ecs.csus.edu 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.
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Soo-Young Chang, CSUS
Slide 1
Submission
2
WAVEFORM MODULATED LOW RATE UWB SYSTEM-
Proposal for 15.4a alt PHY-
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• Soo-Young Chang
• California State University

Soo-Young Chang, CSUS
Slide 2
Submission
3
INTRODUCTION
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• 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 location 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

Soo-Young Chang, CSUS
Slide 3
Submission
4
PLAUSIBLE MYTHS
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• 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.

Soo-Young Chang, CSUS
Slide 4
Submission
5
CONSIDERATIONS FOR LOW RATE UWB (1)
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• 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 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/MHz7500MHz -2.54dBm
  0.5mW
• More transmit power needs more power consumption
  ???
• ? New waveform is needed to fit exactly to
  frequency mask

Soo-Young Chang, CSUS
Slide 5
Submission
6
CONSIDERATIONS FOR LOW RATE UWB (2)
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• 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.
• 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 gt 1 Gsamples/sec

Soo-Young Chang, CSUS
Slide 6
Submission
7
KEY CONSIDERATIONS
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• Modulation/demodulation
• Source coding
• Channel coding (FEC)
• ARQ not considered
• Interleaving
• Pulse generation
• Antenna
• Multiple access

• Synchronization
• LNA
• Message relaying
• Simultaneously operated piconet (SOP)
• Localization function
• Transmit only device

Soo-Young Chang, CSUS
Slide 7
Submission
8
FREQUENCY PLAN
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• 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 pulses
  case in the same frequency band
• ? 3.8 dB more margin for link budget

Soo-Young Chang, CSUS
Slide 8
Submission
9
FREQUENCY SUBBANDS
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• 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
w21
w22
w23
w24
base waveform
Soo-Young Chang, CSUS
Slide 9
Submission
10
PULSE WAVEFORM OF SUBBAND
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• Pulse waveform shape
• Mathematical derivation/expression
• Shape duration 9 ns
• Spectrum 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

Soo-Young Chang, CSUS
Slide 10
Submission
11
TYPICAL PULSE WAVEFORM AND ITS SPECTRUM
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• 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

Soo-Young Chang, CSUS
Slide 11
Submission
12
POSSIBLE MODULATIONS
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• OOK
• Two levels 1, -1
• Anti-podal BPSK
• Two levels 1, -1
• OOK Anti-podal
• Three levels 1, 0, -1
• n level modulation
• nQAM

Soo-Young Chang, CSUS
Slide 12
Submission
13
MODULATION/MA EFFICIENCY
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• Energy or power efficient? joule/sec
• Energypowertime
• Power limited by FCC mask
• Pmax-41.3dBm/MHz7500MHz-2.54dBm0.5mW
• To use more energy, more time needs to be
  transmitted ? totally related to time
• for UWB, BWgt500MHz or fractional BWgt20 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

Soo-Young Chang, CSUS
Slide 13
Submission
14
MODULATION PROPOSED
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• 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
  OOKBPSK

Soo-Young Chang, CSUS
Slide 14
Submission
15
WAVEFORMS FOR EACH GROUP
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005
group 1
group 2
group 3
group 4
f
3.1 GHz
10.6 GHz
m1,1(t)
m1,1(t)
m1,1(t)
m1,1(t)
m1,1(t)
m1,1(t)
m1,1(t)
m2,1(t)
m1,1(t)
m1,1(t)
m1,1(t)
m3,1(t)
m4,1(t)
m1,2(t)
m1,2(t)
m1,2(t)
m1,2(t)
m1,2(t)
m1,2(t)
m1,2(t)
m2,2(t)
m1,2(t)
m1,2(t)
m1,2(t)
m3,2(t)
m4,2(t)
m1,16(t)
m1,16(t)
m1,16(t)
m1,16(t)
m1,16(t)
m1,16(t)
m1,16(t)
m2,16(t)
m1,16(t)
m1,16(t)
m1,16(t)
m3,16(t)
m4,16(t)
Soo-Young Chang, CSUS
Slide 15
Submission
16
SUBGROUPS FOR EACH GROUP
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005
group 1
group 2
group 3
group 4
f
3.1 GHz
10.6 GHz
SG1
SG2
SG3
SG4
Soo-Young Chang, CSUS
Slide 16
Submission
17
BASE WAVEFORM FOR ONE GROUP
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• For four subbands assuming each has 1 GHZ BW
• If smaller BW, larger pulse width

t (ns)
0
4
Soo-Young Chang, CSUS
Slide 17
Submission
18
EXAMPLES OF WAVEFORMS
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• m1,5(t) m1,12(t) m1,16(t)

Soo-Young Chang, CSUS
Slide 18
Submission
19
CORRELATIONS
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• of samples 180 of samples 90
• Correlation ratio autocorrelation/crosscorrelati
  on

Soo-Young Chang, CSUS
Slide 19
Submission
20
DATA RATES
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• 1 Mbps max with 100 overhead ? Tb 1/2 Mbps
  500 ns
• Pulse width 9 ns ? Duty cycle 2

500 ns
500 ns
Soo-Young Chang, CSUS
Slide 20
Submission
21
MULTIPLE ACCESS (1)
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• Possible MAs considered
• Frequency hopping (FH) among groups
• Not efficient because of uncertainty of FCCs
  ruling on FH so far and less usage of power
• TDMA
• Less time efficient
• Direct-sequence (DS) CDMA
• Less time efficient and more complex

f
Group 4
Group 3
Group 2
Group 1
t4
t2
t3
t1
t5
t
16 frequency bins time domain bins
Soo-Young Chang, CSUS
Slide 21
Submission
22
MULTIPLE ACCESS (2)
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• 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)
• m1,10, m1,2 w1, m1,3 w2, . . . . , m4,16 w13
  w14 w15 w16

Soo-Young Chang, CSUS
Slide 22
Submission
23
MULTIPLE ACCESS (3)
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• Correlation
• where kth sample of ith waveform of a
  subband for N samples
• 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
• mijmij(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?

Soo-Young Chang, CSUS
Slide 23
Submission
24
ORTHOGONALITY OF SINUSOIDS
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• 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. N100 for 4 ns pulse duration, fs25 GHz
• fkk25109/1002.5108k0.25k 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

Soo-Young Chang, CSUS
Slide 24
Submission
25
MAPPING FREQUENCY BINS TO WALSH ENCODED SYMBOLS
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005
Soo-Young Chang, CSUS
Slide 25
Submission
26
MUTIPLE ACCESS (4)
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• 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 one time domain bit deliver
  two bits
• 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

Soo-Young Chang, CSUS
Slide 26
Submission
27
TRANSMITTER STRUCTURE
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• Simple structure with impulse radio concept
• FEC encoder
• Interleaver
• Pulse generator
• Modulator
• Antenna

antenna
This part can be realized using digital processing
Data in
Data manipulator
modulator
Source coding Channel coding interleaving
Pulse generator
Soo-Young Chang, CSUS
Slide 27
Submission
28
TRANSMITTER BLOCK DIAGRAM
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005
data manipulator
S/P converter
input data
encoding interleaving encryption
ROM, group 1
DAC
waveform transformer

• ROM, group 2

DAC
waveform transformer
ROM, group 3
DAC
waveform transformer
ROM, group 4
DAC
waveform transformer
Soo-Young Chang, CSUS
Slide 28
Submission
29
RECEIVER STRUCTURE
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• Simple receiver structure
• Antenna - Pulse generator
• LNA - Location processor
• Demodulator
• Data detector
• De-interleaver
• Channel decoder
• Synchronizer

location
Pulse generator
Synch Information retriever
demodulator
Data De-manipulator
Data out
detector
antenna
LNA
Soo-Young Chang, CSUS
Slide 29
Submission
30
RECEIVING BLOCK
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005
received signal
correlation
pulse generator
Time correlator concept
ROM
waveform conditioner
ADC
correlator
correlation
LNA
6 bit Flash
Soo-Young Chang, CSUS
Slide 30
Submission
31
LINK BUDGET ANALYSIS
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• AWGN and 0 dBi gain at TX/RX antennas assumed.
  Fc5.73GHz

Soo-Young Chang, CSUS
Slide 31
Submission
32
WHY THIS PROPOSAL?
doc. IEEE 802.15-05-0028-00-004a
Jan. 2005

• 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, i.g., mixers Los,
  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.

Soo-Young Chang, CSUS
Slide 32
Submission