DS-UWB-responses-to-MB-OFDM-voter-NO-comments

1
Project IEEE P802.15 Working Group for Wireless
Personal Area Networks (WPANs) Submission Title
DS-UWB Proposal Update Date Submitted May
2004 Source Reed Fisher(1), Ryuji Kohno(2),
Hiroyo Ogawa(2), Honggang Zhang(2), Kenichi
Takizawa(2) Company (1) Oki Industry
Co.,Inc.,(2)National Institute of Information and
Communications Technology (NICT) NICT-UWB
Consortium Connectors  Address (1)2415E.
Maddox Rd., Buford, GA 30519,USA, (2)3-4,
Hikarino-oka, Yokosuka, 239-0847, Japan
Voice(1)1-770-271-0529, (2)81-468-47-5101,
FAX [phone], E-Mail(1)reedfisher_at_j
uno.com, (2)kohno_at_crl.go.jp, honggang_at_crl.go.jp,
takizawa_at_crl.go.jp Source Michael Mc
Laughlin Company decaWave, Ltd. Voice353-1-2
95-4937, FAX -, E-Mailmichael_at_decawave.com
Source Matt Welborn Company Freescale
Semiconductor, Inc Address 8133 Leesburg Pike
Vienna, VA USA Voice703-269-3000,
E-Mailmatt.welborn_at_freescale.com Re
Abstract Technical update on DS-UWB (Merger
2) Proposal Purpose Provide technical
information to the TG3a voters regarding DS-UWB
(Merger 2) Proposal 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.
2
Outline

• DS-UWB Overview
• Complexity
• Performance
• Scalability of UWB implementations
• CSM for coexistence and interoperability
• Interference issues

3
Overview of DS-UWB Proposal

• Support for much higher data rates
• BPSK modulation using variable length spreading
  codes
• At same time, much lower complexity and power
  consumption
• Essential for mobile handheld applications
• Digital complexity is 1/3 of previous approaches,
  yet provides good performance at long range and
  high rates at short range
• Harmonization interoperability with MB-OFDM
  through a Common Signaling Mode (CSM)
• A single multi-mode PHY with both DS-UWB and
  MB-OFDM
• Best characteristics of both approaches with most
  flexibility

4
Advantages of the DS-UWB Solution

• DS-UWB is not burdened with the multiple
  interference issues that continue to plague the
  MB-OFDM proposal
• DS-UWB is shown to have equal or better
  performance to MB-OFDM in all modes and multipath
  conditions for a fraction of the complexity
  power
• Increases options for innovation and regulatory
  flexibility to better address all applications
  and markets
• Our vision A single PHY with multiple modes to
  provide a complete solution for TG3a
• Base mode that is required in all devices, used
  for control signaling CSM for beacons and
  control signaling
• Higher rate modes also required to support 110
  200 Mbps
• Compliant device can implement either DS-UWB or
  MB-OFDM (or both)

5
DS-UWB Operating Bands SOP
Low Band
High Band
3
4
5
6
7
8
9
10
11
3
4
5
6
7
8
9
10
11
GHz
GHz

• Each piconet operates in one of two bands
• Low band (below U-NII, 3.1 to 4.9 GHz)
• High band (optional, above U-NII, 6.2 to 9.7 GHz)
• Support for multiple piconets
• Classic spread spectrum approach
• Acquisition uses unique length-24 spreading codes
• Chipping rate offsets to minimize
  cross-correlation

6
DS-UWB Signal Generation
Scrambler
K6 FEC Encoder
Conv. Bit Interleaver
Input Data
Bit-to-Code Mapping
Pulse Shaping
Center Frequency
Gray or Natural mapping
K4 FEC Encoder
4-BOK Mapper
Transmitter blocks required to support optional
modes

• Data scrambler using 15-bit LFSR (same as
  802.15.3)
• Constraint-length k6 convolutional code
• K4 encoder can be used for lower complexity at
  high rates or to support iterative decoding for
  enhanced performance (e.g. CIDD)
• Convolutional bit interleaver protects against
  burst errors
• Variable length codes provide scalable data rates
  using BPSK
• Support for optional 4-BOK modes with little
  added complexity

7
Data Rates Supported by DS-UWB
Data Rate FEC Rate Code Length Range (AWGN)
28 Mbps ½ 24 35 m
55 Mbps ½ 12 27 m
110 Mbps ½ 6 22.2 m
220 Mbps ½ 3 16.2 m
500 Mbps ¾ 2 7.5 m
660 Mbps 1 2 4.7 m
1000 Mbps ¾ 1 4.8 m
1320 Mbps 1 1 3.3 m
Similar Modes defined for high band
8
Digital DS-UWB Receiver Architecture
cos
(
2
p
f
t
)
c
Pre-Select
I
Filter
LPF
GA/ VGA
ADC 1326 MHz, 3-bit ADC
DFE, De- Interleave FEC Decode
Synch. Rake
LNA
Q
LPF
GA/ VGA
ADC 1326 MHz, 3-bit ADC
p
sin
(
2
f
t
)
c

• Architecture assumptions
• Front-end filter LNA
• IQ sampling using 3-bit ADCs
• 16-finger rake (at 110 Mbps) with 3-bit complex
  rake taps
• Decision feedback equalizer at symbol rate
• Viterbi decoder for k6 convolutional code

9
Interference Issues (1)

• Hopped versus non-hopped signal characteristics
• ITS and FCC studies are underway
• Goal is to see if interference characteristics of
  MB-OFDM are acceptable for certification (using
  DS-UWB/noise/IR for comparison)
• Use of PN-modulation to meet 500 MHz BW
• Recent statements by NTIA emphasize importance of
  minimum
• Desire is to ensure protection for restricted
  bands
• DS-UWB bandwidth is determined by pulse shape and
  pulse modulation
• Spectrum exceeds 1500 MHz
• MB-OFDM bandwidth for data and pilot tones is 466
  MHz, guard tones are used to increase bandwidth
  to 507 MHz
• Guard tones carry no useful information, only
  to meet BW reqt.
• See authors statements in 802.15-03/267r1 (July
  2003, page 12)

10
Compliance with 500 MHz Minimum Bandwidth
DS-UWB Symbol Bandwidth (no hopping)
Bandwidth of DS-UWB gt 1500 MHz
DS-UWB uses no guard tones, signal always fills
gtgt 500 MHz minimum bandwidth with useful signal
energy
Bandwidth without Guard Tones 466 MHz
Total of 40 MHz (per hop) is filled with noise
emissions in order to meet bandwidth requirements
Bandwidth with Guard Tones 507.4 MHz
MB-OFDM Symbol Bandwidth (on each hop)
11
Interference Issues (2)

• Spectral flexibility to support a potential for
  enhanced coexistence
• DS-UWB can use pulse shaping to modify spectrum
• Transparent to receiver, requires no coordination
• Dynamic or static using a number of techniques
  (such as SSA)
• Applies to both acquisition preamble AND payload
• MB-OFDM proposes dynamically turning on/off bands
  and tones
• Requires coordination between transmitter and
  receiver
• Does not account for PHY preamble which uses a
  fixed time sample sequence and cannot support
  notching like OFDM
• For medium-to-short packets, preamble can be gt50
  of energy

PHY Preamble
Headers
Variable length payload
Time
12
Spectral Notching for DS-UWB and MB-OFDM
DS-UWB Notched Spectrum
Notch is present in signal spectrum of PREAMBLE
based on pulse shaping
Notch ALSO present in signal spectrum of payload
based on the same pulse shaping
MB-OFDM Notched Spectrum
Spectrum of PREAMBLE is not flexible cannot be
changed by turning off tones
Notch is present ONLY in payload portion of
signal if specific OFDM tones are nulled
Spectrum of PREAMBLE
Spectrum of payload
13
What can be done?

• The simplicity of the MB-OFDM approach was that
  frequency domain filtering (nulling tones) was
  simple and low cost
• Now we find that we need to generate a different
  acquisition sequence for each desired tone
  configuration
• This is the same as generating a time-domain
  pulse shape with arbitrary notches (like SSA)
• No simulation results showing
• How deep can the notches be made (dB)?
• What are the DAC quantization effects?
• How does this affect acquisition performance?

14
Relative Complexity

• Gate counts are drawn based on estimates and
  methodology presented by MB-OFDM proposal team
• Clock speeds are normalized to 85.5 MHz for
  comparison

Component MB-OFDM (Doc 03/268r3) DS-UWB 16-Finger Rake Architecture DS-UWB 32-Finger Rake Architecture
Matched filter rake or FFT 100K 26K 45K
Viterbi decoder 108K 54K 54K
Synchronization ? 30K 30K
Channel estimation ? 24K 24K
Other Miscellaneous including RAM 247K 30K 30K
Equalizer Freq Domain 20K 20K
Total gates _at_ 85.5 MHz 455K 184K 203K
15
Multipath Performance for 110 Mbps
110 Mbps 90 Outage Range (meters) Mean of Top 90 Range (meters)
CM1 13.5 16.9
CM2 11.7 14.6
CM3 11.4 13.4
CM4 10.8 13.0
Simulation Includes 16 finger rake with
coefficients quantized to 3-bits 3-bit A/D (I
and Q channels) RRC pulse shaping DFE trained
in lt 5us in noisy channel (12 Taps) Front-end
filter for Tx/Rx 6.6 dB Noise Figure Packet
loss due to acquisition failure
16
Multipath Performance for 220 Mbps
220 Mbps 90 Outage Range (m) 8-finger rake 90 Outage Range (m) 16-finger rake Mean of Top 90 Range (m) 8-finger rake Mean of Top 90 Range (m) 16-finger rake
CM1 8.4 - 10.2 -
CM2 5.8 7.2 8.2 8.8
CM3 4.9 7.0 6.2 8.4
Simulation Includes 8 finger (16 finger) rake
with coefficients quantized to 3-bits 3-bit A/D
(I and Q channels) RRC pulse shaping DFE
trained in lt 5us in noisy channel (12 Taps/24
Taps) Front-end filter for Tx/Rx 6.6 dB Noise
Figure Packet loss due to acquisition
failure AWGN Range _at_220 Mbps 16.2 m
17
Multipath Performance for 500 Mbps
500 Mbps 90 Outage Range (m) Mean of Top 90 Range (m)
CM1 3.0 4.8
CM2 1.9 3.2
Simulation Includes 16 finger rake with
coefficients quantized to 3-bits 3-bit A/D (I
and Q channels) RRC pulse shaping DFE trained
in lt 5us in noisy channel Front-end filter for
Tx/Rx 6.6 dB Noise Figure Packet loss due to
acquisition failure
18
AWGN SOP Distance Ratios
Test Distance 1 Interferer Distance Ratio 2 Interferer Distance Ratio 3 Interferer Distance Ratio
110 Mbps 15.7 m 0.65 0.92 1.16
220 Mbps 11.4 m 0.90 1.28 1.60
500 Mbps 5.3 m 2.2 3.3 -

• AWGN distances for low band
• High band ratios expected to be lower
• Operates with 2x bandwidth, so 3 dB more
  processing gain

19
Multipath SOP Distance Ratios
Test Transmitter Channels 1-5 Single Interferer
Channels 6-10 Second Interferer Channel 99 Third
Interferer Channel 100
110Mbps 1 Interferer Distance Ratio 2 Interferer Distance Ratio 3 Interferer Distance Ratio
CM1 0.66 0.86 1.09
CM2 0.64 0.91 1.14
CM3 0.72 0.97 1.24

• High band ratios expected to be lower (3 dB more
  processing gain)

20
Scalability

• Baseline devices support 110-200 Mbps operation
• MB-OFDM device
• Reasonable performance in CM1-CM4 channels
• Complexity/power consumption as reported by
  MB-OFDM team
• DS-UWB device
• Less than half the digital complexity of an
  MB-OFDM receiver
• Equal or better performance than MB-OFDM in
  essentially every case
• What about
• Scalability to higher data rate applications
• Scalability to low power applications
• Scalability to different multipath conditions

21
High Data Rate Applications

• Critical for cable replacement applications such
  as wireless USB (480 Mbps) and IEEE 1394 (400
  Mbps)
• High rate device supporting 480 Mbps
• DS-UWB device uses shorter codes (L2, symbol
  rate 660 MHz)
• Uses same ADC rate bit width (3 bits) and rake
  tap bit widths
• Rake use fewer taps at a higher rate or same
  taps with extra gates
• Viterbi decoder complexity is 2x the baseline
  k6 decoder
• Can operate at 660 Mbps without Viterbi decoder
  for super low power
• MB-OFDM device
• 5-bit ADCs required for operation at 480 Mbps
• Increased internal (e.g. FFT, MRC, etc)
  processing bit widths
• Viterbi decoder complexity is 2x the baseline
  k7 decoder (4x k6)
• Increased power consumption for ALL modes (55,
  110, 200, etc.) results when ADC/FFT bit width is
  increased

22
Low Power Applications

• Critical for handheld (battery operated) devices
  that need high rates
• Streaming or file transfer applications memory,
  media players, etc.
• Goal is lowest power consumption and highest
  possible data rates in order to minimize session
  times for file transfers
• Proposal support for scaling to lower power
  applications
• DS-UWB device
• Has very simple transmitter implementation, no
  DAC or IFFT required
• Receiver can gracefully trade-off performance for
  lower complexity
• Can operate at 660 Mbps without Viterbi decoder
  for super low power
• Also can scale to data rates of 1000 Mbps using
  L1 (pure BPSK) or 4-BOK with L2 at
  correspondingly shorter ranges (2 meters)
• MB-OFDM device
• Device supporting 480 Mbps has higher complexity
  power consumption
• MB-OFDM can reduce ADC to 3 bits with
  corresponding performance loss
• It is not clear how to scale MB-OFDM to gt480 Mbps
  without resorting to higher-order modulation such
  as 16-QAM or 16-PSK
• Would result in significant loss in modulation
  efficiency and complexity increase

23
Scalability to Varying Multipath Conditions

• Critical for handheld (battery operated) devices
• Support operation in severe channel conditions,
  but also
• Ability to use less processing ( battery power)
  in less severe environments
• Multipath conditions determine the processing
  required for acceptable performance
• Collection of time-dispersed signal energy (using
  either FFT or rake processing)
• Forward error correction decoding Signal
  equalization
• Poor receiver always operates using worst-case
  assumptions for multipath
• Performs far more processing than necessary when
  conditions are less severe
• Likely unable to provide low-power operation at
  high data rates (500-1000 Mbps)
• DS-UWB device
• Energy capture (rake) and equalization are
  performed at symbol rate
• Processing in receiver can be scaled to match
  existing multipath conditions
• MB-OFDM device
• Always requires full FFT computation regardless
  of multipath conditions
• Channel fading has Rayleigh distribution even
  in very short channels
• CP length is chosen at design time, fixed at 60
  ns, regardless of actual multipath

24
The Common Signaling ModeWhat Is The Goal?

• A common signaling mode (CSM) arbitrates between
  multiple UWB PHYs
• Multiple UWB PHYs will exist in the world
• DS-UWB MB-OFDM are first examples
• We need an etiquette to manage peaceful
  coexistence between the different UWB PHYs a
  CSM does this
• Planned cooperation (i.e. CSM) gives far better
  QoS and throughput than allowing un-coordinated
  operation and interference
• CSM improves the case for international
  regulatory approval
• CSM provides flexibility/extensibility within the
  IEEE standard
• Allows future growth scalability
• Provides options to meet diverse application
  needs
• Enables interoperability and controls interference

25
What Does CSM Look Like?One of the MB-OFDM bands!
Proposed Common Signaling Mode Band (500 MHz
bandwidth) 9-cycles per BPSK chip
DS-UWB Low Band Pulse Shape (RRC) 3-cycles per
BPSK chip
3978
Frequency (MHz)
3100
5100
MB-OFDM (3-band) Theoretical Spectrum
26
CSM Specifics

• We have designed a specific waveform for the CSM
• BPSK modulation for simple and reliable
  performance
• Length 24 spreading codes using 442 MHz chip rate
• Harmonically related center frequency of 3978 MHz
• Rate ½ convolutional code with k6
• Provides 9.2 Mbps throughput (can use L12 codes
  for 18.4 Mbps)
• It allows co-existence and interoperability
  between DS-UWB and MB-OFDM devices
• Prevents coexistence problems for multiple
  different UWB PHYs
• Provides interoperability in a shared piconet
  environment
• CSM supports the 802.15.3 MAC
• Achieves desired 10 Mbps data rates and robust
  performance
• Negligible impact on piconet throughput (beacons
  are lt1)
• Requires very low additional cost/complexity
• Almost no additional complexity for either
  MB-OFDM or DS-UWB

27
Conclusions

• DS-UWB is shown to have equal or better
  performance to MB-OFDM in all modes and multipath
  conditions for a fraction of the complexity
  power
• DS-UWB is not burdened with the multiple
  interference issues that continue to plague the
  MB-OFDM proposal
• Our vision A single PHY with multiple modes to
  provide a complete solution for TG3a
• Base mode that is required in all devices, used
  for control signaling CSM for beacons and
  control signaling
• Higher rate modes also required to support 110
  200 Mbps
• Compliant device can implement either DS-UWB or
  MB-OFDM (or both)
• Increases options for innovation and regulatory
  flexibility to better address all applications
  and markets

28

• Back-up slides

29
NTIA Comments on Using Noise to meet FCC 500 MHz
BW Requirement

• NTIA comments specifically on the possibility
  that manufacturer would intentionally add noise
  to a signal in order to meet the minimum FCC UBW
  500 MHz bandwidth requirements
• Furthermore, the intentional addition of
  unnecessary noise to a signal would violate the
  Commissions long-standing rules that devices be
  constructed in accordance with good engineering
  design and manufacturing practice.
• And
• It is NTIAs opinion that a device where noise
  is intentionally injected into the signal should
  never be certified by the Commission.
• Source NTIA Comments (UWB FNPRM) filed January
  16, 2004
• available at http//www.ntia.doc.gov/reports.html
  

30
FCC Rules Regarding Unnecessary Emissions

• FCC Rules in 47 CFR Part 15 to which NTIA refers
• 15.15 General technical requirements.
• (a) An intentional or unintentional radiator
  shall be constructed in accordance with good
  engineering design and manufacturing practice.
  Emanations from the device shall be suppressed as
  much as practicable, but in no case shall the
  emanations exceed the levels specified in these
  rules.