Ultra-wideband Standards and Technology Development

1
Ultra-wideband Standards and Technology
Development

• Jeff Foerster, Ph. D.
• Wireless Researcher
• Corporate Technology Group
• Intel Corporation
• WCNC 2003
• March 19, 2003

2
Unique industry opportunities

• New enhanced apps. for high-rate WPANs
• Multimedia streaming capability
• Better end-user experiences with very low-latency
• Reinforce FCC landmark decision (7.5 GHz of new
  spectrum)
• New spectrum overlay based regulations creates
  opportunity but still must prove peaceful
  coexistence
• Demonstrate intelligent and responsible spectrum
  usage
• International regulatory environment uncertain
• Show how UWB can peacefully coexist via standards
• Meet the interests of the PC, CE, and mobile
  communities
• Desire a single, unified, short-range wireless
  access standard
• Enable interoperability between different market
  segments

3
Desired UWB PHY Traits

• High bit rates 480 Mbps at 4-5 m range (USB
  2.0)
• 802.15.3a target rate of 110 Mbps at 10 m range
  is just a starting point
• System should be optimized for data rate rather
  than range
• Narrowband technologies better at longer ranges
• Multi-hop networks can help extend range
• Flexible spectrum usage
• Coexistence with 802.11a (and other WLANs)
  critical
• 4.9 GHz in Japan
• May have to adapt to different country
  regulations (allow for non-contiguous spectrum
  allocation)
• Robust to multipath, multiple access interference
• Low cost and low power consumption
• Full transceiver could be integrated into CMOS

4
Intels Technology DirectionA multi-band
(multi-carrier) approach

• Divide spectrum into bands (700 MHz)
• Allow devices to statically or dynamically select
  which bands to use for transmission
• Decision based on device throughput requirements,
  interference environment, geographical location,
  etc.
• Use well-defined beacon for negotiation
• Modulate data using QPSK MBOK RS coding with
  hybrid DS-FH CDMA alternate FDM modes

Single Symbol
5
Next Steps

• Goal Single, industry supported standard that
  meets technical and business requirements
• Standards and a high level of device
  interoperability critical for high-volume markets
• Work with 802.15.3a members towards single
  standard
• Major next technical steps for 802.15.3a
• Digest all (22) presentations from last week and
  look to merger best ideas quickly
• Lots of similarities
• Most avoided 5 GHz 802.11a bands for better
  coexistence
• Most used multiple bands (2, 3, up to 16 bands)
• How to divide and use the spectrum?
• One band vs. multi-band simultaneous operation
• Wider bands (2 GHz) vs. narrower bands (500
  MHz)
• Need to better understand implications on
  spectrum flexibility, robustness to
  multipath/MAI, complexity, power consumption

6
Backup
7
UWB usage models

Local high throughput delivery
wired wireless
wired wireless
Broadband
wired wireless
Long range delivery wired wireless
wired wireless
wired wireless
UWB complements longer range access technologies
8
Intels Submission to the IEEE 802.15.3a task
groupMarch 2003
9
Project IEEE P802.15 Working Group for Wireless
Personal Area Networks (WPANs) Submission Title
Intel CFP Presentation for a UWB PHY Date
Submitted 3 March, 2003 Source Jeff
Foerster, V. Somayazulu, S. Roy, E. Green, K.
Tinsley, C. Brabenac, D. Leeper, M. Ho Company
Intel Corporation Address JF3-212, 2111 N.E.
25th Ave., Hillsboro, OR, 97124 Voice
503-264-6859, FAX [phone]
E-Mailjeffrey.r.foerster_at_intel.com Re The
contribution is in response to the Call for
Proposals for a high-rate WPAN extension to be
developed in the IEEE 802.15.3a task
group. Abstract This contribution details a
proposal for a high-rate, short-range WPAN
physical layer approach based upon a multi-banded
UWB system architecture. The system has variable
data rates to address numerous application
requirements flexible spectrum management
techniques to adapt, either dynamically or
statically, to different interference and
regulatory environments good performance in the
presence of multipath and multiple access
interference with several areas for improvement
in the future and scalable levels of complexity
and power consumption to support devices with
different device implementation
targets. Purpose This contribution is given to
the IEEE 802.15.3a task group for consideration
as a possible high-rate, short-range physical
layer solution for WPAN applications. Notice Thi
s 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.
10
Intels Multi-band UWB PHY Proposal for IEEE
802.15.3a

• Jeff Foerster, V. Somayazulu, S. Roy, E. Green,
  K. Tinsley, C. Brabenac, D. Leeper, M. Ho
• Intel Corporation

11
Overview of Presentation

• Why UWB for 802.15.3a and why spectrum agility?
• Proposed multiband UWB PHY system architecture
• Modulation, coding, pulse shaping
• Link budget and supported data rates
• Multiple access techniques and performance
• Channelization methods
• Multipath mitigation techniques and performance
• Coexistence and narrowband interference
  mitigation
• Acquisition and preamble definition
• Implementation feasibility
• Summary
• Backup

12
Why UWB and why spectrum agility?

• Why UWB for IEEE 802.15.3a?
• UWB technology is uniquely suited for high-rate,
  short range access
• Theoretical advantages for approaching high rates
  by scaling bandwidth
• Newly allocated unlicensed spectrum (7.5 GHz)
  that does not take away from other narrowband
  systems (licensed or unlicensed)
• CMOS implementations now possible at these higher
  frequencies
• Why spectrum agility for a UWB solution?
• Just because the FCC allows UWB to transmit on
  top of other services does not mean we should!
• Government regulations should be broader than
  industry requirements
• Spectrum usage and interference environment
  changes by country location, within a local usage
  area, and over time
• Enable adaptive detection and avoidance
  strategies for better coexistence and possible
  non-contiguous spectrum allocations for flexible
  regulations in future
• Allow for simple backward compatibility and
  future scalability

13
A Multi-banded approach for Spectrum Agility

• Divide spectrum into separate bands (BW gt 500
  MHz)
• Allow devices to statically or dynamically select
  which bands to use for transmission
• Decision based on device throughput requirements,
  interference environment, geographical location,
  etc.
• Modulate data in an appropriate manner using a
  concatenation of these bands

Single Symbol
14
Proposed Multi-band UWB PHY System Architecture
15
UWB PHY System Architecture

• Transmitter and example receiver block diagrams
• Coding/Interleaving/Modulation

16
UWB PHY System Architecture

• Proposed Modulation and Coding
• M-ary Binary Orthogonal Keying (MBOK) QPSK
  Modulation
• Power efficient modulation
• Orthogonal code (Walsh-Hadamard) with
  interleaving allows for symbol decision feedback
  equalization
• Fast Hadamard Transforms exist with low latency
  and low complexity
• Outer Reed-Solomon Code
• Reed-Solomon used to correct burst errors
• System architecture can accommodate any of these
  alternate coding options
• Punctured Convolutional Codes
• Concatenated Convolutional Reed-Solomon
• Turbo codes (convolutional or product code based)
• Low density parity check (LDPC) codes

17
UWB PHY System Architecture

• Waveform Shape and Frequency Mapping
• 3 nsec pulse with rectified cosine shape (700
  MHz 10-dB bandwidth)
• Frequency separation 550 MHz
• Center Frequencies
• 1st 7 bands 3.6, 4.15, 4.7, 5.25, 5.8, 6.35,
  6.9 GHz
• 2nd 6 bands 7.45, 8, 8.55, 9.1, 9.65, 10.2 GHz
• Frequency offset of 275 MHz support for enhanced
  channelization
• 1st 7 bands 3.875, 4.425, 4.975, 5.525, 6.075,
  6.625, 7.175
• 2nd 5 bands 7.725, 8.275, 8.825, 9.375, 9.925

18
UWB PHY System Architecture

• Framing and non-overlapping symbol mapping
  (extended time-frequency codes)
• Extension factor (N) of symbols Tx before
  hopping to new frequency (N4 selected for this
  proposal)

19
UWB PHY System Architecture
4

• Mapping and interleaving of bi-orthogonal
  codewords
• Block interleave 4 bi-orthogonal codewords (as
  shown below)
• 6/3 byte interleaving delay (depending on I/Q
  interleaving strategy)

read
32
write
20
Link Budget and Supported Data Rates
21
Link Budget and Supported Data Rates

• Assumptions (see backup for more details)
• 7 dB system noise figure
• 0 dBi Tx/Rx antennas
• 3 dB implementation margin
• 7 bands (3.6 6.9 GHz)

22
Link Budget and Supported Data Rates

• Alternate rates can be supported using different
  number of bands (gt7 bands supported through
  parallel transmission)

MBOK rate 13-band 7-band 6-band 3-band 1-band
3/3 1073 577 494 247 82
3/4 804 433 370 185 61
4/8 536 288 246 123 41
5/16 335 180 154 77 25
6/32 201 108 92 46 15
6/64 100 54 46 23 7

• Possible signaling schemes for Beacon
• Allows for lower complexity devices to join the
  network
• Bands could be located between 3.1-5.1 GHz for
  easier coexistence with 802.11a

23
Multiple Access Techniques and Performance
24
Channelization for multiple piconets

• System uses a combination of DS/FH CDMA with
  optional FDM
• DS enabled through use of random PN mask applied
  to every chip low rate code
• Different users use different offset of long PN
  sequence
• FH enabled through periodic Time-Frequency (FH)
  codes (7 bands numbered 06)
• 6 codes available
• FDM enabled through piconet coordination
• Receiver implementations
• Rake receiver improves piconet isolation

Time slots in frame
0
1
2
3
4
5
6
1
0
2
4
6
1
3
5
2
0
3
6
2
5
1
4
Piconet number
3
0
4
1
5
2
6
3
4
0
5
3
1
6
4
2
5
0
6
5
4
3
2
1
6
TDMA used within a piconet
25
Multiple Access Performance

• Simulation results based on
• 108 Mbps mode with 7 bands, RS encoder, 6/32
  MBOK, 200 packets (221 byte packets), No AWGN
  (for simplicity)
• CM1(1) channel used for desired user (normalized
  total energy to onetake out effects of
  shadowing)
• One interfering user tested using 25 CM1, CM2,
  and CM3 channels (normalized total energy to
  onechannels selected were 2-26)
• Random propagation delay between desired and
  interfering user
• No frequency offset (simulations show 2-3 dB ISR
  improvement with offset)
• Metric used Maximum Interference-to-signal ratio
  (ISR)
• Results ( channels with 0 packet errors)

ISR (dB) 5 6 7 8 9 10 11 12 13
CM1 88 84 80 72 28
CM2 92 84 68 44 32 16
CM3 96 80 60 28
26
Multiple Access Performance

• Interpretation of results
• Results based on single user interference yields
  total interference margin
• Margin can be divided between small number of
  close-in interferers or larger number of further
  away interferers (correlation of random PN mask
  and long MBOK codeword makes interference look
  noise-like)
• Example Assume desired user operating at 5 m
  distance
• ISR 6 dB allows one interferer at 2.5 m
  distance or 4 interferers at 5 m distance
• Results show 6 dB of protection for most
  channels tested
• Many CM3 channels with 7 dB of protection
• Many CM1 and CM2 channels with 10 dB of
  protection

27
Multiple Access Performance

• How much is enough?
• Protection needed only when simultaneous
  transmissions occur
• Not all devices will be transmitting at the same
  time
• Always cases when more protection is needed
• Uncoordinated techniques for improved MAI
  rejection
• With increasing levels of SIR degradation due to
  MAI
• use offset frequency bands (improves ISR by 2-3
  dB)
• reduce code rate
• reduce number of occupied bands (drop heavily
  interfered bands)
• Coordinated techniques for improved MAI rejection
• Use child piconet mechanism in 802.15.3 MAC to
• Create time slots for the interfering piconets
• Create frequency band-sets for the interfering
  piconets (FDM)
• Piconets do not need time synchronization after
  coordination
• Could help address severe near-far problems

28
Multipath Mitigation Techniques and Performance
29
Multipath Mitigation Methods

• Multipath mitigated through 4 techniques
• Interleaving MBOK chips over different
  frequencies provides frequency diversity
• MRC of chips in MBOK decoder
• Time-frequency codes results in 72 nsec
  separation between frequency on times (allows
  for multipath to ring down)
• ISI between 4 adjacent chips during on time
  requires equalization
• Interleaving MBOK codewords allows for effective
  decision feedback equalizer
• Feed-forward filter can capture energy of
  multipath during 4-chip on time
• Additional rake fingers could also be used

30
Multipath Performance

• Simulation results based on
• 108 Mbps mode with 7 bands, RS encoder, 6/32 MBOK
• 200 packets (221 byte packets)
• 100 realizations of CM1, CM2, and CM3 (CM4 in
  future)
• 333 MHz sample rate (one sample per chip)
• Fixed sample time between samples (sub-optimum
  sampling per band)
• Simple decision feedback equalizer 4-tap
  feed-forward rake filter
• No rake
• Results ( channels with 0 packet errors)

Eb/No (dB) 8 10 12 14 16 gt18
CM1 57 75 86 87
CM2 59 75 86 92
CM3 35 54 67 76 80 86
SNR at 10 m
31
Multipath Performance

• Interpretation of results
• Link performance dominated by energy capture
  (shadowing finite length rake)
• Simple equalizer not sufficient for 10 of
  channels in each case
• Maximum Eb/No 12.8 dB _at_ 10 m can be supported
  (includes the implementation marginsome
  implementation losses captured in sims)
• Can close-the-link for all channels in which
  Eb/No12 dB yields 0 packet errors
• Lots of room for improvement
• Improved receiver design
• Improved equalizer rake combining schemes
  (4-tap MMSE equalizer)
• Add more rake arms
• Detect partial overlapping pulses within 12 nsec
  interval
• Add parallel receiver branches to capture energy
  in 24 nsec intervals
• Improved sampling time by optimizing for each
  band
• Alternate FEC schemes

32
Coexistence and Narrowband Interference Mitigation
33
Coexistence Strategies

• Static Control
• Pre-configure device (through software control)
  not to use a particular band
• Based on geographic region or device usage
• Dynamic Control
• Allow device to detect presence of NBI and avoid
• Device interoperability requirements could
  specify detection requirements to ensure adequate
  control
• Similar methods used in 802.11h for WLAN
  coexistence with radar systems in Europe
• UWB power emitted into 802.11a bands
• Avoiding 5.25 (5.8) GHz band for lower (upper)
  UNII band coexistence lt -20 dB attenuation from
  Part 15 limits at band edge
• UWB power emitted into 4.9 GHz WLAN band in Japan
• Avoiding 4.7 (4.975 using frequency offset
  channels) GHz band lt -10 dB (lt-20 dB)
  attenuation from Part 15 limits at band edge

34
Narrowband Interference

• RF Front End Implications
• All UWB systems must deal with strong
  interference at antenna (not unique to multi-band
  solutions)
• Can be handled through filters, component
  linearity requirements, and power consumption
• For strong NBI
• Detect and avoid use of band via signaling to PNC
• Rely on adjacent channel rejection of filters
  receiver signal processing
• For moderate or weak NBI sources (SIR lt X dB)
• Let link design and receiver implementations
  mitigate interference
• UWB pulsed signaling MBOK RS coding
• Interference suppression and/or cancellation
  techniques

35
Acquisition and Preamble Definition
36
Preamble Definition

• Goal Pfa and Pmd 10 of 8 PER target, i.e. lt
  0.008
• Simulations in multipath so far show estimated
  preamble lengths
• to be quite conservative
• Preamble divided into two parts
• CCA/packet detection coarse timing acquisition
• Fine timing adjustment channel estimation SIR
  estimation

Step 1 CCA/packet detect, Coarse Timing 5.4ms
Step 2 Fine timing channel, SIR estimation 4ms
Total proposed preamble time 9.4ms

• Beacon packets use the basic preamble structure
  shown
• Actual preamble sequence discussed in back-up
  based on concatenation of CAZAC sequences
• Shorter preamble options can be used for higher
  throughputs

37
Implementation feasibility
38
Implementation feasibility

• Proposed multi-band architecture has many
  elements designed to reduce complexity and power
  consumption
• Non-overlapped timing
• Shared pulse generator, ADC, correlator,
• Reduced power consumption via duty cycle of bands
• Dont necessarily require N continuously running
  PLLs
• ADC sampling at symbol rate (330 MHz for 1
  sample/symbol or 660 MHz for 2 samples/symbol)
• Reused circuits smaller die area
• Many elements in common with other UWB
  architectures
• LNA, mixers, BP/LP filters, AGC, VGA, digital
  processing (FEC, equalization, etc.)
• Many possible transceiver implementations

39
Implementation feasibility
40
Implementation feasibility
RX Oversampling Factor
0.18um mixed signal CMOS (all components,
including LNA), 5-bit ADCs, digital processing
excluded, estimates for smaller of bands not
optimized.
41
Summary
42
Summary

• Proposed UWB multi-band system architecture
  provides spectrum flexibility for
• Good coexistence with narrowband systems
• Adapting to different regulatory environments
• Future scalability of spectrum use (dont need to
  occupy all 7.5 GHz of spectrum today)
• Good performance with multiple access
  interference and multipath
• Additional back-off modes for improved robustness
• Room for improvement in receiver implementations
• Next steps
• Work with IEEE 802.15.3a members to merge ideas
  towards a single UWB PHY

43
802.15.3a Early Merge Work
Intel will be cooperating with

• Time Domain
• Discrete Time
• General Atomics
• Wisair
• Philips
• FOCUS Enhancements
• Samsung

• Objectives
• Best Technical Solution
• ONE Solution
• Excellent Business Terms
• Fast Time To Market

We encourage participation by any party who can
help us reach our goals.
44
Backup Material
45
Backup Material

• Self-evaluation matrix
• Example Link Budget Calculation
• Piconet setup example for selecting channels
• Simulation results for multiple access
  interference with multipath
• Simulation results for single user in multipath
• Preamble definition and detection characteristics
• Ranging techniques
• Channel characteristics vs. pulse bandwidth

46
Self-evaluation Matrix General Solution
47
Self-evaluation Matrix PHY Protocol
48
Self-evaluation Matrix MAC Enhancements
49
Example Link Budget Calculation
50
Piconet Setup Example
51
Multiple Access Performance Simulations

• CM1(1) desired path, CM1(2-26) interfering path

52
Multiple Access Performance Simulations

• CM1(1) desired path, CM2(2-26) interfering path

53
Multiple Access Performance Simulations

• CM1(1) desired path, CM3(2-26) interfering path

54
Single-user Multipath Performance Simulations
CM1 (5 nsec RMS delay)
55
Single-user Multipath Performance Simulations
CM2 (8 nsec RMS delay)
56
Single-user Multipath Performance Simulations
CM3 (14 nsec RMS delay)
57
Preamble Definition
Step 1 CCA/packet detect, Coarse Timing
Step 2 Fine timing, channel estimation, SIR
estimation
Step 1
Total 16 reps of CAZAC-16 sequence per band x
84ns frame time 5.4 ms
s0s0s0s0
s1s1s1s1
s1s1s1s1
s0s0s0s0
Frequency band
s15s15s15s15
12 ns
84 ns
CAZAC-16 sequences s0s1s15, s0s1s15,
s0s1s15 s0s1s15,
58
Preamble Definition
Step 2
12 reps of CAZAC-16 sequence per band x 84ns
frame time 4 ms
s0s0s0s0
s1s1s1s1
s0s0s0s0
s1s1s1s1
Frequency band
s15s15s15s15
12 ns
84 ns
CAZAC-16 sequences s0s1s15, s0s1s15,
s0s1s15 s0s1s15,
59
Detection Characteristic for Packet
Detection/Coarse Timing

• Goal Pfa and Pmd 10 of 8 PER target, i.e. lt
  0.008
• Simulations so far show derived preamble lengths
• to be quite conservative

60
UWB Ranging via Two-Way Time Transfer
tp (unknown)
Device clocks are offset by to (unknown)
B
Devices A B swap two range messages M and M
TB TA to tp
TA TB - to tp
Two equations in two unknowns yield
tp ½ ( TA TA TB TB )
Is independent of Tx/Rx turn-around time.
Can rely on sub-ns Tx/Rx clocking circuits. Is
nearly independent of chosen UWB pulse width.
Accuracy Precision
US Naval Observatory, Telstar Satellite, circa
1962 http//www.boulder.nist.gov/timefreq/time/two
way.htm
61
Channel Characteristics vs. Pulse Bandwidth
Total energy capture greater for narrowband
pulses
Channel fading greater for narrowband pulses
Results for 1-arm rake and averaged over all
CM1-4 channels