Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANS)

1
Project IEEE P802.15 Working Group for Wireless
Personal Area Networks (WPANS)

• Submission Title General Atomics Call For
  Proposals Presentation
• Date Submitted 3 March 2003 7 March 2003-
  rev1
• Source Naiel Askar, General Atomics- Photonics
  Division, Advanced Wireless Group, 10240 Flanders
  Ct, San Diego, CA 92121-2901, Voice 1 (858)
  457-8700, Fax [phone], E-mail
  naiel.askar_at_ga.com
• Re 802.15.3a Call For Proposal, Spectral
  Keying UWB Multi-Band Technology
• Abstract This presentation outlines General
  Atomics PHY proposal to the IEEE 802.15.3a Task
  Group
• Purpose To communicate a proposal for
  consideration by the standards committee
• 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 or organization. The material in this
  document is subject to change in form and content
  after further study. The contributor reserves 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
Overview of General Atomics PHY Proposal to IEEE
802.15.3a

• Presented by Naiel Askar
• www.ga.com/uwb

3
Outline of Presentation

• Description of Spectral KeyingTM (SK)
• SK parameters and operating frequencies
• Channelization scheme
• SK performance
• Implementation issues
• Interference and co-existence
• Preamble definition
• Self-evaluation
• Conclusions

4
Summary of Proposal

• Scalable data rates from 15-1300 Mbps
• Spectral KeyingTM modulation
• Compliant with FCC 02-48, UWB Report Order
• Multi-Band system, scalable from 4-12 bands,
  occupying 2 - 6 GHz total bandwidth
• Supports at least 4 co-located piconets
• Spectral KeyingTM is a registered trademark of
  General Atomics

5
Key Features

• A new modulation scheme which has been optimized
  for UWB systems
• Low symbol rate with guard time between symbols
• Enhanced multipath immunity by limiting
  channel-induced inter symbol interference (ISI)
• Low duty cycle allows power saving features
• Minimizes collisions between colocated piconets
• Set of allowable symbols increases with the
  factorial of the number of frequencies
• Bit rate scalable with power consumption, cost
  and occupied frequency
• Enhanced co-existence with IEEE 802.11a

6
UWB Multi-Band Technology

• UWB spectrum divided into multiple bands
• One symbol will be composed of subpulses from
  multiple bands
• Excellent performance in multipath
• Scalability
• Bit rate
• Power consumption
• Range
• Complexity / Cost
• Coexistence
• IEEE 802.11a
• Regulatory
• Compliant with US FCC
• Flexibility for world-wide regulatory action

7
Spectral Keying Modulation
UWB Symbol in Time

• Transmit 2 or more subpulses using different
  bands
• Order of bands defines symbol

Voltage
Time (ns)
8
SK Definitions

• Data encoded with
• Sequence of bands in the pulse
• Phase information on the subpulses

9
Spectral Keying General Case

• An SK symbol X, where can be defined in terms
  of the location in a MxT matrix, B and P
• where
• 0 means no transmission
• 1 allows Binary Phase Shift Keying (BPSK)
• i allows Quadrature Phase Shift Keying (QPSK)
• M is of frequency bands
• T is of time slots
• B is of non-zero entries
• P is of polarity bits
• N is of available bits

where
For Optimum BER Performance in SK use MTB
10
SK Rate Scalability Examples
2 bands no polarity
5 bands, with BPSK 8 bands with
QPSK Sequence bits/sym. 1 6.5
15 Phase bits /sym. 0 5
16 Total bits/sym. 1 11.5
31
For sequence bits, the set of allowable symbols
increases with the factorial of the number of
bands
11
Data Rate Examples
12
SK Parameters For Base Rates
13
Transmit Sub-pulse Shaping

• A rectangular 2 ns pulse is low pass filtered
  (2nd order) to suppress out of band emissions
• 3 dB bandwidth 440 MHz
• 10 dB BW 700 MHz

14
Frequency Plan for 110/200 Mbps
Piconet 1 Piconet 2 Piconet 3 Piconet 4

• Define 20 bands centered 3.4-7.2 GHz
• Bands are spaced 200 MHz apart
• Piconets will have different bands
• 4 piconets will have 5 unique bands
• Bands in each piconet will have 800 MHz
  separation
• Other piconets will share some frequencies, less
  separation

15
4 Piconets at 110/200 Mbps

• Systems will be able to cancel or modify the
  frequency of one band to avoid interference
• Reducing receive filter bandwidth can reduce
  interference from adjacent piconets

16
Piconet Isolation

• Performance improved by 3 factors

• Frequency separation isolation
• Low symbol rate reduces collision rate between
  piconets random or passively synchronized
• Coding gain of SK and channel coding

17
Passive Synchronization for Channels

• Time interleaving may be used by channels 3, 4 to
  minimize interference

• Passive scanning of bands will identify best
  time slots
• Improved performance with lower symbol rate
• Has reasonable margin for
• channel delay spread
• timing uncertainty due to near-far problem
• Clock synchronization can be avoided by repeated
  scanning

18
Performance Bounds for SK

• Case when M T B, P 1
• The Euclidian Distance (ED) when a frequency is
  in error has a value of 2
• Similar to antipodal modulation BPSK
• SK will require lower EbNo for the same
  performance compared to BPSK because of the
  higher order modulation
• Where
• M is of frequencies
• T is of time slots
• B is of non-zero entries
• P is of polarity bits
• Ps is the probability of subpulse error
• Es is the energy per subpulse
• No is the noise spectral density
• EbNo is the ratio of bit energy to noise density

19
SK Error Rate Performance Predictable Analysis
vs. Simulation Results
TM
20
BER Performance of 5 Band SK in AWGN Improvement
Over BPSK
TM
21
Channel Capacity in AWGN (Coherent Receiver)

• M is of frequency bands
• T is of time slots
• Q is of non-zero entries
• P is of polarity bits

Operating Point
22
Channel Capacity in AWGN (Non coherent receiver)

• M is of frequency bands
• T is of time slots
• Q is of non-zero entries
• P is of polarity bits

Operating Point
23
Error Correction Coding Approach

• Coding algorithm Turbo Convolutional Code (TCC)
• Best performance
• Manageable cost and power consumption
• Best in flexibility in selection of code rate, on
  the fly code change
• Already selected for 3GPP, DVB, etc.
• Cost
• Estimated power consumption 35 mW.
• Estimated chip area 3 mm2 in 0.13 mm CMOS
• Parameters
• Overall code rate 4/5
• Memory size (4k bits), larger packets will be
  concatenated
• Number of iterations 4, 3 bits of quantization
• EbNo 3.6 dB for BER 1e-5
• Turbo code simulation (DLL) and performance
  supplied by iCODING Technologies

24
Turbo Code Scalability

• Range of Performance
• 1 iteration matches performance of K7
  convolutional code
• 1.5 or more iterations exceeds performance of K7
  convolutional code
• 3 or more iterations substantial performance
  gains (2-4 dB)
• Code rate is adjustable for longer range mode(s)
• Power consumption can be reduced by early
  stopping
• Larger frame size (up to 8K) can further increase
  performance
• Extreme low cost, low power low latency option
• K4 constituent code can be used as stand alone
  FEC option.
• Uses same encoder components as full Turbo Code
• Area less than 0.25 mm2 in 0.18u process
• 1/8th the complexity of a K7 CC with upwards
  scalability built in
• Very high coding gains in frequency selective
  fading channel
• 2-4 dB gain in AWGN can translate to 4-7 dB gain
  in frequency selective fading channels over
  non-iterative techniques.

25
Bit to Symbol Mapping

• Maximum of frequency bits in SK symbol
  (MTB5, P0) log2 120 6.9 (excluding
  polarity bits)
• Simple mapping will produce 6.5 bits,13 bits from
  2 symbols
• The 3rd frequency of 2 symbols are combined to
  produce 3 bits
• Reserved symbols for preambles are available

Time slot number No of choices Available bits Used bits
T1 5 2.3 2
T2 4 2 2
T3 3 1.6 1.5
T4 2 1 1
T5 1 0 0
26
SK Simulation in AWGN with Channel Decoder
8 PER
1e-5 BER
27
Link Budget
28
Transceiver Block Diagram
29
Example of a Spectral Keying Transmitter
30
Example of a 5-Band SK Receiver
31
Unit Manufacturing Complexity

• Preliminary area estimates
• 3 mm2 for RF
• 7.0 mm2 for digital
• The target is to have a one chip solution
• First implementation may have separate RF and
  digital chips
• The receiver has one signal chain per band (5
  total)
• Allows implementing Rake receiver without extra
  hardware
• Having multiple receive chains increases area
  0.5 mm, but has little impact on overall
  complexity
• Allows tracking signal peak on each band
  individually giving improved performance
• Low risk

Estimates based on collaboration with Philips
Semiconductors
32
Power Consumption

• Power consumption will be dominated by
• Oscillators trade performance for low current
• ADCs limit number of bits to 3
• Front end receiver dominated by NF/11a
  interference requirements
• Minimize by designing with adaptive
  linearity/power tradeoff
• Low symbol rate gives low duty cycle allowing
  power saving techniques to be applied

Estimates based on collaboration with Philips
Semiconductors
33
Manufacturability Technical Feasibility

• Use of proven technology and processes
• No high risk components or technology
• Immune from distortion or ringing from antennas
  or filters owing to relatively long subpulse time
• Relaxed antenna characteristics
• Modules already tested in the lab

34
Experimental Results of SK Validate Simulations
35
Scalability

• Power consumption
• Scalable from 127 to 425 mW based on rate
  (55-200Mbps)
• Data rate
• Scalable from 23 1300 Mbps
• Range
• Scalable with more rakes, more coding, lower
  symbol rate
• Complexity
• Lower complexity, lower performance system
  possible

36
Interference from 802.11a

• Flexibility in choice of bands is key to
  performance
• Bands centered at 5.0, 5.2, 5.4 GHz will be
  avoided
• Table below based on selection criteria
  parameters
• Bands centered on 4.8, 5.6 will be marginal at 1m
• Bands centered on 4.6, 5.8 will be OK at 1m
  separation between interferer and victim,
  marginal at 0.3m separation
• All other bands are OK

37
802.11a Co-existence

• Flexibility in removing bands from or moving to
  adjacent bands improves co-existence
• Interference from UWB is much lower than an
  802.11a device at same distance
• SIR levels are based on 802.11a minimum
  sensitivity of -82 dBm for 6 Mbps rate

38
PHY Preamble

• Utilize the same preamble as the 15.3 PHY for
  each band separately
• Composed of 16 Constant Zero Autocorrelation
  (CAZAC) symbols
• The pattern is repeated 10 times
• Last symbol will have inverted polarity
• Total 160 symbols lasting 12.3 µsec.
• Detection miss probability and false alarm rate lt
  10-3 in multipath are achievable
• Detection is declared when a threshold is
  exceeded in 2 out of the 5 bands

39
General Solution Criteria (1/2)
40
General Solution Criteria (2/2)
41
Conclusions

• A UWB system based on Spectral KeyingTM will meet
  or exceed all selection criteria
• Spectral KeyingTM is a Multi-Band scheme
• Good multipath performance
• Flexibility in assigning bands for regulatory and
  interference avoidance
• Unique high order modulation allows low symbol
  rate with long guard time between symbols
• Minimizes ISI - At maximum data rate no equalizer
  needed
• Off period is 75 at 13 MHz symbol rate - Allows
  power conservation
• Efficient spectrum utilization allows frequency
  based channels
• Provides scalability for power consumption, rate,
  range and complexity
• Technology proven with demonstrations
• Letter of assurance for essential patents
  submitted to the IEEE 802.15.3a leadership
• The May 2003 presentation will focus on analysis
  and simulation

42
802.15.3a Early Merge Work
General Atomics will be cooperating with

• Discrete Time
• Focus Enhancements
• Intel
• Philips
• Samsung
• Time Domain
• Wisair

• 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.