Project: IEEE P802'15 Working Group for Wireless Personal Area Networks WPANS

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Project IEEE P802.15 Working Group for Wireless
Personal Area Networks (WPANS)
January 2005
doc. IEEE 802.15-04/704r1

• Submission Title Staccato UWB PHY Proposal for
  TG4a
• Date Submitted January 2005
• Revised
• Source Roberto Aiello, Ph.D., Torbjorn Larsson,
  Ph.D. Company Staccato Communications E-mail
  roberto_at_staccatocommunications.com
• Re 802.15.4a Call for proposal
• Abstract This presentation represents Staccato
  Communications proposal for the 802.15.4a PHY
  standard, based on UWB
• Purpose Response to WPAN-802.15.4a Call for
  Proposals
• 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.

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Staccato CommunicationsUWB PHY Proposal for TG4a

• Roberto Aiello, Ph.D.
• Torbjorn Larsson, Ph.D.
• Staccato Communications
• r_at_staccatocommunications.com

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Goals

• Good use of UWB unlicensed spectrum
• Good system design
• Path to low complexity CMOS design
• Path to low power consumption
• Scalable to future standards
• Graceful co-existence with other services
• Graceful co-existence with other UWB systems

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Introduction

• Staccato is MBOAs founding member, promoter BOD
  member
• This proposal is based on band limited impulse
  radio
• OFDM is optimal solution for high performance
  systems
• Impulse radio has attractive features for 15.4a
  applications

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Features

• Meets all system requirements
• Low signal repetition frequency to reduce ICI/ISI
  and need for high speed digital circuits (lower
  power consumption)
• Narrow UWB bandwidth to reduce complexity
• Use of differential encoding on chip level to
  reduce receiver complexity and provide maximum
  robustness

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Summary

• Band limited UWB system compliant with FCC 02-48,
  UWB Report Order
• 500MHz bandwidth at -10dB
• Two bands centered at 4.752 GHz and 5.252 GHz
  (MB-OFDM band 4 and 5)
• Symbol rates varying from 12.5 kbps to 1.6 Mbps
  at PHY-SAP
• Due to time constraints, this presentation
  addresses
• Modulation scheme, channelization and packet
  structure
• Performance in AWGN
• Remaining material will be presented at the next
  opportunity in March 2005
• Performance in multipath
• Implementation feasibility
• Self evaluation criteria
• Other issues that will emerge from groups
  feedback

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Multipath
CM8 (Industrial NLOS) PRF 3.2 MHz
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System Description
PRF 3.2 MHz
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System Description, Continued

• Impulse radio combined with direct-sequence
  spreading
• Differential BPSK modulation of chips
• A code word covers one BPSK-modulated symbol
• Different piconets use different code words
• Differential encoding of chips allows the use of
  differential chip detection in the receiver
• Differential detection is carried out separately
  for each multipath component
• Differential combining of multipath components
• No need for channel estimation
• Simple receiver structure with decent performance

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System Description, Continued

• For improved performance, non-coherent symbol
  detection (with coherent energy integration
  across one code word) can be used
• Symbol detection is carried out separately for
  each multipath component
• Non-coherent combining of multipath components
• Still no need for channel estimation
• PRF (chip rate) 3.2 MHz
• Low enough to avoid interchip interference (ICI)
  with all 802.15.4a multipath models
• High enough to eliminate the need for frequency
  offset correction (with some performance loss)
  when differential detection is used
• Pulse shape 3rd-order Butterworth or similar
• FEC 16-state rate-1/2 convolutional code and
  symbol repetition

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Differential Multipath Combining
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System Parameters
PHR PHY Header PSDU PHY Service Data Unit
SFD Start-of-Frame Delimiter

• Length of spreading code in preamble is always 16
• Duty cycle lt 100 means that code words of length
  16 are transmitted with a space in between
• An extra initial chip is added to serve as phase
  reference for the first chip in the code word
• For instance, to achieve a duty cycle of
  approximately 50, 17 chips are transmitted
  followed by a space equivalent to 15 chip periods

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Packet Structure
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Spreading Codes (Length 16)
-1    -1     1    -1    -1     1    -1     1   
-1    -1    -1     1     1     1     1     1
-1     1    -1     1    -1    -1     1     1   
-1    -1    -1    -1     1     1     1     1
 -1     1     1    -1     1    -1    -1    -1   
-1    -1     1     1     1    -1     1     1
-1    -1    -1    -1    -1     1     1     1    
1    -1     1     1    -1     1    -1     1

• These code words (c) were found by exhaustive
  search based on the three following properties
• Low cyclic autocorrelation
• Low cyclic cross-correlation between code words c
• Low cross-correlation between code words (1,c)
  and (1,-c)

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Throughput

• The length of the data PSDU (payload) is 32
  octets. The data rate is 100 kbps (this is X0 in
  this proposal)
• Assumptions (refer to the figure on page 20 in
  the PHY selection criteria document)
• aMinLIFSPeriod 40 symbol periods
• aTurnaroundTime 12 symbol periods
• aUnitBackoffPeriod 20 symbol periods
• Length of ACK PSDU 5 octets
• t_ack is the time between the end of the data
  frame and the beginning of the ACK frame
• worst case, is t_ack aTurnaroundTime
  aUnitBackoffPeriod 32
• best case, t_ack is t_ack aTurnaroundTime 12

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Receiver Architectures
A.
Differential chip detection during both
acquisition and data demodulation
B.
Differential chip detection during acquisition
and non-coherent symbol detection during data
demodulation
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More on Receiver Architectures

• In both architectues, acquisition is based on
  differential detection/combining
• Does not require frequency offset correction and
  therefore leads to shorter preamble (gt less
  overhead)
• Small performance loss at 20 ppm frequency error
• If desired, frequency offset estimation can be
  carried out in parallel with synchronization
• Architecture A
• Differential chip detection for data demodulation
• Frequency offset correction may still be applied
  during PHR and PSDU to improve performance
• Architecture B.
• Non-coherent symbol demodulation for data
  demodulation
• Significant performance improvement, since we are
  now summing energy coherently across a whole
  codeword (which for data rates lt 100 kbps is 16
  chips long)
• Requires frequency offset estimation (during
  acquisition) and correction (during data
  demodulation)

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Link Budget
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System Simulation Parameters

• Frequency band 4.752GHz (MB-OFDM band 4)
• 10 dB bandwidth 500 MHz
• Transmit power -16.1 dBm
• Transmit/Receive filter 3rd order Butterworth,
  corner frequency 180 kHz
• A/D converter 528 MHz, 3 bits
• Noise figure 7 dB
• Data rate 100 kbps
• PSDU size 32 bytes
• PRF (chip rate) 3.2 MHz
• Length of DS spreading code 16
• Length of preamble 48 bits
• Length of SFD 32 bits
• Length of PHR 48 bits
• Modulation DBPSK
• Demodulation method differential detection
• No frequency offset

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Spectrum
TX Power -16.1 dBm
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PER vs. Distance in AWGN (100 kbps)
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PER vs. Eb/No (100 kbps)
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PER vs. Received Power (100 kbps)
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Conclusions

• UWB band limited system
• Meet all system requirements
• Low signal repetition frequency to reduce ICI and
  need for high speed digital circuits (lower power
  consumption)
• Narrow UWB bandwidth to reduce complexity
• Remaining material will be presented at the next
  opportunity

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802.15.4a Early Merge Work
Staccato Communications is actively
collaborating with others

• 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.