Chirp%20Spread%20Spectrum%20(CSS)%20PHY%20Submission

1
Project IEEE P802.15 Working Group for Wireless
Personal Area Networks (WPANs) Submission Title
DBO-CSS PHY Presentation for 802.15.4a Date
Submitted March 07, 2005 Source (1) John
Lampe, Rainer Hach, and Lars Menzer, (2)
Kyung-Kuk Lee, Jong-Wha Chong, Sang-Hun Yoon,
Jin-Doo Jeong, Sang-Dong Kim, Heun-Uk
Lee Company (1) Nanotron Technologies, (2)
Orthotron Co., Ltd. - Hanyang Univ Address (1)
Alt-Moabit 61, 10555 Berlin, Germany, (2) 709
Kranz Techono, 5442-1 Sangdaewon-dong,
Jungwon-gu, Sungnam-si, Kyungki-do, Korea
462-120 Voice (1) 49 30 399 954 135, (2)
82-31-777-8198 , E-Mail (1) j.lampe_at_nanotron.co
m, (2) kyunglee_at_orthotron.com Re This is in
response to the TG4a Call for Proposals,
04/0380r2 Abstract The Nanotron - Orthotron
DBO-CSS is described and the detailed response to
the Selection Criteria document is
provided Purpose Submitted as the candidate
proposal for TG4a Alt-PHY 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
Differentially Bi-OrthogonalChirp-Spread-Spectrum
PHY Proposal for 802.15.4a
by John Lampe, Rainer Hach, and Lars Menzer
Nanotron Technologies GmbH, Germany j.lampe_at_nanot
ron.com Kyung-Kuk Lee / Jong-Wha Chong Orthotron
Co., Ltd. / Hanyang Univ., Korea
kyunglee_at_orthotron.com
3
Contents

• DBO-CSS System Overview
• Selection Criteria Document Topics
• PAR and 5C Requirement Checklist
• Summary

4
DBO-CSS System Overview The merged proposal is
different than and improves on the two original
proposals!

• Chirp Property
• Concept of Sub-Chirps
• Block-diagram

? DBO-CSS Differentially Bi-Orthogonal
Chirp-Spread-Spectrum
5
DBO-CSS System Overview
Chirp Properties
Linear Chirp Rectangular Window
t
Linear Chirp Raised-Cosine Window
6
DBO-CSS System Overview
Concept of Sub-Chirps
Spectrum
Freq. Time (Pass-band)
fdiff.
fc
I II III IV
0
Fbw 7.0 MHz rolloff 0.25 Fdiff 6.3 MHz Tc
4.8usec
t
fBW
-10
fc
-20
t
-30
fc
t
-40
-50
fc
-20 -10 fc
10 20 (MHz)
t
Same Spectrum with IEEE802.11b
7
DBO-CSS System Overview
Concept of Sub-Chirps
Baseband Waveform
Real Imaginary Envelope
8
DBO-CSS System Overview
Concept of Sub-Chirps
9
DBO-CSS System Overview
Block-diagram DBO-CSS Transmitter
Digital MOD
Low-Pass Filter
I/Q Modulator
LP
I
fT f 10 MHz
LP
Q
LO
fc
10
DBO-CSS System Overview
Block-diagram DBO-CSS Receiver
I/Q Demodulator
Diff Detector Bank
LP
ADC
I
Decode and Cotrol
LP
ADC
Q
Correlator
LO
fR fLO 10 MHz
ToA estimator
fc
Digital Domain
11
DBO-CSS System Overview
Bi-Orthogonal Mapping
8-ary Bi-Orthogonal Symbol Mapping Table
Decimal (m) Binary (b0,b1,b2) Bi-Orthogonal Code (01,02,03,04)








0 000 1 001 2
010 3 011 4
100 5 101 6
110 7 111
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
3 bits/symbol
12
DBO-CSS System Overview
Block-diagram 8-ary Differentially
Bi-Orthogonal
Binary-Chirp-Spread-Spectrum (DBO-BCSS) Modulator
Data-rate 250Kbps
Binary Data
S/P
Symbol Mapper
P/S
1
1
3
1
3
4
1
CSS Gen.
DBO-BCSS
13
DBO-CSS System Overview
Block-diagram 8-ary Differentially
Bi-Orthogonal
Quaternary-Chirp-Spread-Spectrum (DBO-QCSS)
Modulator
Data-rate 1Mbps
S/P
Symbol Mapper
P/S
Mapper QPSK
3
3
4
1
1
Binary Data
12
S/P
1
1
2
2
S/P
Symbol Mapper
P/S
3
3
4
1
1
CSS Gen.
DBO-QCSS
14
DBO-CSS System Overview
Block-diagram 8-ary DBO-QCSS Demodulator
15
Selection Criteria Document Topic

• Band in Use
• Signal Robustness
• interference mitigation techniques.
• Interference Susceptibility
• Coexistence
• Technical Feasibility
• Manufacturability
• Time to Market
• Regulatory Impact
• Backward Compatibility
• Scalability
• Mobility
• MAC Protocol Supplement
• PHY Layer Criteria
• Unit Manufacturing Cost/Complexity (UMC)
• Size and Form Factor
• Payload Bit Rate and Data Throughput

• Simultaneously Operating
• Piconets
• Signal Acquisition
• Clear Channel Assessment
• System Performance
• Error rate
• Receiver sensitivity
• Ranging
• Link Budget
• Power Management Modes
• Power Consumption
• Antenna Practicality

16
Selection Criteria Document Topic
Band in Use

• 2.4GHz ISM Band Same Operating Channels with
  802.11b
• - Non-Overlap fc 2.412GHz, 2.437GHz,
  2.462GHz (North America) / 2.412GHz, 2.442GHz,
  2.472GHz (Europe)
• - Overlap fc 2.412GHz, 2.422GHz, 2.432GHz,
  2.442GHz, 2.452GHz, 2.462GHz (North America,
  Europe) /
• 2.472GHz (Europe)
• 20MHz Bandwidth 4 SOPs per Band

17
Selection Criteria Document Topic
Signal Robustness

• Co-existence / Interference Mitigation
  Technique
• - Orthogonal / Quasi-Orthogonal Signal Set
• - High Spectral Processing Gain Chirp
• - Near-Far Problem FDM Channels (3
  non-overlapping ch _at_2.4GHz)
• - Higher data rate
• - CCA
• - CSMA
• Interference Susceptibility
• - Low Cross-Correlation property with
  Existing Signal
• - Adoption of 802.11 Frequency Channels
• - Higher data rate ? shorter transmit time
• Robustness
• - Heavy Multi-path Environment Differential
  Encoding
• - SOP Good Orthogonality
• Low Sensitivity for Component Tolerance
• - Crystal 40ppm

18
Selection Criteria Document Topic
Signal Robustness Interference Susceptibility
Support for Interference Ingress

• Example (without FEC)
• Bandwidth B of the chirp 20 MHz
• Duration time T of the chirp 4.8 µs
• Processing gain, BT product of the chirp gt 17 dB
• Eb/N0 at detector input (BER10E-4) 12.5 dB
• In-band carrier to interferer ratio
• C/I _at_ BER10-4 gt 12.5 17 -4.5 dB

19
Selection Criteria Document Topic
Signal Robustness Coexistence

• Low interference egress
• IEEE 802.11b receiver
• More than 30 dB of protection in an adjacent
  channel
• Almost 60 dB in the alternate channel
• These numbers are similar for the 802.11g
  receiver

20
Selection Criteria Document Topic
Signal Robustness Coexistence
System performance with IEEE802.11b Interference
DBO-CSS Signal is not susceptible to W-LAN
Interference
Same Tx Power
Receiver
WLAN Transmitters
Desired
Under
Transmitter
Test
Dint.
Dref.
21
Selection Criteria Document Topic
Technical Feasibility Manufacturability

• No special components (precise crystal, SAW
  filter,) required
• Can be manufactured in single-chip CMOS 0.18
  µm, or less
• RF-CMOS 0.18µm Die Area 4.42 mm2
• RF-CMOS 0.13µm Die Area 3.70 mm2

22
Selection Criteria Document Topic
Technical Feasibility Time to Market

• No regulatory hurdles
• Chirp based chips are available on the market
• No big research barriers well known technology
• Standard design and product cycles will apply

23
Selection Criteria Document Topic
Technical Feasibility Regulatory Impact

• Devices manufactured in compliance with the
  DBO-CSS proposal can be operated under existing
  regulations in all significant regions of the
  world
• - Including but not limited to North and South
  America, Europe, Japan, China, Korea, and most
  other areas
• - There are no known limitation to this proposal
  as to indoors or outdoors
• The DBO-CSS proposal would adhere to the
  following worldwide regulations
• - United States Part 15.247 or 15.249
• - Canada DOC RSS-210
• - Europe ETS 300-328
• - Japan ARIB STD T-66

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Selection Criteria Document Topic
Technical Feasibility Backward Compatibility

• Due to the usage of state of the art RF
  architecture it is possible to implement this
  proposal in a manner that will allow
  backward-compatibility with the 802.15.4 2.4 GHz
  standard.
• The transmitter changes are relatively
  straightforward.
• Changes to the receiver would mainly consist of
  additions for ToA estimation and ranging
• Optional methods for backward-compatibility could
  be left up to the implementer
• - Mode switching
• - Dynamic change (on-the-fly) technique
• This backward-compatibility would be a
  significant advantage in the marketplace by
  allowing these devices to communicate with
  existing deployed 802.15.4 infrastructure and
  eliminating customer confusion.

25
Selection Criteria Document Topic
Scalability Data-rate

• Mandatory rate 1 Mb/s
• Optional rate 250 Kb/s
• Lower data rate is achieved by using interleaved
  FEC

26
Selection Criteria Document Topic
Scalability Frequency Bands

• The proposer is confident that the DBO-CSS
  proposal would also work well in other frequency
  bands in future revisions of the standard
• For example 5 GHz UNII / ISM bands

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Selection Criteria Document Topic
Scalability Power Levels

• For extremely long ranges the transmit power may
  be raised to each countrys regulatory limit, for
  example
• The US would allow 30 dBm of output power with up
  to a 6 dB gain antenna
• The European ETSI limits would specify 20 dBm of
  output power with a 0 dB gain antenna
• Note that even though higher transmit power
  requires significantly higher current it doesnt
  significantly degrade battery life since the
  transmitter has a much lower duty cycle than the
  receiver, typically 10 or less of the receive
  duty cycle.

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Selection Criteria Document Topic
Mobility

• Communication
• No system inherent restrictions are seen for this
  proposal
• The processing gain of chirp signals is extremely
  robust against frequency offsets such as those
  caused by the Doppler effect when there is a high
  relative speed vrel between two devices.
• The Doppler effect must also be considered when
  one device is mounted on a rotating machine,
  wheel, etc.
• The limits will be determined by other, general
  (implementation-dependent) processing modules
  (AGC, symbol synchronization, etc.).
• Ranging
• The ranging scheme proposed in this document
  relies on the exchange of two hardware
  acknowledged data packets
• One for each direction between two nodes
• The total time for single-shot (2 data, 2 Ack)
  ranging procedure between the two nodes is the
  time tranging which, depending on the
  implementation, might be impacted by the uC
  performance. During this time the change of
  distance should stay below the accuracy da
  required by the application. The worst case is

• For da 1m
• tranging 2 ms this yields
• vrel ltlt 1000 m/s

29
Selection Criteria Document Topic
MAC Protocol Supplement

• There are very minimal anticipated changes to the
  15.4 MAC to support the proposed Alt-PHY.
• 13 (11 for US) FD times 4 CD channels are called
  for with this proposal and it is recommended that
  the mechanism of channel bands from the proposed
  methods of TG4b be used to support the new
  channels.
• There will be an addition to the PHY-SAP
  primitive to include the choice of data rate to
  be used for the next packet. This is a new field.
• Ranging calls for new PHY-PIB primitives are
  expected to be developed by the Ranging
  subcommittee.

30
Selection Criteria Document Topic
PHY Layer Criteria Manufacturing Cost/Complexity
BaseBand Digital BaseBand Digital Estimated Complexity 1Mbps / 250Kbps gates Estimated Complexity 1Mbps / 250Kbps gates Data-Rate Data-Rate
BaseBand Digital BaseBand Digital Estimated Complexity 1Mbps / 250Kbps gates Estimated Complexity 1Mbps / 250Kbps gates 250 Kbps 1Mbps
Tx Scrambler 154 1.5K / 1.6K O O
Tx FEC Encoder (r1/2) 100 1.5K / 1.6K O X
Tx Symbol Mapper 13 1.5K / 1.6K O O
Tx Differential Encoder 56 1.5K / 1.6K O O
Tx Chirp-pulse Modulator 290 1.5K / 1.6K O O
Tx Framer Others 1K 1.5K / 1.6K O O
Rx Differential Detector 39k 53.7K / 148.6K O O
Rx Symbol Demapper 200 53.7K / 148.6K O O
Rx Correlator 4.2 53.7K / 148.6K O O
Rx Max Selector 100 53.7K / 148.6K O O
Rx FEC Decoder (r1/2) (95K) 53.7K / 148.6K O X
Rx Descrambler 154 53.7K / 148.6K O O
Rx Deframer Others 10K 53.7K / 148.6K O O
Common Common 5K 5K O O
Transceiver Transceiver Transceiver Transceiver 155.2K 60.2K
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Selection Criteria Document Topic
PHY Layer Criteria Size and Form Factor

• The implementation of the DBO-CSS proposal will
  be much less than SD Memory at the onset
• Following the form factors of Bluetooth and IEEE
  802.15.4 / ZigBee
• The implementation of this device into a single
  chip is relatively straightforward
• As evidenced in the Unit Manufacturing
  Complexity slides

32
Selection Criteria Document Topic
PHY Layer Criteria Size and Form Factor
SD Memory (32mm X 24 mm)
2.4 GHz

• Ex)
• Battery Capacity 3V x 30mAh (324Joule)
• Dimension 10 x 2.5 (Dia. x Ht. mm)

33
Selection Criteria Document Topic
PHY Layer Criteria Bit Rate and Data Throughput

• Payload Bit-rate
• Data-rate 1MHz / 250Kbps per piconet
• Aggregated Data-rate Max. 4Mbps (4 X 1Mbps)
  per FDM Channel
• FDM Channels 13 (11) CH. (2.4GHz)
• Data Throughput
• Payload bit-rate 1Mbps / 250Kbps
• Throughput 330 Kbps / 148 Kbps

Payload 32byte
5byte
DATA Frame
ACK Frame
DATA Frame
TACK
TLIFT
114 / 240 µsec
330 / 1104 µsec
574 / 1474 µsec
TACK TLIFS 192usec
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Selection Criteria Document Topic
PHY Layer Criteria Bit Rate and Data Throughput
Data Frame Payload bit-rate 1Mbps (r1) /
250Kbps (r1/2)
5 Chirps 1Chirp 6Chirps
43 Chirps (1Mbps) / 172 Chirps (250Kbps)
Preamble
Delimiter
Length Rate
MPDU
(8 1)bit
(32X8 2) bit
330 µsec (1Mbps) / 1104 µsec (250Kbps)
ACK Frame Payload bit-rate 1Mbps(r1) /
250Kbps (r1/2)
5Chirps 1Chirp 6Chirps
7Chirps (1Mbps) / 28Chirps (250Kbps)
Preamble
Delimiter
Length Rate
MPDU
(8 1)bit (5X8 2) bit
114 µsec (1Mbps) / 240 µsec (250Kbps)
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Selection Criteria Document Topic
PHY Layer Criteria Bit Rate and Data Throughput
Octets 4 1 or 2 1 Variable (up to 256)
Preamble SFD Frame length (8 bits) PHY payload
SHR SHR PHR PSDU

• The SFD structure has different values for, and
  determines, the effective data rate for PHR and
  PSDU
• The Preamble is 32 bits in duration (a bit time
  is 1 µs)
• In this proposal, the PHR field is used to
  describe the length of the PSDU that may be up to
  256 octets in length
• In addition to the structure of each frame, the
  following shows the structure and values for
  frames including overhead not in the information
  carrying frame

36
Selection Criteria Document Topic
PHY Layer Criteria Bit Rate and Data Throughput
797 Kb/s
1 Mb/s plot
330 Kb/s
250 Kb/s plot
230 Kb/s
148 Kb/s
Tack 192 µs SIFS 192 µs
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Selection Criteria Document Topic
Simultaneously Operating Piconets

• Separating Piconets by frequency division
• This DBO-CSS proposal includes a mechanism for
  Frequency Devision (FD) by utilizing the
  frequency bands defined by 802.11 b, g and also
  802.15.3
• It is believed that the use of these bands will
  provide strong orthogonality which can easily
  combat the Near/Far problem
• Furthermore this DBO-CSS proposal offers a
  mechanism for Code Devision (CD) utilizing the
  good correlation features of the Chirp signal.
• It is believed that this will offer sufficient
  orthogonality for many situations
• The proposed chirp signal has a rolloff factor of
  0.25 which in conjunction with the space between
  the adjacent frequency bands allows filtering out
  of band emissions easily and inexpensively.

38
Selection Criteria Document Topic
Simultaneously Operating Piconets
Correlation Power (For Preamble Detection)
CSS Signal Quasi-Orthogonal Property
Correlation Property between the piconet Does not
need Synchronization inter-piconet
Each of CSS Signal consists of 4 sub-chirp
signals.
39
Selection Criteria Document Topic
Simultaneously Operating Piconets
Complex Amplitude (for Data Demod)
I II III IV
CSS Signal Quasi-Orthogonal Property
Correlation Property between piconet
Each of CSS Signal consists of 4 sub-chirp
signals.
40
Selection Criteria Document Topic
Simultaneously Operating Piconets

• SOP Assigning Different Time-Gap between the
  CSS Signal
• Minimize ISI for CM8 NLOS Assign the Time-Gap
  between symbol more then 200nsec

41
Selection Criteria Document Topic
Simultaneously Operating Piconets
Interference Tested by Packet (32 bytes Random
Data)
I II III IV
Differential Detection Property between piconet
Each of CSS Signal consists of 4 sub-chirp
signals.
42
Selection Criteria Document Topic
Simultaneously Operating Piconets

• Available SOPs
• 2.4GHz 4piconets/FDM Ch. x 3FDM Ch. 12
  SOPs
• 2.4GHz 4piconets/FDM Ch. x 13FDM Ch. 52
  SOPs

43
Selection Criteria Document Topic
Signal Acquisition Block-diagram
Differential Detector (T1)
Select Largest
A/D
Symbol De-Mapper
Data
Differential Detector (T2)
44
Selection Criteria Document Topic
Signal Acquisition Miss Detection Probability, Pm
n2
Preamble Detection
45
Selection Criteria Document Topic
Signal Acquisition

• This DBO-CSS proposal is based upon a preamble of
  5 Chirp symbols which results in a duration of 30
  µs. This value is significantly below the
  duration of preamble defined in 15.4 and thus
  increases the available throughput.
• Existing implementations demonstrate that
  modules, which might be required to be adjusted
  for reception (gain control, frequency control,
  peak value estimation, etc.), can settle in this
  time.

46
Selection Criteria Document Topic
Clear Channel Assessment

• A combination of symbol detection (SD) and energy
  detection (ED) has proven to be useful in
  practice (e.g. 802.11x, 802.15.4).
• CCA is used by the 15.4 MAC to significantly
  increase the number of active nodes possible by
  reducing the probability of collisions.

47
Selection Criteria Document Topic
System Performance

• This proposal refers to the 2.4GHz ISM band.
  Although some channel models start at 3 GHz and
  thus dont include the 2.4 GHz band, simulations
  will be run over all channel models in order to
  prove the strength of this proposal.
• As minimum the transmissions of 100 packets with
  32 bytes over each channel realization are
  simulated

48
Selection Criteria Document Topic
System Performance

• For some channel models the path loss exponent
  given is relatively small (e.g, for CM1 n1.79)
• In order to stimulate transmission errors,
  simulations have to be performed for ranges much
  beyond what the channel models have been
  specified for.

49
Selection Criteria Document Topic
System Performance
50
Selection Criteria Document Topic
System Performance
AWGN Data Rate 1Mbps (QPSK)
n2
Distance (meter)
51
Selection Criteria Document Topic
System Performance
Residential 7m20m
CM1 LOS (n1.79)
CM2 NLOS (n4.58)
52
Selection Criteria Document Topic
System Performance
Office 3m28m
CM3 LOS (n1.63)
CM4 NLOS (n3.07)
53
Selection Criteria Document Topic
System Performance
Industrial 2m8m
CM8 NLOS (n2.15)
54
Selection Criteria Document Topic
Ranging
TOA Estimation

• Coarse Differential demodulation peak
• Fine Correlation peak
• Precise Receive signal post-processing
  e.g. Spectrum estimation, curve fitting,

TOA Processing

• SDS TWR Technique
• Error Sensitivity Analysis
• Simulation Results

55
Selection Criteria Document Topic
Ranging TOA Estimation for Ranging
Noise and Jitter of Band-Limited Pulse Given a
band-limited pulse with noise su we want to
estimate how the jitter (timing error) st, is
affected by the bandwidth B. Jitter can be
represented as a variation in the rising edge of
a pulse through a given threshold,
56
Selection Criteria Document Topic
Ranging TOA Estimation for Ranging

• The SN at the matched filter output is 2Es/N0
• If we assume a pulse with a rise time trise which
  is the inverse of the pulse bandwidth B (trise
  1/B) we can derive
• Bandwidth and signal to noise ratio can be traded
  against each other.
• This proposal provides a signal to noise ratio
  which is high enough to compensate its limited
  bandwidth!

57
Selection Criteria Document Topic
Ranging TOA Estimation Using Chirp Signals

• Coarse Timing Detection
• - Peak of Differential Detection
• Fine Timing Detection
• - Cross-Correlation of Sampled Input Signal
• - Fine Timing by Interpolation (Fraction of
  Sampling-Clock Resolution lt 1nsec)
• - Ranging Resolution better than 1m _at_ Eb/No
  gt 24dB

58
Selection Criteria Document Topic
Ranging TOA Estimation Using Chirp Signals

• Estimation Error lt 1m _at_ Eb/No greater than
  24dB

Timing-error Variance (Chirp BW 20MHz)
AWGN
59
Selection Criteria Document Topic

• Ranging TOA Estimation Using Chirp Signals
• Precise Timing Detection Spectrum estimation

• One special property of chirp signals is that
• Time shifts can be transformed into frequency
  shifts
• ?
• TOA estimation can be transformed to spectrum
  estimation.
• Advantages
• Wide bandwidth and high sampling frequency are
  not required
• Spectrum estimation is a well studied problem

60
Selection Criteria Document Topic

• Ranging TOA Estimation Using Chirp Signals
• Precise Timing Detection Spectrum estimation

A
Assume a linear chirp signal
t
and a time-shifted copy of this signal
f
t
A
t
By multiplying the two, a constant frequency
signal is generated!
f
t
61
Selection Criteria Document Topic

• Ranging TOA Estimation Using Chirp Signals
• Precise Timing Detection Spectrum estimation

h
Given a channel impulse response (CIR),
t
A
t
transmitting a chirp signal over it,
f
t
and multiplying with a chirp signal of equal
characteristic
A
t
will result in a signal with frequency
components corresponding to the pulses of the CIR.
f
power
t
frequency
62
Selection Criteria Document Topic

• Ranging TOA Estimation Using Chirp Signals
• Precise Timing Detection Spectrum estimation

• From the estimated frequency components, the time
  positions of the multipath components can be
  calculated
• thus
• The time of the first arrival can be found!

63
Selection Criteria Document Topic
Ranging TOA Estimation Using Chirp Signals

• Precise Timing Detection curve fitting,
• Curve fitting and other approaches for TOA
  estimation exist. They are currently under
  investigation.
• Thus a number of choices will be available!

64
Selection Criteria Document Topic

• Ranging TOA Processing
• A method is required in order to minimize errors
  caused by
• crystal oscillator
• Resolution
• Accuracy
• Drift
• Aging

65
Ranging TOA Processing Symmetrical Double-Sided
Two-Way Ranging (SDS TWR)

• Accuracy of range estimation is restricted by
  various factors
• E ECLOCK ETOA_res ETOA_noise
  ETOA_offset

Error Caused by Multiple Transmission Paths
Total Error of Range Estimate
Error Caused by Noise, Jitter, Interference,
Error caused by time base accuracy
Error of TOA estimation caused by restricted
clock resolution
66
Ranging TOA Processing SDS TWR

• SDS TWR elegantly cancels time base offset errors
• E ECLOCK ETOA_res ETOA_noise
  ETOA_offset

Error caused by time base accuracy
67
Ranging TOA Processing SDS TWR

• How to measure a message sequence of
  milliseconds-length and achieve
  picoseconds-accuracy ?
• Error of commercial quartz crystals is 40 ns
  over 1 ms (40ppm, over a temperature range
  -40..85C)
• Remind 40 ns is equal to a distance of 12 m (40
  feet) !

Source Jauch Quartz GmbH
68
Ranging TOA Processing SDS TWR
Double-Sided Each node executes a round trip
measurement. Symmetrical Reply Times of both
nodes are identical (TreplyA TreplyB). Results
of both round trip measurements are used to
calculate the distance.
Tround ... round trip time Treply ... reply
time Tprop ... propagation of pulse
69
Ranging TOA Processing SDS TWR in Words
Node A sends a first request message to Node B.
After reception the message is checked. If the
check succeeds, a first reply message is sent
back to node A after a predetermined delay. This
message sequence is repeated a second time, but
initiated from the other node. Node B sends a
second request message to node A, where a second
reply message is sent back to node B after the
successful check and the predetermined delay. The
detected departure and arrival times of the
request and reply messages are used to count the
precise round trip (Tround) the reply times
(Treply). The time from the transmission of the
request message to the arrival of the reply
message is the round trip time. The time from the
arrival of the request message to the
transmission of the reply message is the reply
time. The distance between node A and B can be
calculated from the measured round trip and reply
times and the speed of light. The two round trip
and the two reply times determine an average air
propagation time. As known the distance can be
calculated by multiplication of the air
propagation time and the speed of light (see
slide 7). To achieve the highest accuracy of the
distance despite the presence of unsynchronized
an imprecise time bases (clock errors) in nodes A
and B, the reply times of the two message
sequences should be almost identical. This double
message exchange sequence with the identical
reply times we call the Symmetrical Double-Sided
Two Way Ranging (SDS TWR). In real
implementations identical reply times are not
possible, but the method allows a good margin for
the differences of the reply times (symmetry
error ?Treply) and achieves still a very high
accuracy (see slide 9).
70
Ranging TOA Processing Accuracy of SDS TWR

• Calculation of Distance d
• Calculation of Distance Error EAB
• Result Distance accuracy is equivalent to the
  average of time base accuracies (some tens ppm of
  distance only) ! Distance accuracy is independent
  of round trip reply time !
• c speed of light, EtA ... error of time base at
  node A, EtB ... error of time base at node B

71
Ranging TOA Processing Symmetry Error of SDS TWR

• Symmetry Error is Present in Practical
  Implementations
• Calculation of Distance Error EAB
• Result Distance accuracy is independent of round
  trip reply time ! Distance accuracy increases
  with decreasing of the Symmetry Error
• ?Treply !
• c speed of light, EtA ... error of time base
  at node A, EtB ... error of time base at node B

72
Selection Criteria Document Topic
Ranging Influence of Symmetry Error
Example system EtA 40 ppm, EtB 40 ppm
(worst case combination)
d ?d (?Treply 20 ns) ?d (?Treply 200 ns) ?d (?Treply 2 µs) ?d (?Treply 20 µs)
10 cm 0.012 cm 0.12 cm 1.2 cm 12 cm
1 m 0.012 cm 0.12 cm 1.2 cm 12 cm
10 m 0.05 cm 0.12 cm 1.2 cm 12 cm
100 m 0.4 cm 0.4 cm 1.2 cm 12 cm
1 km 4 cm 4 cm 4 cm 12 cm
10 km 40 cm 40 cm 40 cm 40 cm

• A ?Treply of between 2 µs and 20 µs is typical
  for a low-cost implementation.
• Implementations with symmetry error below 2 µs
  are feasible.
• Conclusion Even a 20 µs symmetry error allows
  excellent single-pulse accuracy of distance.

73
Selection Criteria Document Topic
Ranging Simulation of a SDS TWR System
Example system Simulates SDS TWR
Dithering Averaging Crystal Errors 40
ppm Single shot measurements _at_ 1 MBit/s data rate
(DATA-ACK) Transmit Jitter 4 ns
(systematic/pseudo RN-Sequence) Pulse detection
resolution 4 ns Pulses averaged per packet
32 Symmetry error 4 µs (average) Distance 100
m Results of Distance Error ?d ?dWC lt 50
cm ?dRMS lt 20 cm
74
Selection Criteria Document Topic
Link Budget
Parameter mandatory option 1 option 2
Peak payload bit rate(Rb) 1000 250 250 kbps
Average Tx Power(Pt) 10 10 1000 mW
Average Tx Power(Pt) 10 10 30 dBm
Tx antenna gain(Gt) 0 0 0 dBi
fc' sqrt(fminfmax) -10dB 2.44 2.44 2.44 GHz
Path loss at 1meter(L120log10(4pifc'/c)) 40.2 40.2 40.2 dB
Distance 30 100 1000 m
Path loss at d m(L220log10(d)) 29.5 40 60 dB
Rx antenna gain(Gr) 0 0 0 dBi
Rx power(Pr PtGtGr-L1-L2(dB)) -59.7 -70.2 -70.2 dBm
Average noise power per bit -114.0 -120.0 -120.0 dBm
Rx Noise Figure(Nf) 7 7 7 dB
Average noise power per bit(PnNNf) -107.0 -113.0 -113.0 dBm
Minimum Eb/No(S) 12.5 12.5 12.5 dB
Implementation Loss(I) 3 3 3 dB
Link Margin (MPr-Pn-S-I) _at_ distance d 31.8 27.3 27.3 dB
Proposed Min. Rx Sensitivity Level -91.5 -97.5 -97.5 dBm
75
Selection Criteria Document Topic
Sensitivity

• The sensitivity to which this DBO-CSS proposal
  refers is based upon differential detection
• It is understood that coherent detection will
  allow 2 - 3 dB better sensitivity but at the cost
  of higher complexity (higher cost?) and poorer
  performance in some multipath limited
  environments
• The sensitivity for the 1 Mb/s mandatory data
  rate is -91.5 dBm for a 1 PER in an AWGN
  environment with a front end NF of 7 dB
• The sensitivity for the optional 250 kb/s data
  rate is -97.5 dBm for a 1 PER in an AWGN
  environment with a front end NF of 7 dB

76
Selection Criteria Document Topic
Power Management Modes

• Power management aspects of this proposal are
  consistent with the modes identified in the IEEE
  802.15.4 2003 standard
• There are no modes lacking nor added
• Once again, attention is called to the 1 Mbit/s
  basic rate of this proposal and resulting shorter
  on times for operation

77
Selection Criteria Document Topic
Power Consumption

• The typical DSSS receivers, used by 802.15.4,
  have a complexity which is similar to the
  envisioned DBO-CSS receiver
• Major differences are the differential encoder
  and decoder
• The power consumption for a 10 dBm transmitter
  should be 198 mW or less
• The receiver for the DBO-CSS can if restricted to
  differential detection be implemented with to
  slightly complexity than that of the DSSS with
  the major difference that for communication no
  chip rate correlator is required.
• The difference in power consumptions between
  these correlators is negligible so the power
  consumption for a 6 dB NF receiver should be 40
  mW or less
• Power save mode is used most of the time for this
  device and has the lowest power consumption
• Typical power consumptions for 802.15.4 devices
  are 3 µW or less
• Energy per bit is the power consumption divided
  by the bit rate
• The energy per bit for the 10 dBm transmitter is
  less than 0.2 µJ
• The energy per bit for the receiver is 60 nJ
• As an example, the energy consumed during an
  exchange of a 32 octet PDU between two devices
  would be 70.6 µJ for the sender and 33.2 µJ for
  the receiver.

78
Selection Criteria Document Topic
Power Consumption
1Mbps 1Mbps 1Mbps 250Kbps (FEC r1/2) 250Kbps (FEC r1/2) 250Kbps (FEC r1/2)
Logic Die Area Power Logic Die Area Power
RF _at_ Tx Power 10mW Tx D/A - 1.7 mm2 187 mW - 1.7 mm2 187 mW
RF _at_ Tx Power 10mW Rx A/D - 1.6 mm2 28.9 mW - 1.6 mm2 28.9 mW
RF _at_ Tx Power 10mW Common - 0.3 mm2 10 mW - 0.3 mm2 10 mW
Baseband _at_ Sampling-rate 40MHz Tx 1.5K 0.04 mm2 0.48 mW 1.6K 0.06 mm2 0.52 mW
Baseband _at_ Sampling-rate 40MHz Rx 53.7K 0.69 mm2 0.77 mW 148.6K 1.54 mm2 2.18 mW
Baseband _at_ Sampling-rate 40MHz Common 5K 0.08 mm2 0.42 mW 5K 0.08 mm2 0.42 mW
Total Tx 60.2K 4.41 mm2 197.9 mW 155.2K 5.28 mm2 198 mW
Total Rx 60.2K 4.41 mm2 40.1 mW 155.2K 5.28 mm2 41.5 mW
Deep Sleep Deep Sleep 3 µW 3 µW
Target Library 0.18 um Technology

• Power Consumption for Average Throughput 1
  Kbps (w/o FEC)
• - PTX 197.9mW / 330 600 µW
• - PRX 40.1mW /330 121.5 µW
• Battery 324Joule for Button Cell (10mm D. X
  2.5mm H) / 12,000Joules for AA Alkaline Cell
• - (PTX 50 X PRX)/51 130.9uW -----
  (Assume TTX TRX 150 duty-cycle for sensor
  node)
• - Battery Life TB 324/130.9e-6/3600/24
  28.6 days Continuously (Button Cell)
• - Battery Life TB 12000/130.9e-6/3600/24/3
  65 2.91 years Continuously (AA Alkaline Cell)

79
Selection Criteria Document Topic
Antenna Practicality

• The antenna for this DBO-CSS proposal is a
  standard 2.4 GHz antenna such as widely used for
  802.11b,g devices and Bluetooth devices.
• These antennas are very well characterized,
  widely available, and extremely low cost.
• Additionally there are a multitude of antennas
  appropriate for widely different applications.
• The size for these antennae is consistent with
  the SCD requirement.

80
Selection Criteria Document Topic
Antenna Practicality

• Antenna Size
• - Smaller than SD-Memory 24mm X 14mm
  _at_2.4GHz
• 
  
• Frequency / Impulse Response
• - Almost flat frequency response
  narrow-band
• Radiation Characteristics
• - Isotropic 0dBi

81
PAR and 5C Requirement Checklist
82
Requirements Checklist

• DBO-CSS Proposal Meets the PAR and 5C
• Precision ranging capability accurate to one
  meter
• or better
• Extended range over 802.15.4-2003
• Enhanced robustness over 802.15.4-2003
• Enhanced mobility over 802.15.4-2003
• International standard
• Ultra low complexity (comparable to the goals
  for
• 802.15.4-2003)
• Ultra low cost (comparable to the goals for
  802.15.4-2003)
• Ultra low power consumption (comparable to the
  goals
• for 802.15.4-2003)
• Support coexisting networks of sensors,
  controllers,
• logistic and peripheral devices in multiple
  compliant
• co-located systems.

83
Summary The merged proposal is different than
and improves on the two original proposals!
84
Summary

• DBO-CSS is simple, elegant, efficient
• Combines DSSS and UWB strengths
• Precise location-awareness
• Robustness multipath, interferers, correlation,
  FEC, channelized, CCA
• Mobility enhanced
• Optional backward compatibility with
  802.15.4-2003
• Excellent throughput
• SOPs FD channels and CD channels
• Signal Acquisition excellent
• Link Budget and Sensitivity excellent
• Very minimal MAC changes, CCA supported
• Power Management and Consumption - meets or
  exceeds requirements
• Antenna many good choices
• Can be implemented with todays technologies
• Low-complexity, low-cost
• Size and Form Factor meets or exceeds
  requirements
• Low power consumption
• Globally certifiable