IEEE 802.15.3a Ultra Wideband techniques (UWB)

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IEEE 802.15.3a Ultra Wideband techniques (UWB)

• Mikko Leimio
• Kari Nokkala

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Outline

• Introduction
• OFDM-UWB
• DS-UWB
• Current status of 802.15.3a
• References

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(No Transcript)
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Introduction

• UWB research started in 2002, when 3.1 10.6 GHz
  band approved by FCC
• Based on IEEE 802.15 task group 3a (started 2003)
• TG3a purpose is provide high data rates and add
  support to imaging and multimedia applications
  (QoS)
• Today there are two competing proposals
• OFDM-UWB and DS-UWB
• Need 75 of all votes

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Introduction (cont.)

• Short-range radio technology (WPAN)
• Is ideal for WPANs and can offer greater date
  rates than Bluetooth
• Low transmit power
• Low cost and single-chip solutions
• Low complexity
• With UWB you could eliminate wires
• e.g. connect digital camera or printer to your PC
  without any wires
• E.g. USB and FireWire could operate on top of UWB

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OFDM-UWB(orthogonal frequency division
multiplexing) 2
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OFDM Advantages

• OFDM was invented almost 50 years ago, so its a
  mature technology
• Currently used in
• ADSL, 802.11a/g, European digital TV and Digital
  Audio Broadcast
• Being considered in
• 4G, 802.11n, 802.16a, 802.20
• High spectral efficiency
• Low multi-path distortion
• Channels are typically multipath-channels

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Multi-band OFDM (MB-OFDM)

• Spectrum is divided into bands that are 528 MHz
• Frequency hopping between these bands
• Provide robustness against multi-path and
  interference
• Typically there are 3 bands and hopping occurs
  after every OFDM symbol

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OFDM symbols

• Prefix provides robustness against multi-path
• Insert a Guard Interval between OFDM symbols in
  order to allow enough time to switch between
  channels

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MB-OFDM (cont.)

• Works in different locations
• With turning on or off frequency bands it allow
  for local limitations
• It allows data rates from 53.3 Mb/s to 480 Mb/s
  (QPSK)
• Changing QPSK to 16-QAM, we might get date rate
  up to 1 Gb/s
• OFDM subcarriers modulated using QPSK
• Data divided into groups of 2 bits ? QPSK
  constellation

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MB-OFDM System Parameters
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Ranges with different data rates

• Scalable data rates from 53.3 Mb/s to 480 Mb/s

Range AWGN LOS
110 Mb/s 20.5 m 11.4 m
200 Mb/s 15.1 m 6.9 m
480 Mb/s 8.9 m 2.9 m
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Band plan

• 5 band groups are defined
• Band Group 1 intented for 1st generation
  devices, Mode 1 devices (3.1 4.9 GHz)
• Band Group 2 5 Reserved for future use

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PLCP Frame Format

• Supports all data rates from 53.3 Mb/s to 480
  Mb/s
• Support for 53.3, 106.7, 110 and 200 Mb/s are
  mandatory
• Header is sent always at an information data rate
  of 53.3 Mb/s

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MAC layer

• Same as IEEE 802.15.3 MAC, but
• Time-division multiple-access (TDMA) with QoS
  guarantees
• There was own presentation on this subject

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MB-OFDM Advantages

• One transmit and one receive chain at all times
• Inherent robustness to multi-path environments
• Excellent robustness to ISM, U-NII and other
  generic narrowband interference
• Ability to comply with worldwide regulations
• Enhanced coexistence with current and future
  devices
• Scalability

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DS-UWBDirect Sequence Ultra Wideband
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DS-UWB

• uses widest possible bandwith to produce the
  shortest possible pulses
• Another main proponent for 802.15.3a PHY layer

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DS-UWB Two operating bands
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Low band 1,75 GHz 3,1
to 4,85 GHz
High band 3,5 GHz
6,2 to 9,7GHz

• High band is two times wider than low band
• Double chip rate
• Double power

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DS-UWB Channels

• DS-UWB support for a total of 12 piconets
• 6 piconets in low band and 6 in high band
• unique operating frequencies
• devices are required to implement 1-4 piconets in
  low band, other are optional

Piconet Channel Chip Rate Center Frequency
1 1313 MHz 3939 MHz
2 1326 MHz 3978 MHz
3 1339 MHz 4017 MHz
4 1352 MHz 4056 MHz
5 1300 MHz 3900 MHz
6 1365 MHz 4094 MHz
7 2626 MHz 7878 MHz
8 2652 MHz 7956 MHz
9 2678 MHz 8034 MHz
10 2704 MHz 8112 MHz
11 2600 MHz 7800 MHz
12 2730 MHz 8190 MHz
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DS-UWB Pulse shapes

• Low Band
• Pulse duration 0,75ns
• ie. chip rate 1326 MHz
• t 1/chip rate 0,754ns

High Band Pulse duration 0,375ns ie. chip rate
2626 MHz t 1/chip rate 0,38ns
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DS-UWB Spreading codes

• Pulses are transmitted in sequences
• Ternary sequences elements are 1,-1 or 0
• Each symbols are series of pulses or chips
• Different sequence lengths different bit or
  symbol lengths
• Sequences range from length L24 down to length
  L1
• Leads to longer or shorter symbols

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DS-UWB Modulation

• Two possible methods to modulate data symbols
• BPSK (mandatory)
• each symbol carries only a single data bit
• 4-BOK (optional, required for transmit)
• each symbol carries two data bits

Because of the high pulse rate and signal
bandwidth, DS-UWB does not need to use
higher-order modulation to reach extremely high
date rates (lt1 Gb/s). Scaling a system to higher
data rates using high-order modulation will also
lead to increased complexity.
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DS-UWB PHY signal flow

• A scrambler shall be employed to ensure an
  adequate number of bit transitions to support
  clock recovery
• The convolutional encoder (FEC) is used to encode
  data so that the decoder can correct errors
  introduced due to noise in the channel ( rates ½,
  ¾, 1)
• Higher data rates are derived from convolutional
  encoders by using puncturing
• Bit interleaving provides robustness against
  burst errors
• Proposal doesnt specify the receiver, but give
  general receiver performance guideline

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DS-UWB PHY frame format

• For all data rate modes
• The UWB PHY prepends the PHY header to the MAC
  header
• Then it calculates the HCS (header check
  sequence) from PHY and MAC headers
• MAC header is unchanged from IEEE Std
  802.15.3-2003
• If frame bodyFCS, in bits, is not an integer
  multiple of the bits/symbol add stuff bit (1
  or 0)
• The tail bits are used for terminate the encoded
  trellis sequence in a known state to aid the
  decoding process

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DS-UWB Preamble structure
Acq seq 9?s SFD (32 bit) Data Field (24 bit) Training (various lengths) PHY Header MAC Header Data
General preamble structure

• Preamble
• achieve clock synchronization
• modulation method
• spreading code length

There are 3 preamble lengths depending upon the
application bit rate Short preamble 5 ?S in
length that requires a high SNR with low channel
dispersion - it is most suitable for high bit
rate, short range links (lt3 meters) Nominal
preamble 15 ?S in length that requires a nominal
SNR with a nominal channel - it is the default
preamble choice Long preamble 30 ?S in length
that is used for a poor SNR and/or highly
dispersive channel - it is intended for
extended range applications
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Available data rates in lower band
Data Rate FEC Rate BPSK Code Length 4-BOK Code Length Symbol Rate
28 Mbps ½ L24 - Fchip/L
55 Mbps ½ L12 - Fchip/L
110 Mbps ½ L6 L12 Fchip/L
110 Mbps 1 L12 L24 Fchip/L
220 Mbps ½ L3 L6 Fchip/L
220 Mbps 1 L6 L12 Fchip/L
330 Mbps ½ L2 L4 Fchip/L
440 Mbps 1 L3 L6 Fchip/L
500 Mbps ¾ L2 L4 Fchip/L
660 Mbps 1 L2 L4 Fchip/L
660 Mbps ½ L1 L2 Fchip/L
1000 Mbps ¾ L1 L2 Fchip/L
1320 Mbps 1 L1 L2 Fchip/L

• Different data rates depends on
• FEC rate
• Spreading code length
• Chip rate is 1300 MHz

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Available data rates in higher band
Data Rate FEC Rate BPSK Code Length 4-BOK Code Length Symbol Rate
55 Mbps ½ L24 - Fchip/L
110 Mbps ½ L12 - Fchip/L
110 Mbps 1 L24 - Fchip/L
220 Mbps ½ L6 L12 Fchip/L
220 Mbps 1 L12 - Fchip/L
330 Mbps ½ L4 L8 Fchip/L
440 Mbps ½ L3 L6 Fchip/L
440 Mbps 1 L6 L12 Fchip/L
500 Mbps ¾ L4 L8 Fchip/L
660 Mbps 1 L4 L8 Fchip/L
660 Mbps ½ L2 L4 Fchip/L
1000 Mbps ¾ L2 L4 Fchip/L
1320 Mbps 1 L2 L4 Fchip/L
1320 Mbps ½ L1 L2 Fchip/L
2000 Mbps ¾ L1 L2 Fchip/L
Chip rate is 2600 MHz
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How to form bit rates?

• Example
• Chip rate 1300 MHz
• Spreading code L 6
• FEC rate 1/2
• Symbol rate 1300 / 6 216,66MHz
• Using BPSK (1 symbol 1 bit)
• Bit rate symbol rate
• FEC decoding bit rate 108,33Mbit/s
• 110 Mbit/s (defined in proposal)
• Conclusion Bit rate depends on spreading code
  and FEC rate

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Some ranges with different data rates 5

• High band
• Centre frequency twice as high lose 6dBm
• 2 x bandwidth 2 x total power gain 3dBm
• 3dB loss equates to a range factor 70
• Much more simulation results
• in reference 5

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Current status of 802.15.3a 1/3

• PHY selection have reached a deadlock
• Several votings have kept during 03-05
• Either of OFDM or DS-UWB doesnt achieved
  required 75

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Fighting Groups

• MBOA (Multiband OFDM Alliance)
• Formed in July 2003
• Over 170 companies
• March 05 MBOA-SIG merged with WiMedia Alliance
• WiMedia-MBOA

• UWB FORUM
• Formed in late 2004
• Over 100 companies

• Other industry groups
• Wireless USB Promoter Group, 1394 TA, CEA

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Current status of 802.15.3a 2/3

• Markets wait for UWB-devices
• Both groups want own proposal to come general
  standard
• Merging these two proposals is not feasible
• Technically too different
• Too late to do so

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Comparing
OFDM DS-UWB
Data rates 53.3, 80, 110, 160, 200, 320, 400, and 480 Mbps 28, 55, 110, 220, 500, 660,1000, 1320, 2000 Mbps
Frequency band 3,168 GHz 10,56 GHz, (14528 MHz) 3,1-4,85 GHz (low) 6,2-9,7 GHz (high)
Modulation OFDM/QPSK BPSK 4-BOK
Channels/Piconets 43 bands 12 bands 14 6 in low 6 in high 12
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CSM (common signaling mode)

• CSM allows interoperability between DS-UWB and
  MB-OFDM devices
• One waveform that would be straightforward for
  either class of device is a BPSK signal centered
  in the middle of the low band at 4GHz
• Both MB-OFDM and DS-UWB devices can generate such
  a signal using existing RF and digital blocks

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Current status of 802.15.3a 3/3

• March 05 proposal for one frequency plan and
  two PHY layers (OFDM DS)

Frequency plan
Frequency plan is the same as OFDM band group 1
no major changes needed
DS-UWB must change piconets center frequences,
3960 n12 , n 16 Scale PHY for higher
chipping rate Radio has to be changed to support
new frequency plan
Frequency Span (3168MHz-4752MHz) BW 1584
MHz Center Frequency 3960 MHz
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References

• 1 Multi-band OFDM Physical Layer Proposal for
  IEEE 802.15 Task Group 3a. March 2004
• 2 Achieving High Speed Wireless Communications
  Using a MultiBand OFDM UWB System. Anuj Batra.
  May 23, 2004.
• 3 http//www.prosessori.fi/es04/ARKISTO/PDF/
  UWB_TEKNIIKKA.PDF (6.4.2005)
• 4 DS-UWB Physical Layer Submission to 802.15
  Task Group 3a. January 2005
• 5 Detailed DS-UWB simulation results. November
  2004.
• 6 UWB Forum, http//www.uwbforum.org
• 7 Multiband OFDM Alliance, http//www.multibando
  fdm.org
• 8 http//www.intel.com/technology/comms/uwb/down
  load/ wireless_pb.pdf (5.4.2005)