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Title: WIRELESS USB: WIMEDIA


1
WIRELESS USB WIMEDIA UWB
  • Deepak Chellamani
  • 2308366
  • cdeepak_at_ku.edu
  • EECS 766 Technology Presentation
  • 05/06/2008

2
ABSTRACT
  • Wireless USB (WUSB) is a growing short range
    wireless mode of connectivity among devices in
    WPAN. WUSB is rapidly becoming the substitute for
    wired USB without cables. Certified WUSB promoter
    group WiMedia Alliance develop specifications to
    standardize the technology by providing Ultra
    Wideband radio platforms for WUSB
    implementations. This presentation provides a
    descriptive study of WUSB in context of its
    underlying physical and MAC layers, evolution,
    architecture, protocol stack and future prospects
    of the technology.

Wireless USB WiMedia UWB
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3
OUTLINE
  • Introduction
  • WiMedia Alliance
  • Ultra wideband Technology
  • UWB Physical Layer
  • MAC Layer
  • Higher Layers
  • WUSB Architecture
  • WUSB Protocol Stack
  • Recent Developments and Future prospects
  • Conclusion

Wireless USB WiMedia UWB
3
4
INTRODUCTION
  • PERSONAL AREA NETWORK
  • Network range of few tens of feet
  • Generally associated with peripheral and
    hand-held devices
  • Operate in close proximity
  • Standard - IEEE 802.15
  • Bluetooth, ZigBee, USB and IrDA
  • WAN devices used in close proximity are
    subjected to interference
  • PAN devices used in broad networks become
    infrastructure prohibitive
  • As we travel down from WAN to PAN
  • The power requirement decreases (from few watts
    to 0.1W)
  • The bandwidth requirement increases (from 16kb to
    400Mb)

Wireless USB WiMedia UWB
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5
WIMEDIA ALLIANCE
  • An ISO-published radio platform standard for
    high-speed wireless transmission in UWB
  • WiMedia Alliance develop and maintain
  • PHY and MAC Layers
  • Certifications test
  • Design pan radios and protocol stacks by toolkit
    approach
  • Sense and prevent collision with higher priority
    transmission is an important issue since these
    devices operate at extremely close proximities
  • While sensing Radar signal which has higher
    priority WiMedia device will switch off i.e.
    power level adjusted to -70dBm
  • While sensing WiMax devices in following ranges
  • Power level adjusted to -80 dBm _at_ 36cm
  • Power level adjusted to -70 dBm _at_ 22m
  • Ignore if distance gt 22m

Wireless USB WiMedia UWB
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6
ULTRA WIDEBAND TECHNOLOGY
  • A low energy level, short-range large bandwidth
    technology in radio frequency spectrum
  • Bandwidth usually gt 500 MHz
  • Shannons Law C Blog2(S/N)
  • Definition of a UWB transmission signal having
    fractional bandwidth ? gt0.25, where
  • fh and fl are highest and lowest frequency
  • Energy per frequency band is very small
  • Goal of UWB system is to co exist with other
    narrow band wireless transmission systems

Figure 1. Comparison of various coexisting
wireless transmission schemes
From Australian National University
http//www.anu.edu.au/RSISE/teleng/teleng2004/res
earch/uwb.php
Wireless USB WiMedia UWB
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7
ULTRA WIDEBAND TECHNOLOGY
  • Attempt standard IEEE 802.15.3a
  • Task group voted to withdraw
  • Evolved into WiMedia Alliance
  • Faces significant regulatory hurdles
  • MultiBand OFDM was popular among the proposals
  • FCC specify average power/MHz of spectrum space
  • Between 3.1 GHz and 10.7 GHz
  • Power level - 43.1 dBm/MHz
  • High data rates and exploit vast amount of
    spectrum

Figure 2. Detect and Avoid frequency hop model
for MB OFDM From http//www.extremetech.com/art
icle2/0,1697,2129892,00.asp
Wireless USB WiMedia UWB
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8
UWB PHYSICAL LAYER
  • MB-OFDM technology viewed as combination of
    frequency hopping (FH) and OFDM technologies
  • Transmitter
  • Series of tones or sine waves at regularly spaced
    frequencies
  • Each group has two or three sub-bands each
    having bandwidth of 528MHz (128 4.125 MHz)
  • FH preamble patterns are used to differentiate
    simultaneously operating piconets (SOPs)
  • Sub carriers used for coherent detection, pilots,
    guard carriers and nulls
  • Multi-band OFDM is 165 samples long transmitted
    through a sub-band separated by FH patterns
  • Ecma-368 standard specifies a MB-OFDM scheme to
    transmit information
  • Frequency, time domain spreading FECs used to
    vary data rates

Figure 3. Multi Band OFDM Transmitter
From "Performance evaluation of MB-OFDM and
DS-UWB systems for wireless personal area
networks" Oh-Soon Shin Ghassemzadeh, S.S.
Greenstein, L.J. Tarokh, V. Div. of Eng. Appl.
Sci., Harvard Univ., MA, USA Proceedings of IEEE
International Conference 2005
Wireless USB WiMedia UWB
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9
UWB PHYSICAL LAYER
  • Receiver takes 128 samples of effective data by
    detaching prefix from the signal
  • Null suffix used instead of cyclic suffix to
    prevent ripples in spectrum
  • Inter-carrier Interference can be removed by
    cyclic addition
  • FFT and QPSK demodulation with channel
    estimation.
  • Least square channel estimation assumed in
    absence of ideal channel estimation
  • Repetitions are combined using Maximal Ratio
    Combining (MRC)

Figure 4. Receiver for MB OFDM
From "Performance evaluation of MB-OFDM and
DS-UWB systems for wireless personal area
networks" Oh-Soon Shin Ghassemzadeh, S.S.
Greenstein, L.J. Tarokh, V. Div. of Eng. Appl.
Sci., Harvard Univ., MA, USA Proceedings of IEEE
International Conference 2005
Wireless USB WiMedia UWB
9
10
UWB PHYSICAL LAYER
  • Direct Sequence UWB
  • Two separate bands to prevent interference with
    IEEE 802.11a
  • Lower Band (3.1 GHz 4.85 GHz) Higher Band
    ( 6.2 9.7 GHZ)
  • U NII Bands ( 5.15- 5.35 GHz and 5.725 5.825
    GHz)
  • Each data symbol spread by specific spreading
    code to form a transmit sequence as well as
    offsets in chip rates
  • Frame structure similar to MB-OFDM system
  • Preamble divided into acquisition sequence, start
    frame delimiter and training sequence
  • Transmits data by pulses of energy generated at
    very high data rates

Figure 5. DS UWB Transmitter
From "Performance evaluation of MB-OFDM and
DS-UWB systems for wireless personal area
networks" Oh-Soon Shin Ghassemzadeh,
S.S.Greenstein, L.J.Tarokh, V.Div. of Eng.
Appl. Sci., Harvard Univ., MA, USA Proceedings of
IEEE International Conference 2005
Wireless USB WiMedia UWB
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11
UWB PHYSICAL LAYER
  • Rake Receivers and Chip Matched Filter (CMF)
  • Hard decision based Decision Feedback Equalizer
    (DFE) to suppress ISI (tap coefficients depend on
    MMSE)
  • Matched Filter Bound
  • Soft decision Viterbi Decoding

Figure 6. DS UWB Receiver
From "Performance evaluation of MB-OFDM and
DS-UWB systems for wireless personal area
networks" Oh-Soon Shin Ghassemzadeh,
S.S.Greenstein, L.J.Tarokh, V.Div. of Eng.
Appl. Sci., Harvard Univ., MA, USA Proceedings of
IEEE International Conference 2005
Wireless USB WiMedia UWB
11
12
UWB PHYSICAL LAYER
  • A reliable channel model, which captures the
    important characteristics of the channel, is a
    vital prerequisite for system design
  • Channel Models
  • Rayleigh fading model, Saleh-Valenzuela model,
    ?-K model
  • S-V model prevailed
  • Multi-path arrivals in clusters rather than in
    continuum
  • Four models - based on LOS(0-4m), NLOS (0-4m),
    NLOS (4-10m) and to fit 25ns RMS delay spread
  • All models are based on 167 picoseconds sampling
    time
  • IEEE 802.15 model is not a stochastic.

CM1
CM2
CM3
CM4
Table 1. Model characteristics for UWB standard
model
From Foerster Channel Models for UWB Personal
Area Networks J.R.Foerster, M.Pendergrass,
A.F.Molisch proceedings of IEEE conference Dec
2003
Wireless USB WiMedia UWB
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13
UWB PHYSICAL LAYER
PERFORMANCE COMPARISON
  • Simulations using MATLAB
  • Assumptions
  • Quantization effects neglected
  • Ideal Channel Estimation
  • FER lt 0.08 with 90 probability
  • Results show MB-OFDM performs better than DS UWB
  • But in case of MFB the trend gets reversed
  • At the higher bit rates, MB-OFDM uses less
    coding hence less able to exploit the inherent
    diversity of channel frequency selectivity.
  • Due to finite number of taps DS-UWB performance
    is affected by ISI

Table 2. Comparison of Physical Layers
From "Performance evaluation of MB-OFDM and
DS-UWB systems for wireless personal area
networks" Oh-Soon Shin Ghassemzadeh,
S.S.Greenstein, L.J.Tarokh, V.Div. of Eng.
Appl. Sci., Harvard Univ., MA, USA Proceedings of
IEEE International Conference
13
14
MAC LAYER
  • The IEEE 802.15.3 network called a piconet
    consists of Piconet Controller (PNC) and devices
    associated with it
  • Communications can only be carried out when
    enabled by PNC similar to IEEE 802.11
    infrastructure of centralized control
  • Disadvantages
  • When PNC disappears it may require several
    seconds before the rest of the devices reorganize
    and re-elect a new PNC
  • QoS cannot be sustained
  • Centralized TDMA efficiency degrades with
    overlapping piconets
  • Lack of coordination
  • WiMedia MAC distributed architecture
  • Better support in mobility and QoS

Figure 7. IEEE 802.25.3 piconets and potential
interference
From Mobility Support Enhancements for the
WiMedia UWB MAC Protocol Chun-Ting Chou, Javier
del Prado Pavon, and Sai Shankar N proceedings
of IEEE International conference, Oct 2005
14
15
MAC LAYER
  • WiMedia MAC protocol all devices perform
    identical functionality using local information
  • Time divided into super frames each of duration
    65.536 ms and further divided 256 slots each of
    256 µs
  • Superframe contains
  • Beacon Period (BP) divided into 85 µs slots and
    extend over one or more MASs
  • Data Transfer Period (DTP) Priority Channel
    Access (PCA) or Distributed Reservation Protocol
    (DRP) to access the slots
  • Each device transmits a beacon frame during BP
  • Provides fast device discovery and
    synchronization
  • Provides information for power management
    reservation
  • Provides a neighborhood information to remove
    hidden node problem
  • Permit spatial re-use of medium

Figure 8. Superframe structure in WiMedia MAC
protocol
From Mobility Support Enhancements for the
WiMedia UWB MAC Protocol Chun-Ting Chou, Javier
del Prado Pavon, and Sai Shankar N proceedings
of IEEE International conference, Oct 2005
15
16
MAC LAYER
  • A device may create its own BP with own Beacon
    Period Starting Time (BPST)
  • Devices scan for one superframe to prevent
    overlapping between devices in proximity
  • If a beacon is received device sends its beacon
    in available slot
  • Otherwise creates its own BP
  • Information included in BPs are called
    Information Elements (IE)
  • Beacon Period Occupancy IE (BPOIE) contains list
    of devices in devices beacon group (BG)
  • On reception device records the Device Address of
    transmitter and beacon slot number
  • Neighborhood information used to detect
    collisions
  • If own address is not found then conclude that
    collision occurred previous superframe
  • On repetition the colliding device will change
    its beacon slot
  • To minimize the collisions initial scan
    determines the beacon slots for its transmission
  • Devices transmit only in that slots till
    collision occurs
  • Devices with two hops may use different beacon
    slots to avoid collisions
  • In case of more than two hops same beacon slots
    is used thus enabling spatial re-use of beacon
    slots

Wireless USB WiMedia UWB
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MAC LAYER
  • Overlapping of superframes due to clock drifting
    or mobility
  • Solution Merging two BPs into one BP
  • On reception of beacon from device outside BG
    (called alien devices) multiple times, the device
    adjusts its own BPST to relocate its beacon slot
    in new BP
  • To ensure unanimous merging the device must
    initiate merger in BPMergerWaitTime 128
    superframes
  • By merging WiMedia MAC protocol provides
    mobility support in distributed manner
  • Limitations
  • Lack of Coordination when device is beyond the
    radio range of alien beacons may result in loss
    of communication
  • Enhancements Coordinated Merger and Merger
    weights

Figure 10. Potential Beacon collisions after a
merger of BPs
Figure 9. Merger of two BPs due to Mobility
From Mobility Support Enhancements for the
WiMedia UWB MAC Protocol Chun-Ting Chou, Javier
del Prado Pavon, and Sai Shankar N proceedings
of IEEE International conference, Oct 2005
Wireless USB WiMedia UWB
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18
HIGHER LAYERS
  • The higher layer could be any of following
    Wireless USB, Bluetooth or 1394 (fire wire)
  • Focus here on WUSB
  • WUSB is a protocol promulgated by the USB-IF that
    uses WiMedia's UWB radio platform
  • A logical bus that connects host and devices
    simultaneously
  • Motivation
  • Ease-of-use
  • Port-expansion
  • Goals
  • Intelligent hosts and behaviorally simple devices
  • Security as in wired system
  • Investment preservation
  • Provide effective power management
  • Capacity of 480 Mbps _at_ 3 meters and 110 Mbps _at_ 10
    meters range

Figure 11. WiMedia Architecture
From WiMedia UWB Technology, A Reality Press
Event Video (http//www.wimedia.org/en/resources/i
ndex.asp?idres)
Wireless USB WiMedia UWB
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WIRELESS USB - ARCHITECTURE
  • USB systems consist of a host and some number of
    devices
  • Three definitional areas Host, Interconnect and
    Devices
  • Topology connection mode between USB devices and
    host
  • USB schedule shared interconnect and scheduled
    to support isochronous data transfers and
    eliminate arbitration overhead
  • Hub and spoke model
  • Each spoke is a point-to-point connection between
    the host and device
  • WUSB hosts can support up to 127 devices
  • Due to absence of physical ports port expansion
    is easy
  • Host
  • USB interface of host computer system Host
    Controller
  • Wire Adapters
  • Devices can be printers, camera, speakers mass
    storage etc
  • Required to carry self information for self ID
    and generic configuration

Figure 12. Wireless USB Topology
Modified from Wireless USB Specifications
Accessed through http//www.usb.org/developers/do
cs/
Wireless USB WiMedia UWB
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WIRELESS USB - ARCHITECTURE
  • WUSB logically a polled, TDMA based protocol like
    wired USB
  • Packets contain token, data and handshake
  • Multiple token information are combined into
    single packet to eliminate costly transactions
  • Host indicates the specific time when the
    appropriate devices should either listen (IN) or
    transmit (OUT)
  • Data transfer between end points referred to as
    pipe
  • WUSB defines new packet sizes for some endpoint
    types to enhance channel efficiency
  • AES-128/CCM encryption providing integrity as
    well as encryption

Figure 13. Comparison of Wired USB and WUSB
protocol
From Wireless USB Specifications Accessed
through http//www.usb.org/developers/docs/
20
21
WIRELESS USB - ARCHITECTURE
  • Communication topology of WUSB is identical to
    USB 2.0
  • Function layer has little or no change only
    difference being isochronous transfer model has
    enhancements to react unreliability of bus layer
  • Device Layer has small changes in framework
    extensions for security and management commands
  • Bus Layer includes significant changes to provide
    an efficient communication service over wireless
    media
  • Host and devices in the range form WUSB cluster
  • Physical topology of Wireless USB is a 11 match
    with logical topology familiar to USB
    architecture

Figure 15. Physical topology of WUSB
Figure 14. Data flow Model for WUSB
Modified from Wireless USB Specifications
Accessed through http//www.usb.org/developers/do
cs
21
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WIRELESS USB - ARCHITECTURE
  • WUSB preserves the device endpoint as the
    terminus of communication flow between host and
    device
  • All devices must implement at least the Default
    Control Pipe (Endpoint zero) which is a pipe used
    for device initialization and logical device
    management
  • WUSB information Exchange methods three
    functional buckets host transmitted,
    asynchronous device transmitted and WUSB
    transaction protocol
  • WUSB device notification Time Slots
  • Broadcast control information
  • WUSB Transactions
  • Self Beaconing devices implements full MAC
    layer protocol and manages synchronization
  • Device identifies hosts or a cluster member DRP
    IEs based on following keys
  • Reservation type field is Private
  • Stream index field derived from MAC Header
    Delivery ID field
  • DevAddr field set to channel broadcast or hosts
    Cluster ID

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WIRELESS USB PROTOCOL STACK
Figure 19. WUSB Packet format
From Wireless USB Specifications Accessed
through http//www.usb.org/developers/docs/
Wireless USB WiMedia UWB
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WIRELESS USB
  • Three basic parts of addressing
  • All packet transmissions use same stream index
    field of MAC Layer Header
  • Unique device address is assigned in WUSB
    relative to cluster
  • Packets which originate or terminate on function
    endpoint must include Application Header
  • Several possible states visible to the host or
    internal to devices
  • Unconnected not established connection with any
    established communication
  • default state on power up, reconnection attempt
    fails, 4-way handshake does not complete
    successfully
  • Unauthenticated substate of connected state
    only security messages allowed
  • Authenticated normal operating state
  • Default
  • Address
  • Configuration
  • Reconnecting on timeouts

Figure 16. States of WUSB
From Wireless USB Specifications Accessed
through http//www.usb.org/developers/docs/
Wireless USB WiMedia UWB
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RECENT DEVELOPMENTS AND FUTURE PROSPECTS
  • Main players Agere Systems, HP, Intel, Microsoft
    Corporation, NEC, Philips, Semiconductors and
    Samsung Electronics
  • Computer manufactures Lenovo and Fujistu will
  • offer CWUSB as an option in their laptops later
  • this year
  • Barriers to Success
  • Keeping cost down and performance up
  • Competitions such as from Bluetooth
  • Predictions
  • In 18 months most laptops will have
  • the technology
  • In couple of years data rates from
  • 2 to 3 Gbps possible
  • Lower power consumption for better
  • support for mobile devices
  • 4 billion USB-enabled devices
  • worldwide by 2011 with 503 million,

Figure 18. Stat predictions for WUSB in future
years
From Future of Wireless USB starts now Neal
Leavitt proceedings of IEEE Computer magazine
July 2007
Wireless USB WiMedia UWB
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SCENARIO
Figure 19. BELKIN Wireless USB Hub
From http//catalog.belkin.com/IWCatProductPage.p
rocess?Product_Id377793
Wireless USB WiMedia UWB
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27
CONCLUSION
  • Wireless USB is a fast growing PAN technology,
    its the latest iteration of USB technology, will
    offer the same functionality as standard wired
    USB devices but without the cabling. In this
    presentation its underlying UWB technology along
    with its architecture were visited. As the new
    Wireless USB Promoter Group prepares to develop
    the specifications that will help standardize the
    technology, the industry is planning products
    that can take advantage of the convenience and
    mobility that this new device interconnect will
    offer.

27
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REFERENCES
  • Wireless USB Specifications Accessed through
    http//www.usb.org/developers/docs/
  • Performance evaluation of MB-OFDM and DS-UWB
    systems for wireless personal area networks"
    Oh-Soon Shin Ghassemzadeh,S.S. Greenstein, L.J.
    Tarokh, V. Proceedings of IEEE International
    Conference Sep 2005
  • Mobility Support Enhancements for the WiMedia
    UWB MAC Protocol Chun-Ting Chou, Javier del
    Prado Pavon, and Sai Shankar N proceedings of
    IEEE International conference, Oct 2005
  • Ultra Wideband Radio Technology Kazimierz Siwiak
    and Debra McKeown John Wiley Sons Ltd. Edition
    2004
  • WiMedia UWB Technology, A Reality Press Event
    Video Accessed through http//www.wimedia.org/en/r
    esources/index.asp?idres
  • Future of Wireless USB starts now Neal Leavitt
    proceedings of IEEE Computer magazine July 2007
    accessed through http//www.leavcom.com/pdf/Wirel
    essUSB.pdf

Wireless USB WiMedia UWB
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REFERENCES
  • 7. Channel Models for UWB Personal Area Networks
    J.R.Foerster, M.Pendergrass, A.F.Molisch
    proceedings of IEEE conference Dec 2003
  • 8. Intel Corporation Wireless USB The First
    High Speed Personal Wireless Interconnect
  • White Paper Intel Developer Forum March
    14, 2004
  • http//www.intel.com/technology/ultrawideba
    nd/downloads/wirelessUSB.pdf
  • 9. MAC Protocols for Ultra-Wide-Band (UWB)
    Wireless Networks Impact of Channel Acquisition
    Time Jin Ding, Li Zhao, Sirisha R. Medidi and
    Krishna M. Sivalingam
  • http//catalog.belkin.com/IWCatProductPage.process
    ?Product_Id377793
  • http//www.extremetech.com/article2/0,1697,2129892
    ,00.asp
  • Wikipedia Article Ultra-wideband.
    http//en.wikipedia.org/wiki/Ultra-wideband
  • http//www.extremetech.com/article2/0,1697,2129892
    ,00.asp
  • http//www.anu.edu.au/RSISE/teleng/teleng2004/rese
    arch/uwb.php

Wireless USB WiMedia UWB
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