2. 2 11/24/2008
Not to be confused with
Ultra Mobile Broadband
(UMB) from Qualcomm!!!
Word of caution
3. 3 11/24/2008
Recap
• Short range transmission
o High directivity
o Low power
o Large bandwidth
• Wireless Personal Area Networks
o Range limited to ~ 10 m
o Ad-hoc networks - infrastructureless
o Wheel-and-Spoke piconet topology
o Master-Slave and “anchored” P2P communication
4. 4 11/24/2008
Recap
• Multiple “open” standards for different app
scenarios
o Wireless USB
o IEEE802.15.3a
o Ecma368
• Multiple stakeholders
o WiMedia/MBO Alliance
o ECMA
o UWB – IEEE802.15.3x WG and WUSB Forum
o WiHD Forum
o Wireless HDMI Forum
o Sony Corporation (TransferJet)
5. 5 11/24/2008
Recap
• RF bandwidth allocations
o Licensed vs. unlicensed spectrum
• Applications
o HDTV
o HD Audio
o IPTV
6. 6 11/24/2008
Recap
• Operational limits
o Unlicensed usage
• FCC mandates “Do no evil, tolerate all evil”
• Devices using unlicensed spectrum
o Must be able to “coexist” in an “uncontrolled”
environment
o Must not “interfere” with the operation of devices
operating on licensed spectrum
7. 7 11/24/2008
UWB - Basics
• First bandwidth allocation by the FCC in 2002
• 10 dB bandwidth > 500 MHz = “Ultra-Wide
Band”
• Typical bandwidth of >= 7.5 GHz
o FCC mandates 3.1 – 10.6 GHz band
• Severe power restrictions
o FCC mandates <= -41 dBm/Hz EIRP
o “Narrow Band” wireless consumer devices do not
“accumulate” enough interference within their
operational bandwidth limits
o Short range (SR) and Close Proximity (CP)
communications
8. 8 11/24/2008
UWB - Basics
• Competing proposals (current)
o Multiband OFDM-UWB from the Multiband OFDM
Alliance (MBOA)
Supported by WiMedia Alliance
o Direct Sequence-UWB from the UWB Forum
Almost defunct
• Advantages of MB-OFDM
o More robust to multipath
o Easier spectrum sculpting
o Less prone to interference
9. 9 11/24/2008
Approaches to UWB
• Tradeoff between total power and bandwidth
o Either have very high power and operate on narrow
bands
o Or, have very low power and operate over very large
bandwidths
2 5 10 f (GHz)
PSD (Watts/Hz)
Noise Floor
WLAN IEEE
802.11a
UMTS
3GPP UWB
10. 10 11/24/2008
Common Platform
IEEE 802.15.3x Architecture
IEEE 802.15.3a UWB PHY
IEEE 802.15.3 UWB MAC
Convergence Layer
Wireless
USB
Bluetooth
3.0
Non IP P2P
(Wireless
Firewire)
IP (UPnP)
MB-OFDM
Alliance
WiMedia
Alliance
11. 11 11/24/2008
Power Management
• Power depends on several factors
o Digital modulation used (QPSK)
o ADC/DAC resolution
o Internal resolution of the FFT
All values are for 90 nm
fab process
14. 14 11/24/2008
Traditional UWB
• Data is modulated onto a Gaussian
monocycle pulse train
o Pulse Position Modulation (PPM)
o Pulse Time Modulation (PTM)
• Zero-IF modulation requires no intermediate
up/down conversion to RF
o Homodyne receiver architecture makes design
simpler
15. 15 11/24/2008
Modern Approaches to UWB
• Multi-carrier OFDM (traditional OFDM)
o IEEE802.15.3a
• Single carrier Direct Sequence-UWB (DS-
UWB) based on 16-finger RAKE receiver
o IEEE802.15.3a
• Multi-Band OFDM
o 528 MHz sub-channels
o Supported by the WiMedia/MBO Alliance
• Single carrier Direct Sequence-UWB (DS-
UWB) based on M-ary bi-orthogonal keying
(MBOK)
16. 16 11/24/2008
DS-UWB
• DS-UWB
o Single Carrier
o 1368 MHz chip rate
o 16-finger RAKE receiver
• Indoor environments are highly dispersive
o RMS delay spread ranges from 14 ns to 25 ns
• To boost the received signal, receivers
collect signal energy from as many delayed
“copies” of the signal as possible
o Larger number of RAKE fingers required
• Larger Inter-Symbol Interference (ISI)
17. 17 11/24/2008
MB-OFDM
• Multi Band-Orthogonal Frequency Division
Multiplexing
• MBOA stipulates 5 channels
o 5 channels for a 7.5 GHz UWB
o Channels 1-4 have 3 sub-bands each; Channel 5 has
2 sub-bands
o Each sub-band = 528 MHz
o One OFDM symbol (with 128 sub-carriers)
transmitted in one time slot per channel
19. 19 11/24/2008
MB-OFDM
• Time-Frequency Coding
o 1-3-2 shown earlier
• Guard Interval (GI) to switch between
channels
o 9.5 ns
• Cyclic Prefixing to reduce the complexity of
the Rx circuitry
o 60.6 ns
o Simple multiplication operations instead of Shift-
Multiply-Add in frequency domain
20. 20 11/24/2008
MB-OFDM
• Larger GI and CP values contribute to system
latency and redundancy
• Shorter GI complicates channel switching
hardware circuitry
• Larger CP increases overhead but also
increases the “accumulated” multipath signal
strength
o CP duration should be in direct proportion to delay
spread
• Multipath signals not “accumulated” manifests
as Inter-Channel Interference (ICI)
• Zero Prefixing (ZP) may also be used
o Larger latency but less spectral leakage
21. 21 11/24/2008
MB-OFDM
• WiMedia/MBO Alliance has effectively won
the contest (as of 2007!!)
• Advantages of using Multi Band approach
over DS-UWB
o Higher spectral efficiency inherent in OFDM
o Resilience to RF interference
o Robustness to multipath effects
o Proven technology in indoor
environments(IEEE802.11a/g)
22. 22 11/24/2008
UWB PHY
Scrambler Convolutional
Encoder
Pu
nc
tur
er
In
te
rl
e
a
v
er
Constellation
Mapper
IFFT
Insert Pilot
Carriers
Insert CP and
GI
DAC
Time Frequency
Kernel
fc
100 data points
12 points
10 points + 6
nulls
23. 23 11/24/2008
UWB MAC
• Data is requested using Information Elements
(IE)
• Actual data is sent in the form of bursts of
MAC Protocol Data Units (MPDU)
• Prioritized Channel Access (PCA)
o Based on Enhanced Distributed Channel Access
(EDCA) used by IEEE802.11x
o Utilizes Carrier Sense Multiple Access/Collision
Avoidance (CSMA/CA)
• Distributed Reservation Protocol (DRP)
o “Collision Free” channel access
25. 25 11/24/2008
UWB MAC PCA
• Short InterFrame Space (SIFS)
o At the end of a MPDU
• Minimum InterFrame Space (MIFS)
o In between 2 consecutive burst frames
• Soft Reservation policy
o Inferior QoS
26. 26 11/24/2008
UWB MAC DRP
• 1 Super Frame = 256 Medium Access Slots
(MAS)
o 1 MAS = 256 µs
• Each SF begins with a Beacon Period (BP)
o 1 BP = n MAS (n < 256)
• At the end of BP, Data Transfer Period (DTP)
is sent
o DTP contains actual data payload
o 1 DTP = (256-n) MAS
• Beacons are used for synchronization, device
discovery, sleep mode operation and
reservation request
• Hard Reservation policy
o Higher QoS applications
