ULTRA WIDEBAND

1
ULTRA WIDEBAND

• Soo-Young Chang

2
TABLE OF CONTENTS

• Introduction
• Mathematical backgrounds
• Channel characteristics
• Optimal baseband waveforms
• Modulation schemes
• Multiple access techniques
• Detection
• Synchronization

• Antenna
• Transmitter structure
• Receiver structure
• MAC layer
• UWB networking
• Performance evaluation
• Future research issues

3
INTRODUCTON
4
DEFINITION

• Bandwidth more than 20 of carrier frequency or
  more than 0.5 GHz (defined by FCC)
• Very short duration pulses less than a few nsec
  transmitted typically less than 1 nsec

5
UWB RADIO

• Impulse
• Time domain
• Non-sinusoidal
• Baseband
• Video pulse

• Carrierless
• Carrier-free
• Super wideband
• Ultrahigh resolution

6
HISTORY

• Radar history

7
ULTIMATE GOAL OF WIRELESS COMM.

• Goal of Generic wireless
• Amount of information a lot of data
• Range very far
• Data rate very fast
• No. of users for many users
• Real time all at once
• Trend short range wireless
• favor for freq reuse

• UWB
• Amount of information a lot of data
• Range very small
• Data rate very fast
• No. of users for many users
• Real time all at once
• wired infrastructure
• growth of high- speed wired

8
UWB BASIC CHARACTERISTICS

• Ultra wide Bandwidth
• Energy bandwidth (BE)
• Percent bandwidth contains 99 power
• Proportional bandwidth
• Time-bandwidth product (TB) for practical
  example, IS-95 has around 0.5, and for CDMA2000
  and WCDMA numbers between 0.5 and 1.0 are
  proposed
• Fractional bandwidth
• Relative bandwidth
• Narrowband conventional comm
• wideband 3G cellular technology
• ultra wideband wide bandwidth and carrierless

9
UWB BASIC CHARACTERISTICS

• High spatial capacity bits/sec/m2
• Low power portable device needed
• 802.11b Bluetooth 802.11a UWB
• range (m) 100 10
  50 10
• BW (MHz) 80 200
  7500
• data rate (Mbps) 11 1
  54 110
• spatial cap (b/s/m2) 1,000 30,000
  83,000 2,000,000
• All systems are bounded by the channel capacity
  which says that the capacity increases linearly
  with bandwidth but only logarithmically with S/N.
  
• ? None can not reach the speed of UWB.
• C B log (1 S/N)

10
UWB BASIC CHARACTERISTICS

• Relatively simple in transceiver architecture
• Transmitter pulse generator antenna
• Receiver antenna LNA receiver (matched
  filter or correlator) detector
• no power amp, no transmit filter, no VCO, no
  mixer, no PLL, no ref osc. etc
• Low cost and power consumption
• Simple hardware entails low cost
• Due to low semiconductor cost and power
  consumption for signal processing
• makes UWB technology practical

11
UWB BASIC CHARACTERISTICS

• LOW PROBABILITY OF INTERCEPT (LOI)

12
CHARACTERISTICS FOR UWB COMM.

• Very low power level below kT thermal noise level
  
• Short duration pulse less than 1 nsec
• Ultra wide bandwidth larger than 20 of carrier
  frequency
• High data rate achieved higher than 110 Mbps
• High processing gain the ratio of the RF
  bandwidth of the signal to the information
  bandwidth of the signal
• For ex., 7.5 GHz channel bandwidth with 100 MHz
  information bandwidth has a processing gain of
  75.
• The duty cycle of the transmission of 1 yields
  a processing gain of 100 (20 dB)
• Low probability of intercept and detection
• Low-cost digital signal processing hardware is
  often used in modern digital radios to generate
  several modulation methods These systems can
  step down the information density in their signal
  to serve users at greater distances (range)
• A UWB radio can use several pulses to send one
  information bit thereby increasing SNR in the
  receiver
• Under software control, the UWB system can
  dynamically trade date rate, power consumption,
  and range.
• Enable the power constrained portable computing
  applications of the future.

13
ADVANTAGES OF UWB OVER NARROWBAND

• Potential advantages
• Low cost, low power simple implementation
• Carrierless, direct baseband signal
• Low duty cycle operation
• Potential for high capacity high throughput
• Large effective processing gain
• Share the spectrum with many users
• Low noise power spectral density
• Improved co-existence
• Ideally no frequency planning
• Good propagation quantities
• Multipath resistant, cm location
• High penetration (high BW, low freq.)
• Fine time resolution

• Potential issues
• Regulatory
• Limits, thresholds, bands
• Noise aggregation issues
• Wireless internet connectivity issues
• Lack of standards
• In development, but lengthy process
• Utility not clear in all cases
• Performance and implementation
• Synch., jitter, sampling, etc.
• Susceptibility to interference
• Short range (a few meters to a few km)
• Low power direct pulse operation
• Low antenna transmit efficiency (BW-1/QF)
• Amount of digital computation

14
UWB vs SPREAD SPECTRUM

• Both tech for spectrum spread
• Direct sequence
• Frequency hopping
• Pulsed-FM or chirp
• Time hopping

15
CHALLENGES FOR UWB REALIZATION

• Regulatory issues
• Finding a way to make the technology legal
  without causing unacceptable interference to
  other users that share the same frequency bands
• Power efficient and low cost implementation
• Fulfillment of spectral mask, but full
  exploitation of allowed power Interference
  suppression
• Technique which adaptively suppress interference
  from other systems

16
CHALLENGES IN TECHNICAL AREAS

• Susceptible to being unintentionally jammed by
  traditional narrowband transmitter
• Filter matching accuracy FOER01
• Extreme antenna bandwidth requirements
• Accurate timing synchronization for a
  correlated-based receiver due to short pulse
  durations
• Amount of energy in the multipath components
  caused by reflections in the channel Rake
  receiver is a candidate
• Noise from on-board microcontroller

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GOALS FOR UWB IMPLEMENTATION

• Fulfillment of spectral mask, but full
  exploitation of allowed power. Interference
  suppression
• Cheap implementation
• Robustness to multipath
• Scalability

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UWB PHY LAYER COMPONENTS

• Transmitter
• Source coding / channel coding
• Pulse generation
• Code sequence generation for multiple access
• Modulation
• Power control
• Antenna

• Receiver
• Low noise amplifier
• Synchronization detection
• Demodulation
• Cross correlation detection (using template) or
  matched filtering
• Channel decoding / source decoding

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UWB MAC LAYER COMPONETS

• Initially 802.15.3 MAC protocol is to be applied.
• UWB MAC questions
• Are standard MAC protocols applicable to UWB
  (e.g., 802.15.3 and 802.11b)?
• What, if any, UWB specific features may be
  required within the MAC?
• Can the UWB MAC facilitate co-existence with
  other systems (e.g., WLAN and 802.16)?
• MAC design considerations
• Scalability of personal operating space based on
  UWB localization
• Improved co-existence with other systems
• Reduced power consumption
• Scalability in terms of range and throughput
  trades
• PRF and peak power can vary inversely providing
  for constant average power
• This enables signaling of different data rates on
  a per packet or link basis based on the range
  FOER
• Synchronization of received packets at different
  receivers
• Receivers in a multicast network based on UWB
  localization FOER

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UWB APPLICATIONS

• Radar
• Passive target identification
• Target imaging and discrimination
• Signal concealment from electronic warfare and
  anti-radiation missile
• Detection or remote sensing
• Ground penetration radar
• Locating
• Communications

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UWB APPLICATIONS FOR COMM

• Home
• Entertainment
• Proximity detectors
• Tracking
• Industrial
• Automotive
• Military
• Law enforcement/rescue

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FCC ACTIVITIES

• NOI (Notice of Interest) Sep. 1998
• Ask feedback from the industry regarding the
  possibility of allowing UWB emission on an
  unlicensed basis following power restrictions
  described in the FCC Part 15 rules.
• More than 500 comments have been filed.
• P E2 4 R2 /
• where P emitted power (W)
• E electric field strength (V/m)
• R radius of the sphere (m)
• characteristic impedance of a vacuum (377
  ohms)
• NPRM (Notice of Proposed Rule Making) May 2002
• Ask feedback from the industry on specific rule
  changes that could allow UWB emitters under the
  Part 15 rules.
• First RO (Report and Order) Feb. 2002
• Frequency assignments 3.1 10.6 GHz
• Frequency mask indoor and outdoor

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FCC MASK

• Factors which affect how UWB impacts other
  narrowband systems
• Separation between the devices
• Channel propagation losses
• Duty cycle
• Modulation techniques
• Pulse repetition frequency (PRF) employed by the
  UWB system
• Receiver antenna gain of the narrowband receiver
  in the direction of UWB transmitter
• Three types of UWB devices
• Imaging systems (medical, surveillance, ground
  penetrating radar) which may operate either below
  960 MHz or between 1.99 and 10 GHz
• Vehicular radar systems (above 24.075 GHz)
• Communications and measurements systems
  restricted to
• Indoor networks or hand-held devices working on a
  peer-to-peer basis
• Operating between 3.1 to 10.6 GHz, FCC 15 rules
  applied (limits)
• FCC mask
• ETSI limits are expected to be similar SORENSEN

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FCC MASK (contd)
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FCC FREQUENCY ASSIGNMENT

• Feb. 2002
• Assigned frequency band of 3.1 -10.6 GHz 7.5 GHz
  Bandwidth
• To be deployed on an unlicensed basis following
  the Part 15.209 rules for radiated emissions of
  intentional radiators
• With frequency mask which constrains the transmit
  power

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OPPONENTS

• Airlines
• GPS
• Cell phone companies
• Department of Defense
• Baby monitor companies

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IEEE802 STANDARD ACTIVITIES

• IEEE802 standards for LAN/MAN
• IEEE802.15 WPAN (Wireless Personal Area
  Networks)
• Deals with short range comm. Including Bluetooth
• IEEE802.15.3 high rate short range
  communications up to 55 Mbps
• IEEE802.15.3a task group for alternate PHY for
  high rate short range communications higher than
  110 Mbps
• IEEE802.18 coexistence between wireless
  applications currently study coexistence between
  802.11 802.15.3a

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IEEE802.15.3a

• For alternate PHY for high rate WPAN (802.15.3)
• Date rate Higher than 110 Mbps up to 480 Mbps
  (possibly 1 Gbps)
• Key Applications multimedia and imaging
• PHY UWB
• MAC modified IEEE15.3 MAC
• Became a formal task group (TG) in Jan. 2003
• Leading companies
• XtremeSpectrum (Motorola), Time Domain, General
  Atomics, Intel, Texas Instruments, CRL (Japan),
  STMicronics (Switzerland), etc

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802.15.3a STANDARD ACTIVITIES

• PHY requirements
• Low power consumption
• Small form factor
• MAC requirements
• Modified 802.15.3 high rate MAC
• Target applications
• indoor application for short range less than 10 m
• Coexistence with other narrowband systems
• 802.11x, 802.15.3, Bluetooth, HomeRF, HyperLAN,
  GPS, PCS, future satellite, etc

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802.15.3a TARGET APPLICATIONS

• Short range indoor comm.
• Up to 10 m range
• Video and imaging applications
• digital camera, DVD, MP3, video streaming, etc

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802.15.3a TECHNICAL REQUIREMENTS
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IEEE802.15 AND RELATED ORGANIZATIONS
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BLUETOOTH (IEEE802.15.1)
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ZIGBEE (IEEE802.15.4)

• Low rate wireless personal area networks
  (LR-WPAN)
• in residential and industrial environments
• Connectivity among inexpensive fixed, portable,
  moving devices
• Other home networking attempts wired and
  wireless
• HomePNA
• Homeplug Powerline Alliance
• CEA R-7
• HomeRF
• Echonet
• Wireless for home networking reduction in
  installation cost
• Internet connectivity
• Multi-PC connectivity
• Audio/video networking
• Home automation
• Energy conservation
• Security
• Relaxed throughput requirements for home
  automation, security, and gaming
• Eliminate complexity of heavy protocol stacks
• Needs power consumption

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ZIGBEE (IEEE802.15.4)

• Key features
• Low throughput 250 Kbps
• Low cost module cost estimated 2
• Ultra low complexity
• Low installation cost
• Low power consumption last between 6 months and
  2 years with AA batteries according to
  applications
• Bluetooth and IEEE802.11
• High throughput
• Zigbee and IEEE802.15.4
• IEEE802.15.4
• Define PHY and MAC layer specifications
• Zigbee
• Define application profiles and interoperability
• Products availability
• Initial release of IEEE802.15.4 standard
• First integrated circuits to implement draft
  standard early 2003
• First Zigbee embedded products Q3 2003

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ZIGBEE (IEEE802.15.4)

• Technical parameters

• Applications
• Industrial control and monitoring
• Public safety
• Sensing and location determination at disaster
  sites
• Automotive sensing
• Tire pressure monitoring
• Smart badges and tags
• Precision agriculture
• Sensing of soil moisture, pesticide, herbicide,
  and pH levels
• Home automation and networking
• PC peripherals wireless mice, keyboards,
  joysticks, low-end PDAs, and games
• Consumer electronics Radio, TV, VCRs, CDs,
  DVDs, remote controls
• Home automation heating, ventilation, and air
  conditioning (HVAC), security, lighting, and
  control of objects such as curtains, windows,
  doors, and locks
• Health monitoring sensors, monitors, and
  diagnostics
• Toys and games PC-enhanced toys and interactive
  gaming between individuals and groups

37
ZIGBEE (IEEE802.15.4)

• Network topology
• Star network
• Peer-to-peer network (mesh network)

PAN cordinator
User device
38
ZIGBEE (IEEE802.15.4)
Zigbee spec
Upper layers
Network layer
IEEE802.2 LLC type 1
Other LLC
SSCS
Data link layer
IEEE802.15.4 MAC layer
IEEE802.15.4 868/915 MHZ Physical layer
IEEE802.15.4 2.4 GHZ Physical layer
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UWB vs 802.11x vs Bluetooth
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IEEE802.15.3a vs WiMedia
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IEEE802.15.3a vs IEEE802.15.4
42
UWB RELATED INDUSTRIES

• XtremeSpectrum
• Time Domain
• General Atomics
• AetherWire Location
• Multispectral Solutions (MSSI)
• Pulse-Link
• Appairent Technologies
• Pulsicom
• Staccato communications
• Intel
• TI
• Motorola

• Perimeter players
• Sony
• Fujitsu
• Philips
• Mitsubishi
• Broadcom
• Sharps
• Samsung
• Panasonic

43
COEXISTENCE

• Coexistence with other narrowband systems
• 802.11x, 802.15.3, Bluetooth, HomeRF, HyperLAN,
  GPS, PCS, future satellite, etc
• 802.18 reviews this issue

44
PRODUCSTS RELEASED

• XtremeSpectrum
• Trinity chip set 2 chips
• RF baseband, digital control, MAC
• Time Domain
• PulseOn 100 PPM
• PulseOn 200 PPM and other modulation
• PulseOn 300 other modulation

45
GLOBAL INTEREST
46
ACADEMIA INVOLVED

• University of Southern California, Ultra Lab
• Dr. Scholtz initiated time hopping PPM (TM-PPM)
• One member of MURI
• University of California, Berkley, Berkeley
  Wireless Research Center
• Mainly interested in ASIC implementation
• One member of MURI
• University of Massachusetts
• Mainly research on antenna
• One member of MURI
• University of California, Davis
• Ohio Stat University
• Antenna
• Georgia Tech
• Antenna
• Texas AM
• antenna
• Virginia Polytech
• New Jersey Institute of technology, Center for
  Telecommunication
• Mainly interested in transceiver

47
RELATED ORGANIZATIONS

• UWB Working Group
• NTIA
• published a report analyzing the impact of UWB
  emissions on GPS and suggested an additional
  20-35 dB attenuation beyond the power limits
  described in the FCC Part 15.209.
• Department of Commerce
• Department of Defense
• FCC
• NIST

48
MARKET FORECASTS
49
MATHEMATICAL BACKGROUNDS
50
MATHEMATICAL BACKGROUNDS
51
OPTIMAL BASEBAND WAVEFORMS
52
CHANNEL CHARACTERISTICS FOR UWB COMMUCATIONS
53
UWB CHANNEL MODELING

• In-door propagation modeling and measurements
  propagation and energy transfer
• Cluster
• Multipath
• Path loss model
• Multipath model

54
INDOOR CHANNEL MODELING

• Objective
• Path loss and multipath charateristics of typical
  operational environments
• Help to evaluate the performance of the system
• Fundamental parameters
• Path loss
• Multipath
• RMS delay spread
• Power decay profiles
• Number of path components number of multipath
  arrivals considered (e.g., those within 10 dB of
  the peak multipath arrival
• Associated thresholds
• Environment
• Indoor office and residential
• Line-of-sight (LOS) and non line-of-sight (NLOS)

55
INDOOR NARROWBAND CHANNEL MODEL

• IEEE802.11 CHANNEL MODEL
• Model using an exponentially decaying Rayleigh
  fading tap delay line (TDL)
• Assume that each of the channel taps is drawn
  from an independent complex Gaussian random
  variable with an average power profile that decay
  exponentially
• The probability distribution of the kth tap of
  the channel impulse response hk

56
OPTIMIZATIONS OF TRANSIENT WAVEFORMS AND SIGNALS

• Various solutions for the optimum transmit
  antenna generator waveform are required to
• Maximize receive antenna voltage amplitude (with
  constrained input energy and bandwidth)
• Provides the sharpest received antenna voltage
  waveform (with constrained input energy and
  bandwidth)
• Maximize received energy (with an inequality
  constrained on the radiated power spectral
  density)
• Results are derived for arbitrary antennas
• Effects of generator and load impedances are
  included
• Rigorous EM solutions via moment method
• Closed-form results for short antennas for some
  special cases

57
OPTIMAL BASEBAND WAVEFORMS

• Gaussian impulse
• Monocycle
• Polycycle
• Doublet
• others

58
UWB WAVEFORM IMPLEMENTATION

• Implementation via active pulse shaping
  techniques
• By combining several readily implementable and
  scaled functions, a good approximation of
  Gaussian wavelets can be achieved

59
ONE EXAMPLE (GAUSSIAN PULSE)
60
ANOTHER EXAMPLE
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MULTIPLE ACCESS TECHNIQUES
62
MULTIPLE ACCESS TECHNIQUE

• TDMA
• CDMA
• FDMA
• Time hopping
• random/pseudorandom TH sequence
• Using orthogonal functions
• Walsh functions and other functions
• Analog impulse radio MA receiver (AIRMA)
• Digital impulse radio MA receiver (DIRMA)

63
MODULATION SCHEMES

• Pulse position modulation (PPM) (or
  Time-modulated)
• Pulse amplitude modulation (PAM)
• On-off keying (OOK)
• Biphase (or BPSK or antipodal)
• M-ary
• Spectral Keying (SK)

64
DETECTION

• Template
• Zero crossing detection
• Correlator using coded sequences
  cross-correlation peak calculated
• Maximal sequence codes
• Complementary codes
• Time-integrating correlator
• Time-domain filtering (matched filtering)
• Selective Rake receiver

65
SYNCHRONIZATION

• Clocks and timing
• Protocols for synchronization
• Sync. Training Sequence
• Central timing control timing logic
• Fast acquisition at receiver Mitsubishi
  proposal
• template signal and received signal need to be
  aligned
• standard method serial search (chip by chip)
• but chip duration very short in UWB, takes long
  time
• Block search algorithm
• For LOS
• For NLOS
• Channel estimation needed?

66
CHANNEL CODING

• One example mitsubishi
• rate ½ convolutional code
• requires 4dB SNR for 10-5 BER
• Improvement by 3dB possible by turbo codes

67
POWER CONTROL

• To overcome near-far problem of CDMA

68
EFFICIENT ANTENNA
69
ANTENNA IN COMMUNICATION SYSTEMS

• At transmitter
• Antenna is modeled as a circuit component real
  part in it determines the radiated power (for
  )
• Current in the antenna determines Erad
• At receiver
• E-field at the Rx is translated to a voltage
  source
• By reciprocity theorem, Zant,rxZant,tx
• Transmitter receiver

70
UWB ANTENNA CONSIDERATIONS

• Parameters
• Broadband Low Q low selectivity
• Antenna matching impedance
• Gain
• Polarization
• Antenna efficiency Pradiated / Papplied
• Directivity
• Small size
• VSWR
• Differentiation effect
• Antenna can no longer be optimized at the carrier
  frequency (no carrier in UWB)
• Frequency-independent antenna is needed
• Requirements of UWB antenna
• Two dimensional
• Omni-directional field pattern
• Small size
• Low cost

71
CHALLENGES IN UWB ANTENNA DESIGN

• EM aspects of UWB communication systems have not
  been studied adequately
• Most of the conventional antenna analyses assume
  harmonic time dependent (not the case in UWB)
• Time-domain EM analysis/simulation are needed
• Issues in UWB antenna design
• Efficient pulse generation/reception
• Pulse dispersion problem
• Matching/ringing problem

72
SYSTEM DESIGN PERSPECTIVE

• UWB antenna is not likely to be a purely
  resistive load and may strongly influence the
  transmitter circuits
• Antenna/circuit co-design is necessary
• Efficient pulse-shape design
• Taking pulse-shape design into account adds one
  more dimension to improve the performance of the
  antenna
• Pulse generator bonding wire transmission line
  antenna

73
MONOPOLE ANTENNA (1)

• FREQUENCY RESPONSEs11
• The smaller the s11, the larger the radiation
• Resonant at fc/(0.5lamda), which leads to freq.
  hump
• Two ways to avoid ringing flatten the freq.
  response
• Make the conductive wire more resistive
• Shorten the dipole
• For 6cm monopole, freq. hump at 1.4GHz
• For 2cm monopole, no freq. hump in 0-3 GHz freq.
  range

74
MONOPOLE ANTENNA (2)

• FAR-ZONE ELECTRIC FIELDS OF THE MONOPOLE
• When L is much smaller than lamda/e, no ringing
  happens
• Radiated energy is decreased, but its OK
  sometimes
• Undetectable UWB system transmits at noise level

75
MONOPOLE ANTENNA (3)

• SHORT MONOPOLE INPUT V/I CHARACTERISTICS
• The input V/I behavior resembles that as driving
  a capacitor
• Radiation is too small energy stored in
  near-field
• Modeling a 2cm monopole by a 0.315 pF capacitor
• Given the same Vs Rs, Is in two cases overlap
  perfectly

76
MONOPOLE ANTENNA (4)

• SHORT MONOPOLE RADIATION
• The radiated field is the time-derivative of the
  input current
• The dimension is small. Phase difference between
  I(z) at each part is ignorable ? quasi-static
  condition

77
DIPOLE ANTENNA

• Consists of two straight wires
• Simple scheme, easy to analyze, mechanism is
  well-known
• Popular in narrowband systems
• hump in frequency domain
• Resistively loaded dipoles exibit very broad BW
  since reflection on the antenna is suppressed,
  but
• Radiation efficiency is reduced
• Termination is a problem

78
LOOP ANTENNA

• Circular turns of wire
• To meet the 2D geometry spec only 1 turn is used
• Used for AM radio
• Radiate normally/axially if the loop is
  small/large relative to a wavelength
• A modified version, large current radiator, is
  adopted by Aether Wire Location, Inc., an UWB
  localizer company. Large radiation power can be
  delivered, but its shape is 3D.

79
MICROSTRIP ANTENNA

• Metallic patches sit on a dielectric substrate
• Usually made on PCB
• Low profile, conformable to various surface,
  inexpensive, durable, but narrow-band
• Modify the shape to broaden the bandwidth, e.g.
  bowtie antenna
• antenna patch
• dielectric substrate
• ground

80
UWB ANTENNA

• The E field strength in UWB systems
• proportional to the d/dt of the drive current
  regardless of the waveform ideal antennas
• The antenna can perform filtering functions in
  some cases.
• tx rx
• antenna ---------------------------? antenna
  ---------
• i di/dt d2i/dt2
• Key issue
• Electrically small, adequately efficient antenna
  design

81
TPYES OF ANTENNAS

• Bow-tie
• Relatively high input impedance
• Requires a matching balun to make it usable with
  50 ohm system
• Tapered slot
• Two dimensional microstrip
• Resister loaded dipole
• Low gain and low efficiency
• Diamond dipole developed by Time Domain Corp.
• Emits a waveform similar to a Gaussian third
  derivative
• 75 efficiency with about 31 VSWR
• Discone
• High performance
• 3-D structure difficult to manufacture
• Bicone
• High performance
• 3-D structure difficult to manufacture
• Log-periodic
• Spiral
• Transverse electromagnetic (TEM) horn

82
ANTENNA, ONE EXAMPLE

• One example
• Time Domain Corp. BroadSpec 102
• Planar antenna
• Smaller than a standard business card
• Well matched from 1.7-4.5 GHz with max return
  loss -15 dB and VSWR below 1.51
• Dipole like pattern with gain 0-3 dBi
• Impedance 50j0 ohm
• Efficiency above 90

83
TRNASMITTER STRUCTURE

• Antenna
• Pulse generator
• Clock generator
• Control
• Power control
• Modulator switch

84
RECEIVER STRUCTURE

• Efficient receiver processing
• Coherent signal processing
• Matched filtering
• Use matched filter with processing gain to
  improve SNR
• Analog impulse radio MA receiver (AIRMA)
• Digital impulse radio MA receiver (DIRMA)

85
Rake receiver
86
RECEIVER STRUCTURE

• Low noise amp
• Variable gain amp
• Sample/hold
• A/D converter
• Sampling clock generator
• Pulse generator
• Template generator

87
MAC LAYER
88
UWB NETWORKING (NETEX)

• Overlapped Piconet
• Each piconet has one piconet controller (PNC).
• Intra- and inter-piconet operation
• Multihop operation to reach far region

89
PERFORMANCE EVALUATION

• Interference
• AWGN
• Multipath
• S/N
• Multiple access performance
• Multiple user interference calculation for analog
  impulse radio
• Throughput
• QoS
• Power control

90
FUTURE RESEARCH ISSUES

• UWB imaging algorithm
• Handling on-chip interference
• Computationally efficient ranging algorithms
• Interference excision over ultra wide bandwidths
• UWB node teaming for long-distance transmission
• Efficient pulse shape design