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Transcript of Satya Seminar
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7/31/2019 Satya Seminar
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1
Ultra-Wide BandCommunication
Submitted By:SATYA SANTANU MOHAPATRA
0901289032/07
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CONTENTS
Introduction to Ultra-Wideband communications
Challenges of onboard spacecraftcommunications
Advantages of UWB
UWB applications
Some Modulation techniques
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INTRODUTION TO UWB
Narrowband communications systems modulate continuouswaveform(CW) RF signals with a specific carrier frequency totransmit and receive information.
UWB systems use carrierless, short-duration (picosecond tonanosecond) pulses with a very low duty cycle (less than 0.5percent) for transmission and reception of the information.
Low duty cycle offers a very low average transmission power inUWB communications systems.
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What is Ultra Wideband?
Radio technology that modulates impulse based waveforms instead of
continuous carrier waves
FrequencyModulation
2.4 GHzNarrowban
d
Narrowban
d
Communica
ti
Communica
ti
o
n
o
n0 1 0 1
Impulse
Modulation
3 10 GHzfrequency
Ultrawideband
Ultrawideband
Communication
Communication
Time-domain behavior Frequency-domain behavior
time
1 0 1
(FCC Min=500Mhz)
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From NB to UWB
Spreadingsequence
FTNB
SSWB
UWB
Time
Frequency
BW=KHz
BW=MHz
BW=GHz
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Onboard spacecraftcommunication challenges
Multipath fading
Channel capacity
Multiple access interference
Battery life for handheld devicesImplementation complexity
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Multipath is prominent inonboard spacecraft
communications Multipath is a major limitationof onboard reliable spacecraftcommunications
Multipath phenomenon occurs
when a delayed version of a signalarrives at the receiver due to
reflection from multiple surfaces
M lti th i N b d
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Multipath in NarrowbandSystems
LOS
NLOS
LOS
+
NLOS
Severe performance
degradation due to multipatheffect
Multipath can cause up to 40
dB fading in NB systems
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Multipath in Wideband SpreadSpectrum
Narrowband signals are spread over a wide (MHz)bandwidth
Less sensitive to multipath fading compared to NB
systems due to:Frequency diversity
Larger signal bandwidth than coherence bandwidth
Ultra Wideband is a superior solution for densemultipath environments
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UWB Signal
Time (ns)
Amplitude(Vo
lts)
Frequency (GHz)
Po
werSpectrumM
a
gnitude(dB)
Ul Wid b d Si l
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Ultra-Wideband SignalConcept
Pulses have bandwidth of several GHz withFractional Bandwidth 20%
Where Fractional Bandwidth is:
fH and
fL are highest and lowest cut-off frequencies at
10 dB point.
2( ).100%
f fH LB
f f fH L
=
+
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UWB Advantages
Shares the spectrum with othersHigh channel capacity
Shannons formula
Ability to work with low signal to noise ratios
Low probability of intercept & detection(LPI/LPD)
Low duty cycle, low average power
Low hardware complexity for transmitter andreceiver
Less sensitive to multipath
log (1 )2
SC BN
= +
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Other UWB Applications
Communications
Short range high data rate
LPI/LPD
High resolution radars/sensors
Military and rescue applications
Positioning/location tracking
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Some Modulation Methods
On Off Keying (OOK)
Pulse Amplitude Modulation (PAM)
Pulse Position Modulation (PPM)
Transmitted-Reference Modulation (T-R)
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On Off Keying (OOK)
Presence and absence of a pulse represents thedata
1 0 1 0
Advantage:
Simple implementation Disadvantages: Requires precise synchronization Highly susceptible to noise
P l A lit d M d l ti
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Pulse Amplitude Modulation(PAM)
Variation in pulse amplitude represents thedata
1 0 1 0
Advantage:
Simple implementation Disadvantages: Requires accurate synchronization Sensitive to noise
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Pulse Position Modulation (PPM)
Position of a pulse with respect to a referencepoint represents the data
10
Reference point
Advantage:
Not very sensitive to noise Disadvantages: Requires very accurate synchronization Does not perform well in multipath
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Transmitted ReferenceModulation (T-R)
A symbol consists of a pair of pulses separatedby a unique delay for each user.
Dn
1
Dn
0
Advantage:
Good performance at the presence of Multipath
Disadvantage: MAI increases due to the same pulse shape for all
users
Delays have to be large between users to avoid MAI
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CONCLUSION
Ultra-wideband is a promising technology that providesperformance and cost benefits over narrowband and spreadspectrum systems
The proposed method is simple and efficient in multiple access
systems in high interference environments
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THANK YOU..
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