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    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

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    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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