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8/4/2019 ACM - Introduction - Abreviated
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ADVANCED COMMUNICATION METHOD
SHYAM SHETTY
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Multiplexing Time Division Multiplexing (TDM).
Frequency Division Multiplexing (FDM).
Code Division Multiplexing (CDM).
Orthogonal Frequency DivisionMultiplexing (OFDM).
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TDMA (with FDMA) Principle
Power
Time
Frequency
Time-slots
Carriers
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Direct Sequence CDMA Principle(with FDMA)
Power
Time
Frequency
User CodeWaveforms
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OFDM (with TDMA & FDMA) Principle
Power
Time
Frequency
Time-slots
Carriers
Tones
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Summary of Multiple AccessFDMA
TDMA
CDMA
power
power
pow
er
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FDM and OFDM
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OFDM Signal
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Basics of Radio Propagation
Distance
Power
10-100 m(1-10 sec)
0.1 -1 m(10-100 msec)
Exponential
Long-term Fading
Short-term Fading
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Multi-path Propagation Problems
Tall Buildings.
Vehicular
movements. Ceiling.
Interference ISI.
Fading.
Emission Electrical.
Solar.
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FEC IFFT
DAC
LinearPA
add cyclic extension
bits
fc
OFDM symbol
Pulse shaper&
view this as a time tofrequency
Generic OFDM Transmitter
Serial to
Parallel
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AGC
fc
VCO
Sampler FFTError
gross offset
Slot &
fine offset
Freq. Offset
Estimation
Timing
Sync.
(of all tones sent in one OFDM symbol)
Generic OFDM Receiver
RecoveryP/S and
Detection
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Modern Wireless Systems
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What is required? Signal processing from frequency
domain to time domain, real and
imaginary components of the signal willbe raised.
FD TD (To get rid of complex
elements in processing of signal). Number theoretic transforms.
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Number Theoretic TransformsGeneric NTT is
Generic Inverse NTT is
k=0,1,2. N-1.
n=0,1,2. N-1.
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Basic Calculation (example) Simple example for module 11 (=N).
(N-1) inputs.
Input =[0 4 2 3 2 0 2 3 2 4];
Output =[0 2 9 6 2 6 2 6 9 2];
Inverse Output =[0 4 2 3 2 0 2 3 2 4];
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ACM Advantages
Spreading advantages
Improved interference rejection.
Low density power spectra for signalhandling.
Anti jam capability.
Lower cost implementation. The block diagram for transmission.
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ACM Transmitter Block diagram
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Receiver
Band pass filter.
De-spreading.
Receiver sensitivity .
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ACM Receiver Block diagram
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Advantages of Number Theoretic Transforms
Uses of number theoretic transform
Coding
The data coding on different modules of a ringprovides substantial security against jamming.
Standards are to be made based on thismethod.
Fast DSP algorithms, due to real numberoperations
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Expected Data rates and Results
The theoretical data rate calculated fordifferent time symbols.
Frequency Mod 11 Mod 37 Mod 131 Mod 257
1 MHz 30 Mbps 180Mbps
910Mbps
2048Mbps
2 MHz 60 Mbps 360Mbps
1820Mbps
4096Mbps
3.2 MHz 96 Mbps 576
Mbps
2912
Mbps
6553.6
Mbps
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Expected graph of data rate.
Logarithmic Mod Value
Data rate
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