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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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