Physical Layer

Communication system

Source coding: A/D, Sampling, Compression coding

Channel coding: Block Coding, Convolutional coding

Interleaver: Combination with channel coding, resistance to mobile fading channel impact

Modulator: classic modulation, QAM/PSK, spectrum move; CDMA, OFDM

Scrambler: random XOR, reduce PAPR

Channel coding: Turbo coding, viterbi decoding

Modulator: QPSK, 16QAM, 64QAM

IFFT/FFT: OFDM modulation/demodulation

Coherence bandwidth (Frequency selective fading )

15KHz Subcarrier spacing

Coherence time (ICI,ISI)

CP,CS

OFDMA

Parallel Transmission

Multi carrier structure

Increase in M =>

    high PAPR

SC-FDMA

Serial Transmission

Each symbol

    represented by a

    wide signal – DFT spreads

    symbols over all subcarriers

PAPR not affected by

    increase in M

DFT-Spread OFDMA – Mapping of spread symbols , not original symbols to subcarriers!!!

Channel Coding

MOUDULATION

IFFT/FFT

OFDM output signal(Equivalent complex baseband model) :

OFDM output signal(T/N sampling) :

DFT and IDFT :

synchronization