King Fahd University of Petroleum & Minerals Electrical Engineering Department

EE 578 Simulation of Wireless Systems

Orthogonal Frequency Division Multiplexing Transmission

Assignment # 3

Ali Al-SaihatiID# 200350130

OUTLINEIntroduction.

OFDM Transmission Scheme.

Guard band.

BER & PER Performance.

Pilot Symbol Aided OFDM.

Frame Format Configuration

Introduction

Received signal at the receiver contains reflected waves.

R should be in order of Mb/s for wireless networks.

One way to solve this problem solve this problem is use adaptive equalization at the receiver.

Another way is to use OFDM transmission.

OFDM Transmission Scheme

The multipath fading environment in time domain is characterized by impulse responses with different delays an powers.

In frequency domain, it is characterized by attenuation or enhancement of different frequencies of the impulse responses

OFDM Transmission

The signal is given by:

The subcarrier is given by:

When Bs > Bc, distortion increases but the total received power variation is less.

When Bs < Bc, distortion is little but the total received power is attenuated.

We use parallel transmission to solve this problem.

The high rate is decreased as we multiplex the data while the symbol duration increases.

IFFT Circuit

Guard Bands

Used to eliminate ISI that appears in the received signal.

Ttotal= Tg + Ts

Tg < Ts/4

Results

BER & PER Performance

Thank You

Pilot Symbol Aided OFDM

Compensate for the phase and amplitude fluctuation.

Pilot symbols are inserted in at the transmitter at fixed time interval.

At the receiver, we estimate the channel behavior using the pilot symbols.

Fluctuation is independent of pilot symbols.

Frame Format Configuration

Sampling rate: 20 MHz .

Modulation scheme.

FEC: R= ½, K= 7

Frame format .

Radio channel model.

Frame Format Using Channel Estimation

BER & PER Performance Using Channel Estimation

Thank You