SIMULINK MODEL OF OFDM USING 64 QAM WITH

DIFFERENT COMBINATION OF CHANNEL

NAVEEN KUMAR

Guided By – Ms. Sonu Rana

Global Institute Of Technology & Management, Farukh Nagar, Gurugram

Department Of Electronics & Communication Engineering

concepts of OFDM. The Master’s thesis details the analysis of a generic OFDM system using

64-QAM simulink model with AWGN channel, NONE channel, Rayleigh fading channel,

multipath Rayleigh fading channel plus AWGN and Rician fading channel used to study

delays between transmitted signal and received signal and bit synchronization from

transmitter to receiver. Several channel models are analyzed and added to the transceiver

simulator. The extreme programming methodology is used and evaluated during the

development of the MATLAB simulator for the OFDM system model with different

combination of channels. A brief study of OFDM using 64-QAM simulink with different

channels is very useful to overcome the problems of ISI, ICI and Orthogonality.

1. Introduction

considered to be the most prospective candidate for use in 4th generation mobile

communications, which makes it a good candidate for research. The basic idea of OFDM is to

use a large number of parallel narrow-band sub-carriers instead of a single wideband carrier

to transmit information. This way of transmitting information helps in handling the effects of

multipath propagation efficiently. The transmission is efficient because of the spectral overlap

of narrowband sub-carriers. OFDM supports various modulations techniques like BPSK,

QAM, and QPSK etc. QAM is further divided in 4, 16, 32, 64 and 128 and 256 QAM

techniques.

OFDM is a method of encoding digital data on multiple carrier frequencies. OFDM has

developed into a popular scheme for wideband digital communication, whether wireless or

using AWGN channel, NONE channel, Multipath Rayleigh fading channel, Multipath

Rayleigh fading channel plus AWGN channel and Multipath Rician fading channel. And used

to study delays between transmitted signal and received signal and bit synchronization from

transmitter to receiver.

1.2 Motivation

OFDM is considered to be the most prospective candidate for use in 4th generation mobile

communications, which makes it a good candidate for research. The basic idea of OFDM is to

use a large number of parallel narrow-band sub-carriers instead of a single wideband carrier

to transmit information. The long application list of OFDM includes Asynchronous Digital

operation of OFDM systems if not respected. The orthogonality is provided by IFFT. And the

second problem is synchronization in the receiver to sample the incoming signal correctly.

The objective of this model is to develop and explore a simulink model using QAM

modulation technique the objective of this model is just to study Packet Loss, Bit Loss and

Total Bits counted and effect on bit rate by using 64 QAM when we used Multipath Rayleigh

Fading channel plus AWGN channel both for OFDM. And used to study delays between

transmitted signal and received signal and bit synchronization from transmitter to receiver. It

minimum loss of information with high transmission rate for synchronization of transmitter

with receiver. A brief study of OFDM using 64-QAM simulink with Multipath Rayleigh

Fading channel plus AWGN is very useful to overcome the problems of ISI, ICI and

Orthogonality. This chapter presents the response of OFDM system using 64-QAM with

Multipath Rayleigh Fading channel. Here in this chapter a MATLAB Simulink model of

OFDM using 64-QAM is designed, study, and analyzed to investigate when we use two

channel in a communication system which is a combination of AWGN and Multipath

Rayleigh fading channel. These two channels when used in a single communication system

counts the various parameter like Packet loss during transmission of data, Bits loss and also

used to study between transmitted signal and received signal and bit synchronization from

4.1 Simulink model of OFDM using 64-QAM with AWGN plus Multipath Rayleigh

fading channel:

This is the simulink diagram of OFDM using 64-QAM when there is Multipath Rayleigh

fading channel plus AWGN channel both simunataneously used between transmitter and

receiver. This simulink model in fig. 4.1 gives results which are generated between

transmitter and receiver to study and analyzed effect on bit rate by using 64-QAM and also

count total number of Bits transmitted, Bit losses during transmission and total number of bits

received when there is Multipath Rayleigh fading channel and Additive White Gaussian noise

channel or AWGN channel used in an OFDM system.

fading channel plus AWGN channel.

Here in the figure 4.2 spectrum of transmitting signal when given to OFDM is using 64 QAM

modulation with Rayleigh fading channel plus AWGN shown. The constellation diagram is

useful for QAM, the constellation points are usually arranged in manner with equal vertical

and horizontal spacing although other configurations are possible.

Figure 4.2 Transmitted spectrum when using Multipath Rayleigh fading plus AWGN

By moving a higher-order constellation, like 128 and 256 QAM it is possible to transmit more

bits per symbol. However, if the mean energy of the constellation is to remain the same, the

This is the received spectrum when using Multipath Rayleigh fading channel plus AWGN for

OFDM using 64-QAM modulation technique.

Figure 4.3 Received spectrum when using Rayleigh fading plus AWGN channel

Here the signal in figure 4.3 which is received from OFDM 64-QAM shown.

Graph showing spectrum scope when using Rayleigh fadind channel plus AWGN

channel

In fig above a graph is shown between magnitude (db) and frequency (MHz) which shows

continuous variations between frequency and magnitude. A fluctuation is note down which is

Figure 4.5 OFDM using 64-QAM with Multipath Rician fading channel

Effect on bit rate by using 64-QAM and also count total number of Bits transmitted, Bit

losses during transmission and also total number of bits received when there is Multipath

Rician fading channel used.

5. Result of simulink model

Here we are generating three cases for Multipath Rayleigh fading channel plus AWGN

channel between transmitter and receiver. The result of each system with each step and the

received signal and bit synchronization from transmitter to receiver. It also counts the various

parameters during the communication process like packet loss, bit loss. As we know that by

increasing orthogonality the data rate is decreases because of synchronization problem. When

we used 16 QAM modulation the rate of transmission is low as compared to 64 QAM

modulation techniques but it has one drawback that its orthogonality reduces. At the point of

reception of signal, it is very important to distinguish the starting point of FFT to avoid wrong

Hall publications, 2002.

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assisted modulation for OFDM,” in Proc. IEEE Int. Conf. Personal Wireless

Communications, Dec. 1997, pp. 71–74.

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system,” IEEE Trans. Consum. Electron, vol. 44, pp. 1122–1128, Aug. 1998.