Simulation of hybrid system with(SFBC-STBC-OFDM)‎ in wireless communication system

Dissertant

al-Qaradaghi, al-Thurayya Mahmud Abd al-Samad

University

University of Technology

Faculty

-

Department

Department of Electrical Engineering

University Country

Iraq

Degree

Ph.D.

Degree Date

2008

English Abstract

A space—time code (STC) is a method employed to improve the reliability of data transmission in wireless communication systems using multiple transmit antennas.

STCs rely on transmitting multiple, redundant copies of a data stream to the receiver.

This is done in the hope that at least some of these copies will survive the physical path between transmission and reception in an adequate state, therefore allowing reliable decoding, This thesis focused on the type of channel coding, such as: Convolution codes, Trellis Coded Modulation (TCMJ, Block Coding, and Space-Time Coding (STC).

A modifying Space-Time Block Code-Orthogonal Frequency Division Multiplexing (STBC-OFDM) and a different way of combining STBC and OFDM is called Space-Frequency Block Code- Orthogonal Frequency Division Multiplexing (SFBC-OFDM) are introduced.

A low complexity scheme of STBC-OFDM for static, flat and frequency-selective fading channels over various values of Doppler frequencies has been proposed. Alamouti code was applied to a block of the OFDM symbols instead of one symbol.

A hybrid system with combination of Space-Time (ST) and Space-Frequency (SF) system are proposed to teach the benefits of ST and SF, which are achieved by separating the odd and the even elements.

At the first period, a block of the odd elements is transmitted by the first antenna and the even block is transmitted by the second antenna.

At the second (consequent) period, a block of the minus conjugate of the even elements is transmitted by the first antenna and a block of the conjugate The performance comparisons of bit error probability for the conventional STBC-OFDM, SFBC-OFDM, and proposed STBC-OFDM have been presented, Also an instructional computer program for STBC-OFDM and SFBC-OFDM has been designed in order to improve the student experience in channel coding and to compare the different types of transmits diversity block coding performance. As a result, it can be concluded that the proposed structures achieve much lower bit error rates assuming reasonable choice of the basis function and method of computation; since it shows better performance than the conventional schemes especially under frequency-selective fading conditions.

The conventional STBC-OFDM is very sensitive to Doppier frequency; therefore, the application of this scheme is limited to slow hiding channels, bui the proposed system is so far insensitive to Doppier frequency. Using 2 transmit and 2 receive antennas instead of 2 transmit and 1 receive antennas, improves the system performance, but increasing the number of the receiving antenna to more than 2 increases the receiving system complexity, which is not desirable.

Main Subjects

Telecommunications Engineering

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-305376