The enhancement of the MIMO-OFDMA Technologies

by

DECLARATION

I, [type your full first names and surname here], declare that the contents of this dissertation/thesis represent my own unaided work, and that the dissertation/thesis has not previously been submitted for academic examination towards any qualification. Furthermore, it represents my own opinions and not necessarily those of the University.

Signed __________________ Date _________________

DFT based Channel Estimation Methods for MIMO-OFDM System

Using QPSK modulation technique

[Publication Date]

ABSTRACT

MIMO stands for Multiple Input and Multiple Output Systems. The advantages of using such systems for signal and data transmission includes high data transmission rate, enhanced reliability for wireless communication systems and spectral efficiency. The mentioned parameters can be further enhanced by dealing with fading, whose effect can be minimized by properly estimating the channel at the receiver end. The application of multiple antennas at both receiver and transmitter ends to make multiple input and multiple output channels have shown drastically improved wireless communication systems with remarkably enhanced efficiency. Besides this, the advantages of increased capacity and the capability of the system to speed up the transmission rate in future systems for wireless communication are also achieved. In broadband system of communications, OFDM transfers a selective frequency channel in to a set of parallel flat channels, which are capable of reducing the complexity of the receiver. In this paper the idea of broadening transmitted symbols in OFDM systems by applying Space Time Coded Multiple Input Multiple Output OFDM systems has been discussed. In the system which is proposed in this papers, a multidimensional diversity, comprising of time, frequency, diversities that are related to modulation and space. In this paper a newly discovered approach which is made on the concept of Time Domain Interpolation (TDI) has also been represented. TDI is extracted by flowing estimated path channel to time domain by using Inverse Discrete Transform the concept of zero padding and going back to frequency domain by using discrete Fourier transform DFT.

Keywords: Channel estimation, Discrete Fourier transform, least square error, Minimum mean square error, MIMO- OFDM, QPSK.

I. INTRODUCTION

The hierarchy of mobile communication channeling is very difficult and challenging now a days due to complex multi channel propagation, due to huge number of scattering of signal waves from buildings and other similar constructions in the near locality of a mobile unit [1]. A broad band radio channel path is usually time variant with selective frequency. Due to this reason the duplicates of similar number of signals which have been transmitted at same interval of time reach the receiver end at varying time interval due to the transmission delays and reflections that occur in the path of propagation of the channel and hence causing delay in the signals as well as reducing the strength of the transmitted signal at the receiving end. Multiple input multiple output (MIMO) antenna systems belong to the area of spatial diversity. Making use of multiple antennas at both the receiver and transmitter sides, results in getting extremely high data rate without any need of increasing or enhancing the total transmission power ...