Applying Iterative Demapping and Decoding in Mimo System by Nguyen Quoc

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VIETNAM NATIONAL UNIVERSITY – HOCHIMINH CITY INTERNATIONAL UNIVERSITY SCHOOL OF ELECTRONIC ENGINEERING

APPLYING ITERATIVE DEMAPPING and DECODING in MIMO SYSTEM
By Nguyen Quoc Duc Nguyen Minh Thanh

A thesis submitted to the School of Electronic Engineering in partial fulfillment of the requirements for the degree of Bachelor of Electronic Engineering

Ho Chi Minh city, Vietnam June 2009

APPLYING ITERATIVE DEMAPPING and DECODING in MIMO SYSTEM

APPROVED BY: ________________________________ Nguyen Dinh Uyen, PhD., Chair

________________________________ Ho Van Khuong, PhD.

________________________________ Dang Quang Vinh, Mr.

________________________________ Bui Pham Lan Phuong, Ms.

________________________________ Do Ngoc Hung, Mr.

THESIS COMMITTEE (Whichever applies)

Abstract
In wireless communications nowadays, the use of MIMO (Multiple Input – Multiple Output) systems can improve the quality of received signals and capacity of channel to transmitting faster with fixed bandwidth by deploying multiple antennas at the transmitter and the receiver. In traditional MIMO receivers, the demapper (or demodulator) does not take advantage of the decoded information at the decoder output for enhancing demodulation performance, indirectly increasing the

performance of the decoder. Therefore we propose a MIMO system with the iterative demapping and decoding module in this thesis. By exchanging the information at the outputs of the demodulator and the decoder over several iterations, the original information can be recovered more accurately. Matlab software-based simulation results are going to demonstrate that the proposed iterative demapping and decoding outperforms the conventional one over flat fading channels under different modulation/demodulation schemes. Keywords: MIMO system, iterative demapping and decoding, flat fading channel, AWGN.

Acknowledgment

We would like to say a special thank to Dr. Ho Van Khuong from Ho Chi Minh City University of Technology, our advisor. During the time of Special Study course and working on this final thesis, Dr. Khuong has been helping us a lot in searching information, collecting material and building the MIMO system using Matlab.

List of Figures
1. MIMO with iterative demapping and decoding 2. MIMO with iterative demapping and decoding (2) 3. RSC encoder at rate of 1/3 and constraint length of 4 4. An example of trellis diagram 5. Block diagram of an encoder 6. Trellis diagram 7. A redrawing of trellis diagram in Fig.6. 8. The output symbols after encoding using trellis diagram 9. Examples of constellation modulation – a. 4-QAM – b. 16-QAM 10. Modulation block and V-BLAST technique 11. SISO module 12. An edge of trellis section 13. Traditional (non-iterative) MIMO system 14. Traditional and iterative MIMO system’s performances using 4-QAM modulation and 3 demapping techniques a) ZF – b) MMSE – c) MAP 15. Iterative MIMO system’s performance using 3 modulation schemes a) 4-QAM – b) 16-QAM – c) 64-QAM 16. The performances of 2x2 and 3x3 iterative MIMO systems using 4-QAM modulator and 3 demappers a) ZF – b) MMSE – c) MAP

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List of Tables
1. State transitions while encoding the bit stream 100111011 using encoder in Fig.5. 2. Simulation parameters

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Content
Chapter 1 INTRODUCTION .......................................................................................................................... 1 1.1 1.2 1.3 1.4 Chapter 2 LITERATURE REVIEW .................................................................................................................. 5 Chapter 3 METHODOLOGY ......................................................................................................................... 7 3.1 3.1.1 3.1.2 3.2 3.3 3.4 3.5 3.5.1 3.5.2 3.5.3 3.6 Encoder ....................................................................................................................... 9 Convolutional code...
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