Study & simulation of O.F.D.M. system

Base paper: - http://ijmer.com/papers/vol2_issue1/AL021235241.pdf

Study & Simulation of O.F.D.M System

International Journal of Modern Engineering Research

Abstract:

Orthogonal frequency division multiplexing (OFDM) is becoming the chosen modulation technique for wireless communications. OFDM can provide large data rates with sufficient robustness to radio channel impairments. Many research centers in the world have specialized teams working in the optimization of OFDM for countless applications. Here, at the Georgia Institute of Technology, one of such teams is in Dr. M. A. Ingram’s Smart Antenna Research Laboratory (SARL), a part of the Georgia Center for Advanced Telecommunications Technology (GCATT).

The purpose of this report is to provide Matlab® code to simulate the basic processing involved in the

generation and reception of an OFDM signal in a physical channel and to provide a description of each of the steps involved. For this purpose, we shall use, as an example, one of the proposed OFDM signals of the Digital Video Broadcasting (DVB) standard for the European terrestrial digital television (DTV) service.


OFDM Symbol Generation Simulation

DVB-T Transmitter


A: - OFDM Reception

(a) Time Response of Signal r_tilde at (F)

(b) Frequency Response of Signal r_tilde at (F)


(c) Time Response of Signal r_info at (G)

(d) Frequency Response of Signal r_info at (G)


(e) Time Response of Signal r_data at (H)


(f) Frequency Response of Signal r_data at (H)

(g) info_h Received Constellation Diagram


(h) a_hat Constellation Diagram ( ah at 4-QAM)

B: -


Eq. (1) vs. IFFT


Welch Power Spectral Density Estimate


C: - OFDM Transmission

(a) Time Response of Signal carriers at (B)


(b) Frequency Response of Signal carriers at (B)


(c) Pulse Shape g(t)


(d) Time Response of Signal U at (C)


(e) Time Response of Signal U at (C)


(f) D/A Filter Response


(g) Time Response of Signal UOFT at (D)


(h) Frequency Response of Signal UOFT at (D)


(i) Time Response of Signal s(t) at (E)


(j) Frequency Response of Signal s(t) at (E)


Conclusion:

We can find many advantages in OFDM, but there are still many complex problems to solve, and the people of the research team at the SARL are working in some of these problems. It is the purpose of this project to provide a basic simulation tool for them to use as a starting point in their projects. We hope that by using the specifications of a working system, the DBV-T, as an example, we are able to provide a much better explanation of the fundamentals of OFDM. References:

*1+ “Measurement Challenges for OFDM Systems”, Agilent Technologies

*2+ Denis Petrovic, Wolfgang Rave and Gerhard Fettweis, “Phase Noise Suppression in OFDM Using a Kalman Filter”, Vodafone Chair for Mobile Communications, Dresden University of Technology, Germany

[3] http://digitalradiotech.co.uk/cofdm.htm [ Digital Radio Tech ]

[4] http://www.wi-fiplanet.com/tutorials/article.php/1500641

[5] http://www.ert.rwth-aachen.de/Projekte/Theo/OFDM/node1.html

[6] http://en.wikipedia.org/wiki/OFDM [ Wikipedia ]

[7] http://zone.ni.com/devzone/cda/tut/p/id/3740 [ National Instruments ]

[8] http://www.radio-electronics.com/info/cellulartelecomms/ofdm/ofdm.php

[9] Ove Edfors, Magnus Sandell, Jan Jaap Van de Beek, Daniel Landstorm and Frank Sjoberg, “An introduction to OFDM”, 1996

*10+ J.H.Scott, “Explaining some of the magic of COFDM”, Proceedings of the 20th International Television Symposium, 1997

*11+ “High Speed Wireless OFDM Communication Systems”, Whitepaper, Wi-LAN Inc., 2001

*12+ Tony Gomez, “OFDM for Mobile Data Communications”, Web ProForum Tutorials, The International Engineering Consortium, 2001

*13+ K. Panta and J. Armstrong, “Spectral Analysis of OFDM Signals and its Improvement by Polynomial Cancellation Coding”, IEEE 2003

*14+ Charan Langton, “Orthogonal Frequency Division Multiplexing”, Intuitive guide to Principles of Communications, www.complextoreal.com, 2004

*15+ Henrik Schulze and Christian Luders, “Theory and Applications of OFDM and CDMA”, pp.145-264, 2005, John Wiley & Sons Ltd.

*16+ Andreas F. Molisch, “Wireless Communcations”, pp.399-424, 2005, John Wiley & Sons Ltd.

*17+ L. Henzo and T. Keller, “OFDM and MC-CDMA: A Primer”, pp.21-38, 2006, John Wiley & Sons Ltd.

Study & simulation of O.F.D.M. system

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