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<div id="pf1" class="pf w0 h0" data-page-no="1"><div class="pc pc1 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/622b32beff7f9c46a6ab3f10/bg1.jpg"><div class="t m0 x1 h2 y1 ff1 fs0 fc0 sc0 ls0 ws0">Design and Simulation of</div><div class="t m0 x2 h2 y2 ff1 fs0 fc0 sc0 ls0 ws0">Orthogonal Frequency Division Multiplexing</div><div class="t m0 x3 h2 y3 ff1 fs0 fc0 sc0 ls0 ws0">(OFDM) Signaling</div><div class="t m0 x4 h3 y4 ff1 fs1 fc0 sc0 ls0 ws0">Final Report</div><div class="t m0 x5 h4 y5 ff2 fs2 fc0 sc0 ls0 ws0">Study by:</div><div class="t m0 x6 h5 y6 ff3 fs2 fc0 sc0 ls0 ws0">Alan C. Brooks</div><div class="t m0 x7 h5 y7 ff3 fs2 fc0 sc0 ls0 ws0">Stephen J. Hoelzer</div><div class="t m0 x8 h4 y8 ff2 fs2 fc0 sc0 ls0 ws0">Department:</div><div class="t m0 x9 h5 y9 ff3 fs2 fc0 sc0 ls0 ws0">Electrical and Computer Engineering</div><div class="t m0 x5 h4 ya ff2 fs2 fc0 sc0 ls0 ws0">Advisors:</div><div class="t m0 xa h5 yb ff3 fs2 fc0 sc0 ls0 ws0">Dr. Thomas L. Stewart</div><div class="t m0 x6 h5 yc ff3 fs2 fc0 sc0 ls0 ws0">Dr. In Soo Ahn</div><div class="t m0 xb h5 yd ff3 fs2 fc0 sc0 ls0 ws0">May 15, 2001</div><div class="t m0 xc h5 ye ff3 fs2 fc0 sc0 ls0 ws0">Abstract:</div><div class="t m0 xd h5 yf ff3 fs2 fc0 sc0 ls0 ws0">A MATLAB program has been written to investigate Orthogonal Frequency Division</div><div class="t m0 xc h5 y10 ff3 fs2 fc0 sc0 ls0 ws0">Multiplexing (OFDM) communication systems. This program is valuable for future researchers</div><div class="t m0 xc h5 y11 ff3 fs2 fc0 sc0 ls0 ws0">simulating systems that are too theoretically complex to analyze. Single-carrier QAM and multi-</div><div class="t m0 xc h5 y12 ff3 fs2 fc0 sc0 ls0 ws0">carrier OFDM are compared to demonstrate the strength of OFDM in multipath channels. Two</div><div class="t m0 xc h5 y13 ff3 fs2 fc0 sc0 ls0 ws0">graphical user interface demonstrations show some of the basic concepts of OFDM.</div></div><div class="pi" data-data='{"ctm":[1.568627,0.000000,0.000000,1.568627,0.000000,0.000000]}'></div></div>
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<div id="pf2" class="pf w0 h0" data-page-no="2"><div class="pc pc2 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/622b32beff7f9c46a6ab3f10/bg2.jpg"><div class="t m0 xe h6 y14 ff4 fs2 fc0 sc0 ls0 ws0">1</div><div class="t m0 xc h7 y15 ff1 fs2 fc0 sc0 ls0 ws0">Introduction</div><div class="t m0 xf h5 y16 ff3 fs2 fc0 sc0 ls0 ws0">The Electrical Engineering Senior Capstone Project is intended to give each student</div><div class="t m0 xc h5 y17 ff3 fs2 fc0 sc0 ls0 ws0">experience in completing a sophisticated design project that spans most of the senior year.</div><div class="t m0 xc h5 y18 ff3 fs2 fc0 sc0 ls0 ws0">Planning, management of time, allocation of responsibility, documentation, and presentation of</div><div class="t m0 xc h5 y19 ff3 fs2 fc0 sc0 ls0 ws0">the results are integrated with the technical design task. The students work with one or two</div><div class="t m0 xc h5 y1a ff3 fs2 fc0 sc0 ls0 ws0">faculty advisors who have expertise in the project research area. The student is fully responsible</div><div class="t m0 xc h5 y1b ff3 fs2 fc0 sc0 ls0 ws0">for the design project, with the advisor(s) acting as guide and mentor. Each student is expected to</div><div class="t m0 xc h5 y1c ff3 fs2 fc0 sc0 ls0 ws0">work an eight-hour lab period each week from October through May.</div><div class="t m0 xf h5 y1d ff3 fs2 fc0 sc0 ls0 ws0">A common problem found in high-speed communication is inter-symbol interference</div><div class="t m0 xc h5 y1e ff3 fs2 fc0 sc0 ls0 ws0">(ISI). ISI occurs when a transmission interferes with itself and the receiver cannot decode the</div><div class="t m0 xc h5 y1f ff3 fs2 fc0 sc0 ls0 ws0">transmission correctly. For example, in a wireless communication system such as that shown in</div><div class="t m0 xc h5 y20 ff3 fs2 fc0 sc0 ls0 ws0">Figure 1, the same transmission is sent in all directions.</div><div class="t m0 x10 h7 y21 ff1 fs2 fc0 sc0 ls0 ws0">Figure 1: Multipath Demonstration</div></div><div class="pi" data-data='{"ctm":[1.568627,0.000000,0.000000,1.568627,0.000000,0.000000]}'></div></div>
<div id="pf3" class="pf w0 h0" data-page-no="3"><div class="pc pc3 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/622b32beff7f9c46a6ab3f10/bg3.jpg"><div class="t m0 xe h6 y14 ff4 fs2 fc0 sc0 ls0 ws0">2</div><div class="t m0 xc h5 y15 ff3 fs2 fc0 sc0 ls0 ws0">Because the signal reflects from large objects such as mountains or buildings, the receiver sees</div><div class="t m0 xc h5 y16 ff3 fs2 fc0 sc0 ls0 ws0">more than one copy of the signal. In communication terminology, this is called multipath. Since</div><div class="t m0 xc h5 y17 ff3 fs2 fc0 sc0 ls0 ws0">the indirect paths take more time to travel to the receiver, the delayed copies of the signal</div><div class="t m0 xc h5 y18 ff3 fs2 fc0 sc0 ls0 ws0">interfere with the direct signal, causing ISI.</div><div class="t m0 xc h7 y1a ff1 fs2 fc0 sc0 ls0 ws0">Theory</div><div class="t m0 xf h5 y1b ff3 fs2 fc0 sc0 ls0 ws0">This project will focus on Orthogonal Frequency Division Multiplexing (OFDM)</div><div class="t m0 xc h5 y1c ff3 fs2 fc0 sc0 ls0 ws0">research and simulation. OFDM is especially suitable for high-speed communication due to its</div><div class="t m0 xc h5 y1d ff3 fs2 fc0 sc0 ls0 ws0">resistance to ISI. As communication systems increase their information transfer speed, the time</div><div class="t m0 xc h5 y1e ff3 fs2 fc0 sc0 ls0 ws0">for each transmission necessarily becomes shorter. Since the delay time caused by multipath</div><div class="t m0 xc h5 y1f ff3 fs2 fc0 sc0 ls0 ws0">remains constant, ISI becomes a limitation in high-data-rate communication [1]. OFDM avoids</div><div class="t m0 xc h5 y20 ff3 fs2 fc0 sc0 ls0 ws0">this problem by sending many low speed transmissions simultaneously. For example, Figure 2</div><div class="t m0 xc h5 y22 ff3 fs2 fc0 sc0 ls0 ws0">shows two ways to transmit the same four pieces of binary data.</div><div class="t m0 x11 h7 y23 ff1 fs2 fc0 sc0 ls0 ws0">Figure 2: Traditional vs. OFDM Communication</div><div class="t m0 xc h5 y24 ff3 fs2 fc0 sc0 ls0 ws0">Suppose that this transmission takes four seconds. Then, each piece of data in the left picture has</div><div class="t m0 xc h5 y25 ff3 fs2 fc0 sc0 ls0 ws0">a duration of one second. On the other hand, OFDM would send the four pieces simultaneously</div><div class="t m0 xc h5 y26 ff3 fs2 fc0 sc0 ls0 ws0">as shown on the right. In this case, each piece of data has a duration of four seconds. This longer</div></div><div class="pi" data-data='{"ctm":[1.568627,0.000000,0.000000,1.568627,0.000000,0.000000]}'></div></div>
<div id="pf4" class="pf w0 h0" data-page-no="4"><div class="pc pc4 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/622b32beff7f9c46a6ab3f10/bg4.jpg"><div class="t m0 xe h6 y14 ff4 fs2 fc0 sc0 ls0 ws0">3</div><div class="t m0 xc h5 y15 ff3 fs2 fc0 sc0 ls0 ws0">duration leads to fewer problems with ISI. Another reason to consider OFDM is low-complexity</div><div class="t m0 xc h5 y16 ff3 fs2 fc0 sc0 ls0 ws0">implementation for high-speed systems compared to traditional single carrier techniques [2].</div><div class="t m0 xc h7 y18 ff1 fs2 fc0 sc0 ls0 ws0">Significance</div><div class="t m0 xf h5 y19 ff3 fs2 fc0 sc0 ls0 ws0">With the rapid growth of digital communication in recent years, the need for high-speed</div><div class="t m0 xc h5 y1a ff3 fs2 fc0 sc0 ls0 ws0">data transmission has increased. New multicarrier modulation techniques such as OFDM are</div><div class="t m0 xc h5 y1b ff3 fs2 fc0 sc0 ls0 ws0">currently being implemented to keep up with the demand for more communication capacity.</div><div class="t m0 xc h5 y1c ff3 fs2 fc0 sc0 ls0 ws0">Multicarrier communication systems “were first conceived and implemented in the 1960s, but it</div><div class="t m0 xc h5 y1d ff3 fs2 fc0 sc0 ls0 ws0">was not until their all-digital implementation with the FFT that their attractive features were</div><div class="t m0 xc h5 y1e ff3 fs2 fc0 sc0 ls0 ws0">unraveled and sparked widespread interest for adoption in various single-user and multiple</div><div class="t m0 xc h5 y1f ff3 fs2 fc0 sc0 ls0 ws0">access (MA) communication standards” [2]. The processing power of modern digital signal</div><div class="t m0 xc h5 y20 ff3 fs2 fc0 sc0 ls0 ws0">processors has increased to a point where OFDM has become feasible and economical.</div><div class="t m0 xc h5 y22 ff3 fs2 fc0 sc0 ls0 ws0">Examining the patents, journal articles, and books available on OFDM, it is clear that this</div><div class="t m0 xc h5 y27 ff3 fs2 fc0 sc0 ls0 ws0">technique will have an impact on the future of communication. See the references section</div><div class="t m0 xc h5 y28 ff3 fs2 fc0 sc0 ls0 ws0">(starting on page 21) for a condensed bibliography and list of patents related to this topic. Since</div><div class="t m0 xc h5 y29 ff3 fs2 fc0 sc0 ls0 ws0">many communication systems being developed use OFDM, it is a worthwhile research topic.</div><div class="t m0 xc h5 y2a ff3 fs2 fc0 sc0 ls0 ws0">Some examples of current applications using OFDM include GSTN (General Switched</div><div class="t m0 xc h5 y2b ff3 fs2 fc0 sc0 ls0 ws0">Telephone Network), Cellular radio, DSL & ADSL modems, DAB (Digital Audio Broadcasting)</div><div class="t m0 xc h5 y2c ff3 fs2 fc0 sc0 ls0 ws0">radio, DVB-T (Terrestrial Digital Video Broadcasting), HDTV broadcasting, HYPERLAN/2</div><div class="t m0 xc h5 y2d ff3 fs2 fc0 sc0 ls0 ws0">(High Performance Local Area Network standard), and the wireless networking standard IEEE</div><div class="t m0 xc h5 y2e ff3 fs2 fc0 sc0 ls0 ws0">802.11 [1] [3] [4].</div></div><div class="pi" data-data='{"ctm":[1.568627,0.000000,0.000000,1.568627,0.000000,0.000000]}'></div></div>
<div id="pf5" class="pf w0 h0" data-page-no="5"><div class="pc pc5 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/622b32beff7f9c46a6ab3f10/bg5.jpg"><div class="t m0 xe h6 y14 ff4 fs2 fc0 sc0 ls0 ws0">4</div><div class="t m0 xc h7 y16 ff1 fs2 fc0 sc0 ls0 ws0">Simulation Design</div><div class="t m0 xf h5 y17 ff3 fs2 fc0 sc0 ls0 ws0">This project consists of research and simulation of an OFDM communication system.</div><div class="t m0 xc h5 y18 ff3 fs2 fc0 sc0 ls0 ws0">Figure 3 shows a simplified flowchart of the MATLAB simulation code.</div><div class="t m0 x12 h7 y2f ff1 fs2 fc0 sc0 ls0 ws0">Figure 3: OFDM Simulation Flowchart</div><div class="t m0 xc h5 y30 ff3 fs2 fc0 sc0 ls0 ws0">The transmitter first converts the input data from a serial stream to parallel sets. Each set of data</div><div class="t m0 xc h5 y31 ff3 fs2 fc0 sc0 ls0 ws0">contains one symbol, S</div><div class="t m0 x13 h8 y32 ff3 fs3 fc0 sc0 ls0 ws0">i</div><div class="t m0 x14 h5 y31 ff3 fs2 fc0 sc0 ls0 ws0">, for each subcarrier. For example, a set of four data would be [S</div><div class="t m0 x15 h8 y32 ff3 fs3 fc0 sc0 ls0 ws0">0</div><div class="t m0 x16 h5 y31 ff3 fs2 fc0 sc0 ls0 ws0"> S</div><div class="t m0 x17 h8 y32 ff3 fs3 fc0 sc0 ls0 ws0">1</div><div class="t m0 x18 h5 y31 ff3 fs2 fc0 sc0 ls0 ws0"> S</div><div class="t m0 x19 h8 y32 ff3 fs3 fc0 sc0 ls0 ws0">2</div><div class="t m0 xc h5 y33 ff3 fs2 fc0 sc0 ls0 ws0">S</div><div class="t m0 x1a h8 y34 ff3 fs3 fc0 sc0 ls0 ws0">3</div><div class="t m0 x1b h5 y33 ff3 fs2 fc0 sc0 ls0 ws0">]. Before performing the Inverse Fast Fourier Transform (IFFT), this example data set is</div><div class="t m0 xc h5 y35 ff3 fs2 fc0 sc0 ls0 ws0">arranged on the horizontal axis in the frequency domain as shown in Figure 4.</div></div><div class="pi" data-data='{"ctm":[1.568627,0.000000,0.000000,1.568627,0.000000,0.000000]}'></div></div>
