ece4305_L17

# ece4305_L17 - Orthogonal Frequency Division Multiplexing...

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Orthogonal Frequency Division Multiplexing ECE4305: Software-Deﬁned Radio Systems and Analysis Professor Alexander M. Wyglinski Department of Electrical and Computer Engineering Worcester Polytechnic Institute Lecture 17 Professor Alexander M. Wyglinski ECE4305: Software-Deﬁned Radio Systems and Analysis

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Orthogonal Frequency Division Multiplexing Motivation Mathematical Formulation Equalization in Multicarrier Systems Eﬃcient Implementation Choice of Analysis and Synthesis Filters I We have just seen the general form for multicarrier modulation, which consists of multiplexing and demultiplexing data as well as employ synthesis and analysis ﬁlter banks I Diﬀerent multicarrier implementations are mainly based on the choice of ﬁlters for the signal analysis and synthesis stages I Each of the N subchannels consist of bandwidth Δ f = W / N , where W is the total transmission bandwidth I Division of data into independent subchannels yields an opportunity for a “divide-and-conquer” approach to data transmission I Question: Can we implement multicarrier modulation eﬃciently? Professor Alexander M. Wyglinski ECE4305: Software-Deﬁned Radio Systems and Analysis
Orthogonal Frequency Division Multiplexing Motivation Mathematical Formulation Equalization in Multicarrier Systems Eﬃcient Implementation OFDM Framework I High-speed digital input, d [ m ], is demultiplexed into N subcarriers using a commutator I Data on each subcarrier is then modulated into an M -QAM symbol I For subcarrier k , we will rearrange a k [ ] and b k [ ] into real and imaginary components yielding p k [ ] = a k [ ] + jb k [ ] I In order for the output of the IDFT block to be real, given N subcarriers, we must use a 2 N -point IDFT I Terminals k = 0 and k = N are “don’t care” inputs I For subcarriers 1 k N - 1, the inputs are p k [ ] = a k [ ] + jb k [ ] I For subcarriers N + 1 k 2 N - 1, the inputs are p k [ ] = a 2 N - k [ ] + jb 2 N - k [ ] Professor Alexander M. Wyglinski ECE4305: Software-Deﬁned Radio Systems and Analysis

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Orthogonal Frequency Division Multiplexing Motivation Mathematical Formulation Equalization in Multicarrier Systems Eﬃcient Implementation
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## This note was uploaded on 01/13/2011 for the course ECE 4305 taught by Professor Wy during the Spring '10 term at WPI.

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ece4305_L17 - Orthogonal Frequency Division Multiplexing...

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