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ECE 442 Communication System Design Lecture 2. OFDM

ECE 442 Communication System Design Lecture 2. OFDM. Husheng Li Dept. of EECS The University of Tennessee. History of OFDM. OFDM was originally proposed by Bell Labs in 1960s. OFDM is widely used in various communication systems: Digital subscriber lines (DSL) Wi-Fi (IEEE 802.11)

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ECE 442 Communication System Design Lecture 2. OFDM

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  1. ECE 442 Communication System DesignLecture 2. OFDM Husheng Li Dept. of EECS The University of Tennessee

  2. History of OFDM • OFDM was originally proposed by Bell Labs in 1960s. • OFDM is widely used in various communication systems: • Digital subscriber lines (DSL) • Wi-Fi (IEEE 802.11) • WiMAX (IEEE 802.16) • LTE (Long Term Evolution of 3GPP)

  3. Orthogonal • In OFDM, the spectrum band is divided into K slots. • The signals over different slots are orthogonal: • The output of OFDM can be written as

  4. Structure of OFDM Transmitter

  5. IDFT Realization

  6. Base Band Transmitter

  7. Channel Response • We can consider the channel for OFDM as a series of frequency flat channels.

  8. Prefix • In order to avoid intersymbol interference, we need guard times between consecutive symbols. • We can put prefix in the guard time to make the frequency flat.

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