1. Orthogonal Frequency Division Multiplexing
BOĞAZİÇİ UNIVERSITY
Department of Computer Engineering
CMPE 530 – Mathematical Foundations of Artificial Intelligence
Project Presentation
Orthogonal Frequency Division Multiplexing
Prepared by: Buluç Çelik

2. Outline Introduction Multiplexing Background
Orthogonal Frequency Division Multiplexing
Conclusion

3. Introduction
Orthogonal Frequency Division Multiplexing (OFDM) is a multiplexing technique where the data is distributed over a large number of sub-carriers spaced apart orthogonally.
Benefits:
High spectral efficiency
Resiliency to interference

4. Introduction (Cont...) Application areas include:
Digital Audio Broadcasting (DAB)
Digital Terrestrial Television Broadcasting (DTTB)
Wireless Local Area Networks
Asymmetric Digital Subscriber Line (ADSL) standard
IEEE a

5. Multiplexing Background
The technique of having a transmission capacity to be shared by many transmission sources
MUX
DEMUX
1 data link, n data channels
n inputs
n outputs

6. Multiplexing Background (Cont...)
Time Division Multiplexing
Time
Frequency

7. Multiplexing Background (Cont...)
Frequency Division Multiplexing
Time
Frequency

8. Multiplexing Background (Cont...)
Frequency Division Multiplexing (cont...)

9. Orthogonal Frequency Division Multiplexing
Orthogonal sub carriers satisfying the following conditions are used
The modulation formula of an OFDM signal:

10. Orthogonal Frequency Division Multiplexing (Cont...)
The Fourier transform of each sub-carrier signal is a sinc function in frequency domain
The zeroes of this sinc function occur at intervals f0. Since the sub-carrier spacing is exactly f0, there is no inter sub-carrier interference.
Having overlapping sub-carrier spectrums, OFDM technique uses the spectrum very efficiently.

11. Conclusion OFDM has high spectral efficiency
OFDM is resilient to RF interference
The implementation relies on very high speed DSP, which has only recently become available at a price that makes OFDM a competitive technology in the marketplace.

12. Thank you for your attendance...
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