OFDM (Orthogonal Frequency Division Multiplexing) is a digital multi-carrier transmission technique that distributes data over a large number of carriers that are spaced apart at precise frequencies to prevent interference. It works by splitting the bandwidth into multiple smaller sub-carriers. Types of OFDM include C-OFDM, MIMO-OFDM, V-OFDM, W-OFDM, and Flash-OFDM. OFDM has advantages over other multiplexing techniques like WDM and TDM, including higher bandwidth efficiency and flexibility. Applications of OFDM include digital audio/video broadcasting, ADSL, wireless networking, and power-line technology.

1. OFDM
(Orthogonal Frequency Division Multiplexing )

2. Objectives
 What is OFDM
 How OFDM works
 Types of OFDM
 Differences from other multiplexing
techniques
 Applications

3. What is OFDM
 Definition
 The first OFDM schemes presented in
1966
 Development of OFDM over years

4. A
F

5. How OFDM works
It distributes the data over a large number
of carriers that are spaced apart at precise
frequencies. This spacing provides the
"orthogonality" in this technique which
prevents the demodulators from seeing
frequencies other than their own.

6. Types of OFDM
 C-OFDM
 MIMO-OFDM
 V-OFDM
 W-OFDM
 Flash-OFDM

7. C-OFDM
 Coded OFDM
 Digital Audio
Broadcasting (DAB)
 Digital Video
Broadcasting (DVB-T)
 COFDM offers real
benefit in the
presence of isolated
narrow-band
interfering signals

8. Multiple Input, Multiple Output
OFDM (MIMO-OFDM)
 Developed by Iospan Wireless
 Uses multiple antennas to transmit
and receive radio signals
 Spatial multiplexing

9. V-OFDM
 Vector OFDM
 Developed by CISCO
 Increases subscriber coverage
 Lowers the cost of provisioning and
deploying infrastructure
 Employs both frequency and spatial
diversity
 Creates a robust processing technique for
multi-path fading and narrow band
interference

10. …
Subscriber
Base Station
Paths
…

11. W-OFDM
 Wideband OFDM
 Invented by Wi-LAN
 Large spacing between carriers
 Advantages:
- Optimal performance against Multi-path
- Less sensitive to carrier offset
-Optimal power efficiency of the transmitter
amplifier
- More immune against fading

12. Flash-OFDM
 Fast-hopped OFDM
 Wide-band spread-spectrum
technology
 Avoids the compromises inherent in
other mobile data systems
 Capability to work around interfering
signals

13. Differences from other multiplexing
techniques
 OFDM versus WDM
-more flexible
-higher bandwidth efficiency

14. Differences from other multiplexing
techniques
 OFDM versus TDM
-number of carriers
-synchronization
-sensitivity
-capacity/efficiency advantages
-complexity and cost issues

15. Applications
 Digital Audio and Video
Broadcasting
 Asymmetric Digital Subscriber
Line (ADSL)
 Wireless Networking
 Power-line Technology