This ppt describes some of the information about OFDM i.e. Orthogonal Frequency Division Multiplexing

1. Presented by:
Ashish Soni
ashish.soni.2016@ieee.org
Orthogonal Frequency Division
Multiplexing
(OFDM)

2. Content
 Motivation
 Introduction
 Origin
 Principle
 Features
 Applications
 Problems & ResearchArea
 Conclusion
 References

3. Motivation
 The demand for multimedia wireless communication is
growing today at an extremely rapid pace.
 Multiplexing Schemes: FDM,TDM & CDM [1].

4.  Evolution of Mobile Communication [2].
Generation Standard Data Rate Features
2G GSM 10 kbps DigitalVoice,
SimpleText,
Simple News,
Feeds etc.
2G CDMA 10 kbps
2.5G GPRS 50 kbps
2.5G EDGE 200 kbps
3G WCDMA ~400 kbps DigitalVoice,
Mobile Broadband3.5G HSDPA/HSUPA 4-50 Mbps
4G LTE/WiMAX 100-200 Mbps Live HDTV,
Online Gaming,
High Speed.
4G LTE > 1 Gbps

5. Introduction
 OFDM is promising technique for achieving high data rate
transmission in mobile environment [3].
 It is a special form of multicarrier modulation (MCM),
where a single data stream is transmitted over a number of
subcarriers.

6.  It offers high spectral efficiency, multipath delay tolerance,
robustness to channel fading, immunity to impulse
interference [4].
 Therefore it has been widely deployed in many wireless
communication standards such as Digital Video Broadcasting
(DAB), Asymmetrical Digital Subscriber Line (ADSL),
DigitalTerrestrialTelevision Broadcasting etc.

7. Origin
 Concept of OFDM has existed since 1966.
 But in 1985, Cimini [5] proposed a cellular mobile radio
system based on OFDM.
 In 1995, Wu [4] suggested some high frequency military
systems using OFDM.
 In 1998, Fernando proposed application of OFDM to the
satellite mobile channel.

8. Principle
 Orthogonal Frequency Division Multiplexing technique is
very much alike to Frequency Division Multiplexing.
 Figure shows variation among FDM & OFDM:

9.  Orthogonal sub carriers in OFDM:

10.  OFDMTransceiver

11. Data coded in Frequency Domain Transformation toTime Domain Channel Frequency Response
Frequency Domain SignalTime Domain Signal

12. Features
 High spectral efficiency.
 Can be efficiently implemented using FFT.
 Low efficiency to time synchronization technique.
 OFDM has improved quality of narrowband interference.
 Can easily adapt to severe channel conditions without
complex equalization.
 Robust against inter-symbol interference (ISI) and fading
caused by multipath propagation.
 OFDM has the better resistant quality to fading.

13. Applications
 Digital Audio Broadcasting
 DigitalVideo Broadcasting
 IEEE 802.11 a/g
 IEEE 802.16
 IEEE 802.20 [6].

14. Problems
 Very sensitive to Frequency errors.
 Inter Carrier Interference: Due to Doppler Spreading
 Carrier FrequencyTiming Synchronization: Causes ICI
 Peak toAverage Power Ratio: Reduces power Efficiency.

15. Conclusion
 OFDM has promising Future in wireless networks and
mobile communication.
 OFDM is already playing an important role in WLAN and
will be part of MAN too.
 OFDM with the use of WiMAX and LTE advanced is the
future cellular packet data network.

16. References
1. GSMA Intelligence,April 2014
2. Aditya K Jagannatham, “Principles of Wireless Communication Systems”,
McGrawhill Education
3. Orthogonal Frequency Division Multiplexing (OFDM)-Applications for
Wireless Communications with Coding.
4. Y.Wu and W. Y. Zou, “Orthogonal frequency division multiplexing: A multi-
carrier modulation scheme,” IEEE Trans. Consumer Electronics, vol. 41, Aug.
1995.
5. Leonard J. Cimini, JR.,“Analysis And Simulation Of A Digital Mobile
Channel Using Orthogonal Frequency Division Multiplexing”, Ieee
Transactions On Communications,Vol. Com-33, July-1985.
6. Ramjee Prasad “OFDM for wireless communication system”, universal
personal communication.

17. ThankYou..