An Artificial BEE Colony An Artificial BEE Colony Algorithm For Reduction of Algorithm For Reduction of

PAPR in OFDMPAPR in OFDM

Prashant PatelPrashant Patel

M0923M08M0923M08

ObjectivesObjectives

Overview About OFDMOverview About OFDM Definition and PrinciplesDefinition and Principles OFDM Advantages and drawbacksOFDM Advantages and drawbacks ApplicationsApplications

Overview About OFDMOverview About OFDM OFDM was invented more than 40 years OFDM was invented more than 40 years

ago.ago.The first OFDM schemes presented in The first OFDM schemes presented in 19661966

OFDM has been adopted for several OFDM has been adopted for several technologies:technologies: Asymmetric Digital Subscriber Line (ADSL) Asymmetric Digital Subscriber Line (ADSL)

services.services. IEEE 802.11a/g, IEEE 802.16a.IEEE 802.11a/g, IEEE 802.16a. Digital Audio Broadcast (DAB).Digital Audio Broadcast (DAB). Digital Terrestrial Television Broadcast: DVD in Digital Terrestrial Television Broadcast: DVD in

Europe, ISDB in JapanEurope, ISDB in Japan 4G, IEEE 802.11n, IEEE 802.16, and IEEE 4G, IEEE 802.11n, IEEE 802.16, and IEEE

802.20.802.20.

Why OFDMWhy OFDM??

High bit rate needs are clumped by High bit rate needs are clumped by the nature of communication the nature of communication channels.channels.

Multi-path Propagation effects forbid Multi-path Propagation effects forbid increasing of transmission rates.increasing of transmission rates.

OFDM DefinitionOFDM Definition

OFDM = Orthogonal FDMOFDM = Orthogonal FDM Carrier centers are put on orthogonal frequenciesCarrier centers are put on orthogonal frequencies ORTHOGONALITY - The peak of each signal ORTHOGONALITY - The peak of each signal

coincides with coincides with troughtrough of other signals of other signals Subcarriers are spaced by 1/TsSubcarriers are spaced by 1/Ts

A

F

How OFDM worksHow OFDM works

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

Types of OFDMTypes of OFDM

C-OFDMC-OFDM

MIMO-OFDMMIMO-OFDM

V-OFDMV-OFDM

W-OFDMW-OFDM

Flash-OFDMFlash-OFDM

C-OFDMC-OFDM

Coded OFDMCoded OFDM Digital Audio Digital Audio

Broadcasting (DAB)Broadcasting (DAB) Digital Video Digital Video

Broadcasting (DVB-T)Broadcasting (DVB-T)

COFDM offers real COFDM offers real benefit in the benefit in the presence of isolated presence of isolated narrow-band narrow-band interfering signals interfering signals

Multiple Input, Multiple Output Multiple Input, Multiple Output OFDM (MIMO-OFDM)OFDM (MIMO-OFDM)

Developed by Iospan WirelessDeveloped by Iospan Wireless UUses multiple antennas to transmit ses multiple antennas to transmit

and receive radio signalsand receive radio signals SSpatial multiplexingpatial multiplexing

V-OFDMV-OFDM

Vector OFDM Vector OFDM Developed by CISCODeveloped by CISCO Increases subscriber coverageIncreases subscriber coverage Lowers the cost of provisioning and Lowers the cost of provisioning and

deploying infrastructure deploying infrastructure Employs both frequency and spatial Employs both frequency and spatial

diversity diversity Creates a robust processing technique for Creates a robust processing technique for

multi-path fading and narrow band multi-path fading and narrow band interference interference

…

Subscriber

Base Station

Paths

…

W-OFDMW-OFDM Wideband OFDM Wideband OFDM Invented by Wi-LAN Invented by Wi-LAN Large spacing between carriers Large spacing between carriers Advantages:Advantages:- Optimal performance against Multi-path- Optimal performance against Multi-path

- Less sensitive to carrier offset- Less sensitive to carrier offset

-Optimal power efficiency of the transmitter -Optimal power efficiency of the transmitter amplifieramplifier

- More immune against fading - More immune against fading

Flash-OFDMFlash-OFDM

Fast-hopped OFDM Fast-hopped OFDM Wide-band spread-spectrum Wide-band spread-spectrum

technology technology Avoids the compromises inherent in Avoids the compromises inherent in

other mobile data systems other mobile data systems Capability to work around interfering Capability to work around interfering

signals signals

Differences from other multiplexing Differences from other multiplexing techniquestechniques

OFDM versus WDMOFDM versus WDM

-more flexible -more flexible

-higher bandwidth efficiency -higher bandwidth efficiency

Differences from other multiplexing Differences from other multiplexing techniquestechniques

OFDM versus OFDM versus TDMTDM

-number of carriers -number of carriers

-synchronization -synchronization

-sensitivity-sensitivity

-capacity/efficiency advantages-capacity/efficiency advantages

--complexity and cost issues complexity and cost issues

ApplicationsApplications

Digital Audio and Video Digital Audio and Video BroadcastingBroadcasting

Asymmetric Digital Subscriber Asymmetric Digital Subscriber Line (ADSL)Line (ADSL)

Wireless NetworkingWireless Networking Power-line TechnologyPower-line Technology