OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES &...
-
Upload
grace-scoville -
Category
Documents
-
view
219 -
download
1
Transcript of OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES &...
![Page 1: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/1.jpg)
OFDM, Quick Intro
K7DEN
![Page 2: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/2.jpg)
OUTLINE
OVERVIEW ABOUT OFDMDEFINITION AND PRINCIPLESOFDM ADVANTAGES & DRAWBACKSAPPLICATIONSCONCLUSIONS AND PERSPECTIVES
![Page 3: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/3.jpg)
OVERVIEW ABOUT OFDM
OFDM was invented more than 40 years ago. OFDM has been adopted for several technologies:
Asymmetric Digital Subscriber Line (ADSL) services.
IEEE 802.11a/g, IEEE 802.16a. Digital Audio Broadcast (DAB). Digital Terrestrial Television Broadcast: DVD in Europe, ISDB in Japan 4G, IEEE 802.11n, IEEE 802.16, and IEEE 802.20.
![Page 4: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/4.jpg)
WHY OFDM ?
High bit rate needs are clumped by the nature of communication channels.
Multi-path Propagation effects forbid increasing of transmission rates.
![Page 5: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/5.jpg)
OUTLINE
OVERVIEW ABOUT OFDMDEFINITION AND PRINCIPLESOFDM ADVANTAGES & DRAWBACKS
![Page 6: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/6.jpg)
OFDM DEFINITION
OFDM = Orthogonal FDM Carrier centers are put on orthogonal
frequencies ORTHOGONALITY - The peak of each signal
coincides with trough of other signals Subcarriers are spaced by 1/Ts
![Page 7: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/7.jpg)
Modulation
![Page 8: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/8.jpg)
PRINCIPLES
BASIC IDEA : Channel bandwidth is divided into multiple subchannels to reduce ISI and frequency-selective fading.
Multicarrier transmission : Subcarriers are orthogonal each other in frequency domain.
![Page 9: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/9.jpg)
PRINCIPLES
Time-domain spreading: Spreading is achieved in the time-domain by
repeating the same information in an OFDM symbol on two different sub-bands => Frequency Diversity.
Frequency-domain spreading: Spreading is achieved by choosing conjugate
symmetric inputs for the input to the IFFT (real output)
Exploits frequency diversity and helps reduce the transmitter complexity/power consumption.
![Page 10: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/10.jpg)
FDM OFDM
Frequency Division Multiplexing
OFDM frequency dividing
EARN IN SPECTRAL EFFICIENCY
![Page 11: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/11.jpg)
The baseband OFDM signals can be written as
Where is the central frequency of the mth sub-channel and is the corresponding transmitted symbol.
The signals are orthogonal over [0, T ] as illustrated below:
OFDM THEORY
1
0
0 ,2exp)(N
mm Ttt
T
mjXtx
T
mfm
mX
tT
mj 2exp
ml
T
dttT
ljt
T
mjT )2exp().2exp(1
0
![Page 12: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/12.jpg)
FEC IFFT
DAC
LinearPA
add cyclic extension
bits
fc
OFDM symbol
Pulse shaper &
view this as a time tofrequency mapper
Generic OFDM Transmitter
Complexity (cost) is transferred back from the digital to the analog domain!
Serial toParallel
![Page 13: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/13.jpg)
AGC
fc
VCO
Sampler FFTError
gross offset
Slot &
fine offset
Freq. Offset
Estimation
TimingSync.
(of all tones sent in one OFDM symbol)
Generic OFDM Receiver
RecoveryP/S and
Detection
![Page 14: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/14.jpg)
OUTLINE
OVERVIEW ABOUT OFDMDEFINITION AND PRINCIPLESOFDM ADVANTAGES &
DRAWBACKSAPPLICATIONS
![Page 15: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/15.jpg)
OFDM ADVANTAGES OFDM is spectrally efficient
IFFT/FFT operation ensures that sub-carriers do not interfere with each other.
OFDM has an inherent robustness against narrowband interference. Narrowband interference will affect at most a couple of subchannels. Information from the affected subchannels can be erased and recovered via the forward error correction (FEC) codes.
Equalization is very simple compared to Single-Carrier systems
![Page 16: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/16.jpg)
OFDM ADVANTAGES OFDM has excellent robustness in multi-path environments.
Cyclic prefix preserves orthogonality between sub- carriers. Cyclic prefix allows the receiver to capture multi- path energy more efficiently.
Ability to comply with world-wide regulations: Bands and tones can be dynamically turned on/off to comply with changing regulations.
Coexistence with current and future systems: Bands and tones can be dynamically turned on/off for enhanced coexistence with the other devices.
![Page 17: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/17.jpg)
OFDM DRAWBACKS
High sensitivity inter-channel interference, ICI
OFDM is sensitive to frequency, clock and phase offset
The OFDM time-domain signal has a relatively large peak-to-average ratio tends to reduce the power efficiency of the RF
amplifier non-linear amplification destroys the
orthogonality of the OFDM signal and introduced out-of-band radiation
![Page 18: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/18.jpg)
OUTLINE
OVERVIEW ABOUT OFDMDEFINITION AND PRINCIPLESOFDM ADVANTAGES & DRAWBACKSAPPLICATIONS
![Page 19: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/19.jpg)
Standards
Digital Audio Broadcasting (DAB)Digital Video Broadcasting (DVB)Asymmetric Digital Subscriber Line (ADSL)Wireless LAN IEEE 802.11a
Wireless networking, device connectivityProposed for 802.16 standard
Connection between subscriber's transceiver station and a base transceiver station
![Page 20: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/20.jpg)
Digital Radio
Coded OFDM Transmitter
COFDM Transmitter
![Page 21: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/21.jpg)
DRM
For HF Frequencies 4.5 – 5 kHz for half channel
Data Rates of 4 – 14.5 kbit/s
9 – 10 kHz for full channelData Rates of 8 – 35kbit/s
18-20 kHz for double channelData Rates of 31 – 72kbit/s
![Page 22: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/22.jpg)
Products
AOR ARD9800 http://www.hamradio-dv.org/aor.htm
Icom D-StarWinDRM
![Page 23: OFDM, Quick Intro K7DEN. OUTLINE zOVERVIEW ABOUT OFDM zDEFINITION AND PRINCIPLES zOFDM ADVANTAGES & DRAWBACKS zAPPLICATIONS zCONCLUSIONS AND PERSPECTIVES.](https://reader030.fdocuments.in/reader030/viewer/2022032517/56649cab5503460f9496cf52/html5/thumbnails/23.jpg)
Proprietary OFDM Flavours
Wideband-OFDM(W-OFDM) of Wi-LAN
www.wi-lan.com
Flash OFDMfrom Flarion
www.flarion.com
Vector OFDM(V-OFDM) of Cisco, Iospan,etc.
www.iospan.com
-- 2.4 GHz band-- 30-45Mbps in 40MHz-- large tone-width (for mobility, overlay)
-- Freq. Hopping for CCI reduction, reuse-- 1.25 to 5.0MHz BW -- mobility support
-- MIMO Technology-- non-LoS coverage, mainly for fixed access-- upto 20 Mbps in MMDS
Wi-LAN leads the OFDM Forum -- many proposals submitted to IEEE 802.16 Wireless MANCisco leads the Broadand Wireless Internet Forum (BWIF)