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Principles of3G (CDMA), 4G (OFDMA) and 5G
Part-B
Professor A. Manikas
Imperial College London
EE303
Prof. A. Manikas (Imperial College) EE303: 3G, 4G and 5G (Part B) v16 1 / 35
Table of Contents3 OFDM (4G)
AbbreviationsIntroductionOFDM SubcarriersOFDM - Analogue Block DiagramExample of 4 Subcarriers
OFDM - Digital Block DiagramOFDM Cyclic Prefix (CP)OFDM: Advantages/DisadvantagesWhere OFDM is Used
4 OFDMAOFDM vs OFDMAOFDMA Compared to CDMA
5 SC-FDMA6 5G
Mobile Evolutions from 3G to 5GNarrowband and Wideband SignalsMain Characteristics of 3GPP/ETSI StandardsIMT2020 Spinder DiagramTriangle DiagramEnhanced Mobile BroadabandWide Area IoTHigher Reliability Control
Scalability Across a Broad Variation of Requirements7 Course Concluded Remarks
Importance of 5GMulti-antenna Technology in 5GMAI CancellationCochannel Interference Cancellation with Motion
Topics Covered in this Course (E303)Topics of the Advanced Communication Theory (E401) Course
Prof. A. Manikas (Imperial College) EE303: 3G, 4G and 5G (Part B) v16 2 / 35
OFDM (4G) Abbreviations
Abbreviations
LTE Long-Term EvolutionDAB Digital Audio BroadcastingDVB Digital Video BroadcastingDMB Digital multimedia broadcastingISDB Integrated Services Digital BroadcastingMediaFLO Media Forward Link OnlyADSL Asymmetric Digital Subscriber LineVDSL Very-high-bit-rate Digital Subscriber Line
Prof. A. Manikas (Imperial College) EE303: 3G, 4G and 5G (Part B) v16 3 / 35
OFDM (4G) Introduction
Overview of OFDMIntroduction
Orthogonal Frequency Division Multiplex (OFDM).
Special case of multicarrier transmission −→ overlapping andorthogonal narrowband subchannels.
Prof. A. Manikas (Imperial College) EE303: 3G, 4G and 5G (Part B) v16 4 / 35
OFDM (4G) OFDM Subcarriers
OFDM Subcarriers
The chosen subcarriers are harmonics and hence orthogonal to eachother.No guard band between subcarriers are needed.The peak of a subarrier is precisely at the zero-crossings of itsadjacent subcarriers.
Prof. A. Manikas (Imperial College) EE303: 3G, 4G and 5G (Part B) v16 5 / 35
OFDM (4G) OFDM - Analogue Block Diagram
OFDM - Analogue Block Diagram
Prof. A. Manikas (Imperial College) EE303: 3G, 4G and 5G (Part B) v16 6 / 35
OFDM (4G) OFDM - Analogue Block Diagram
OFDM TX: Example of 4 Subcarriers
Prof. A. Manikas (Imperial College) EE303: 3G, 4G and 5G (Part B) v16 7 / 35
OFDM (4G) OFDM - Analogue Block Diagram
OFDM Tx Output
Prof. A. Manikas (Imperial College) EE303: 3G, 4G and 5G (Part B) v16 8 / 35
OFDM (4G) OFDM - Digital Block Diagram
OFDM - Digital Block Diagram (in Practice)
Prof. A. Manikas (Imperial College) EE303: 3G, 4G and 5G (Part B) v16 9 / 35
OFDM (4G) OFDM - Digital Block Diagram
The stream of modulated symbols is demultiplexed onto Nsc parallelstreams (using a S/P converter) - where Nsc is the number ofsubcarriersThe Nsc parallel streams are fed to the IFFT .Remember :
Frequency-Domain (FD) samples Time-Domain (TD) Samples
X [k ]iFFT7−→ x(t`) =
1Nsc
Nsc -1∑k=0
X [k ] exp(j2πk `Nsc )
X [k ] =Nsc -1∑`=0
x(t`) exp(−j2πk `Nsc )
FFT←− x(t`)
∀k = 0, 1, ...,Nsc − 1 ∀` = 0, 1, ...,Nsc − 1
Orthogonality:Nsc−1∑`=0
exp(−j(2πk `Nsc ) exp(−j(2πm `
Nsc ) = 0, ∀k 6= m
The time samples at the output of the iFFT are multiplexed using aP/S Converter ,Cyclic prefixes are inserted.
Prof. A. Manikas (Imperial College) EE303: 3G, 4G and 5G (Part B) v16 10 / 35
OFDM (4G) OFDM - Digital Block Diagram
Prof. A. Manikas (Imperial College) EE303: 3G, 4G and 5G (Part B) v16 11 / 35
OFDM (4G) OFDM - Digital Block Diagram
TS1 (iFFT output) TS2 (iFFT output)
1st +1 0.5+0.0j 0.5 0 ◦ +1 0.5+0.0j 0.5 0 ◦
2nd +1 0.5+0.0j 0.5 0 ◦ +1 0.0+0.5j 0.5 90 ◦
3rd −1 -0.5+0.0j 0.5 180 ◦ +1 0.5+0.0j 0.5 0 ◦
4th +1 0.5+0.0j 0.5 0 ◦ −1 0.0+0.5j 0.5 -90 ◦
TS3 (iFFT output) TS6 (iFFT output)
1st +1 -0.5+0.0j 0.5 180 ◦ −1 -0.5+0.0j 0.5 180 ◦
2nd −1 0.5+0.0j 0.5 0 ◦ +1 0.0+0.5j 0.5 90 ◦
3rd −1 0.5+0.0j 0.5 0 ◦ −1 -0.5+0.0j 0.5 180 ◦
4th −1 0.5+0.0j 0.5 0 ◦ −1 0.0+0.5j 0.5 -90 ◦
TS5 (iFFT output) TS6 (iFFT output)
1st −1 0.0+0.0j 0 0 ◦ −1 0.0+0.0j 0 0 ◦
2nd +1 -0.5+0.5j√22 135 ◦ −1 -0.5-0.5j
√22 -135 ◦
3rd +1 0.0+0.0j 0 -90 ◦ +1 0.0+0.0j 0 -90 ◦
4th −1 -0.5+0.5j√22 -135 ◦ +1 -0.5+0.5j
√22 135 ◦
Prof. A. Manikas (Imperial College) EE303: 3G, 4G and 5G (Part B) v16 12 / 35
OFDM (4G) OFDM Cyclic Prefix (CP)
Cyclic Prefix, CPThe cyclic prefix is a guard interval (GI) placed to protect OFDMsignals from intersymbol interference in the presence of multipath.
The last section of a symbol is used as a prefix in the front of thesymbol.The duration of the guard interval TGI should be
TGI > Tspread, (1)
to minimise inter-symbol interference (ISI).Prof. A. Manikas (Imperial College) EE303: 3G, 4G and 5G (Part B) v16 13 / 35
OFDM (4G) OFDM: Advantages/Disadvantages
OFDM: Advantages/Disadvantages
Disadvantages:I High peak-to-average-power-ratio (PAPR) [CR] . An OFDM signalhas a relatively large dynamic range, or PAPR. The RF amplifier ishence required to have a larger linear range resulting in a degradedeffi ciency level.
I Carrier Offset and drift sensitivity . OFDM is more sentitive tocarrier offset and drift than single carrier systems.
Advantages:I High spectrum effi ciency . The closely-spaced overlappingsub-carriers yield high spectrum effi ciency.
I Less sensitive to frequency selective fading . The overall channel isdivided into multiple narrowband channels that experience flat fadingindividually.
I Easy channel equalisation . The flat fading narrowband sub-channelsare easy to equalise, compared to CDMA.
Prof. A. Manikas (Imperial College) EE303: 3G, 4G and 5G (Part B) v16 14 / 35
OFDM (4G) Where OFDM is Used
Where OFDM is UsedWireless Standards
Cellular (Mobile) telecommunications : LTE and LTE-AWi-Fi standards : 802.11a, 802.11g, 802.11n, 802.11ac andHIPERLAN/2Mobile broadband wireless access (MBWA) standard: IEEE802.20.Broadcast standards: DAB Digital Radio, DVB and Digital RadioMondiale.Mobile TV standard as DVB-H, T-DMB, ISDB-T and MediaFLOforward link.
Cable Standards
ADSL and VDSL broadband utilising copper wiring.Cable TV, with DVB-C2.Power Line CommunicationsData over cable service interface specification (DOCSIS)
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OFDMA OFDM vs OFDMA
OFDM vs OFDMAOFDMA is the “access”version of OFDM, that is a scheme wherethe access to resources is shared between users.
In OFDM-TDMA, time-slots are attributed to each users and thewhole OFDM symbol is dedicated to one user.In OFDMA, both time and frequency are distributed among users.
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OFDMA OFDMA Compared to CDMA
OFDMA Compared to CDMA
OFDMA CDMAChannelEqualisation
OFDMA chops its largebandwith into subchan-nels that are easy toequalise.
CDMA requires a largebandwidth (more diffi cultto equalise than OFDM).
Mobility Sensitive to Doppler shift. Robust to Doppler shift.Scalability Easy to aggregate addi-
tional spectrum.Hard to support moreusers.
Security May require additional se-cutity measures
PN-codes are an addi-tional level of security.
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SC-FDMA
SC-FDMA
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5G Mobile Evolutions from 3G to 5G
Mobile Evolutions from 3G to 5G
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5G Narrowband and Wideband Signals
Narrowband and Wideband Signals and SystemsUS FCC (Federal Communications Commission): Definition
Fractional Bandwidth Bfr :
Bfr ,BFc
(2)
with B representing the signal bandwidth and Fc denoting the carrierfrequency.
Based on Bfr , the FCC classification is:
0 < Bfr < 0.01⇐⇒ Narrow Band (3)
0.01 < Bfr < 0.25⇐⇒ Wide Band (4)
0.25 < Bfr < 2.00⇐⇒ Ultra Wide Band (5)
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5G Main Characteristics of 3GPP/ETSI Standards
Main Characteristics of 3GPP/ETSI Standards
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5G IMT2020 Spinder Diagram
IMT2020 Spinder Diagram
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5G Triangle Diagram
Triangle Diagram
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5G Triangle Diagram
Enhanced Mobile Broadaband
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5G Triangle Diagram
Wide Area IoT
Prof. A. Manikas (Imperial College) EE303: 3G, 4G and 5G (Part B) v16 25 / 35
5G Triangle Diagram
Higher Reliability Control
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5G Scalability Across a Broad Variation of Requirements
Scalability Across a Broad Variation of Requirements
Prof. A. Manikas (Imperial College) EE303: 3G, 4G and 5G (Part B) v16 27 / 35
Course Concluded Remarks Importance of 5G
Course Concluded Remarks: Importance of 5G
5G = 4th stage of Industrial Revolution!!!
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Course Concluded Remarks Multi-antenna Technology in 5G
Concluded Remarks: Multi-antenna Technology in 5G
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Course Concluded Remarks Multi-antenna Technology in 5G
Multiple Access Interference Cancellation (ULA, N=5)
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Course Concluded Remarks Multi-antenna Technology in 5G
Co-Channel Interference Cancellation with Motion (ULA,N=5)
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Course Concluded Remarks Topics Covered in this Course (E303)
Topics Covered in this Course (E303)
1 Introductory Concepts
2 Digital Communications - An Overview of Fundamentals
1 Information Sources,2 Communication Channels & Criteria and Limits3 Wireless Communications (SISO)4 Constellation Diagram and Digital Modulators/Demodulators5 PN-codes, PN-signals and Basics of Spread Spectrum Comms
3 Principles of PCM
4 Principles of 3G (CDMA), 4G (OFDMA) and 5G
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Course Concluded Remarks Topics of the Advanced Communication Theory (E401) Course
Topics of the Advanced Communication Theory (E401)Course
1 Introduction
2 Principles of M-ary Decision & Detection Theory
3 Principles of Diversity Theory
4 Multi-Antenna Wireless Communications:1 An Intoductory Overview2 SIMO,MISO,MIMO3 Array Receivers for SIMO and MIMO
F Detection ProblemF Estimation ProblemF Reception Problem
4 Massive Systems (maMI and maSI)5 mm-Wave Communications6 Spatiotemporal Wireless Communications7 5G
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Course Concluded Remarks Topics of the Advanced Communication Theory (E401) Course
E303 Exam Paper and other Useful Information
Lecture Notes :http://skynet.ee.ic.ac.uk/notes/notes.html
Classes Weeks A8 and A9:Thurday 9-11am and Friday 9-10am
Exam PaperI Comments:http://skynet.ee.ic.ac.uk/notes/CS_Exam_Comments_2017_Communication_Systems_E303.pdf
I Cover Page:http://skynet.ee.ic.ac.uk/notes/Header_E303_2017.pdf
Exam Date:Week A10, Wed 7th Dec 2016, 9-12am
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Course Concluded Remarks Topics of the Advanced Communication Theory (E401) Course
Thank You!
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