principles of 3g (cdma), 4g (ofdma) and 5g part-b · pdf fileprinciples of 3g (cdma), 4g...

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


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


OFDM (4G) Introduction

Overview of OFDMIntroduction

Orthogonal Frequency Division Multiplex (OFDM).

Special case of multicarrier transmission −→ overlapping andorthogonal narrowband subchannels.


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.


OFDM (4G) OFDM - Analogue Block Diagram

OFDM - Analogue Block Diagram



OFDM TX: Example of 4 Subcarriers



OFDM Tx Output


OFDM (4G) OFDM - Digital Block Diagram

OFDM - Digital Block Diagram (in Practice)



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.



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 ◦


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 ◦


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 ◦


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.


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)


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.


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.


SC-FDMA

SC-FDMA


5G Mobile Evolutions from 3G to 5G

Mobile Evolutions from 3G to 5G


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)


5G Main Characteristics of 3GPP/ETSI Standards

Main Characteristics of 3GPP/ETSI Standards


5G IMT2020 Spinder Diagram

IMT2020 Spinder Diagram


5G Triangle Diagram

Triangle Diagram


5G Triangle Diagram

Enhanced Mobile Broadaband


5G Triangle Diagram

Wide Area IoT


5G Triangle Diagram

Higher Reliability Control


5G Scalability Across a Broad Variation of Requirements

Scalability Across a Broad Variation of Requirements


Course Concluded Remarks Importance of 5G

Course Concluded Remarks: Importance of 5G

5G = 4th stage of Industrial Revolution!!!


Course Concluded Remarks Multi-antenna Technology in 5G

Concluded Remarks: Multi-antenna Technology in 5G



Multiple Access Interference Cancellation (ULA, N=5)



Co-Channel Interference Cancellation with Motion (ULA,N=5)


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


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



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


http://skynet.ee.ic.ac.uk/notes/notes.html

http://skynet.ee.ic.ac.uk/notes/CS_Exam_Comments_2017_Communication_Systems_E303.pdf

http://skynet.ee.ic.ac.uk/notes/CS_Exam_Comments_2017_Communication_Systems_E303.pdf

http://skynet.ee.ic.ac.uk/notes/Header_E303_2017.pdf


Thank You!


principles of 3g (cdma), 4g (ofdma) and 5g part-b · pdf fileprinciples of 3g (cdma), 4g...

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