Physical layer of 5 g

Physical Layer of 5G
01.07.2020
Dr.S.Periyanayagi
Professor & Head/ECE
Ramco Institute ofTechnology
FDP on “Evolution of 5G”

Contents
• 5GTechnology Review
• Key 5G Parameters
• OSI and 5G Network Stack
• Physical Layer of 5G
• 5G - KeyTechnology Components
• Physical Channel & Physical Signals
• Duplex Scheme
• Physical Layer Challenges
01.07.2020 3
FDP on Evolution of 5G

What is 5G?
• 5G is the 5th generation of mobile networks, a
significant evolution of today's 4G LTE networks.
• It’s a next major phase of mobile telecommunications
standards.
• Designed to meet the very large growth in data and
connectivity of today’s modern society, the Internet of
Things with billions of connected devices, and
tomorrow’s innovations.
• Very important advantage of 5G is the fast response
time referred to as latency.
01.07.2020 4

General 5G Cellular Architecture
PictureTaken from: https://www.researchgate.net/figure/A-general-5G-cellular-network-
architecture_fig19_280873356
01.07.2020 5

PictureTaken from: http://www.emfexplained.info/?ID=25916
01.07.2020 6

5G will keep us connected in tomorrow’s smart cities, smart
homes and smart schools, and enable opportunities that we
haven’t even thought of yet.
PictureTaken from: http://www.emfexplained.info/?ID=25916
01.07.2020 7

Contd…
• The scope of 5G will ultimately range from mobile
broadband services to next-generation
automobiles and connected devices.
• The initial 5G New Radio (NR) specification was
completed in June 2018 and published in the
3GPP Release 15 specification.
• Two major trends are behind the race to 5G:
– Explosive growth in demand for wireless broadband
that can carry video and other content-rich services,
– Internet of Things (IoT), where large numbers of
smart devices communicate over the Internet.
01.07.2020 8

To achieve these objectives, 5G will provide extreme
broadband speed, ultralow latency, and ultra-reliable
web connectivity.
PictureTaken from:“5G Development with MATLAB” – ebook by Mathworks
01.07.2020 9

Contd..
• 5G networks and devices will require
– Substantially different architectures
– Radio access technology
– Physical layer algorithms
– Dense networks of small cells will complement macro
base stations
– Operating at millimeter wave technologies
– Employing massive MIMO antenna arrays
• user devices will become more integrated and
adaptive
01.07.2020 10

Contd…
• The vision of 5G wireless access is shown in Figure
PictureTaken from: “5G Physical Layer Principles, Models andTechnology Components”
byAli Zaidi Fredrik et al.
01.07.2020 11

Contd..
• 5G wireless access comprises both 5G NR and LTE
evolution. LTE is continuously evolving to meet a
growing part of the 5G requirements.
• The evolution of LTE towards 5G is referred to as
the LTE Evolution.
• LTE will operate below 6 GHz and NR will operate
from sub-1 GHz up to 100 GHz.
01.07.2020 12

Poll
1. One of the very important advantage of 5G
Technology is
A. Power Consumption is less
B. More Coverage
C. Latency
D. Communicate with More devices
01.07.2020 13

5G Terminology
• eMBB - Enhanced Mobile Broadband
For high-capacity and ultrafast mobile communications for
phones and infrastructure, virtual and augmented reality, 3D
and ultra-HD video, and haptic feedback
• URLLC - Ultra-reliable and Low Latency
For vehicle-to-vehicle (V2V) and vehicle-to-infrastructure
(V2I) communications, autonomous driving
• mMTC - Massive Machine-Type Communications
For consumer and industrial IoT, Industry 4.0 mission-critical
machine-to-machine (MC-M2M)
01.07.2020 14

Key 5G Parameters
Latency in the air link <1 ms
Latency end-to-end (device to core) <10 ms
Connection density 100x vs. current 4G LTE
Area capacity density 1 (Tbit/s)/km2
System spectral efficiency 10 (bit/s)/Hz/cell
Peak throughput (downlink) per
connection
10 Gbit/s
Energy efficiency
>90% improvement over
LTE
Key Parameters
01.07.2020 15

OSI Stack
Presentation Layer
6
Application Layer
7
Network Layer
3
Physical Layer
1
Session Layer
5
Transport Layer
4
Data link Layer
2
1
2
4
OpenWireless
Architecture
Upper Network Layer
Lower Network Layer
OpenTransport
Protocol
Application of Service
5G Network Stack
5G Network Stack
01.07.2020 16

OWA Layer: OWA layer is the short form of OpenWireless
Architecture layer. It functions as physical layer and data link
layer of OSI stack.
Network Layer: It is used to route data from source IP
device to the destination IP device/system. It is divided into
lower and upper network layers.
OpenTransport Layer: It combines functionality of both
transport layer and session layer.
Application Layer: It marks the data as per proper format
required. It also does encryption and decryption of the data.
It selects the best wireless connection for given service.
01.07.2020 17

• The 5G physical layer will depart from 4G LTE in a
number of ways, in order to improve spectral
efficiency and data rates.
• One distinctive feature is a significant jump in the
number of active antennas and antenna arrays, and
the related issues of beam forming and millimeter
wave RF signal processing.
• New modulation and coding schemes, power and
low-noise amplifier designs, and channel models all
need to be developed.
New Physical Layer for 5G
01.07.2020 18

• The physical layer forms the backbone of 5G NR
• The NR physical layer has to support a wide range of
frequencies (from sub-1 GHz to 100 GHz) and various
deployment options (pico cells, micro cells, macro cells)
• Human-centric and Machine-centric use cases
• NR is the first ever mobile radio access technology going
into millimeter-wave frequency range (with frequencies as
high as 100 GHz), targeting channel bandwidths in the GHz
range, and enabling massive multi-antenna systems
Contd..
01.07.2020 19

NR user-plane protocol stack
PictureTaken from: “5G Physical Layer Principles, Models andTechnology Components”
byAli Zaidi Fredrik et al.
01.07.2020 20

Contd…
• The protocol is split into the following layers:
Physical (PHY) layer
Medium access control (MAC) layer
Radio link control (RLC) layer
Packet data convergence protocol (PDCP) layer
 Service data adaptation protocol (SDAP) layer
01.07.2020 21

Contd..
• The SDAP layer handles the mapping between quality of service
(QoS) flow and radio bearers. IP packets are mapped to radio
bearers according to their QoS requirements.
• The PDCP layer is primarily responsible for
 IP header compression/decompression - reduces the number
of bits to transmit over radio interface
 Reordering and duplicate detection -mechanisms allow in-
sequence delivery of data units and removes duplicate data
units.
 Ciphering/deciphering - protects from eavesdropping
 Integrity protection - ensures message integrity
01.07.2020 22

Contd…
• The RLC layer - performs error correction through
 An automatic repeat request 2 (ARQ) mechanism
 Segmentation/resegmentation of (header compressed) IP packets
 In-sequence delivery of data units to higher layers
• The MAC layer - responsible for error correction through
HybridARQ3 (HARQ) mechanism
Uplink and downlink scheduling
The scheduler controls the assignment of uplink and downlink
physical time-frequency resources for transmission
Takes care of multiplexing data across multiple component
carriers when carrier aggregation is employed
01.07.2020 23

Contd…
• The PHY layer handles
 Coding/decoding
 Modulation/demodulation
 Multi antenna processing
 Mapping of signals to physical time-frequency
resources
01.07.2020 24

New Radio Physical Layer
• The key technology components of the NR physical
layer are
 Modulation
 Waveform
 Multi antenna transmission
 Channel coding
01.07.2020 25

Minute paper -Activity
• List - 5GTerminology
• List - 5G Network Stack layer
01.07.2020 FDP on 5G Evolution 26

Answer
5G terminology
• eMBB – Enabled Mobile Broad
Band
• URLLC – Ultra reliable and
Low Latency
• mMTC – Massive machine type
Communication
5G Network Stack layer
• OpenWirelessArchitecture
layer
• Lower & upper Network Layer
• OpenTransport Layer
• Application of Service
01.07.2020 FDP on 5G Evolution 27

MODULATION
• NR supports
 Quadrature phase shift keying (QPSK)
 16 quadrature amplitude modulation (QAM)
 64 QAM
 256 QAM modulation formats for both uplink and
downlink, as in LTE
• π/2-BPSK is supported in uplink to enable a further
reduced peak-to-average power ratio and enhanced power
amplifier efficiency at lower data rates, which is important
for mMTC services.
01.07.2020 28

Waveform
• In the downlink direction, the multiple access is
based on Orthogonal Frequency Division Multiple
Access (OFDMA), similar to LTE.
• In the uplink direction, 5G has adopted both
OFDMA and Single Carrier Frequency Division
Multiple Access (SC-FDMA)
• while LTE uses only SC-FDMA. SC-FDMA is often
denoted also as DFT-Spread OFDMA (DFT-S-
OFDMA).
01.07.2020 29

Contd…
• The motivation for the use of OFDMA comes from
better performance with the multiple antenna
transmission case.
• Traditionally, the use of OFDMA has caused about
1–2 dB loss in the available power for the uplink
transmission compared to the SC-FDMA waveform.
• However, even if the resulting transmission power is
less, the better link performance with multi-antenna
multi-stream transmission makes OFDMA a better
choice when the link budget has some margin.
01.07.2020 30

PictureTaken from: “5G Physical Layer”- Chapter 6 by Mihai Enescu et al.
01.07.2020 31

Contd…
• The other aspect is interference management in
Time Division Duplex (TDD) networks.
• Its easier to handle if both uplink and downlink use
the same multiple access solution.
• The uplink direction uses SC-FDMA (DFT-S-
OFDMA) for the cases when the transmission
power is limited and the use of uplink multi-stream
transmission is not possible.
01.07.2020 32

Contd…
• 5G will fall back to SC-FDMA operation when there is
not enough link quality for multi-stream operation. The
SC-FDMA principle is illustrated in Figure.
• The same principle used in LTE is maintained, with
only one symbol at a time sent using SC-FDMA
transmission.
• The FFT/IFFT pair at the transmitter side allows the
transmission to be placed accurately and without
filtering complexity in the correct place within the
carrier.
01.07.2020 33

PictureTaken from: “5G Physical Layer”- Chapter 6 by Mihai Enescu et al.
01.07.2020 34

Contd..
• Compared to LTE, the new 5G radio needed to be operated
with:
 Higher frequency bands, with the Release 15 frequency
range reaching up to 52.6GHz and studies in Release
17 considering ranges up to 114 GHz
 Higher bandwidths with up to 100MHz on lower
frequency bands (below 7.125 GHz) and up to
400MHz with above-24-GHz bands
 Shorter latency down to the sub-millisecond level
01.07.2020 35

Among the chief advantages of OFDM
and OFDMA
• Ease of implementation of both transmitter and receiver
• use of fast Fourier transform (FFT) and inverse fast
Fourier transform (IFFT) blocks
• Ability to counteract multi-path distortion
• Orthogonality of subcarriers, which eliminates inter-
cell interference
• Easy coupling with adaptive modulation techniques
• Ease of integration with multi-antenna hardware, both
at the transmitter and receiver
01.07.2020 36

New Modulation Formats for
future 5G
 FBMC - Filter-bank Multicarrier
 GFDM - Generalized Frequency Division
Multiplexing
 BFDM -Bi-orthogonal Frequency Division
Multiplexing
 UFMC -Universal Filtered Multicarrier
 TFP -Time-frequency Packing
01.07.2020 37

Multiple Antenna
• Multiantenna techniques in NR - more fundamental
role in the system design.
• Advances in active array antenna technology have
made it possible to have digital control over a large
number of antenna elements, referred to as massive
multiple-input multiple-output (MIMO).
• NR provides better support for multiuser MIMO
(MU-MIMO) and reciprocity-based operation.
01.07.2020 38

Channel Coding
• Channel coding is one of the main hardware critical
components in 5G
• Codes used in 5G are capable of providing good performance
gains with a lower implementation complexity and processing
delays compared to its predecessors
• Selection of the channel coding scheme based on the eMBB
requirements such as
 Performance of the coding scheme
 Implementation complexity
 latency of encoding and decoding
 flexibility (e.g. variable code length, code rate, HARQ)
of the coding scheme
01.07.2020 39

Contd…
• Coding schemes for the data channel and control channel
are based on block sizes and code rates.
• Data channels use Low Density Parity Check (LDPC) codes
• Control channel design is based on polar coding
• quasi-cyclic (QC) LDPC codes are the most realistic type
and provides lower encoding/ decoding complexities
• 5G channel coding - QC-LDPC codes
01.07.2020 40

Physical Channels
• Physical downlink shared channel (PDSCH)- downlink
data transmission.
• Physical downlink control channel (PDCCH) -
downlink control information
scheduling decisions required for downlink data (PDSCH)
reception
scheduling grants giving permission for uplink data (PUSCH)
transmission by a UE
• Physical broadcast channel (PBCH) - broadcasting
system information required by a UE to access the
network.
01.07.2020 41

Contd…
• Physical uplink shared channel (PUSCH) - uplink data
transmission
• Physical uplink control channel (PUCCH) - used for uplink
control information
 HARQ feedback acknowledgments (indicating whether a
downlink transmission was successful or not)
 Scheduling request (requesting time-frequency resources from
network for uplink transmissions)
 Downlink channel-state information for link adaptation.
• Physical random access channel (PRACH) - to request
connection setup referred to as random access.
01.07.2020 42

Modulation Schemes & Channel Coding
01.07.2020 43

Contd..
01.07.2020 44

Physical Signals
• The time-frequency resources that are used by the PHY
layer but do contain information from higher layers (i.e.,
layers above the PHY layer) are termed physical signals
• The physical signals are reference signals used for different
purposes
 Demodulation
 Channel estimation
 Synchronization
 Channel-state information
01.07.2020 45

Contd..
Downlink physical signals:
• Demodulation reference signal (DM-RS)
• Phase tracking reference signal (PT-RS)
• Channel state information reference signal (CSI-RS)
• Primary synchronization signal (PSS)
• Secondary synchronization signal (SSS)
Uplink physical signals:
• Demodulation reference signal (DM-RS)
• Phase tracking reference signal (PT-RS)
• Sounding reference signal (SRS)
01.07.2020 46

Contd…
DM-RS - estimate the radio channel for demodulation
PT-RS – Enable compensation of the oscillator phase noise
(Phase noise increases with frequency)
CSI-RS – Beam Management,Time/Frequency tracking and
Uplink control
SRS – Scheduling and Link Adaptation
PSS & SSS – Synchronization
01.07.2020 47

Duplexing Scheme
• NR Supports
– TDD (Time division Duplexing)
– FDD (Frequency division Duplexing)
• At Low frequencies : Spectrum allocation are paired,
implying FDD
• At High frequencies: Spectrum allocation are unpaired,
implyingTDD
• NR supports dynamicTDD
01.07.2020 48

Physical Layer Challenges
• 5G NR is the first cellular technology to
 Operate at millimeter-wave frequencies
 Support GHz of bandwidths
 Utilize a massive number of antennas
• These aspects impose a number of challenges for
operation of NR physical layer
• Propagation Related Challenges
– Multi antennaTechnique compensate for Loss/ Gain/
Performance
– Beam Forming performance at millimeter wave frequency is
largely unknown
01.07.2020 49

Contd..
• Hardware Related Challenges
 New challenges: Efficient radio implementation as both
the number of deployed transceivers and their operating
frequencies and bandwidths increase.
 RF power amplifier (PA) continues to play a critical role
as a major consumer of power.
 antenna systems using directive transmission is assessing
the distortion behavior
 RF oscillators : Maintaining a stable oscillation becomes
more difficult at very high frequencies
 Advanced signal processing hardware and algorithms
01.07.2020 50

References
1. “5G Physical Layer”- Chapter 6 by Mihai Enescu, Keeth Jayasinghe, Karri
Ranta-Aho, Karol Schober,and Antti Toskala,Nokia Bell Labs, Finland, JohnWiley
& Sons Ltd, 2020
2. “5G Physical Layer Principles, Models and Technology
Components” by Ali Zaidi Fredrik Athley Jonas Medbo Ulf Gustavsson
Giuseppe Durisi Xiaoming Chen (z-lib.org), Elesiver ISBN: 978-0-12-
814578-4.
3. “Signal processing for 5G - algorithms and implementations“ by
Fa-Long Luo, Ph.D., IEEE Fellow Charlie (Jianzhong) Zhang, Ph.D., IEEE
Fellow,Wiley Publication, ISBN 9781119116486.
4. 5G New radio – Physical Layer overview and performance in IEEE
Communication Theory Workshop 2018 by Amibadha Ghosh, Nokia Bell
Labs
01.07.2020 51

5. “5G Development with MATLAB” – ebook by Mathworks
6. Mehrdad Shariat et. al,“A Flexible Network Architecture for 5G
Systems”, HindawiWireless Communications and Mobile
Computing ,Vol. 2019,pp 1-20, doi.org/10.1155/2019/5264012.
7. ‘5G NR Physical layer General description(3GPPTS 38.201 version
15.0.0 Release 15)’, ETSITechnical Specification 138 201V15.0.0
(2018-09)
8. ’Understanding 5G NR Physical Layer’, KeysightTechnology, Nov.
2017
9. https://in.mathworks.com/videos/understanding-and-modeling-
the-5g-nr-physical-layer-1576072995802.html
01.07.2020 52

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