Dar es Salaam Institute of Technology (DIT)
ETCT 06204
Digital Cellular Network
Ally, J
jumannea@gmail.com
DIT
“Most teachers waste their time by asking
questions that are intended to discover what a
pupil does not know, whereas the true art of
questioning is to discover what the pupil does
know or is capable of knowing”
By
Albert Einstein
DIT
LTE and LTE-Advanced
Network
DIT
LTE Requirements
◼
◼
◼
◼
◼
◼
◼
◼
◼
Peak data rate of 50 / 100 Mbps (uplink / downlink)
Reduced latency enabling RTT (round trip time) <10 ms
Packet-optimized
Improved spectrum efficiency between 2- 4 times higher than
Release 6 HSPA
Bandwidth scalability with allocations of 1.4, 3, 5, 10, 15 and
20 MHz
Operation in FDD and TDD modes
Support for inter-working with WCDMA and non-3GPP
systems (i.e. WiMAX)
Good level of mobility: optimized for low mobile speeds (up to
15km/h) but support also high mobile speeds (up to 350km/h)
Improved terminal power efficiency
DIT
Drivers for LTE
◼
There are at least three major key drivers for
LTE mobile broadband networks:
❑ Demand for higher data-rates
◼ increasing device capabilities, growing
mobile data consumption
❑
New spectrum allocation
❑
Maintaining operator profitability while
continued cost reduction and competitiveness.
DIT
LTE and LTE Advanced Comparison
DIT
LTE Overview
◼
The multiple access schemes in LTE:
❑
❑
◼
LTE user transmissions can be divided in frequency and
time
❑
❑
❑
◼
Orthogonal Frequency Division Multiple Access
(OFDMA) in downlink
Single Carrier Frequency Division Multiple Access
(SC-FDMA) in uplink
Better orthogonality between users
Interference is less or can be cancelled more easily
Better network capacity can be achieved
The resource allocation in the frequency domain takes
place with a resolution of 180 kHz resource blocks both
in uplink and in downlink.
DIT
LTE Networks Architecture
DIT
Domains
◼
Three domains: UE, E-UTRAN and EPC form the socalled Internet Protocol (IP) Connectivity Layer. This part
of the system is also called as Evolved Packet System
(EPS).
❑
❑
◼
◼
◼
The main function of EPS is to provide IP based connectivity
All services will be offered on top of IP
The biggest architectural change is that EPC does not
contain a circuit switched domain.
Main functionalities of the EPC are equivalent to the
packet switched domain of the existing 3GPP networks.
As a logical element the SAE GW is a combination of
the two gateways, Serving Gateway (S-GW) and Packet
Data Network Gateway (P-GW)
DIT
Domains
◼
◼
◼
◼
◼
◼
Since interfaces between S-GW and P-GW are defined in
standards, it is possible that S-GW and P-GW are
implemented either separately or together.
E-UTRAN contains only one element type: Evolved Node B
(eNodeB).
All radio functionalities are controlled by eNodeB. All radio
related protocols are terminated in eNodeB.
E-UTRAN network is just a mesh of eNodeBs connected to
neighbouring eNodeBs through the X2 interface.
Functionally eNodeB acts as a layer 2 bridge between UE
and the EPC, by being the termination point of all the radio
protocols towards the UE.
From functionality point of view the UE is similar like in 3G.
DIT
UE and eNodeB
◼
UE
❑
❑
◼
Access device for user.
Provides measurements that indicate channel conditions to the
network.
eNode B performs
❑
❑
❑
❑
❑
❑
Ciphering/deciphering of the User Plane data
Radio Resource Management (resource allocation, prioritizing,
scheduling, resource usage monitoring
eNodeB is also involved with Mobility Management (MM)
The eNodeB controls and analyses radio signal measurements
carried out by the UE.
eNodeB makes signal measurements itself
Based on measurement information eNodeB makes decisions to
handover UEs between cells.
DIT
Mobility Management Entity (MME)
MME is the main control element in the EPC. It is
typically a server in a secure location in the operator’s
premises.
◼ MME operates only in the control plane and is not
involved with the user plane data.
◼ MME also has a direct logical control plane connection
to the UE. Connection is a primary control channel
between the UE and the network.
Main functions of MME:
◼ Authentication and Security
◼ Mobility Management
◼ Managing Subscription Profile and Service Connectivity
◼
DIT
Serving Gateway (S-GW)
◼
S-GW takes care of user plane tunnel
management and switching, and relays data
between eNodeB and P-GW.
◼
The S-GW has a small role in control functions.
◼
When bearers for UEs are set up, cleared or
modified the S-GW allocates its resources
based on requests from MME, P-GW or PCRF.
DIT
Packet Data Network Gateway (P-GW)
◼
◼
◼
◼
P-GW is the edge router between the EPS and external
packet data networks.
P-GW is the highest level mobility anchor in the system,
and usually it acts as the IP point of attachment for the UE.
❑ Thus, typically the P-GW allocates the IP address to the
UE, and the UE uses that to communicate with other IP
hosts in external networks, e.g. the internet.
❑ During mobility between eNodeBs, the S-GW acts as the
local mobility anchor. The MME commands the S-GW to
switch the tunnel from one eNodeB to another.
P-GW performs traffic gating and filtering functions as
required by the service in question.
Both S-GW and P-GW are part of the network infrastructure
maintained centrally in operator premises.
DIT
Policy and Charging Resource Function
(PCRF), Home Subscription Server (HSS)
PCRF is the network element that is responsible for Policy and
Charging Control (PCC).
◼ HSS is the data repository for all permanent subscription data.
Hence, HSS has the master copy of the subscriber profile
Main interfaces
◼ X2 interface: This interface is used in mobility between the
eNodeBs, and it includes functions for handover preparation, and
overall maintenance of the relation between neighbouring
eNodeBs.
◼ S1-MME interface: Reference point for the control plane protocol
between E-UTRAN and MME.
◼ S1-U interface: Reference point between E-UTRAN and Serving
GW for the user plane tunnelling and inter eNodeB path switching
during handover.
◼
DIT
Existing and Future 3GPP Bands
DIT
UE Categories and Capabilities
Maximum Throughput
UE category
Support for 64QAM in
Uplink
Downlink
Uplink
1
10.3 Mbit/s
5.2 Mbit/s
No
2
51.0 Mbit/s
25.5 Mbit/s
No
3
102.0 Mbit/s
51.0 Mbit/s
No
4
150.8 Mbit/s
51.0 Mbit/s
No
5
300.0 Mbit/s
75.4 Mbit/s
Yes
6
301.5 Mbit/s
51.0 Mbit/s
No
7
301.5 Mbit/s
102.0 Mbit/s
No
8
300.0 Mbit/s
149.8 Mbit/s
Yes
9
452.3 Mbit/s
51.0 Mbit/s
No
10
452.3 Mbit/s
102.2 Mbit/s
No
DIT
OFDMA
◼
◼
◼
◼
◼
◼
◼
OFDMA is an extension of the OFDM transmission scheme
by allowing multiple users.
That is, allowing for simultaneous frequency-separated
transmissions to / from multiple mobile terminals.
In OFDM the user data is transmitted in parallel across
multiple orthogonal narrowband subcarriers.
Each subcarrier only transports a part of the whole
transmission.
The orthogonal subcarriers are generated with IFFT
(Inverse Fast Fourier Transform) processing.
The number of subcarriers depends on the available
bandwidth.
In LTE, they range from less than one hundred to more
than one thousand.
DIT
Cyclic Prefix (CP) Principle
◼
◼
◼
◼
Cyclic prefixes are used by OFDM systems to fight against
the Inter Symbol Interference (ISI) due to multipath
environments.
CP consists of a copy of the last part of a symbol shape for
the duration of a guard time and adding it to the beginning
of the symbol.
This guard time needs to be long enough to capture all the
delayed multipath signals and avoid ISI at the receiver.
LTE’s typical symbol duration including the CP is around
71.64 µsec.
DIT
Types of Cyclic Prefix for LTE
There are two cyclic prefix options for LTE:
◼ Normal cyclic prefix: For use in small cells or cells with
short multipath delay spread.
◼ Its length depends on the symbol position within the slot
being 5.21 µsec for the CP in symbol 0 and 4.6 µsec for
the rest of symbols.
◼ The reason for these two different lengths is so that the slot
duration is 0.5ms, facilitating at the same time, that the
terminal finds the starting point of the slot.
◼ Extended cyclic prefix: For user with large cells or those
with long delay profiles.
◼ Its length is 16.67µs and it is constant for all symbols in the
slot.
DIT
OFDMA Benefits and Drawbacks
Benefits
Drawbacks
◼ High spectral efficiency for
◼ Some OFDM Systems can
wideband channels
suffer from high PAPR
◼ OFDM is almost completely
(Peak Average Power
resistant to multi-path
Ratio)
interference due to its very
◼ Loss of orthogonality due
long symbol duration
to frequency errors
◼ Flexible spectrum
◼ Doppler shifts impacts
utilization
subcarrier orthogonaliy
◼ Relative simple
due to ISI
implementation using
◼ Accurate frequency and
FFT/IFFT
time synchronization
◼ Easy MIMO techniques
implementation
DIT
OFDMA Parameters
DIT
LTE Frame Structures
◼
◼
◼
◼
◼
◼
◼
◼
Ts is the basic time unit for LTE.
Ts = 1/(15000 x 2048) seconds or about 32.6 ns.
Downlink and uplink transmissions are organized into frames of
duration Tf = 307200 Ts.
The 10 ms frames divide into 10 subframes.
Each subframe divides into 2 slots of 0.5 ms.
Two frame types are defined for LTE: Type 1, used in
Frequency Division Duplexing (FDD) and Type 2, used in Time
Division Duplexing (TDD).
Type 1 frames consist of 20 slots with slot duration of 0.5 ms.
Type 2 frames contain two half frames. Depending on the
switch period, at least one of the half frames contains a special
subframe carrying three fields of switch information: Downlink
Pilot Time Slot (DwPTS), Guard Period (GP) and Uplink Pilot
Time Slot (UpPTS).
DIT
Frame Type 1 (FDD)
DIT
Frame Type 2 (TDD)
DIT
Uplink-downlink Configurations for the
LTE TDD Mode
D is Downlink subframe, U is Uplink subframe, and S is special
subframe
DIT
The Resource Block
◼
◼
◼
◼
◼
◼
Mapping of channels takes place in the time and
frequency domains in LTE.
The primary element that support the mapping
process is the Resource Block (RB).
The RB has a fixed size and is common to all
channel bandwidths/FFT sizes.
In the time domain the RB is one slot ( 7 x 66.67µS
symbols).
In the frequency domain there are 12 x 15KHz subcarriers.
1 symbol and 1 sub-carrier is known as a resource
element.
DIT
Defining a Resource Block
DIT
Theoretical Data Rates
◼
◼
◼
◼
LTE does not officially meet the 4G requirements issued by
ITU in the definition for IMT-Advanced.
The data rates available in LTE (up to 300 Mbps) are
substantially higher than previous generations of cellular
standards.
It is worth noting that the maximum theoretical data rates of
LTE Advanced (up to 3.08 Gbps) are compliant with the
‘4G’ definition of the IMT-Advanced requirements.
Throughput of digital wireless communications channels is
defined by several factors, including:
symbol period utilization, symbol rate, modulation scheme,
code rate, number of resource blocks, and number of
spatial streams.
DIT
Throughput Calculation for LTE SISO Link
Throughput = Data Subcarriers X Slots per second X
Symbols per Slot X Bits per Symbol X Code
Rate X Spatial Streams
◼ With LTE, the maximum throughput in a 1x1 SISO channel
occurs when the eNodeB allocates all resource blocks
(1200 subcarriers) for a 20 MHz signal bandwidth using the
64-QAM modulation scheme. In this case, the estimated
theoretical throughput is 76.9 Mbps.
Throughput = 1200 data subcarriers X 2000 slots X 7 symbols
X 6 bits X (4/5) code rate x 1 spatial stream
= 76.9 Mbps
DIT
Maximum Downlink Capacity per
Radio Channel
DIT
Maximum Uplink Capacity per
Radio Channel
DIT
LTE Logical Channels
◼
Logical Control Channels
❑
❑
❑
❑
❑
◼
Broadcast Control Channel (BCCH)
Paging Control Channel (PCCH)
Common Control Channel (CCCH)
Multicast Control Channel (MCCH)
Dedicated Control Channel (DCCH)
Logical Traffic Channels
❑
❑
Dedicated Traffic Channel (DTCH)
Multicast Traffic Channel (MTCH)
DIT
LTE Transport Channel
◼
Downlink Transport Channel
❑
❑
❑
❑
◼
Broadcast Channel (BCH)
Downlink Shared Channel (DL-SCH)
Paging Channel (PCH)
Multicast Channel (MCH)
Uplink Transport Channels
❑
❑
Uplink Shared Channel (UL-SCH)
Random Access Channel (RACH)
DIT
LTE Physical Channel
◼
Downlink Physical Channel
❑
❑
❑
❑
❑
❑
❑
◼
Physical Broadcast Channel (PBCH)
Physical Control Format Indicator Channel (PCFICH)
Physical Downlink Control Channel (PDCCH)
Physical Hybrid ARQ Indicator Channel (PHICH)
Physical Downlink Shared Channel (PDSCH)
Physical Multicast Channel (PMCH)
Multicast Channel (MCH)
Uplink Physical Channel
❑
❑
❑
Physical Uplink Control Channel (PUCCH)
Physical Uplink Shared Channel (PUSCH)
Physical Random Access Channel (PRACH)
DIT
Channel Mapping
DIT
LTE Advanced
DIT
3GPP Evolution: Toward LTE Advanced
DIT
What is 4G?
◼
◼
◼
◼
◼
International Mobile Telecommunication (IMT) Advanced
Requirements in ITU M.2134-2008
IP based packet switch network
1.0 Gbps peak rate for fixed services with 100 MHz
100 Mbps for mobile services. High mobility to 500 km/hr
Feature
DL Spectral Efficiency (bps/Hz)
UL Spectral Efficiency (bps/Hz)
◼
◼
◼
Cell
2.2
1.4
Cell Edge
0.06
0.03
Peak
15
6.75
Seamless connectivity and global roaming with smooth handovers
High-Quality Multimedia
ITU has approved two technologies as 4G (Oct 2010)
➢ LTE-Advanced
➢ WiMAX Release 2 (IEEE 802.16m-2011)
DIT
Why LTE-Advanced
DIT
LTE - Advanced Requirements
◼
◼
◼
◼
◼
◼
◼
◼
◼
UMTS Rel. 10, 2011H1
Goal: To meet and exceed IMT-advanced requirements
Data Rate: 3 Gbps downlink, 1.500 Mbps uplink (low mobility) using
100 MHz
Spectral Efficiency: 30 bps/Hz using 8x8 MIMO downlink, 15 bps/Hz
assuming 4x4 MIMO uplink
Cell Spectral Efficiency: DL 3.7 bps/Hz/cell assuming 4x4 MIMO, 2.4
bps/Hz/cell assuming 2x2 MIMO (IMT-Adv requires 2.6 bps/Hz/cell)
Downlink Cell-Edge Spectral Efficiency: 0.12 bps/Hz/User assuming
4x4 MIMO, 0.07 bps/Hz/user assuming 2x2 MIMO (IMT-Adv requires
0.075 bps/Hz/user)
Latency: Less than 10 ms from dormant to active; Less than 50 ms from
camped to active
Mobility: up to 500 kmph
Spectrum Flexibility: FDD and TDD, Wider channels up to 100 MHz
DIT
LTE-Advanced Target
DIT
Key Features of LTE-Advanced
DIT
Throughput Calculation for LTE Advanced
8x8 MIMO Link
For MIMO schemes, the addition of carrier aggregation
increases the theoretical data rates of LTE Advanced
further.
◼ 20 MHz channel bandwidth allows for 1,200 data
subcarriers, the use of five aggregated carriers would
increase the number of data subcarriers to 6,000. the
maximum data rate can be calculated as follows:
Throughput = 6000 data subcarriers X 2000 slots X 7 symbols
X 6 bits X (4/5) code rate x 8 spatial streams
= 3.08 Gbps
LTE Advanced is the first commercial wireless standard that
exceeds the IMT-Advanced requirements for 4G cellular
systems.
◼
DIT
LTE Advanced Pro (4.5G)
DIT
LTE Advanced Pro
DIT
Release 13 Features
1. Active Antenna Systems (AAS)
2. Self-Organizing Networks (SON)
3. Elevation Beamforming
4. Inter-eNB CoMP
5. Indoor Positioning
6. Carrier Aggregation Enhancements
7. License Assisted Access (LAA)
8. LTE-WLAN Aggregation Enhancements
9. Wi-Fi with IP Flow Mobility
10. RAN Sharing
11. Enhanced D2D Proximity Services (PROSE)
12. Dual Connectivity Enhancements
13. MTC Enhancements
14. Single-Cell Point-to-Multipoint (SC-PTM)
DIT
Release 14 Features
1. Enhance Narrowband IoT (eNB-IoT)
2. Enhanced Machine Type Communications (eMTC)
3. Enhanced LWIP (eLWIP)
4. Enhanced LTE-WLAN Aggregation (eLWA)
5. Enhanced License Assisted Access (eLAA)
6. Enhanced Full-Dimension (eFD) MIMO
7. Enhanced Multimedia Broadcast Multicast Service
(eMBMS)
8. Multiuser Superposition Transmission (MUST)
9. Layer 2 (L2) Latency Reduction
10. Vehicle to Vehicle (V2X) Based on Sidelink
11. Uplink (UL) Capacity Enhancements
12. Light Connection
DIT
3GPP Releases
◼
Rel. 8-9: LTE
◼
Rel. 10-12: LTE-Advanced (4G)
◼
Rel. 13-14: LTE Advanced-Pro (4.5G)
◼
Rel. 15-16: LTE NR (5G)
DIT
5G Network
DIT
IMT2020
◼
In the World Radio Communication Conference
2015 hold in Geneva, Switzerland, ITU-R officially
approved three resolutions to facilitate the future
5G research process and formally determined the
name of 5G is "IMT-2020“.
◼
With the launch and implementation of the ITU5G
plan, China has accelerated its pace of 5G network
development. Under the leadership of the
government, China's 5G technology R&D test is
under the control of the IMT-2020 (5G) promotion
team and is being actively implemented.
Challenges in the 5G Era
Ultra high throughput
Ultra-large connection
Ultra-low latency
IMT2020 Vision by ITU
10Gbit/s
eMBB
(1000X traffic)
eMBB
(Enhanced MBB)
VR
VR is going to be the next
social platform
—Zuckerberg keynotes
uRLLC
mMTC
uRLLC
(Massive Machine Type
Communication)
(Ultra-Reliable LowLatency Communication)
1 million connections
per square km
1ms
Source: ITU R. M.[ IMT.VISION]
Interconnect Key
Industries
Intelligent
Manufacturing
Connected car
AI
Cloud-based AI access
requires 1Gbit/s speed
mMTC
Y2025: One Thousand Billion
Connections
Ten Billion
Population
Ninety Billion
Things
Large-Scale IoT Connections
Shared Bicycle
IoT Builds a Better
Connected Society
Smart City
Smart Meter
Smart Parking
Low Latency Requirement of
Automated Driving
System Delay
Increased Brake Distance
Driving Speed: 120km/h
Automatic driving requires
extremely low delay due to
safety reason.
Key KPIs of 5G Network
➢4G cannot fulfill the requirements of the future applications
5G Starts from 3GPP Release 15
5G includes:
• New Radio
• LTE Advanced Pro Evolution
• NextGen Core Network
• EPC Evolution
5G Networking Mode
◼
◼
Phase1.1 launches the 5G non-standalone networking architecture
(NSA, NR+EPC) and uses the MSA technology to implement
collaboration between the two modes.
Phase1.2 launched the 5G independent network architecture (SA,
NR+NGC).
EPC
EPC
S1
LTE
S1
LTE
5G NR
NG CORE
NG-C
5G NR
Control plane
Control plane
User plane
User plane
NSA
NG-U
SA
5G Networking Mode
1. Supports new services such as uRLLC.
2. Decouple from the existing 4G network.
3. The protocol is frozen by the end of 2017, so 5G
can be deployed earlier.
4. The agreement is frozen in 2018.
5. Continuous coverage is required for 5G base
stations.
6. Less investment at the early stage of 5G
deployment.
7. Required to deploy NGC and the deployment
period is long.
5G Will Aggregate All Frequency Bands
Important Highlights on 5G
SA Networking
⚫
5G network consists of the
following components:
NGC
AMF/UPF

AMF/UPF
RAN)
NG-C/U
Core network: NGC (Next
Generation Core)
⚫
NG-
C/U
NG-
NG-C/U
C/U

Xn
Wireless network: NR (New
5G wireless network interfaces
include:
NG-RAN
gNB
gNB
Xn

NG-C (control panel)

NG-U (user plane)

Uu (radio air interface)
Xn
Xn

gNB
NGC Vs EPC
EPC NE function
MME
PDN-GW
Mobility management
Corresponding NGC
NF
AMF
User authentication
AUSF
Session management
SMF
Session management
User plane data forwarding
UPF
SGW
User plane data forwarding
PCRF
QoS policy and charging rules
PCF
HSS
User profile database
UDM
Main Network Functions of the NGC
AMF:
End node of the uplink NAS signaling;
NAS signaling security;
AS security control;
3GPP signaling node for intra-system interoperation;
UE reachability management in idle mode;
UE location management;
UE access authentication;
SMF:
Session management;
UE IP address allocation;
User plane function selection and control;
Service UPF control;
QoS and policy execution;
Downlink data arrival notification;
5G Layer 3 Backhaul to Network Edge- Flexible
Connection
Wireless Cloud RAN Evolution
New Air Interface Technology
High-level adjustment
Large
bandwidth
Massive MIMO
New
Air Interface
Mobile
Internet
Uplink and downlink
decoupling
Flexible frame structure
IoT
Polar/LDPC Code
F-OFDM
The new air interface can flexibly adapt to various
services, supporting higher rate and higher spectral
efficiency
HCIP-R&S-IERS
DIT