2. Content Coverage
5G Introduction
• What is 5G?
• Why do we need
5G?
• Usage of 5G?
• NR
Frequency
Ranges
• Comparison of
LTE and NR
• NR operations
5G
Architectur
e overview
• 5G System
Architectur
e
• 5G Architecture
KPI
• 5G Protocol Stack
5G/NR RRC
Overview
• RRC Overview
• RRC Functions
• NR RRC States
• Need for
RRC_Inacti
ve State?
• How will
RRC_Inactive
state work?
• NR RRC
Interaction with
LTE RRC
• NR RRC with
UTRAN /
GERAN RRC
NR NSA
(Non-
Standalone)
• NSA ENDC
• NSA Option 3a
• NSA Option 3x
• EN-DC
Protocol
Architecture
• EN-DC
Network
Interfaces
• ENDC SN Addition
Procedure
NR SA
(Standalone)
• 5G/NR SA
• NR SA
Initial
Access
Registratio
n
• Voice over 5G
• SMS in NR
3. What is 5G?
• 5G is the fifth generation technology standard for cellular networks
• 5G is also known as NR stands for New Radio
• New network will have greater bandwidth, giving faster download
speeds, eventually up to 10 gigabits per second (Gbps).
• 5G will use mmWave for high bandwidth signal.
• 5G will have two versions, namely, SA (Standalone 5G) and NSA
(non- standalone 5G)
• 5G standard are also known as IMT-2020 Standard as raised by
the ITU- R (International Telecommunication Union -
Radiocommunication Sector)
4. Why do we need 5G?
• Mobile data traffic is rising rapidly, mostly due to
video streaming.
• With multiple devices, each user has a growing
number of connections.
• Internet of Things will require networks that
must handle billions more devices.
• With a growing number of mobiles and increased
data traffic both mobiles and networks need to
increase energy efficiency.
• Network operators are under pressure to reduce
operational expenditure, as users get used to
flat rate tariffs and don't wish to pay more.
• The mobile communication technology can
enable new use cases (e.g. for ultra-low latency
or high reliability cases) and new applications
for the industry, opening up new revenue
streams also for operators.
5. Usage of 5G?
ITU-R has defined the following main usage
scenarios for IMT for 2020
• Enhanced Mobile Broadband (eMBB)
to deal with hugely increased data
rates, high user density and very high
traffic capacity for hotspot scenarios as
well as seamless coverage and high
mobility scenarios with still improved
used data rates
• Massive Machine-type
Communications (mMTC) for the IoT,
requiring low power consumption and
low data rates for very large numbers of
connected devices
and Low
Latency
(URLLC)to cater for
and mission
critical
• Ultra-reliable
Communicatio
ns safety-
critical
applications
6. NR Frequency Ranges
In NR, there are roughly two large frequency range specified in 3GPP. One is sub 6 Ghz called as FR1
and the other is millimeter wave called FR2.
• FR1 extends 4G LTE, from 450 MHz to 6,000 MHz. These bands are specified from 1 to 255.
• FR2 is at a much higher frequency 24,250 MHz (~24GHz) to 52,600 MHz (~52GHz). These bands
are
specified from 257 to 511.
The frequency bands in FR1 utilize many of the same frequency bands as those used for 4GMid-band
spectrum. They can provides faster speeds and lower latency than LTE bands. Expect peak speeds
up to 1Gbps on FR1- band spectrum. FR1 sub-6GHz bands are extremely effective in providing
coverage and have capacity for a wide range of 5G use cases. That means faster, more uniform data
rates both indoors and outdoors for more customers, simultaneously. Another reason to use sub-6GHz
over mmWave is that, this band can travel farther and penetrate solid objects like buildings better than a
higher frequency spectrum such as mmWave.
7. NR Frequency Ranges
FR2 is what delivers the highest performance for 5G, but with major weaknesses. FR2 spectrum can
offer peak speeds up to 10Gbps and has extremely low latency. The main drawback of high-band is
that it has low coverage area and building penetration is poor. That means that to create an effective
high-band network, you’ll need a ton of cells. mmWave have a coverage area about 1 mile (1.6 km).
Although massive MIMO and beam forming ensure that strict line of sight is not a requirement to make
use of millimeter wave. A mmWave signal may not be able to penetrate buildings, but it will bounce
around them to ensure a decent signal. Also mmWave signal strength will degrade somewhat when it
rains, as water drops blocks the high frequency waves.
9. Comparison of LTE and NR
Speed: 4G LTE Advanced provides up to 1Gbps
performance, 5G NR can provide a potential 1-40Gbps
as well.
Latency: 5G can offer a much lower latency than 4G.
Technologies: 4G has grown to accommodate many
different technologies: for example, LWA(LTE-WLAN).
5G scope is designed to be broad and applicable not
just for high- performance devices, but also down to
ultra-low power, long-life and always connected IoT
devices too.
Machine Type Communications: 5G meet the different
requirements of MTC required by IoT applications.
Whereas IoT in the 4G era is a mix of adapted 2G and
4G technologies. 5G services are better equipped to
handle these.
Architecture: Unlike 4G, 5G technologies are designed
to take advantage of cloud-based or virtual Radio
Access Networks.
Device Intelligence: Unlike 4G, 5G has the capability to
differentiate between fixed and mobile devices. It uses
10. NR operations
According to the 3GPP Release 15 standard that covers 5G networking, the first wave of networks and
devices will be classed as Non-Standalone (NSA), i.e., 5G networks will be supported by existing 4G
infrastructure. Here, 5G-enabled smartphones will connect to 5G frequencies for data-throughput
improvements but will still use 4G for non-data duties such as talking to the cell towers and servers.
The initial roll-out of 5G cellular infrastructure will focus on enhanced mobile broadband (eMBB) to
provide increased data-bandwidth and connection reliability via two new radio frequency ranges FR1
and FR2.
The 5G Standalone (SA) network and device standard is still under review and is expected to be signed-
off by 3GPP by 2020. The advantage of Standalone is simplification and improved efficiency, which will
lower cost, and steadily improve performance in throughput up to the edge of the network, while also
assisting development of new cellular use cases such as ultra-reliable low latency communications
(URLLC).
12. 5G System Architecture
AMF - The Access and Mobility Management function (AMF) includes the following
functionality.
o NAS ciphering and integrity protection.
o Registration management.
o Connection management.
o Reachability management.
o Mobility Management.
o Access Authentication & Access Authorization.
o Provide transport for SMS messages between UE and SMSF.
o Location Services management for regulatory services.
o EPS Bearer ID allocation for interworking with EPS.
SMF - The Session Management function (SMF) includes the following functionality.
o Session Management.
o UE IP address allocation & management.
o DHCPv4 (server and client) and DHCPv6 (server and client) functions.
o Configures traffic steering at UPF to route traffic to proper destination.
o Termination of interfaces towards Policy control functions.
o Control and coordination of charging data collection at UPF.
o Roaming functionality:
13. 5G System Architecture
UPF - The User plane function (UPF) includes the following functionality.
o Anchor point for Intra-/Inter-RAT mobility.
o External PDU Session point of interconnect to Data Network.
o Packet routing & forwarding.
o Packet inspection.
o QoS handling for user plane.
o Functionality to respond to Address Resolution Protocol (ARP) requests.
PCF - The Policy Control Function (PCF) includes the following functionality:
o Supports unified policy framework to govern network behavior.
o Accesses subscription information relevant for policy decisions in a Unified Data Repository (UDR).
NEF - The Network Exposure Function (NEF) supports the following independent functionality:
o Exposure of capabilities and events.
o Secure provision of information from external application to 3GPP network.
o Translation of internal-external information.
o Receives information from other network functions and store the received information as structured
data to a Unified Data Repository (UDR).
AF - The Application Function (AF) interacts with the 3GPP Core Network in order to provide services.
14. 5G System Architecture
UDM - The Unified Data Management (UDM) includes support for the following functionality:
o Generation of 3GPP AKA Authentication Credentials.
o User Identification Handling.
o Access authorization based on subscription data (e.g. roaming restrictions).
o Support to service/session continuity e.g. by keeping SMF/DNN assignment of ongoing sessions.
o Subscription management.
o SMS management.
AUSF - The Authentication Server Function (AUSF) supports authentication for 3GPP access and
untrusted
non-3GPP access.
UDR - The Unified Data Repository (UDR) supports the functionality of storage and retrieval of
subscription data by the UDM and policy data by the PCF.
NSSF - The Network Slice Selection Function (NSSF) supports the following functionality:
o Selecting the set of Network Slice instances serving the UE.
o Determining the AMF Set to be used to serve the UE.
CHF – SMF uses the Charging Function (CHF) to manage the charging for a PDU Session. SMSF
uses CHF to
15. 5G Architecture KPI
5G network architecture is much more service oriented than previous generations. Some Key
introduction in 5G architecture are as below:
Network Slicing
Perhaps the key ingredient enabling the full potential of 5G architecture is network slicing. A network
slice is an independent end-to-end logical network that runs on a shared physical infrastructure,
capable of providing a negotiated service quality. A network slice could span across multiple parts of the
network. A network slice comprises dedicated and/or shared resources, e.g. in terms of processing
power, storage, and bandwidth and has isolation from the other network slices. Operators can
effectively manage diverse 5G use cases with differing throughput, latency and availability demands by
partitioning network resources to multiple users or “tenants”.
Network slicing becomes extremely useful for
applications like the IoT where the number of
users may be extremely high, but the overall
bandwidth demand is low. Each 5G vertical will
have its own
requirements. Costs, resource management and
flexibility of network configurations can all be
optimized with this level of customization.
16. 5G Architecture KPI
Beamforming
Another breakthrough technology integral to the success of 5G is beamforming. Conventional base
stations have transmitted signals in multiple directions without regard to the position of targeted users or
devices. Through the use of multiple-input, multiple-output (MIMO) arrays featuring dozens of small
antennas combined in a single formation, signal processing algorithms can be used to determine the
most efficient transmission path to each user while individual packets can be sent in multiple directions
then choreographed to reach the end user in a predetermined sequence.
With 5G data transmission occupying the millimeter wave, free space
propagation loss, proportional to the smaller antenna size, and diffraction
loss, inherent to higher frequencies and lack of wall penetration, are
significantly greater. On the other hand, the smaller antenna size also
enables much larger arrays to occupy the same physical space. With
each of these smaller antennas potentially reassigning beam direction
several times per millisecond, massive beamforming to support the
challenges of 5G bandwidth becomes more feasible. With a larger
antenna density in the same physical space, narrower beams can be
achieved with massive MIMO, thereby providing a means to achieve high
throughput with more effective user tracking.
19. 5G Protocol Stack
Physical Layer (PHY)
• On PDSCH and PUSCH, i.e. downlink and uplink shared channels , PHY layer performs all the
actions required to turn the transport block generated by the MAC layer into a physical signal on the
air interface, i.e.
o CRC attachment to transport block or code blocks
o Segmentation of transport block into code blocks
o Channel coding
o Processing of HARQ
o Rate matching and scrambling
o Mapping to assigned resources and antenna ports
o Signal modulation and waveform generation
• PDCCH and PUCCH, i.e. downlink and uplink control channels can be used to
o Schedule transmission in uplink and downlink
o Notify the UE about the utilized slot format
o Provide power control commands
o Perform RACH procedure
o Generate reference signal used for layer1 and layer3 measurement
o Send scheduling request to gNB
20. 5G Protocol Stack
Medium Access Control (MAC)
• Maps logical channel onto transport channels
• Multiplexes and DE multiplexes MAC SDUs into transport blocks
• Is used for scheduling information reporting
• Performs error correction using HARQ
• Handles priority between different types of data
• Adds padding bits
Radio Link Control (RLC)
RLC sub layer supports three transmission modes: Transport Mode (TM), Unacknowledged mode (UM),
and Acknowledged mode (AM). Services and functions of RLC depend on the utilized transmission
mode :
• Sequence numbering independent of the one in PDCP
• Error Correction through ARQ
• Segmentation and re-segmentation
• Segmentation and re-segmentation of RLC SDUs
• Reassembly of SDU from segments
• RLC SDU discard
• RLC re-establishment
21. 5G Protocol Stack
Packet Data Convergence Protocol (PDCP)
Functions of PDCP sub-layer depend mainly on whether the processed data unit belongs to control
plane or user plane:
• Sequence numbering of PDCP PDUs (both UP and CP)
• Header compression and decompression using ROHC only (UP only)
• Reordering and Duplicate detection (both UP and CP)
• In-order delivery of PDCP SDUs to higher layers (both UP and CP)
• Retransmission of PDCP SDUs (UP only)
• Ciphering and Deciphering (both UP and CP)
• PDCP SDU discard (UP only)
• PDCP re-establishment and data recovery for RLC AM (UP only)
• Duplication of PDCP PDUs to enhance reliability of transmission
Service Data Adaptation Protocol (SDAP)
Only protocol not present in LTE and applied when base station is connected to 5GC. Main functions are
• Mapping between a QoS flow and a data radio bearer
• Marking QoS flow ID (QFI) in both DL and UL packets
22. 5G Protocol Stack
Radio Resource Control (RRC)
• Broadcast of System Information
• Controlling UE access to network
• Paging of the UE based on request from 5GC
• Management of RRC connection between UE and NG-RAN
• Security functions
• Management of SRBs and DRBs
• Mobility functions for UE
• Measurement reporting of UE
Non Access Stratum (NAS)
Its termination points are UE on one side and AMF on the other. Used to provide core network control :
• Managing mobility of UE including procedures for authentication and identification
• Session management for establishment and maintenance of data connectivity
• NAS transport procedure for support of transport messages related to applications such as, SMS,
LPP, 5G system session management
23. RRC Overview
RRC stands for Radio Resource Control. As UE and Network is communicating via radio channel,
RRC is the common language understood by both network and UE. RRC is the control mechanism
used by parties to reach agreement on common configurations.
Another central role of RRC within each communicating party is to work as a control center for all of
the lower layers within each system. The collection of all the lower layers within UE or base station is
called 'Radio Resource'. The major role of RRC is to control (configure) all the Radio Resources (PHY,
MAC, RLC, PDCP) to make it possible to communicate between UE and the base station.
Services provided to upper layers by RRC
• Broadcast of common control information;
• Notification of UEs in RRC_IDLE, e.g. about a mobile terminating call;
• Notification of UEs about ETWS and/or CMAS
• Transfer of dedicated signaling.
Services expected from lower layers
• Integrity protection, ciphering and loss-less in-sequence delivery of information without duplication;
24. RRC Functions
• Broadcast of system information
• RRC connection control:
Paging;
Establishment/modification/suspension/resumption/release of RRC connection;
Access barring;
Initial AS security activation;
RRC connection mobility, associated AS security handling, specification of RRC context
information;
Establishment/modification/suspension/resumption/release of RBs carrying user data (DRBs);
Radio configuration control;
Cell management in case of DC and CA;
QoS control
Recovery from radio link failure.
• Inter-RAT mobility including e.g. AS security activation, transfer of RRC context information;
• Measurement configuration and reporting:
• Other functions including e.g. generic protocol error handling, transfer of dedicated NAS
information, transfer of UE radio access capability information.
25. NR RRC States
5G has three RRC states RRC CONNECTED, RRC IDLE
and RRC Inactive state. Unlike LTE, in NR there is a
addition RRC states between RRC Connected and Idle and
Network/UE can optionally stay in INACTIVE state without
completely releasing the RRC when there is no traffic and
quickly switch back to CONNECTED states when
necessary.
A UE is either in RRC_CONNECTED state or in
RRC_INACTIVE state when an RRC connection has
been established. If this is not the case, the UE is in
RRC_IDLE state.
When UE is power up it is in Disconnected mode/Idle mode,
It can move RRC connected with initial attach or with
connection establishment. If there is no activity from UE for
a short time, It can suspend its session by moving to RRC
Inactive and can resume its session moving to RRC
connected mode.
A UE can move to RRC Idle mode from RRC connected
26. NR RRC States
RRC_IDLE:
• A UE specific DRX may be configured by upper layers.
• UE controlled mobility based on network configuration;
• The UE:
a. Monitors Short Messages transmitted with P-RNTI over DCI;
b. Monitors a Paging channel for CN paging using 5G-S-TMSI;
c. Performs neighboring cell measurements and cell (re-)selection;
d. Acquires system information and can send SI request.
RRC_INACTIVE:
• Performs all operations of RRC IDLE state;
• UE controlled mobility based on network configuration;
• The UE stores the UE Inactive AS context;
• A RAN-based notification area is configured by RRC layer;
• The UE:
a. Performs RAN-based notification area updates periodically and when moving outside the
configured RAN-based notification area;
b. All UE operations of RRC IDLE mode
27. NR RRC States
RRC_CONNECTED:
• The UE stores the AS context;
• Transfer of unicast data to/from UE;
• At lower layers, the UE may be configured with a UE specific DRX;
• For UEs supporting CA, use of one or more SCells, aggregated with the SpCell, for increased
bandwidth;
• For UEs supporting DC, use of one SCG, aggregated with the MCG, for increased bandwidth;
• Network controlled mobility within NR and to/from E-UTRA;
• The UE:
a. Monitors Short Messages transmitted with P-RNTI over DCI (see clause 6.5), if configured;
b. Monitors control channels associated with the shared data channel to determine if data is
scheduled for it;
c. Provides channel quality and feedback information;
d. Performs neighboring cell measurements and measurement reporting;
e. Acquires system information.
28. Need for RRC_Inactive State?
The idea behind this new state is to hide the radio connection state from the core network to reduce the
number of signaling and tunnel establishments and tear-downs between the radio network and the core
network.
The RRC Inactive State is a solution to the system access, power saving, and mobility optimization.
5G has to support eMBB, URLLC, and Massive IoT services at same cost and energy dissipation per
day per area. To meet these different services characteristics it requires new RRC state model.
• To support URLLC services which transmits small packets that require ultra-low latency and/or
high
reliability
• Massive IoT Devices wakes up seldom power saving mode to transmit and receive a small payload.
• Devices need to camp in low activity state, and sporadically transmits UL data and/or status reports
with small payload to the network.
• Devices need periodic and/or sporadic DL small packet transmission.
• Smartphones and consumer devices which eMBB UE have periodic and/or sporadic UL and/or DL
small packet transmission and extreme data rates.
29. How will RRC_Inactive state work?
The idea behind this new state is to reduce the number of signaling and tunnel establishments. Even
when the screen is turned-off, background applications continue to exchange data with the Internet to
keep the TCP connections alive on a frequent basis. For this, LTE always requires a new tunnel setup
because the radio has been put into RRC_Idle state to conserve energy.
The 5G radio network can instruct a mobile device to go to RRC_Inactive state with an RRC Release
message that contains a ‘suspendConfig’. The radio link is then taken down to conserve energy but
the logical signaling link to the AMF in the core network and the user data tunnel to the UPF remain in
place. When new data arrives from the network side, the core network just forwards it to the gNB to
which the user data tunnel is connected to. The gNB then organizes a RAN-based paging on all
gNBs that are in same RAN notification area in which the mobile device is free to roam without
having to inform the network about its new location. If the mobile device responds to the RAN based
paging with an RRC Resume Request from a different gNB, the radio bearer and signaling context has
to be transferred to the other gNB, as well as the signaling link and user data tunnel.
In case the mobile device moves to a cell that is outside the configured RAN Notification Area (RNA) it
has to establish an RRC connection and send an RNA Update message. The gNB then contacts the
previous gNB and the user’s context is transferred to the new gNB. The RRC connection can then be
set to RRC_Inactive again and a new RAN notification area is configured in the mobile device in which
it can roam freely without notifying the network.
30. NR RRC Interaction with LTE RRC
• In CONNECTED mode, Handover can be performed between NR-cell to LTE-cell and LTE-cell
to NR-cell
• In IDLE state, NR can reselect to LTE and LTE can reselect to NR
• In RRC INACTIVE state, NR can reselect LTE but LTE can not reselect to NR RRC INACTIVE
state
31. NR RRC with UTRAN / GERAN RRC
• In IDLE state, NR can reselect to UMTS (UTRA) and UMTS (UTRA) can reselect to NR
• In NR INACTIVE state, NR can reselect the UMTS IDLE, but UMTS IDLE can not reselect the NR
INACTIVE state
• NR can reselect the GSM (GERAN) while it is in IDLE state
• GSM can do CCO (Cell Change Order) to NR while they are in IDLE state
32. NSA EN-DC
5G can be deployed in two different options, where SA
(standalone) consist of only one generation of radio access
technology and NSA (non-standalone) consist of two
generations of radio access technologies (4G LTE and 5G).
Multi-Radio Dual Connectivity (MR-DC) is a generalization of
the Intra-E-UTRA Dual Connectivity (DC), where a multiple
Rx/Tx capable UE may be configured to utilize resources
provided by two different nodes. One node acts as the MN
(Master Node) and the other as the SN (Secondary node). The
MN and SN are connected via a network interface and at least
the MN is connected to the core network.
E-UTRAN supports MR-DC via E-UTRA-NR Dual
Connectivity (EN-DC), in which UE is connected to one eNB
that acts as a MN and one en- gNB that acts as a SN. The eNB
is connected to the EPC via the S1 interface and to the en-gNB
via the X2 interface. The en-gNB might also be connected to the
EPC via the S1-U interface. UE is communicating with both eNB
abd gNB but all those (signaling and data) are going through
LTE core network.
ENDC
Architecture
33. NSA EN-DC
For a successful deployment of EN-DC the 4G network needs to support dual connectivity between E-
UTRAN and NR. Typically the 4G radio will be used to carry control signalling while NR and/or LTE will
be used for user data.
The standardised NSA EPC networking architecture includes three variants of NSA,
• In the Option 3 networking mode, the X2 interface traffic between eNB and gNB has NSA user
plane traffic.
• In the Option 3a networking mode, there is only control plane traffic in the X2 interface.
• In the Option 3x networking mode, there is a little LTE user plane traffic in the X2 interface.
3x variant has low impact on EPC and enables data to route directly to the NR gNB to avoid
excessive user plane load on the existing LTE eNB. From the perspective of the impact on the existing
network, the Option 3x is relatively small and has become the mainstream choice for NSA networking.
36. EN-DC Protocol Architecture
Control
Plane
• RRC PDUs generated by the SN can be transported via the MN to the
UE. The MN always sends the initial SN RRC configuration via MCG
(Master cell group) SRB (SRB1), but subsequent reconfigurations may be
transported via MN or SN.
• In EN-DC, at initial connection establishment SRB1 uses E-UTRA PDCP.
After initial connection establishment, MCG SRBs (SRB1 and SRB2) can
be configured by the network to use either E-UTRA PDCP or NR PDCP.
• If the SN is a gNB, the UE can be configured to establish a SRB with the
SN (SRB3) to enable RRC PDUs for the SN to be sent directly between
the UE and the SN. Measurement reporting for mobility within the SN can
be done directly from the UE to the SN if SRB3 is configured.
• Split SRB is supported for all MR-DC options, allowing duplication of RRC
PDUs generated by the MN, via the direct path and via the SN. Split SRB
uses NR PDCP.
• In EN-DC, the SCG configuration is kept in the UE during suspension.
The UE releases the SCG configuration (but not the radio bearer
configuration) during resumption initiation.
SgNB
NR RRC
Uu
X2-C
S1
MeNB
RRC
Uu
UE
RRC
(MeNB
state)
37. EN-DC Protocol Architecture
User Plane
• In MR-DC, from a UE perspective, three
bearer types exist: MCG bearer, SCG
bearer and split bearer.
• In EN-DC, the network can configure
either E-UTRA PDCP or NR PDCP for
MN terminated MCG bearers while NR
PDCP is always used for all other
bearers.
• From a network perspective, each bearer
(MCG, SCG and split bearer) can be
terminated either in MN or in SN.
• In split bearer, NR PDCP is used both in
LTE Anchor and NR. Splitting of data
stream is done by PDCP.
38. EN-DC Network Interfaces
• In Control Plane in EN-DC, the MME is the core network entity
between the MN and the SN for control plane signalling and
coordination. For each UE, there is also one control plane
connection between the MN and a corresponding CN entity.
• The MN and the SN involved in EN-DC for a certain UE control
their radio resources and are primarily responsible for allocating
radio resources of their cells.
• S1-MME is terminated in MN and the MN and the SN are
interconnected via X2-C
• In User plane in EN-DC, SGW is the network interface for the
eNB and gNB.
• X2-U interface is the user plane interface between MN and SN,
and S1- U is the user plane interface between the MN, the SN or
both and the S-GW.
39. ENDC SN Addition Procedure
The Secondary Node Addition procedure is initiated by the MN and is used to establish a UE context at
the SN to
provide resources from the SN to the UE.
40. ENDC SN Addition Procedure
1. MN (Master Node : LTE eNB) send SgNB Addition Request to SN (Secondary Node : NR gNB).
LTE eNB forward following informations to NR gNB.
• E-RAB Characteristics (E-RAB Parameters, TNL address information)
• The requested SCG configuration information including the entire UE capabilities and UE
capability
coordination result
• The latest measurement result for SN to choose
• Securiy Information to enable SRB3
• In case of bearer option that requires X2-U between MN and SN, X2-U TNS address
information
• In case of SN terminated split bearers, the maximum supportable QoS level
1. (If SN decided to accept the request), it sends SgNB Addition Request Acknowledge performing
followings
• Allocate the necessary radio resources transport network resources
• decides Pscell and other SCG Scells and provide the new SCG radio resource configuration to
MN
• In case of bearer options that requires X2-U between MN and SN, provides X2-U TNS
address information
• In case of SCG radio resources being requested, provide SCG radio resource configuration
2. If NR gNB accept the SN addition request and provides all the necessary information to LTE eNB,
41. ENDC SN Addition Procedure
4. After UE received RRCConnectionReconfiguration, it checks if all the configurations in the message
is doable in UE side, it sends RRCConnectionReconfigurationComplete message. This message
includes NR RRC Response as well.
5. Once MN (LTE eNB) received RRCConnectionReconfigurationComplete from UE, the MN informs
SN(NR
gNB) that UE has completed the reconfiguration procedure by SgNB Reconfiguration Complete.
6. UE acquire all the information required for RACH procedure from RRC Connection Reconfiguration
message instead of SIB. If configured with bearers requiring SCG radio resources, the UE
performs synchronisation towards the PSCell of the SN.
7. If PDCP termination point is changed to the SN for bearers using RLC AM, and when RRC full
configuration
is not used, the MN sends the SN Status Transfer.
8. For SN terminated bearers moved from the MN, dependent on the bearer characteristics of the
respective E-RAB, the MN may take actions to minimize service interruption due to activation of
EN-DC (Data forwarding).
9. If applicable, the update of the UP path towards the EPC is performed.
42. 5G/NR SA
• NR SA (Standalone) option is the option with 5G core.
• In 5G SA Option 2, New Radio (NR) access network consisting of gNBs connected to 5G Core
(5GC).
• The user-plane and control-plane of SA Option 2 are using NR and are completely independent of
Long Term
Evolution (LTE).
Possible Evolution Path from NSA option 3 to SA
option 2
43. NR SA Initial Access Registration
U
E
gN
B
AM
F
SM
F
UP
F
AUS
F
PC
F
5G
C
Msg1 : Random Access
Preamble (PRACH)
Msg2 : Random Access
Response
Msg3 :
RRCSetupRequest
Msg3 :
RRCSetup
RRC_Connect
ed
Msg3 :
RRCSetupComplete
Initial UE Message
NAS-PDU : Registration
Request
NAS Identity
Request
NAS Identity
Response
44. NR SA Initial Access Registration
U
E
gN
B
AM
F
SM
F
UP
F
AUS
F
PC
F
5G
C
Nausf_UEAuthenticate_authenticate
Request
Nausf_UEAuthenticate_authenticate
Response
NAS Authentication
Request
NAS Authentication
Response
NAS Security Mode
Command
NAS Security Mode
Complete
Npcf_AMPolicyControl_Create
Request
Npcf_AMPolicyControl_Create
Response Nsmf_PDUSession_UpdateSMContext Request
PFCP Session Modification Request
45. NR SA Initial Access Registration
U
E
gN
B
AM
F
AUS
F
PC
F
5GC
SMF
UP
F
PFCP Session Modification
Response
Nsmf_PDUSession_UpdateSMContext
Response
Initial Context Setup
Request NAS-PDU :
Registration Accept
SecurityModeCommand
SecurityModeComplete
RRCReconfigurati
on [Registration
Accept]
RRCReconfigurationComp
lete]
NAS Registration Complete
Uplink Data
Downlink
Data
46. Voice over 5G
• 3GPP has specified that 5G uses the 4G voice/video communication
architecture and still provides voice/ video communication services
based on the IMS known as Voice over NR (VoNR).
• In VoNR, UEs camp on the NR network, and voice/video
communication and data services are carried on the NR network with
gNB.
• VoNR cannot represent all 5G voice/video communication solutions
implemented by the 5G core network (5GC). Vo5G is needed to
summarize all 5G voice/video communication solutions which includs
VoNR, VoeLTE, EPS FB, and RAT FB.
• The 5GC does not provide the CSFB solution to simplify the
network and
accelerate the exit of the CS voice.
• According to 3GPP, EVS and H.265 are mandatory codec for voice and
video communication services in Vo5G. EVS and H.265 require fewer
bandwidths to provide better user experience.
47. VoNR
• In initial stage, the NR network does not provide voice/video communication services. If the UE
camping on the 5G NR network makes a call, the voice/video communication and data services fall
back to the 4G network. The gNB sends a redirection or inter-RAT handover request to the 5GC.
Then, the UE handovers to the LTE network, and the VoLTE service is provided. This is knows as
EPS Fallback. The advantage of EPS FB is that the UE or gNB only needs to support the IMS
signaling channel.
• In VoeLTE, UEs camp on the eLTE network (5GC with evolved eNB), and voice/video
communication and data services are carried on the eLTE network.
• Similar to EPS FB, in this case, the gNB sends a redirection or inter-RAT handover request to the
5GC to fall
back to the eLTE network and use the VoeLTE service. This is known as RAT FB.
48. SMS in NR
• NR supports SMS over NAS and SMS over IP.
• Within 5G Core, SMS Function (SMSF)
supports
SMS over NAS (SMSoNAS).
• Besides, SMSoIP can also be considered as
IMS based SMS solution under 5G network.
SMSoIP can be deployed simultaneously with
voice service over IMS to provide both voice
and short message service.
• It is recommended to use SMSoNAS solution if
voice services over IMS is not supported or for
a 5G data card/Machine Type
Communications (MTC)/Non-IMS device
without voice service.
49. References
3GPP TS references
1. 3GPP TS 23.501, V15.9.0, System architecture for the 5G System (5GS);
2. 3GPP TS 37.340, V15.8.0, Evolved Universal Terrestrial Radio Access (E-UTRA) and NR; Multi-
connectivity;
3. 3GPP TS 38.101-1, V15.9.0, User Equipment (UE) radio transmission and reception; Part 1:
Range 1
Standalone
4. 3GPP TS 38.101-2, V15.9.1, User Equipment (UE) radio transmission and reception; Part 2: Range
2 Standalone
5. 3GPP TS 38.300, V15.9.0, NR; NR and NG-RAN Overall Description
6. 3GPP TS 38.331, V15.9.0, NR; Radio Resource Control (RRC) protocol specification
URL References
1. http://www.sharetechnote.com/
2. http://www.eventhelix.com/
3. http://www.techplayon.com/
4. https://www.gsma.com/futurenetworks/wiki/5g-
implementation-
guidelines/#eb7ab6a5ffdc39e6149fecbcf21794c1
5. https://www.huawei.com/en/industry-insights/technology/vo5g-technical-white-paper
