New Radio Access Technology in 3GPPstd-share.itri.org.tw/Content/Files/Event/Files/2. New...•Data flow aggregation across LTE eNB and NR gNB via EPC. 12 E P C LTE eNB NR gNB CP +

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New Radio Access Technology in 3GPP

陳宏鎮

工研院資通所

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Agenda

• Scenarios and Requirements for 5G-NR

• Deployments Scenarios for 5G-NR

• LTE-NR Tight Interworking

• NR Architecture Design

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Scenarios and Requirements for 5G-NR

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• TR 38.913 “Study on Scenarios and Requirements for Next Generation Access Technologies”

• A fully mobile and connected society is expected in the near future, which will be characterized by a tremendous amount of growth in connectivity, traffic volume and a much broader range of usage scenarios.

• The families of usage scenarios for IMT for 2020 and beyond include: • eMBB (enhanced Mobile Broadband) • mMTC (massive Machine Type Communications) • URLLC (Ultra-Reliable and Low Latency Communications)

• (RP-160671: Target a single technical framework addressing all usage scenarios, requirements and deployment scenarios defined in TR38.913)

• (TR 38.804: TR for Study on New Radio Access Technology Radio Interface Protocol Aspects)

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Reference: RWS-150055


Scenarios and Requirements for 5G-NR • Deployment Scenarios

• Indoor Spot: Focus on small coverage per site/TRP (transmission and reception point) and high user throughput or user density in buildings.

• Dense Urban: Focus on macro TRPs with or without micro TRPs and high user densities and traffic loads in city centres and dense urban areas.

• Rural: Focus on larger and continuous coverage (for high speed vehicles). • Urban Macro: Focus on large cells and continuous coverage. • High Speed: Focus on continuous coverage along track in high speed trains. • Extreme rural for the Provision of Minimal Services over long distances: Allow the Provision

of minimal services over long distances for Low ARPU and Low density areas including both humans and machines.

• Extreme rural with extreme Long Range: allow for the Provision of services for very large areas such as wilderness or areas where only highways are located primarily for humans.

• Urban coverage for massive connection: Focus on large cells and continuous coverage to provide mMTC.

• Highway Scenario: Focus on scenario of vehicles placed in highways with high speeds. • Urban Grid for Connected Car: Focus on scenario of highly densely deployed vehicles placed

in urban area.

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• KPI of NR • Control Plane Latency from a power efficient state to a data transmission state 10ms

• User Plane Latency 0.5ms for URLLC

• User Plane Latency 4ms for eMBB

• Latency for infrequent small packets 10s

• Mobility interruption time 0ms

• 15 years battery life with a sparse small packet traffic model

• Mobility in the range from 0km/h to 500km/h

• The RAN system shall have the capability to minimize the backhaul and signalling load

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• Requirements for architecture and migration of Next Generation Radio Access Technologies • The RAN architecture shall support tight interworking between the new RAT and LTE.

• Considering high performing inter-RAT mobility and aggregation of data flows via at least dual connectivity between LTE and new RAT. This shall be supported for both collocated and non-collocated site deployments.

• The RAN architecture shall support connectivity through multiple transmission points, either collocated or non-collocated.

• Different options and flexibility for splitting the RAN architecture shall be allowed.

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Deployments Scenarios for 5G-NR

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• In terms of cell layout, the following scenarios are assumed: • Homogeneous deployment where all of cells provide the similar coverage, e.g. macro

or small cell only;

• Heterogeneous deployment where cells of different size are overlapped, e.g. macro and small cells.

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LTE NR

LTE (macro cell)

NR (small cell)Co-located cell

Non-co-located cell



• The deployment scenarios in terms of CN-RAN connection are classified into the following cases: • LTE eNB is a master node;

• NR gNB is a master node;

• eLTE eNB is a master node; • Definition: The evolution of eNB that supports connectivity to EPC and NextGen Core.

• Inter-RAT handover between NR gNB and (e)LTE eNB.

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• LTE eNB as a master node: • Data flow aggregation across LTE eNB and NR gNB via EPC.

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EPC

LTE eNBNR gNB

CP + UP

1) NR tightly integrated in LTE

via EPC

CP

+ UP

UP

The C plane latency requirement from the RAN requirements TR does not have to be met for the LTE-NR interworking case. FFS what are the U plane latency requirements for LTE-NR interworking case.



• NR gNB acts as a master node: • NR gNB is connected to NextGen Core;

• Data flow aggregation across NR gNB and eLTE eNB via NextGen Core.

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NR Node BeLTE eNB

CP + UP

2) LTE tightly integrated in NR

via NextGen Core

NextGen Core

UP

CP + U

P

NR gNB

1) NR gNB is connected to

NextGen Core

NextGen Core



• eLTE eNB acts as a master node: • eLTE eNB is connected to NextGen Core;

• Data flow aggregation across eLTE eNB and NR gNB via NexGen Core.

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eLTE eNB

1) eLTE eNB is connected

to NextGen Core

NextGen Core

eLTE eNBNR gNB

CP + UP

2) NR tightly integrated in LTE

via NextGen Core

NextGen Core

UP

CP + U

P



• Inter-RAT mobility: • LTE eNB is connected to EPC and NR gNB is connected to NextGen Core;

• eLTE eNB and NR gNB is connected to NextGen Core.

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LTE eNB

1) LTE eNB is connected to EPC and NR

gNB is connected to NextGen Core;

EPC

eLTE eNB

2) eLTE eNB and NR gNB are

connected to NextGen Core

NextGen Core

NR gNB NR gNB

NextGen CoreFFS



• Interworking with WLAN • WLAN is integrated in NR via NextGen Core

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2) WLAN aggregation with NR

NR gNBWT

UP

NextGen Core

CP + U

P

1) WLAN interworking with NR

NR gNBWLAN

UP

NextGen Core

CP



• The other scenarios under the scope of the NR study such as wireless relay and D2D (device to device) are also taken into account although not explicitly described in this technical report.

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NR

CP

+ UP

1) NR is connected to NextGen Core

NextGen Core

Wireless relay

Central unit

5G Macro

Distributed unit

Wireless relay

Backhaul link

Access link

Mobile relay

Multiple hop relayMultiple donor relay

Single hop relay

Reference: R2-164800


LTE-NR Tight Interworking

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Evolution of Dual Connectivity

• Rel-12 Dual Connectivity • SI: Study on Small Cell Enhancements for E-UTRA and E-UTRAN

• WI: Dual Connectivity for LTE • DC Control Plane

• DC User Plane

• DL Bearer Split

• Rel-13 Dual Connectivity Enhancements • WI: Dual Connectivity Enhancements

• UL Bearer Split

• Rel-14 Dual Connectivity for LTE-NR Tight Interworking • SI: Study on New Radio Access Technology

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General Introduction of Rel-12 Dual Connectivity

• E-UTRAN supports Dual Connectivity (DC) operation whereby a multiple RX/TX UE in RRC_CONNECTED is configured to utilise radio resources provided by two distinct schedulers, located in two eNBs connected via a non-ideal backhaul over the X2 interface.

• eNBs involved in DC for a certain UE may assume two different roles: an eNB may either act as an MeNB or as an SeNB. • MeNB: Master eNB

• In dual connectivity, the eNB which terminates at lease S1-MME.

• SeNB: Secondary eNB • In dual connectivity, the eNB that is providing additional

radio resources for the UE, but is not the Master eNB.

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MeNB

MME

SeNB

S1

-MM

E

X2-C


General Introduction of Rel-12 Dual Connectivity

• Interaction between MeNB and SeNB • The MeNB maintains the RRM measurement configuration of the UE.

• In the case of the SCG addition and SCG SCell addition, the MeNB may provide the latest measurement results for the SCG cell(s)

• Upon receiving the request from the MeNB, a SeNB may create the container that will result in the configuration of additional serving cells for the UE (or decide that it has no resource available to do so).

• For UE capability coordination, the MeNB provides (part of) the AS- configuration and the UE capabilities to the SeNB. (UE Capabilities Negotiation)

• The SeNB decides which cell is the PSCell within the SCG. • The MeNB does not change the content of the RRC configuration provided by the

SeNB. • When adding a new SCG SCell, dedicated RRC signalling is used for sending all

required system information of the cell as for CA, except for the SFN acquired from MIB of the PSCell of SCG. (System Information Update in DC for serving cell is similar to that in CA)

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Overall Architecture – Control Plane

• Each eNB involved in DC for a certain UE controls its radio resources and is primarily responsible for allocating radio resources of its cells.

• For a UE configured with DC, all RRC messages, regardless of the SRB used and both in downlink and uplink, are transferred via the MCG.

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X2


Overall Architecture – User Plane

• In DC, the radio protocol architecture that a particular bearer uses depends on how the bearer is setup.

• U-plane connectivity depends on the bearer option configured: • MCG bearers

• Split bearers • Re-ordering Function in PDCP, Flow control between MeNB and SeNB

• SCG bearers

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MeNB

S-GW

SeNB

S1

-U

X2-U

S1-U

MeNB

PDCP

RLC

SeNB

PDCP

RLC

S1

X2

RLC

MAC MAC

PDCP

RLC

S1

MCG bearer Split bearer

SCG bearer

Neither direct bearer type change between Split bearer and SCG bearer nor simultaneous configuration of SCG and Split bearer are supported.


LTE-NR Tight Interworking Deployment Scenarios

• LTE-NR aggregation for tight interworking • In terms of CN-RAN connection

• NR tightly integrated in LTE via EPC

• LTE tightly integrated in NR via NextGen Core

• NR tightly integrated in LTE via NexGen Core

EPC

LTE eNBNR Node B

NR Node BeLTE eNB

CP + UP CP + UP

1) NR tightly integrated in LTE via EPC 2) LTE tightly integrated in NR via NextGen Core

NextGen Core

CP

+ UP

UP

UP

CP + U

P

eLTE eNBNR Node B

CP + UP

3) NR tightly integrated in LTE via NextGen Core

NextGen Core

UP

CP + U

P

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LTE-NR Tight Interworking Deployment Scenarios

• New Bearer Type to be considered • Split bearer via SCG

• In this bearer type, C-plane connection is served by a master node (MeNB or MgNB) while U-plane data for the same bearer is delivered by leveraging radio resources across a master node and a secondary node via SCG.

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MeNB (LTE)

PDCPLTE

RLCLTE

MACLTE

SgNB (NR)

PDCPNR

RLCNR

MACNR

S1 or NG3

Xn

RLCLTE

MACLTE

MgNB (NR)

PDCPNR

RLCNR

MACNR

SeNB (LTE)

PDCPLTE

RLCLTE

MACLTE

NG3

Xn

RLCNR

MACNR


Control Plane Options for Tight Interworking • Option C1: Only the MeNB generates the final RRC messages to be sent towards the UE after the

coordination of RRM functions between MeNB and SeNB. The UE RRC entity sees all messages coming only from one entity (in the MeNB) and the UE only replies back to that entity.

• Option C2: MeNB and SeNB can generate final RRC messages to be sent towards the UE after the coordination of RRM functions between MeNB and SeNB and may send those directly to the UE and the UE replies accordingly.

Control Plane

Option 1

SeNB

Control Plane

Option 2

Uu

Xn

MeNB

RRC

UE

RRC

MeNB

SeNB

UE

RRC

Anchor RRC

AssistingRRC

Uu

Uu

Xn

Uu

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Control Plane Options for Tight Interworking

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Comparison aspect Option C1 Option C2

NR RRC message configuration

MeNB prepares the LTE RRC message including NR configuration.

SgNB prepares the NR RRC message including NR configuration.

Signalling latency Additional latency to transport the SgNB configuration over X2-link interface and encoding using the LTE RRC format.

No additional latency for direct signalling when the messages are sent over the NG1 interface provided by SgNB.

Measurement control and reporting

LTE RRC controls measurement configuration and reporting for NR.

NR specific measurements could be reported to NR RRC directly.

Coordination with M-RRC LTE RRC validates the NG configuration and generates the LTE RRC message

LTE RRC may not validate the NG Configuration. Coordination is still needed between LTE RRC and NR RRC.

Overall view LTE RRC needs to adapt to NR RRC changes, not allowing LTE RRC and NR RRC to evolve independently

NR RRC is isolated with respect to LTE RRC allowing independent evolution of both these protocols. In addition, this model allows more flexible operation compared to Option 1 and may benefit from lower latency on the NR interface for control plane configurations. Finally, the model is also flexible to support tight interworking where NR is the anchor.




• Agreements • UE has a single RRC state machine based on the master, and single control plane

connection to CN.

• Network has two RRC entities that can generate ASN.1.

• ASN.1 generated by the secondary can be transported by the master (at least in some cases, e.g. for first configuration).

• Some coordination is required between LTE (respectively NR) master node and NR (respectively LTE) secondary node.

• LTE (respectively NR) master node should not need to modify or add to the NR (respectively LTE) configuration of the UE.

• From a RAN2 perspective, we aim to have an independent capability information for NR and LTE (meaning that node of one RAT does not need to look at the capabilities of the other RAT). Does not preclude that capabilities of one RAT might contain some information related to the other RAT (e.g. at least measurement capabilities)

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• FFS • Is ASN.1 generated by one node transparent (no necessity for the master to

understand the ASN.1 generated by the secondary) to the other node? • Whether UE capabilities are involved in the coordination?

• Whether LTE (respectively NR) master node should not be required to understand NR (respectively) configuration of the UE?

• Can NR and LTE generate final RRC messages?

• Can secondary send messages directly to UE over the secondary radio (e.g. an SRB on the secondary)?

• Can messages generated by master node can be transported over the secondary radio?

• Can a single message generated by master/secondary node can be transported over both master and secondary radio?

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• Solutions on the table: • Alternative 1:

• SCG configuration is transparent to MCG. Any coordination necessary is done using XN2 signalling. (Rely on the interface between the nodes.)

• Alternative 2: • SCG configuration is always understood by MCG and vice versa (similar to LTE DC).

• Alternative 3: • Parts of the SCG configuration is transparent to MCG.

• Alternative 4: • Coordination is done in UE, e.g., hard capability split.

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NR Architecture Design

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NR Architecture

• CU: Central Unit

• DU: Distributed Unit • As in LTE, NR shall study lower layer aggregation (e.g. CA-like) and upper layer

aggregation (e.g. DC-like)

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NextGenCore

CUSnew-C/UNGFI

DU

DU

DU



Mobility

• Two levels of network controlled mobility: • 1: RRC driven at 'cell' level.

• 2: Zero/Minimum RRC involvement (e.g. at MAC /PHY)

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Beam Index

#1Beam Index

#2

Beam Index

#N

NG-NB

Beam Level Mobility

Cell Level Mobility

Cell1 Cell2

Beams of Cell1

Beams of Cell2



Mobility

• In LTE, xSS based mobility is used for inter-cell mobility. The xSS contains the cell-id (PCI), and the UE reports the PCI together with the cell quality determined based on CRS.

• In LTE, RS-set based mobility is used in COMP scenario 4 (intra-cell). The UE measures on the configured RE’s, which could contain UE dedicated or common RS, and reports the measured quality.

• RAN2 understanding of RAN1 agreement: There is an "xSS" (similar as LTE cell specific RS). On the "xSS" there is at least a NR Cell Id. The xSS is at least used in idle.

• In the 5G system, the UE camps on the best cell. FFS how the UE determines the best cell

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Mobility

• RAN2 will study mobility in connected active state based on UL signals . Study should at least consider power consumption, network internal signalling aspects, scalability, mobility performance, etc.

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a) The UE sends a single signal (denoted by SRS1) which in

turn is received by both serving and neighbouring cell(s), as

depicted in Figure 1a

b) The UE sends separate signals: SRS1 to the serving cell

and SRS2 to a neighbouring/candidate cell, as depicted in

Figure 1b

SRS2 is different from SRS1 in a sense that it is tailored to

cell 2, e.g. SRS2 might be in-sync with cell 2, it may use a

Tx power controlled by cell 2, it may use pilot sequences

configured by cell 2, etc. Reference: R2-164893


NR Protocol Functions

1. Study whether a single packet reordering function is possible.

2. Study whether segmentation function can be configured (enabled/disabled) to support different services.

3. Study whether concatenation function can be moved to lowest L2 sublayer.

4. Study whether retransmission of PDU segments can be removed (i.e. only complete PDU level retransmission).

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Protocol Legacy U-plane functions

PDCP

IP header compression and encryption of user data (security) In-order delivery to upper layer and duplicate detection Packet-level retransmissions across links (upon connection re-establishment)

RLC

Concatenation Segmentation and reassembly In-order delivery to upper layer and duplicate detection Byte-level retransmissions (AM only)

MAC Priority handling between logical channels Concatenation, (De)multiplexing of MAC SDUs and padding


New RRC State

• Connected State • Data Transmission/Reception

• Handover procedure for inter-cell mobility

• IDLE State • Power Saving

• UE mobility in Tracking Area

• Transition between IDLE State and Connected State result in signalling overhead and long CP/UP delay.

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New RRC State

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New RRC State

• Connected State • Data Transmission/Reception

• IDLE State • Power Saving

• New RRC State (e.g., Inactive State) • The connection (both CP and UP) between RAN and Core should be maintained in

the “new state”.

• For the UE in the “new state”, a RAN initiated notification procedure should be used to reach UE. And the notification related parameters should be configured by RAN itself.

• For the UE in the “new state”, RAN should be aware whenever the UE moves from one “RAN-based notification area” to another.

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New RRC State

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UE eNB MME SGW

1. RA msg1

2. RA response msg2

3. RA msg3

RRC resume request

4. RRC connection resume

5. RRC connection

resume complete

6. UL data

7. DL data

S1-C kept

S1-U kept


New RRC State

• RAN-based notification area

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eNB-1

Cell 1

(anchor cell)

eNB-2

Cell 2UE

Cell 3UE mobility area in

RTA


RAN-based notification area


New RRC State

• RAN initiated notification

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eNB 1

MME / S-GW

eNB 2

DL d

ata

Paging Area

PagingPaging

Context

of UE



New RRC State

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e.g. Expiration of RAN PA Update timer + reselection to

TRP/cell not in configuration, reselection failure, power off.

Potential Design for State Transition


New RRC State

• Further Consideration • The overall procedure/singnalling for state transition is still under discussion.

• How the RAN-initiated notification will be transmitted (e.g. via a beam, broadcast, etc)

• The overall RAN-initiate notification procedure is still under discussion.

• How CN location updates and RAN updates interact, if needed?

• Study the possibility for the UE to perform data transmission without state transition from the 'new state' to full connected.

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Thanks

[email protected]

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Documents

New Radio Access Technology in 3GPPstd-share.itri.org.tw/Content/Files/Event/Files/2. New...•Data flow aggregation across LTE eNB and NR gNB via EPC. 12 E P C LTE eNB NR gNB CP +