3 LTE Smalltel Cell Evolution

2013 Nokia Solutions and Networks. All rights reserved.

LTE Small Cell Evolution

October 2013

Bong Youl (Brian) Cho, [email protected]

Disclaimer

LTE , NSN .

TTA LTE Standards/Technology Training

2 2013 Nokia Solutions and Networks. All rights reserved.

Why Small Cell?

Pico cell and eICIC/FeICIC

Relay

Small Cell Enhancement in Release 12



Our vision: Mobile networks are able to deliver one Gigabyte of personalized data per user per day profitably

Key requirements for networks towards 2020

Support up to 1000 times more capacity

Teach networks to be self-aware

Reinvent Telcos for the cloud

Flatten total energy consumption

Reduce latency to milliseconds

Personalize network experience

for profitability and a quantum leap in flexibility



1000x capacity can be done with tech evolution

ASA

Smart Scheduler

New bands

Carrier Aggregation

HetNet management

Advanced macros

Flexible small cells

MIMO & adv. receiver

eCoMP



?

(cellular network) (frequency reuse) ?

AMPS 7 CDMA 1 (, )

Small cell: Macro > Micro > Pico > Femto

HetNet (Heterogeneous Network) with Interference Management

?

data rate

(Cooperative Multi-Point transmission and reception, CoMP)

? Higher order & advaned MIMO: 2x2 4x4 8x8 AAS, 3D beamforming, FD-MIMO, etc

? = x

,

Carrier Aggregation



Radio Technology Evolution

LTE Rel-8 and Rel-9

LTE Advanced Rel-10 and Rel-11

LTE Advanced Evolution

Rel-12 and Rel-13

5G

2010+

2013+

2015+

2020+

Optimize data performance and

architecture

Squeeze macro cells

Small cells &

new service enablers

Small Cell Enhancements

Macro Cell Enhancements

Machine-Type Communication, Device-to-Device

SON, WLAN Integration, Public

Safety



3GPP* LTE Base Station Classes (1/2)

3GPP* defined RF requirements separately per BS class

Wide area

Medium range

Local areas

Home

The BS classes

Defined based on distance between user and antennas

Measured as Minimum Coupling Loss (MCL)

Differences in RF requirements

Frequency stability

Spurious emissions

Sensitivity

Dynamic range

Blocking requirements

RF requirements for small BSs

More relaxed than for high power BSs

Make it further possible to reduce the cost of RF sections

* 3GPP TS 36.104



3GPP* LTE Base Station Classes (2/2)

Cells MCL Power level Description Deployment

Macro >70dB Typical up to 100 W per sector (no upper limit),

3-6 sectors

Big, outdoors, high power

Operators deploy

thousands nationwide

Micro >53dB Max 5 W Small, outdoors, medium power

Operators deploy in

selected urban areas

Pico >45dB Max 0.25 W Small, indoors, low power

Operators or integrators deploy in enterprises

Femto - Max 0.10 W Very small, indoors,

very low power

Consumers deploy up to millions

* MCL = Minimum Coupling Loss between terminal and base station antennas

* 3GPP TS 36.104



Frequency Use Options for small cells



Why Small Cell?


Relay




Network Densification

Homogeneous network

Heterogeneous network



HetNet problems in non-homogeneous deployment

Consist of deployments where low power nodes are placed throughout a macro-cell layout

The interference characteristics in a heterogeneous deployment can be significantly different than in a homogeneous deployment

Mainly, two different heterogeneous scenarios are under consideration Macro-Femto (CSG: Closed Subscriber Group) case

Macro-Pico case



Range Extension (of picocell)

The current cell selection algorithm is DL oriented

So, it may not be the optimum for UL perspective.

Further more, too high DL power of macro cell is too costly in cellular network

Range extension of picocell

but, this can lead to significant interference issue in extended range



Motivation for new ICIC techniques

The frequency domain ICIC (defined in Rel-8) is not sufficient.

Because DL control channels (PCFICH/PHICH/PDCCH) are spread over the entire system bandwidth.

With a cell-specific interleaving structure

ICIC in another resource domain becomes necessary



Why ALMOST blank subframe?

Because some channels/signals should be transmitted for the legacy UE

operation.

CRS (If ABS coincides with MBSFN subframe not carrying any signal in data region, CRS is not

present in data region )

PSS, SSS, and PBCH

PRS and CSI-RS

SIB1/Paging with associated PDCCH

No other signal is transmitted

Some interference still exists.

To be studied in the next release.



Almost Blank Subframe (ABS) introduced

Aggressor cell silences for some time For victim cell to have protected resources

Still PSS, SSS, PRS, CSI-RS, SIB1, Paging transmitted for backward compatibility, so called it Almost

Victim cell makes use of the silences time For victim cell to schedule UEs in victim cell

For UE in victim cell to check its serving cell radio condition

For UE in victim cell to measure its serving cell

For UE in other cell to measure victim cell



Coordination between two cell layers



TDM eICIC Principle - example with macro & HeNBs

Requires strict time-synchronization between macro & HeNBs

Macro-layer

HeNB-layer

One sub-frame

Macro-UEs close to non-allowed CSG HeNBs:

(i) To be scheduled in sub-frames where the HeNB layer is muted.

(ii) Should ideally also only do RLF monitoring in subframes where the HeNB layer is muted. Otherwise, RLF may be triggered, even though the UE can actually get data.

HeNB-UEs only scheduled in normal subframes.

Macro-UEs that does not experience excessive interference from non-allowed CSG HeNBs can be scheduled also in sub-frames where the HeNB-layer is not muted.

Almost blank, or MBSFN sub-frame

Sub-frame with normal transmission



TDM eICIC Principle - example with macro & Pico

Requires strict time-synchronization between macro & Pico

Macro-layer

Pico-layer

One sub-frame

Other pico-UEs that are closer to their serving pico node and therefore less restricted by macro-layer interfence canbe scheduled in any subframe.

Pico-UEs sensitive to macro-cell interference are only scheduled in subframes where Macro use ABS. This allows scheduling of pico-UEs using larger pico node cell selection offsets (range extension).





TDM eICIC Principle - combined macro+pico+HeNB case



Macro-layer

Pico-layer

HeNB-layer

Pico-nodes can schedule UEs with larger RE, if not interfered

from non-allowed CSG HeNB(s)

Macro-eNBs and Pico-eNBs can schedule also users that are close to non-allowed CSG

HeNB(s), but not pico-UEs with larger RE.

Pico-UEs with larger RE,

close to CSG HeNB(s) are schedulable (as well as pico-UEs

without RE).



Baseline Assumptions for Network Configuration of Muting Patterns: HeNB

Macro + HeNB scenario: Muting patterns are assumed to be statically configured from OAM

Both macro and HeNB needs to know the muting pattern:

HeNB will apply the muting pattern (i.e. will mute some of its subframes)

Macro-eNB needs to know so it only schedule its users close to non-allowed CSG HeNBs during muted subframes + can configured Rel-10 UEs with appropriate measurement restrictions.

Centralized concept



Baseline Assumptions for Network Configuration of Muting Patterns: pico

Macro + pico scenario: Muting patterns are assumed to be dynamically configured, assisted by new

X2 signalling introduced in Rel-10.

Both macro and pico needs to know the muting pattern:

Macro-eNB will apply the muting pattern (i.e. will mute some of its subframes)

Pico-eNB needs to know so it only schedule its users with large range extension during muted subframes + can configured Rel-10 UE measurement restrictions for those UEs.

Distributed concept



New X2 eICIC Related Signalling

ABS information in IE This IE provides information about which subframes

the sending eNB is configuring as ABS and which subset of ABS are recommended for configuring measurements towards the UE.

Macro can signal ABS muting pattern to the pico nodes in ABS information IE.

A neighbouring macro-cell receiving this information may aim at using similar muting pattern (but it is optional if macro-eNB follows such recommendation).

Invoke information IE This IE provides an indication that the sending eNB would like to receive ABS

information.

Can be used by pico nodes to suggest macro-eNB to start scheduling ABS, i.e. that the pico serves UEs suffering high interference.

Both the ABS information IE and/or Invoke IE is part of the LOAD INFORMATION message. Therefore, both of them can be exchanged between any two eNBs connected with X2, also between macros.

X2-AP: LOAD INFORMATION

eNB eNB



TS36.423 X2AP: Load Information

9.1.2.1 LOAD INFORMATION This message is sent by an eNB to neighbouring eNBs to transfer load and interference co-ordination

information.

Direction: eNB1 eNB2.

IE/Group Name Presence Range IE type and

reference

Semantics

description

Criticality Assigned

Criticality

Message Type M YES ignore

Cell Information M YES ignore

>Cell Information Item 1 ..

EACH ignore

>>Cell ID M ECGI Id of the

source cell

>>UL Interference

Overload Indication

O

>>UL High Interference

Information

0 ..

>>>Target Cell ID M ECGI Id of the cell

for which the

HII is meant

>>>UL High Interference

Indication

M

>>Relative Power (RNTP) O >>ABS Information O 9.2.54 YES ignore

>>Invoke Indication O 9.2.55 YES ignore



TS36.423 Invoke IE & ABS Information IE


reference

Semantics description

CHOICE ABS Information M >FDD

>>ABS Pattern Info M BIT STRING

(SIZE(40))

Each position in the bitmap represents a DL

subframe, for which value "1" indicates ABS and value "0" indicates non ABS. The first position of the ABS pattern

corresponds to subframe 0 in a radio frame

where SFN = 0. The ABS pattern is

continuously repeated in all radio frames.

The maximum number of subframes is 40.

>>Number Of Cell-specific

Antenna Ports

M ENUMERATED

(1, 2, 4, ) P (number of antenna ports for cell-specific

reference signals) defined in TS 36.211 [10]

>>Measurement Subset M BIT STRING

(SIZE(40))

Indicates a subset of the ABS Pattern Info

above, and is used to configure specific

measurements towards the UE.


reference

Semantics description

Invoke Indication M ENUMERATED (A

BS Information, )



New X2 eICIC Related Signalling (cont)

Macro-eNB can send a resource request to the pico-eNB.

Pico-eNB response with ABS status

The ABS status is basically a load measure of how much the pico-eNB uses the subframes where the macro-eNB is muted.

It is intended that only ABS allocated to UEs that would not cope otherwise are reported

This information can be used by the macro-eNB to get an idea of the consequences of increasing/decreasing the number of muted subframes. It can be combined with information about

overall load in the pico.

9.2.58 ABS Status The ABS Status IE is used to aid the eNB designating ABS to evaluate the need for modification of the ABS pattern.

eNB1 eNB2

RESOURCE STATUS REQUEST

RESOURCE STATUS RESPONSE

DL ABS status M INTEGER (0..100) Percentage of resource blocks of ABS allocated for UEs

protected by ABS from inter-cell interference. This

includes resource blocks of ABS unusable due to other

reasons. The denominator of the percentage calculation is

indicated in the Usable ABS Information.

>> Usable ABS Pattern Info M BIT STRING (SIZE(40)) Each position in the bitmap represents a subframe, for which

value "1" indicates ABS that has been designated as protected from inter-cell interference and value "0" indicates ABS that is not usable as protected ABS from inter-cell interference. The pattern represented by the bitmap is a subset of, or the

same as, the corresponding ABS Pattern Info IE conveyed in

the LOAD INDICATION message.



ABS patterns

Pattern 1: RRM/RLM measurement resources restriction for the serving cell

Serving cell RLM results look more stable. As a result, For PUE (UE under Pico), RLF declaration avoided at CRE of pico cell

For MUE (UE under Macro), RLF declaration avoided at femto cell area



ABS patterns contd

Pattern 2: RRM measurement resources restriction for neighboring cells

Neighboring cell looks more optimistic MUE can be handed over to in CRE area of pico cell

One pattern with PCI list



ABS patterns contd

Pattern 3: Resources restriction for CSI measurement of the serving cell

Two subsets for pattern 3: for eNB to obtain multiple channel status measurement for scheduling, e.g.,

CSI measurement on ABS

CSI measurement on non-ABS



UE Operation for eICIC: Example



Performance enhancement example through Pico Cells and eICIC

UE1

UE2 UE3

Macro

Pico Pico

0

10

20

30

40

50

60

70

UE1 UE2 UE3 Total

Mbps

No eICIC

eICIC with 50% ABS

System Capacity with HetNet and eICIC +50%



CA approach to interference avoidance in HetNet



With or without cross-carrier scheduling



FeICIC in Rel-11

eICIC is introduced in LTE Rel-10 and further enhanced in Rel-11 eICIC = enhanced Inter Cell Interference Coordination

FeICIC = Further enhanced Inter Cell Interference Coordination

eICIC consists of three design principles Time domain interference management (Rel-10)

Severe interference limits the association of terminals to low power cells

Cell range expansion (Rel-10/11)

Time domain resource partitioning enables load balancing between high and low power cells

Resource partitioning needs to adapt to traffic load

Interference cancellation receiver in the terminal (Rel-11/12)

Ensures that weak cells can be detected

Inter cell interference cancellation for control signals (pilots, synchronization signals)

Ensures that remaining interference is removed

Inter cell interference cancellation for control and data channels (PDCCH/PDSCH)

* source: Qualcomm



eICIC and FeICIC

FeICIC (Further enhanced non CA-based ICIC for LTE)

WI was completed in Dec. 2012

Support of larger CRE(up to 9dB) for better load balancing

Macro eNB provides Picos SIB1 to the UE in larger CRE region via dedicated signaling

* source: ETRI

eICIC in Rel-10 FeICIC in Rel-11



FeICIC Performance

* source: Qualcomm



FeICIC Performance contd

* source: Qualcomm



Why Small Cell?


Relay




Relay

Relay as a tool to improve, e.g.

the coverage of high data rates

group mobility

temporary network deployment

the cell-edge throughput

provide coverage in new areas

Various relay types

Type1 vs. Type2

In-band vs. out-band

Stationary vs. mobile

Single hop vs. multi-hop

Etc



Proxy Functionality

DeNB plays S1/X2-AP and S-GW proxy role for RN

DeNB appears to RN as

Control plane: MME for S1, eNB for X2

User Plane: S-GW



In-band Relay

Interference b/w access link and backhaul link

Inband relay - Un and Uu links are isolated in time



In-band Relay contd

Using MBSFN subframe for relay operation Multiplexing b/w access and backhaul links

RN subframe configuration



RN Startup Procedure - Phase I

Attach for RN Pre-configuration



RN Startup Procedure - Phase II

Attach for RN Operation



Rel-10 Relay Node Simplification

Deployment Scenario Simplification

No RN mobility

No multi-hop RN

No inter-RN handover

Radio Protocol Simplification

No additional header compression

No data forwarding at handover

No semi-persistent scheduling

No TTI bundling

No MBMS on Relay



FS_LTE_mobRelay Study on Mobile Relay for E-UTRA

Rapporteur: CATT

Schedule: Start (July 2007) Finish (Dec 2013, estimated)

Latest SID: RP-131375 (RAN#61) The objective shall focus on the backhaul design of mobile relays

Identify the target deployment scenarios first (RAN3)

Identify the key properties of mobile relays and assess the benefits of mobile relays over existing solutions (e.g. L1 repeaters) in fast-moving environments

Evaluate suitable mobile relay system architecture and procedures, including procedures for group mobility (RAN3)

Comparison based on higher layer considerations, e.g.

Group mobility, etc. (RAN3)

Comparison based on PHY layer considerations (RAN1)

Analyze the potential impact of moving cells created by mobile relays

Latest Status Report: RP-131380

Latest 3GPP TR and/or TS: 36.836



A reference scenario for high speed train



Alternative 1

Alt.1 relay architecture

The same RN as Rel-10 with minor difference that MRN supports NNSF.



Alternative 2

PGW/SGW (RN)

Relay GW

E-UTRA UE

Un

eNB

UE

Uu

MME/SGW (UE)

E-UTRA UE

Un

eNB

eNB

UE

Uu

eNB

PGW/SGW (RN)

Relay GW

Initial DeNB Target DeNB

S1-U

Alt.2 with Relay GW and PGW/SGW collocated with initial DeNB

Alt.2 with Relay GW and PGW collocated with initial DeNB



Alternative 2 contd

Alt.2 with dual Rel-10relays for HO Alt.2 with Relay GW and PGW/SGW separated from initial DeNB



Alternative 4

User-UE

SGW/PGW

S11

(UE)

User-UE

MME

Donor-eNB

(Proxy)

User-UE

E-UTRA-Uu(UE)

UE Network Elements

IPRelay

UE related

S1 msg

User-Plane

data(UE)

S1-U

(UE)

Un

interface

S1-M

ME

(UE

)

Relay Network ElementsRelay-UEs

MME

Relay-UEs SGW/PGW

S1-M

ME

(Rela

y)

S1-U

(Relay)

S11

(Relay)IP

New model

New functionalities needed for one-to-one mapping between two DRBs (one over Un and one over Uu) that need to be kept synchronized.



Why Small Cell?


Relay




FS_LTE_SC_enh_req Study on Scenarios and Requirements of LTE Small Cell Enhancements for E-UTRA and E-UTRAN

Rapporteur: China Mobile

Schedule: Start (Sep 2012) Finish (Dec 2012)

Latest SID: RP-121418 (RAN#57) Identify the target deployment scenarios and the relevant characteristics:

Definition and characterization of small cells;

Targeted deployment scenarios e.g. used spectrum, backhaul and synchronization.

Identify the key requirements for small cell enhancements:

Deployment related requirements;

Capability related requirements e.g. peak data rate;

System performance requirements e.g. spectrum efficiency, coverage and mobility (in idle and connected states);

Operational requirements, e.g. architecture, complexity, cost, energy efficiency etc.





Small cell deployment scenario

With and without macro coverage

Outdoor and indoor (UE mobility)

Ideal and non-ideal backhaul

Sparse and dense

Synchronized and un-synchronized



More specified small cell deployment scenario



Spectrum

Applicable to all existing and as well as future cellular bands, with special focus on higher frequency bands, e.g., the 3.5 GHz band

Also take into account the possibility for frequency bands that, at least locally, are only used for small cell deployments.

Co-channel deployment scenarios between macro layer and small cell layer should be considered as well.



FS_LTE_SC_enh_L1 Study on Small Cell Enhancements for E-UTRA and E-UTRAN Physical-layer aspects

Rapporteur: Huawei

Schedule: Start (Dec 2012) Finish (Dec 2013, estimated)

Latest SID: RP-122032 (RAN#58) Objective

Define channel characteristics of small cell deployments and UE mobility scenarios.

Study potential enhancements to improve the spectrum efficiency, including Introduction of a higher order modulation scheme (e.g. 256 QAM) for the downlink.

Enhancements and overhead reduction for UE-specific reference signals and control signaling in downlink and uplink based on existing channels and signals

Study efficient operation of a small cell layer composed of small cell clusters. Mechanisms for interference avoidance and coordination among small cells adapting to

varying traffic and the need for enhanced interference measurements.

Mechanisms for efficient discovery of small cells and their configuration.

Physical layer study and evaluation for small cell enhancement higher-layer aspects, in particular concerning the benefits of mobility enhancements and dual connectivity to macro and small cell layers and for which scenarios such enhancements are feasible and beneficial.



FS_LTE_SC_enh_L1 contd Study on Small Cell Enhancements for E-UTRA and E-UTRAN Physical-layer aspects

The study should address small cell deployments taking into account existing mechanisms (e.g., CoMP, FeICIC) wherever applicable.

Coordinated and time synchronized operation of the small cell layer and between small cells and the macro layer can be assumed.

Backward compatibility, i.e. the possibility for legacy (pre-R12) UEs to access a small-cell node/carrier, shall be guaranteed





Link level evaluation results of 256QAM

SINR range in which a gain is

observed

Observed maximum spectrum efficiency gain

0% Tx EVM 4% Tx EVM 6% Tx EVM

Source 1 >27dB (rank adaptation, 0% or

4% Tx EVM) 33%

30%(0% Rx EVM)

15%(2% Rx EVM)

Source 2 >25dB (rank2, 0% or 4% Tx

EVM) 33% 15% 2%

Source 3 >30dB(rank2)

>20dB(rank1)

33% (rank2)

33% (rank1)

17%(rank2)

25%(rank1)

Source 4 >30dB(rank2, TM3)

>36dB(rank2, TM3, 4% Tx EVM) 30%(TM3, @38dB) * 3%(TM3, @38dB) * -30% (TM3)

Source 5 >25 dB(rank adaptation, 0% or

4% Tx EVM) 25%(@40dB)*

10%(@40dB)*

8% (2% Rx EVM,

@40dB) *

3%(4% Rx EVM)

1%

Source 6

>25 dB(rank2, 0% or 4% Tx EVM)

>18 dB(rank1, 0%, 4% or 6% Tx

EVM)

15%*(rank2, @30dB) *

33% (rank1)

10% (rank2, @30dB) *

29%(rank1)

-4%(rank2)

25%(rank1)

Source 7

(fixed coding

rate of 5/6)

>30dB(0% Tx EVM, rank 2)

>38dB(4% Tx EVM, rank2)

25% (rank 2)

-13% (rank2, RX IQ

imbalance with -25dB

IMRR)

10% (rank2)

-9% (rank2, RX IQ


IMRR)

-30% (rank2)

-3% (rank2, RX IQ


IMRR)

Source 8

>27dB(rank adaptation, 0% Tx

EVM)

>30dB(rank adaptation, 4% Tx

EVM)

23.1%(@40dB)* 9.4%(@40dB)*

0%(4% Rx EVM)

Source 9 >28dB (rank2)

>24dB (rank1)

20%(rank2, @32dB) *

30% (rank1, @32dB) * 15%(@32dB)* 0%

Source 10 >22dB dB (rank1) 28% (rank1, @32dB) * 15% (rank1)



UE-specific RS overhead reduction

Overhead reduction of downlink UE-specific reference signal

Overhead reduction of uplink UE-specific reference signal

SINR Average gain

5dB 0.9%

20dB 2.4%

30dB 3.9%

Table 6.2.1-2 Observed spectrum efficiency gain

SINR Average gain

3dB 7.8%

10dB 8.7%

20dB 6.4%

Table 6.2.2-2 Observed spectrum efficiency gain



Interference Avoidance and Coordination

Small cell on/off Baseline schemes without any on/off

Long-term on/off schemes for energy saving

Semi-static on/off schemes

Ideal, dynamic on/off schemes

NCT with NCTCRS (i.e., reduced CRS)

Enhanced power control/adaptation

Enhancement of frequency domain power control and/or ABS to multi-cell scenarios

Load balancing/shifting

Please refer to 3GPP TR 36.872



Efficient discovery of small cells & configurations

Enhancements of small cell discovery PSS/SSS interference cancellation

Burst transmission of DL-SS/RS

If small cell on/off mechanisms are supported, a small cell in dormant state or DTX state transmits a DL-SS/RS burst with low duty cycle.

Network synchronization and assistance

New discovery mechanism

Transmission of DL-SS/RS at specific carrier

Etc

Necessity of PCI extension??

It is observed from the evaluation results that in terms of PCI collision, assuming a completely random PCI allocation, the probability of PCI collision is less than 2%.

For PCI confusion, the existing mechanism of reading the Cell Global Identifier from SIB1 utilizing autonomous gaps is deemed sufficient. However, it was also observed that SI reading may become

more frequent in dense small cell scenarios.

As a conclusion, the existing cell discovery signals are sufficient in terms of number of individually identifiable cells



Radio-interface based synchronization

Network listening

UE-assisted synchronization

The synchronization between the source cell and the target cell can be achieved by some information provided by or obtained from UEs.

It is observed that the availability and selection of the UEs to assist synchronization may impact the performance of the synchronization.

We cannot rely on UE based synch if you want to serve pre-release 12 UEs.

So, UE assisted synchronization will not be studied further, as suggested by NSN in RAN#61.

Both solutions have the following potential standards impacts:

The indication of the synchronization stratum level

The maximum supported hop number

Applicability/compatibility of synchronization approaches with other ongoing studies



FS_LTE_SC_enh_hilayer Study on Small Cell Enhancements for E-UTRA and E-UTRAN Higher-layer aspects

Rapporteur: NTT DOCOMO


Latest SID: RP-122033 (RAN#58) Identify and evaluate the benefits of UEs having dual connectivity to macro

and small cell layers served by different or same carrier.

Identify and evaluate potential architecture and protocol enhancements particular for the feasible scenario of dual connectivity and minimize core network impacts if feasible, including:

Overall structure of control and user plane and their relation to each other, e.g., supporting C-plane and U-plane in different nodes, termination of different protocol layers, etc.

Identify and evaluate the necessity of overall RRM structure and mobility enhancements for small cell deployments:





Increased signalling load due to frequent handover

Increase in number of handovers where 10 small cells are deployed per macro cell in deployment scenario #1



Scenario #2: Method A

Method A For UEs served by a single cell only, i.e., either by a macro or a small cell

Statistics for number of mobility events per UE per hour for Method A

0

500

1000

1500

2000

3 kmph 2 Picos

30 kmph 2 Picos

60 kmph 2 Picos

3 kmph 10 Picos

30 kmph 10 Picos

60 kmph 10 Picos

Events per UE per hour

PP HO

PM HO

MP HO

MM HO



Scenario #2: Method B

Method B For UEs configured to deliver data via macro and small cells simultaneously

Statistics for number of mobility events per UE per hour for Method B

0

500

1000

1500

2000

3 kmph 2 Picos

30 kmph 2 Picos

60 kmph 2 Picos

3 kmph 10 Picos

30 kmph 10 Picos

60 kmph 10 Picos

Events per UE per hour

SCell Change

SCell Removal

SCell Add

PCell HO



Dual Connectivity

Benefits of Dual Connectivity hides small cell mobility to CN

throughput enhancements with inter-site CA

maximum BW allocated to the UE can consist of the BW offered by the macro + the BW offered by the small cell

traffic offload to small cell

macro can be relieved from the lower layer processing of all user plane data

One target scenario

U-Plane aggregated from macro & pico, mobility management/RRC from macro

Expected Changes & Impacts dual connectivity will require changes to user plane protocols

how to serve non-CA capable UEs in enhanced small cells

Macro #1

Pico #1

Pico #2

Pico #3

Macro #2

SCell Addition

SCell Removal

SCell Change

SCell Addition

SCell Removal

PCell Handover



U-plane Bearer Split Options

Option 1: S1-U also terminates in SeNB;

Option 2: S1-U terminates in MeNB, no bearer split in RAN;

Option 3: S1-U terminates in MeNB, bearer split in RAN.

Option 3Option 1

MeNB

SeNB

EPS bearer #1

EPS bearer #2

UE

S-GW

Option 2

MeNB

SeNB

EPS bearer #1

EPS bearer #2

UE

S-GW

MeNB

EPS bearer #1

SeNB

EPS bearer #2

UE

S-GW



Control Plane architecture

It is assumed that there will be only one S1-MME Connection per UE

Alt. 1: Centralised RRM, with one RRC connection/signalling b/w UE and macro cell eNB

Alt. 2: Distributed RRM, with one RRC connection/signalling b/w UE and macro cell eNB

Alt. 3: Distributed RRM, with two RRC connection/signalling b/w UE macro cell eNB, and UE small cell eNB

* source: NTT docomo

Selected



Overall technical issues considered in small cell

* source: ETRI



FS_UTRA_LTE_WLAN_interw Study on WLAN/3GPP Radio Int

Rapporteur: Intel


Latest SID: RP-122038 (RAN#58) Justification

WLAN interworking and integration is currently supported at the CN level, including both seamless and non-seamless mobility to WLAN.

However, as operator controlled WLAN deployments become more common and WLAN usage increases, RAN level enhancements for WLAN interworking which may improve user experience, provide more operator control and better access network utilization and reduced OPEX may be needed.

The following issues should be taken into account during the study:

Operator deployed WLAN networks are often under-utilized

User experience is suboptimal when UE connects to an overloaded WLAN network

Unnecessary WLAN scanning may drain UE battery resources



FS_UTRA_LTE_WLAN_interw contd Study on WLAN/3GPP Radio Int

Objective

In a first phase: Identify the requirements for RAN level interworking, and clarify the scenarios to be

considered in the study while taking into account existing standardized mechanisms.

In a second phase: Identify solutions addressing the requirements identified in the first phase which cannot be

solved using existing standardized mechanisms, including:

Solutions that enable enhanced operator control for WLAN interworking, and enable WLAN to be included in the operators cellular Radio Resource Management.

Enhancements to access network mobility and selection which take into account information such as radio link quality per UE, backhaul quality, load, etc for both cellular and WLAN accesses

Evaluate the benefits and impacts of identified mechanisms over existing functionality, including core network based WLAN interworking mechanisms (e.g. ANDSF).





WLAN Interworking

Assumptions Solutions developed as a result of this study should not rely on standardized

interface between 3GPP and WLAN RAN nodes.

UE in coverage of a 3GPP RAT when accessing WLAN will still be registered to the 3GPP network and will be either in IDLE mode or in CONNECTED mode.

User preference always take precedence over RAN based or ANDSF based rules.

Requirements Improve bi-directional load balancing between WLAN and 3GPP

Improve the utilization of WLAN when it is available and not congested.

Reduce or maintain battery consumption (e.g. due to WLAN scanning/discovery).

Compatible with all existing CN WLAN related functionality

Backward compatible with existing 3GPP and WLAN specifications

Avoid changes to IEEE and WFA specifications.

Per target WLAN system distinction (e.g. based on SSID) should be possible.

Per-UE control for traffic steering should be possible.

Avoid ping-ponging between UTRAN/E-UTRAN and WLAN.



WLAN Interworking: Solution 1

RAN provides RAN assistance information to the UE through broadcast signaling (and optionally dedicated signaling)

UE uses the RAN assistance information UE measurements and information provided by WLAN and policies that are obtained via the ANDSF or via existing OMA-DM mechanisms or pre-configured at the UE to steer traffic to WLAN or to RAN

eNB/RNC WLAN APUE

SystemInformation




RAN provides assistance information to the UE through dedicated and/or broadcast signaling

UE steers traffic to a WLAN or RAN, based on this information, UE measurements and information provided by WLAN and rules specified in the RAN specification

eNB/RNC WLAN APUE

1. Parameters

2. Steer traffic

to/from WLAN

according to RAN

rule and ANDSF




The traffic steering for UEs in RRC CONNECTED state is controlled by the network using dedicated traffic steering commands, potentially based also on WLAN measurements (reported by the UE)

For UEs in IDLE mode, the solution can be similar to solution 1 or 2

Alternatively, UEs in those RRC states can be configured to connect to RAN and wait for dedicated traffic steering commands

eNB/RNC WLAN AP

2. Measurement report

3. Steering command

4. UE Ack/Response

UE

1. Measurement control

Event

trigger

Steer traffic to/from

WLAN

RRC connection

request



Small Cell Summary

LTE Rel-8 and Rel-9

LTE Advanced Rel-10 and Rel-11

LTE Advanced Evolution

Rel-12 and Rel-13

5G

2010+

2013+

2015+

2020+

Optimize data performance and

architecture

Squeeze macro cells

Small cells &

new service enablers

Small Cell Enhancements

Macro Cell Enhancements

Machine-Type Communication, Device-to-Device

SON, WLAN Integration, Public

Safety


THANK YOU!

3 LTE Smalltel Cell Evolution

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