3 lte smalltel cell evolution
DESCRIPTION
lte cell detailsTRANSCRIPT
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LTE Small Cell Evolution
October 2013
Bong Youl (Brian) Cho, [email protected]
Disclaimer
LTE , NSN .
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Why Small Cell?
Pico cell and eICIC/FeICIC
Relay
Small Cell Enhancement in Release 12
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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
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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
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?
(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
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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
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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
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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
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Frequency Use Options for small cells
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Why Small Cell?
Pico cell and eICIC/FeICIC
Relay
Small Cell Enhancement in Release 12
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Network Densification
Homogeneous network
Heterogeneous network
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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
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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
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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
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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.
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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
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Coordination between two cell layers
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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
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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).
Almost blank, or MBSFN sub-frame
Sub-frame with normal transmission
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TDM eICIC Principle - combined macro+pico+HeNB case
Almost blank, or MBSFN sub-frame
Sub-frame with normal transmission
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).
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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
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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
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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
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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
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TS36.423 Invoke IE & ABS Information IE
IE/Group Name Presence Range IE type and
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.
IE/Group Name Presence Range IE type and
reference
Semantics description
Invoke Indication M ENUMERATED (A
BS Information, )
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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.
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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
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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
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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
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UE Operation for eICIC: Example
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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%
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CA approach to interference avoidance in HetNet
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With or without cross-carrier scheduling
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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
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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
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FeICIC Performance
* source: Qualcomm
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FeICIC Performance contd
* source: Qualcomm
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Why Small Cell?
Pico cell and eICIC/FeICIC
Relay
Small Cell Enhancement in Release 12
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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
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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
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In-band Relay
Interference b/w access link and backhaul link
Inband relay - Un and Uu links are isolated in time
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In-band Relay contd
Using MBSFN subframe for relay operation Multiplexing b/w access and backhaul links
RN subframe configuration
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RN Startup Procedure - Phase I
Attach for RN Pre-configuration
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RN Startup Procedure - Phase II
Attach for RN Operation
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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
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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
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A reference scenario for high speed train
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Alternative 1
Alt.1 relay architecture
The same RN as Rel-10 with minor difference that MRN supports NNSF.
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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
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Alternative 2 contd
Alt.2 with dual Rel-10relays for HO Alt.2 with Relay GW and PGW/SGW separated from initial DeNB
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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.
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Why Small Cell?
Pico cell and eICIC/FeICIC
Relay
Small Cell Enhancement in Release 12
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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.
Latest Status Report: RP-121651
Latest 3GPP TR and/or TS: 36.932
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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
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More specified small cell deployment scenario
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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.
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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.
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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
Latest Status Report: RP-131373
Latest 3GPP TR and/or TS: 36.872
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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
imbalance with -25dB
IMRR)
-30% (rank2)
-3% (rank2, RX IQ
imbalance with -25dB
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)
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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
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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
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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
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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
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FS_LTE_SC_enh_hilayer Study on Small Cell Enhancements for E-UTRA and E-UTRAN Higher-layer aspects
Rapporteur: NTT DOCOMO
Schedule: Start (Dec 2012) Finish (Dec 2013, estimated)
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:
Latest Status Report: RP-131087
Latest 3GPP TR and/or TS: 36.842
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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
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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
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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
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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
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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
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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
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Overall technical issues considered in small cell
* source: ETRI
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FS_UTRA_LTE_WLAN_interw Study on WLAN/3GPP Radio Int
Rapporteur: Intel
Schedule: Start (Dec 2012) Finish (Dec 2013, estimated)
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
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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).
Latest Status Report: RP-131077
Latest 3GPP TR and/or TS: 37.834
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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.
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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
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WLAN Interworking: Solution 2
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
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WLAN Interworking: Solution 3
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
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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
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THANK YOU!