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LTE-Advanced (3GPP Rel-10)

LTE-Advanced Enhanced LTE & additional features to meet ITU-R IMT-Advanced minimum requirements

Additional features *Carrier aggregation *Downlink reference signals: Introduction of CSI-RS & URS in DL*Enhanced Downlink MIMO: support up to 8Tx*Uplink MIMO: support up to 4TxLayer 3 RelayHeterogeneous network

*Required to meet the ITU-R requirements

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LTE-Advanced (3GPP Rel-10)

Carrier aggregationLTE-Advanced requirement

Scalable transmission bandwidth up to 100 MHzBackward compatibility

Support of a large transmission bandwidthTwo or more component carriers (CCs) are aggregated to support transmission bandwidths up to 100MHz Allowed channel bandwidths for each component carrier

1.4 MHz, 3 MHz, 5MHz, 10 MHz, 15 MHz and 20 MHzSupports both contiguous and non-contiguous aggregations

A large contiguous band is not available in some parts of the world Physically disjoint bands -> a logically contiguous band

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LTE-Advanced (3GPP Rel-10)

Carrier aggregationCross-carrier scheduling

PDCCH on a carrier can schedule PDSCH (or PUSCH) on other carriers. Carrier Indication Field (CIF) in PDCCH indicates the scheduled carrierUseful for HetNet interference coordination

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Heterogeneous network (HetNet) Low power nodes are placed throughout a macro-cell layout

Low power nodes: picocell, femtocell, RRH, relay nodesInterference problems in HetNet

Large interference due to restricted access Femto (with CSG(Closed Subscribed Group)) – Macro interferenceFemto – Femto interference

Dominant interference condition may happen when a pico cell expands its cell range for traffic off-loading from a macro cell to a pico cell

LTE-Advanced (3GPP Rel-10)

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Heterogeneous network (HetNet) CA based solution

Basic signals/control channels are transmitted only on the main carrier

Non-CA based solution ABS(Almost Blank Subframe): Subframes with reduced transmit power (including no transmission) on some physical channels and/or reduced activityABS information is transferred from aggressor cells to victim cells

Aggressor cell

LTE-Advanced (3GPP Rel-10)

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Technologies for 3GPP Rel-11

CoMP (Coordinated Muti-Point Tx & Rx)CA enhancementEnhanced DL control channel(s)Further enhanced DL MIMOMTC (Machine Type Communications) & low cost MTCNetwork energy savingFurther LTE SON enhancementEnhancement of Minimization of Drive Tests

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CoMP (Coordinated Muti-Point Tx & Rx)

Cooperative multi-point transmission/receptionimplies dynamic coordination among multiple geographically separated transmission/reception points

Point: Set of geographically co-located antennasNote that sectors of the same site correspond to different points

improves the coverage of high data rates, the cell-edge throughput and/or to increase system throughput

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CoMP – Scenarios (1/2)

Scenario 1: Homogeneous network with intra-site CoMP

Scenario 2: Homogeneous network with high Tx power RRHs (remote radio heads)

eNB

Coordination area

High Txpower RRH

Optical fiber

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CoMP – Scenarios (2/2)

Scenario 3/4: Heterogeneous network with low power RRHs within the macro cell coverage where the transmission/reception points created by the RRHs have different cell IDs (scenario 3) or the same cell IDs (scenario 4) as the macro cell

Other scenariose.g., small cells with the same cell ID

Low Tx power RRH(Omni-antenna)

eNB

Optical fiber

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CoMP-Downlink Schemes

Joint Processing (JP)Joint transmission (JT)

PDSCH transmission from multiple points at a time

Dynamic point selection (DPS)PDSCH transmission from one point at a time

Dynamic multi-point cooperation

Coordinated Scheduling/Beamforming(CS/CB)

Scheduling/beamforming coordination among multi points

Semi-static multi-point coordination

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CoMP-Uplink Schemes

Uplink CoMP schemesJoint Reception (JR)

Data transmitted by the UE is received jointly at multiple points (part of or entire CoMP cooperating set) at a time, e.g., to improve the received signal quality

Coordinated Scheduling and Beamforming (CS/CB)User scheduling and precoding selection decisions are made with coordination among points corresponding to the CoMP cooperating setData is intended for one point only

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CoMP-Network Deployment and Operation

Intra-eNB cooperation JT/JRConventional sectored cells belonging to the same eNB

Collocated antennaseNB connected with remote radio heads (RRHs)

Geographically separated antennasConnection via optical fiber, latency ~ a few us

Inter-eNB cooperation CS/CBInformation exchange over X2 interface

Latency ~ 10ms or more, QoS is not guaranteed

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Enhanced DL Control Channel(s)

Based on considerations from CA Enhancement in relation to the provision of a new carrier type, CoMP, and DL MIMOEnhanced physical downlink control channel(s) that is/are able to operate on

legacy carriersnew carrier type

Enhanced physical downlink control channel(s) shall be able to support increased control channel capacityto support frequency domain ICICto achieve improved spatial reuse of control channel resourceto support beamforming and/or diversityto operate in MBSFN subframes (also in non-MBSFN subframes)to coexist on the same carrier as legacy UEs

It is also desirable for the enhanced physical downlink control channel

to be able to be scheduled frequency-selectivelyto be able to mitigate inter-cell interference

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Requirements of Rel-12 and Onwards

Capacity increase to cope with traffic explosionEnergy savingCost efficiencySupport for diverse application and traffic typesHigher user experience/data rateBackhaul enhancement

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Potential Technologies for Rel-12 and Onwards

Enhanced small cell Interference coordination / managementFrequency separation between macro and small cells with higher frequency band for the small cellsDynamic DL/UL configuration in TDDInter-site CA / macro cell assisted small cellsEnhanced discovery / mobilityWireless backhaul for small cell

Multi-antenna/site technologiesFurther CoMP/MIMO enhancements3D beamforming & Massive MIMO

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Potential Technologies for Rel-12 and Onwards

New procedures and functionalities for LTE to support diverse traffic types

Control signaling reduction, etc.

LTE Device to Device (D2D)D2D device discoveryD2D communications

Enhanced interworking with other RATs such as WiFi, HSPAContinuous enhancements for MTC, SON, MDT Advanced terminal receivers (assisted by network)Enhanced positioning

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Enhanced Small Cell

Further densification of the network: a key tool to improve traffic capacityMacro deployment heterogeneous deployment

Very difficult to get a new site for an additional macro base stationMajority of traffic in local/hotspot scenarios

Number of small cells in a macro coverage will continue to be increased

(Panasonic)

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Enhanced Small Cell

Heterogeneous deploymentMacro cell for full-area coverageSmall cells for very high traffic capacity and service level locallyIn small cell coverage,

Traffic dynamics will be largeRelatively low average load High instantaneous data rates

User terminals will be stationary or only slowly moving

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Enhanced Small Cell

Frequency separation between macro and small cells3GPP activities on heterogeneous deployments have up to and including Rel-11 primarily focused on same-frequency operationNew spectrum mainly at higher frequencies, 3.5 GHz and above

Higher frequency bands are less suitable for use within a macro deployment Primarily suitable for the small cells Small cells operating on higher frequency bands with the overlaid macro call operating on lower cellular bands

Benefits of frequency-separated deployments Relaxing the RF requirements for local-area access nodesAllowing for different duplex schemes in the wide-area and local-area layers

(NTT docomo)

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Enhanced Small Cell

Dynamic DL/UL configuration in TDDTo better handle the high traffic dynamics in a local-area scenario, where the number of terminals transmitting to/receiving from a small cell can be very small, dynamic TDD is beneficialDynamic TDD requires a frequency-separated small cell deployment to avoid inter-layer interference

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Enhanced Small Cell

Macro cell assisted small cells - Soft cell (Ericsson)Terminal has dual connectivity

to the wide-area layer through an anchor carrier used for system information, basic radio-resource control (RRC) signaling and possible low-rate/high-reliability user datato the local-area layer through a ultra lean booster carrier used for large amounts of high-rate user data

Benefits in terms of robustness and mobilityIn case the booster connection is lost the terminal is still connected through the anchor carrierMacro cell can also aid the terminal in reducing complexity and power consumption (e.g., small cell discovery)

Split of C-Plane and U-plane between macro & small cells (NTT docomo)

C-plane: Macro cell maintains robust connectivity and mobility using lower frequency bandsU-plane: Small cell provides higher throughput and more flexible / cost-energy efficient operations using higher/wider frequency bands

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Enhanced Small Cell

Inter-site CA (multi-flow aggregation)Backhaul with (limited bandwidth and) higher latency needs to be supported as well

In Rel-11, CoMP and CA solutions are limited to intra-site and fiber based fast backhaul scenarios

Inter-site CA is an alternative to fiber based cloud-RAN (Samsung)Traffic splitting in CN or macro cell?If splitting in RAN, how to transport user data over X2 interface?

Macro cell can handle traffic steering and control plane (Huawei)

Enhanced small cell discovery / mobilityInter-frequency measurement enhancements for small cells UE battery saving while achieving good small cell discoveryEfficient mobility among small cells based on the discovery

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(Enhanced) New Carrier Type

New carrier typeMinimizing the transmission of “always-on” signals

Reduced CRS(cell-specific reference signal) or CRS free carrierePDCCH for control signaling

BenefitsImproved network energy efficiency

Base stations can turn off transmission circuitry when there is no data to transmit

Reduced interference level at low-to-medium loadsNo interference when no traffic

NCT is not backwards compatibleNot all signals expected by legacy terminals will be transmittedDeployment of a NCT may, in practice, primarily be limited to frequency bands not yet used by LTE

TypesIn conjunction with CA only (in Rel-11)Stand-alone NCT

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Enhanced Small Cell

Wireless backhaul for small cellIn addition to wired backhaul, small cells need cost effective wireless backhaul solutionIn-band: need to enhance the DeNB-RN link capacityOut-of-band: multiple access using higher frequency over 10GHz

Higher order modulation for small cell accessSmall cell supports 256QAM to exploit higher SINR in its coverage

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Multi-antenna Technologies

3D beamformingBoost capacity in the urban jungle

Increase SINRSupport higher user densities

By using active antenna arrays at the base stationAdaptive UE-specific 3D MIMO/beamforming in both vertical and horizontal directions (MU-MIMO)Vertical cell splitting (sectorization)Proactive cell shaping

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Multi-antenna Technologies

Massive MIMO for higher frequency bands (over 10GHz)In higher frequency, antenna elements can be miniaturized and their number can be increased

Pass loss can be compensated for via larger beamforming gainAdaptive very narrow beamforming

Huge beamforming gain with compact-sized antenna at both BS and MS (suitable for the small cell deployment)

Adaptive Pencil-Beamforming(Samsung)

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LTE Device to Device

D2D use cases (3GPP SA1 ProSe)Commercial/social use

Finding friends that are in proximity and sharing dataProximity-based multiplayer gamingLocal advertisingEtc.

Network offloadingPublic SafetyIntegration of current infrastructure services

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LTE Device to Device

LTE D2D discovery (Qualcomm)Over the top providers are introducing proximity discovery & services (e.g. Foursquare Radar, Sonar, Glancee)

LTE operators can enable these services under their controlNetwork-assisted discovery

Resources semi-statically allocated by the RAN & time-syncedUEs transmit discovery signals within the discovery resourcesDiscovery signals encode informationUEs decode everyone else’s signals

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LTE Device to Device

Types of D2D communicationsIntra/inter-cell D2D unicast/relayD2D broadcast/multicast (point to multi-point direct communications)Relay for device out of coverageD2D unicast/broadcast for devices out of coverage

Intra-cell D2D unicast/relay

Inter-cellD2D

unicast/relay

D2D link

Cellular link

D2Dbroadcast/ multicast

D2D unicast/broadcastfor devices out of

coverage(for public safety)

Relay for device out

of coverage(for public

safety)

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LTE Device to Device

SpectrumShared spectrumDedicated spectrumDedicated spectrum shared by multiple operators

Approaches Network-controlled D2D

Connection controlResource allocationLink adaptation

UE-controlled D2DDistributed connection/link scheduling

Network- and UE-controlled D2DHybrid control by network and UE

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