INTERFERENCE COORDINATION AND MITIGATION TECHNIQUES FOR LTE

1 © 2013 InterDigital, Inc. All rights reserved. © 2013 InterDigital, Inc. All rights reserved.

IWPC Workshop :

Tunable Solutions and

Advanced Receivers for

Multiband/Multimode Devices

INTERFERENCE

COORDINATION AND

MITIGATION

TECHNIQUES FOR LTE

2 © 2013 InterDigital, Inc. All rights reserved.

Outline

About InterDigital

Inter-Cell Interference Coordination (ICIC) for HetNets

Interference Avoidance for In-Device Coexistence (IDC)

Coordinated Multipoint Operation (CoMP)

Advanced Receivers for LTE

3GPP Standardization Timeline


InterDigital Snapshot – Invention, Collaboration,

Contribution

InterDigital develops fundamental

wireless technologies that are at

the heart of mobile devices,

networks, & services worldwide. Vision

As a long time contributor to the

wireless industry, we have solved

many of the most critical mobile

challenges for 30+ years

Our technology is used in all 2G,

3G and LTE devices providing

support for new mobile broadband

& richer multimedia experience

We offer our technologies to the

market in IP blocks and full

product solutions and have been

key in high profile OEM offerings

Technology

Standards

Solutions

Four decades of discovery and innovation in wireless communications


3GPP Standardization Timeline

2008 2009 2010 2011 2012 2013 2014

Release 8

Release 9

Release 10

Release 11

Release 12

LTE is fastest developing mobile technology*

474 operators investing in LTE (deployments and trials)

222 LTE networks commercially launched

1000+ LTE user devices launched

*Based on Global mobile Suppliers Association (GSA) “Evolution to LTE Report” – October 2013

ICIC eICIC

FeICIC

CoMP

IDC

Advanced Rx

Advanced Rx


Inter-Cell Interference Coordination for HetNets (1)

Inter-Cell Interference Coordination (ICIC) enables frequency reuse 1 operation for LTE

Frequency

Tx Power

Frequency

Tx Power

Frequency

Tx Power

Cell Edge Resource Blocks (RBs)

Cell Centre RBs

Cell Edge RBs

Frequency Domain

Coordination

Frequency domain interference coordination over X2 interface: Relative Narrowband Transmit Power (RNTP) indicator High Interference Indicator (HII) Interference Overload Indicator (OI)

3GPP

Release 8

ICIC



Time Domain ICIC enhancements targeting two Heterogeneous Network scenarios

Supporting Macro Cell UEs under heavy

interference from CSG HeNBs

Offloading Macro Cell UEs to Pico Cells

using Cell Range Expansion (CRE)

Macro – Aggressor Cell

Pico – Victim Cell

Macro – Victim Cell

HeNB – Aggressor Cell

Bias applied to pico cell to “artificially” increase its footprint Cell splitting gain achieved by offloading traffic to pico cells Rebalancing UL and DL channel characteristics on cell association

Cell Range

Expansion

Scenario 1: Scenario 2:

Interference Interference

Non CSG Member UE

HeNB


Introduction of Almost Blank Subframes concept: ABSs are subframes in aggressor cell with reduced or no transmit

power on some physical channels. ABSs protect resources in victim cell experiencing strong inter-cell

interference eNB ensures backwards compatibility by transmitting control

channels and physical signals (e.g. CRS) required for legacy procedures during ABS

UEs in victim cell are provided a pattern (set of subframes) to perform RRM-related and CSI measurements

3GPP

Release 10

Enhanced ICIC

(eICIC)


CRS interference mitigation: CRS assistance information provided to UEs for CRS-based measurements and improved demodulation

Transfer of SIB1 via dedicated RRC signaling for UEs experiencing strong interference from neighboring cells

3GPP

Release 11

Further

Enhanced ICIC

(FeICIC)

Almost Blank Subframe (ABS) introduced to enable time domain coordination in HetNets


Coordinated Multipoint Operation – CoMP (1)

Transmitting and/or receiving network nodes cooperate to improve cell-edge performance

CoMP Transmission Techniques CoMP Deployment Scenarios

Homogeneous Networks (Scenarios 1&2)

Heterogeneous Networks

Coordinated

Scheduling/

Beamforming

(CS/CB)

Joint

Transmission/

Processing

(JT/JP)

Scenario 3:

Different

Cell IDs

Scenario 4:

Same Cell IDs

Coordination

Area

Optical Fiber


Coordinated Multipoint Operation – CoMP (2)

CoMP introduced in 3GPP Release 11 for ideal backhaul between coordination points (eNB ↔ RRH)

Multiple transmission points coordinated for downlink data transmission

New approach to Channel State Information (CSI) reporting to enable DL CoMP scheduling CSI-interference measurement (CSI-IM) resource: set of REs

on which the UE measures interference CSI process concept: measurement associated with one CSI-

RS resource (desired signal) and one CSI-IM resource (interference signal)

A CSI process can represent a CoMP transmission hypothesis

Downlink

CoMP

Transmission

Multiple reception points coordinated for uplink data reception UE configured with UE-specific parameters for PUSCH DMRS,

PUCCH sequence and PUCCH region for hybrid-ARQ Virtual Cell ID concept introduced to replace physical cell

identity of the UE’s serving cell

Uplink

CoMP

Reception

Ongoing Study Item in 3GPP Release 12 for CoMP with non-ideal backhaul (eNB ↔ eNB)


LTE with GPS for

navigation and/or

location-based

services

LTE with WiFi for traffic

offloading or tethering

Interference Avoidance for In-Device Coexistence (1)

Enabling coexistence of multiple radio transceivers (LTE, Bluetooth, WiFi and GNSS) within a UE

Use

Cases

Problem

Scenarios

LTE with Bluetooth for

hands-free operation

(VoIP, multimedia)

LTE Bands 7/13/14: LTE Tx radio interferes

with GNSS receiver

LTE Band 7: LTE UL transmission (Tx radio) interferes ISM band Rx radios (BT and WiFi)

LTE Band 40 : Two way interference Interference caused by LTE Tx radio to

ISM band Rx radio (BT and WiFi) Interference caused from ISM band Tx

radio (BT and WiFi) to LTE Rx radio

Extreme proximity of radio transceivers operating on adjacent or sub-harmonic frequencies

Interference from transmitter may be much higher than received power of desired signal


Interference Avoidance for In-Device Coexistence (2)

Phase 3: Network-

Controlled IDC Solution

eNB provides solution to IDC interference problem

Two approaches: (1) FDM: Move LTE signal away from ISM band (2) TDM: Provide TDM patterns (using LTE DRX) to ensure that transmission and reception of different radio signals do not coincide

Phase 2: IDC

Interference Notification

Phase 1: IDC

Interference Detection

UE initiates transmission of the IDC indication to eNB

IDC indication includes necessary assistance information for eNB to solve problem:

List is problematic LTE frequencies

Direction of interference Interference pattern

UE detects the start of IDC interference

Detection may rely on (1) Existing LTE measurements (2) UE internal coordination to assess the interference

Coordination amongst RATs within same device is assumed

UE can autonomously deny LTE UL transmission to protect ISM if necessary eNB configures long-term maximum denial rate through dedicated control signalling UE should also autonomously deny ISM transmission to ensure LTE connectivity

Signaling and Procedures for In-Device Coexistence (IDC) introduced in 3GPP Release 11

Autonomous

Denials


Advanced Receivers for LTE: R8 R12

Increasing the role of UE receivers to improve spectral efficiency as LTE evolves

Baseline receivers for R8: MMSE – Minimum Mean-Square Error MRC – Maximal Ratio Combining

Introduction of new receiver requirements for R11: MMSE- IRC (Interference Rejection Combining) : Practical

linear interference suppression (IS) receiver that does not require any transmission coordination

CRS Cancellation: non-linear interference cancellation receivers mitigating strong CRS interference (R11 FeICIC)

Studying more advanced receiver architectures for R12+: CRS Cancellation: CRS interference mitigation (R11 FeICIC

hetnet concept) for homogeneous networks NAICS: Network-Assisted Interference Cancellation and

Suppression

3GPP

Release 8

3GPP

Release 11

3GPP

Release 12+


Advanced Receivers for LTE: R12+ NAICS

Network-Assisted Interference Cancellation and Suppression (NAICS) being studied for R12+

Mitigation of intra-cell and inter-cell

interference from control and data

channels

Multiple candidate receiver types grouped into 3 categories:

Interference Suppression (IS)

Applies linear filtering to received signal to suppress interference instead of explicitly cancelling interference

Interference parameters enabling interferer channel estimation are used

Maximum Likelihood (ML)

Joint detection of desired and interference signals using ML criterion Interference parameters enabling interferer channel estimation and interferer

detection are used

Interference Cancellation (IC)

Successive application of detection, decoding, re-encoding and cancellation Interference parameters enabling interferer channel estimation and interferer

detection are used

eNB provides interference knowledge to UE: Presence and characteristics of interference Transmission schemes (incl. resource allocation) Reference symbols to enable channel estimation Modulation format and/or coding rate


Thank You!

Christopher Cave Director, Innovation Labs InterDigital Communications Montreal , QC, Canada +1 514.904.6264 [email protected]

23

October

INTERFERENCE COORDINATION AND MITIGATION TECHNIQUES FOR LTE

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