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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
3 © 2013 InterDigital, Inc. All rights reserved.
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
4 © 2013 InterDigital, Inc. All rights reserved.
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
5 © 2013 InterDigital, Inc. All rights reserved.
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
6 © 2013 InterDigital, Inc. All rights reserved.
Inter-Cell Interference Coordination for HetNets (2)
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
7 © 2013 InterDigital, Inc. All rights reserved.
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)
Inter-Cell Interference Coordination for HetNets (3)
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
8 © 2013 InterDigital, Inc. All rights reserved.
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
9 © 2013 InterDigital, Inc. All rights reserved.
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)
10 © 2013 InterDigital, Inc. All rights reserved.
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
11 © 2013 InterDigital, Inc. All rights reserved.
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
12 © 2013 InterDigital, Inc. All rights reserved.
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+
13 © 2013 InterDigital, Inc. All rights reserved.
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
14 © 2013 InterDigital, Inc. All rights reserved.
Thank You!
Christopher Cave Director, Innovation Labs InterDigital Communications Montreal , QC, Canada +1 514.904.6264 Christopher.Cave@InterDigital.com
23
October
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