02 Interference Avoidance Techniques

8/6/2019 02 Interference Avoidance Techniques

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Future Network 6th FP7 Concertation Workshop

October 18, Brussels, Belgium

Valeria DAmico Telecom Italia

Advanced Radio Interface TechnologIes for 4G SysTems 1

Interference Avoidance Techniques


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Advanced Radio Interface TechnologIes for 4G SysTems2

Presentation outline The interference problem

Interference avoidance in 3GPP activities

The interference avoidance approach in ARTIST4G

Work organization of Work Package 1

Task 1.1: Advanced transmitter signal processing techniques

Single-cell Multi-User MIMO schemes

Multi-cell Multi-User MIMO schemes

Advanced 3D-Beamforming

Channel estimation

Feedback design

Task 1.2: Advanced scheduling and cross-layer design

Clustering & user grouping

Inter-Cell Interference Coordination

Coordinated scheduling

Scheduling for joint processing

Game theory based scheduling

Conclusions


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The interference problem In current cellular mobile systems the achievable data rates are strongly

dependent on the users positions in the network. In these systems, a

considerable gap between cell-edge and cell-centre performance is observed

due to inter-cell interference, which poses the main limitation of state-of-the art

mobile networks.

It is of great importance to deliver the same user experience across the whole

cellular network in order to satisfy the users expectations.

The innovative technologies developed in ARTIST4G WP1 aim to bridge such

gap.


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Interference avoidance in 3GPP activities The 3GPP has been working on LTE-Advanced since early 2008. In June 2008

the LTE-Advanced targets were set and the dedicated Study Item was created.

The 3GPP initiated a Study Item on Coordinated Multiple Point (CoMP). ForRelease 10, there will be no new standardised X2 interface communication for

support of multi-vendor inter-eNB CoMP. For the time being, the Study Item on

CoMP was placed on hold until December 2010.

In March 2010 the LTE-Advanced Study Item was closed and a Work Item onextended Inter-Cell Interference Coordination (eICIC) for co-channel

deployments of heterogeneous networks was started.

The first decisions have been taken and will form the basis for LTE-Advanced

standardization in Release 10 that are being reflected in the 3GPP Technical

Report TR 36.814.


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ARTIST4G project is organized in 3 innovation and 4 transversal work packages.

The innovation work packages are responsible for determining new concepts for

future cellular networks aiming at improving the end-user experience. They correspond to 3 major research topics.

WP1InterferenceAvoidance

ARTIST4G Work Package 1



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Interference avoidance approachIt is the main objective of ARTIST4G Work Package 1 (WP1):

To investigate, define and validate advanced signal processing algorithms and

resource allocation & scheduling techniques that will cope with interference

management by following an interference avoidance approach, by also

introducing a certain level of coordination among different non co-located

transmission points and by designing accordingly the generated radio signals.

To design innovative, practical, scalable and cost-effective interference avoidance

solutions to be used at the transmitter side of a communications system, also in a

de-centralized manner, with a good trade-off between performance and

complexity,

To identify optimal strategies taking into account the impacts on the real system.

To scale this technological strategy, extending the concept of coordination also to

heterogeneous deployments, so that interference avoidance will be achieved in

scenarios where different network topologies coexist.



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Methods targeting interference avoidance in WP1 will be accomplished at

different levels of the protocol stack, by either designing algorithms based on

the physical layer solely, or also involving higher layers.

In order to fulfill the previous objectives, work within WP1 is split into two

tasks:

WP1

Interference Avoidance

Task 1.1Advanced transmitter signalprocessing techniques

Task 1.2Advanced scheduling andcross-layer design

WP1

Interference Avoidance

Task 1.1Advanced transmitter signalprocessing techniques

Task 1.2Advanced scheduling andcross-layer design

Work organization

7Advanced Radio Interface TechnologIes for 4G SysTems


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Task 1.1: Advanced transmitter signal processing techniques

Objective: propose and define innovative advanced signal processing algorithms to be

applied at the transmitter end of a communication system, in order to achieve

interference avoidance, taking advantage of all the degrees of freedom offered by

optimized multiple antenna processing.

Main Classes of Innovation (CoI):

Single-cell Multi-User MIMO schemes

Multi-cell Multi-User MIMO schemes

Advanced 3D-Beamforming

Channel estimation

Feedback design

Requirement analysis related to each CoI is collected in D1.1 Definitions and

architecture requirements for supporting interference avoidance techniques.

Innovations will be presented in the upcoming deliverable D1.2 Innovative advanced

signal processing algorithms for interference avoidance.

Task 1.1



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Single-cell MU-MIMO schemes

Objective:

A single eNB serves multiple UEs on a single

time-frequency resource. No coordination ofmultiple eNBs is considered.

Key challenges:

Limited or no channel information

High complexity of optimal adaptation

Proposed WP1 innovations:

Reduction of intra-cell interference betweenmultiple UEs sharing the same frequency-time

resource and improvement of the link quality

between the eNB and a particular UE. Schemes for designing the precoding matrixes

and receive filters are considered.


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TX1

RX2

TX2 TXNcells

RX1 RXNcells

NtNetworkMIMO# Transmitantennas:Nt x Ncells

S1 S2 SNcells^ ^ ^

S1,S2,SNcellsData

NrTX1

TX2

RX2

TX5 TX4

TX3

RX1

RX3

RX4

RX5

Coordination Links (fibers,wireless,..)

Multi-cell MU-MIMO schemes Objective: Address multi-cell interference problem by letting several eNBs jointly serve multiple

users (in distinct cells), in MIMO fashion or exchange control information towards interference

canceling.

Key challenges: eNBs must share user data, be synch-ed. Fast CSI fed back to eNBs. ->significant complexity, overhead and sensitivity.


Low complexity and decentralized beamforming design (independent CSI at the cooperatingnodes).

Robust codebooks and beamforming (wrt imperfectly shared CSI).

Power control schemes for JP CoMP.

Precoding scheme suited to partial user data sharing.

Inter-cell interference rejection techniques


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Advanced 3D-Beamforming Conventional fixed downtilt causes interference at cell border even without UEs

located there.

Objective: exploit also elevation dimension for adaptive beamforming, targeting

dynamic adaptation of the downtilt for each UE individually. Key challenges: identification of relevant system parameters and related

antenna properties, coordination algorithms for 3D beamforming, channel

modeling.

Proposed WP1 innovations: exploration of different realization options foradvanced 3D beamforming with and without exchange of control information

among cooperating base stations.


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Channel estimation

Objective:

Accurate channel estimation (CE) with moderate

overhead is basis of any advanced CoMP scheme.

CE might be decisive regarding the success of

CoMP.

evolution over time / location

0 5 10 15 20 25 30 35 40 45 50-20

-15

-10

-5

0

5phase evolution of the MPCs of the channel[rad]

location iL

v= 3.6kmh

t= 500ms1 FB / 10ms

good predictability

Key challenges:

High # of channel components per CA

Multi cell environment with strong inter cell

interference

Strong variation of path loss over different cells

Fast outdating of CSI

Proposed WP1 innovations: Analysis of pilot design for low power cells

Robust CSI prediction schemes


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Feedback design Objective:

Feedback of channel information:

allows transmitter adaptation and enables interference avoidance

consumes reverse link capacity

Key challenges:

accurate channel information for multiple links (CoMP)

tradeoff performance gain vs. reverse link penalty


Hierarchical feedback: provide more information

on stronger (more relevant) transmitters

Feedback compression: Lossless vs. lossy Channel tracking: only provide feedback info

for channel evolution

Feedback combined with channel prediction

Feed-

back


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Task 1.2: Advanced scheduling and cross-layer design

Objective: propose and define innovative scheduling and cross layer design techniques

to be applied at the transmitter end of a communication system, in order to achieve

interference avoidance. Extend interference management strategies in heterogeneous

deployments.

Main Classes of Innovation (CoI):


Inter-Cell Interference Coordination




Requirement analysis related to each CoI is collected in D1.1 Definitions and

architecture requirements for supporting interference avoidance techniques.

Innovations will be presented in the upcoming deliverable D1.3 Innovative

scheduling and cross layer design techniques for interference avoidance.

Task 1.2



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Objective:

To reduce the amount of feedback needed from the users and the amount of signalingexchange required between the base stations in the implementation of CoMP

schemes, especially when the number of involved users and base stations increases. Key challenges:

To identify the best trade-off between the maximum achievable system performanceand the price to pay in terms of requirements, overhead and implementation burden.

a cell and its coordination areaa cell and its coordination area


Clustering techniques: to divide the system into a set ofgiven base stations or areas where to limit the specifiedtype of cooperation (clusters).

Network-centric clustering techniques (static).

User-centric clustering techniques (dynamic). Semi-static techniques based on top-clusters.

User grouping techniques: to identify the best choice ofusers to simultaneously serve on selected physicalresources.


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Inter-Cell Interference Coordination Objective:

Obtain a long-term SINR improvement by low-overhead cooperation techniques including

schedulling and power control.

Improve the interference control for heterogeneous networks.

Key challenges:

For the LTE-A deployment, heterogeneous deployments put new challenges for the ICIC.

The non-uniform and random deployment of stations of different types makes crucial the

self-organizing RRM features.

The cooperation of nodes is sometimes impossible due the specific nature of the

heterogeneous network architecture.


Blind or low-overhead eNB/HeNB ICIC with a large number of HeNBs under the eNB

coverage (according to HeNB blind measures).

Distributed ICIC algorithms.


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Objective:

Interference avoidance or suppression in order to enhance thesystem performance specially at the cell edge

No user data sharing Information exchange as less as possible

Key Challenges:

Impact of the delay between the time of reception of thecoordinated information and the time of scheduling decision

Synchronization of the multi-point in the coordination area

Impact of long and short term CSI

Impact on the backhaul overhead: knowledge of all or a part of theusers' channels in the coordination area

Proposed WP1 innovations: Precoding techniques combined with dynamic resource allocation

Beam collision avoidance by exchanging different kind ofinformation: restriction request, 3B Beamforming constraint

Coordinated scheduling for heterogeneous networks

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Collision

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Collision


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Selection of CoMP usersScheduling in time and

frequencySelection of trx. scheme



Objective: Design and performance evaluation of scheduling solutions suitable forsystems allowing joint processing.

Key challenges: selection of the optimum subset of users to be served, resource

allocation over multiple dimensions (in time, frequency and space), and theselection/configuration of the JP scheme that serves the user.


In macro-cellular networks, research iscarried out to characterize when the gains

related to JP CoMP are worthwhile, i.e.,when the performance gain-overheadtradeoff of JP is positive, or to developsolutions that reuse the SU-MIMOscheduling technique available in LTERelease 8

Fast scheduling for time reversalcooperating femtos in indoor environments.In this case, a gateway is needed tocoordinate the HeNBs

CoMPusers


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Objective: Design of cross-layer scheduling algorithms based on team andcompetitive games (distributed with different levels of channel knowledge to reducesignaling and improve scalability; low complexity). Analysis of impact on performanceof different levels of system knowledge at the scheduler.

Key challenges: Cross-layer design (joint power and rate allocation, scheduling,)has high complexity. Signaling is very costly for centralized cross-layer design.Scaling problems.


To use team and competitive Bayesiangames.

Maximizing individual or sum throughputsubject to:

Medium queue occupancy

Maximum power

System to work at an equilibrium pointusing local system knowledge.


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This presentation has given an introduction to interference avoidance as it is

treated in the ARTIST4G project.

The set of classes of innovations studied in the ARTIST4G Work Package 1

(WP1) have been introduced.

Preliminary results will be obtained by means of numerical simulations and test-

bed measurements run in the field, aiming to show improvements in terms of

system performance.

The activities ongoing in ARTIST4G WP1 can be followed directly on the project

official website: https://ict-artist4g.eu


Conclusions


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Thank you


Valeria DAmico

TELECOM ITALIA

Telecom Italia Lab (TILAB)

Email: [email protected]

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02 Interference Avoidance Techniques