Top Banner
Future Network 6th FP7 Concertation Workshop October 18, Brussels, Belgium Valeria D’Amico – Telecom Italia Advanced Radio Interface TechnologIes for 4G SysTems 1 Interference Avoidance Techniques
21

02 Interference Avoidance Techniques

Jan 24, 2023

Download

Documents

Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Page 1: 02 Interference Avoidance Techniques

Future Network 6th FP7 Concertation WorkshopOctober 18, Brussels, Belgium

Valeria D’Amico – Telecom Italia

Advanced Radio Interface TechnologIes for 4G SysTems 1

Interference Avoidance Techniques

Page 2: 02 Interference Avoidance Techniques

Advanced Radio Interface TechnologIes for 4G SysTems 2

Presentation outlineThe 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

Page 3: 02 Interference Avoidance Techniques

Advanced Radio Interface TechnologIes for 4G SysTems 3

The interference problemIn 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.

Page 4: 02 Interference Avoidance Techniques

Advanced Radio Interface TechnologIes for 4G SysTems 4

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). For Release 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 on extended 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.

Page 5: 02 Interference Avoidance Techniques

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.

WP1Interference Avoidance

ARTIST4G Work Package 1

Advanced Radio Interface TechnologIes for 4G SysTems 5

Page 6: 02 Interference Avoidance Techniques

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.

Advanced Radio Interface TechnologIes for 4G SysTems 6

Page 7: 02 Interference Avoidance Techniques

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:

WP1Interference Avoidance

Task 1.1Advanced transmitter signal

processing techniques

Task 1.2Advanced scheduling and

cross-layer design

WP1Interference Avoidance

Task 1.1Advanced transmitter signal

processing techniques

Task 1.2Advanced scheduling and

cross-layer design

Work organization

7Advanced Radio Interface TechnologIes for 4G SysTems

Page 8: 02 Interference Avoidance Techniques

Task 1.1: Advanced transmitter signal processing techniquesObjective: 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

8Advanced Radio Interface TechnologIes for 4G SysTems

Page 9: 02 Interference Avoidance Techniques

Advanced Radio Interface TechnologIes for 4G SysTems 9

Single-cell MU-MIMO schemes

Objective:A single eNB serves multiple UEs on a single time-frequency resource. No coordination of multiple eNBs is considered.

Key challenges:Limited or no channel informationHigh complexity of optimal adaptation

Proposed WP1 innovations:Reduction of intra-cell interference between multiple 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.

Page 10: 02 Interference Avoidance Techniques

TX1

RX2

TX2 TXNcells

RX1 RXNcells

NtNetwork MIMO# Transmit antennas: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 schemesObjective: 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.Proposed WP1 innovations:

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

Page 11: 02 Interference Avoidance Techniques

Advanced Radio Interface TechnologIes for 4G SysTems 11

Advanced 3D-BeamformingConventional fixed downtilt causes interference at cell border even without UEslocated 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 for advanced 3D beamforming with and without exchange of control information among cooperating base stations.

Page 12: 02 Interference Avoidance Techniques

Advanced Radio Interface TechnologIes for 4G SysTems 12

Channel estimationObjective:

• 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

5

phase evolution of the MPCs of the channel[rad]

location iL

v= 3.6kmhΔt= 500ms 1 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

Page 13: 02 Interference Avoidance Techniques

Advanced Radio Interface TechnologIes for 4G SysTems 13

Feedback designObjective: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

Proposed WP1 innovations:Hierarchical feedback: provide more informationon 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

Page 14: 02 Interference Avoidance Techniques

Task 1.2: Advanced scheduling and cross-layer designObjective: propose and define innovative scheduling and cross layer design techniquesto 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):− Clustering & user grouping− Inter-Cell Interference Coordination− Coordinated scheduling− Scheduling for joint processing− Game theory based scheduling

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

14Advanced Radio Interface TechnologIes for 4G SysTems

Page 15: 02 Interference Avoidance Techniques

Advanced Radio Interface TechnologIes for 4G SysTems 15

Clustering & user groupingObjective:To reduce the amount of feedback needed from the users and the amount of signaling exchange required between the base stations in the implementation of CoMPschemes, especially when the number of involved users and base stations increases.Key challenges:To identify the best trade-off between the maximum achievable system performance and the price to pay in terms of requirements, overhead and implementation burden.

a cell and its coordination areaa cell and its coordination area

Proposed WP1 innovations:Clustering techniques: to divide the system into a set of given base stations or areas where to limit the specified type 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 of users to simultaneously serve on selected physical resources.

Page 16: 02 Interference Avoidance Techniques

Advanced Radio Interface TechnologIes for 4G SysTems 16

Inter-Cell Interference CoordinationObjective:

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.

Proposed WP1 innovations:Blind or low-overhead eNB/HeNB ICIC with a large number of HeNBs under the eNBcoverage (according to HeNB blind measures).

Distributed ICIC algorithms.

Page 17: 02 Interference Avoidance Techniques

Advanced Radio Interface TechnologIes for 4G SysTems 17

Coordinated scheduling

Objective:• Interference avoidance or suppression in order to enhance the system 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 the coordinated 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 the users' channels in the coordination area

Proposed WP1 innovations:• Precoding techniques combined with dynamic resource allocation• Beam collision avoidance by exchanging different kind of information: restriction request, 3B Beamforming constraint…• Coordinated scheduling for heterogeneous networks

RdRdRd

RdRdRd

Collision

RdRdRd RdRdRd

RdRdRd RdRdRd

Collision

Page 18: 02 Interference Avoidance Techniques

Selection of CoMP usersScheduling in time and frequencySelection of trx. scheme

Advanced Radio Interface TechnologIes for 4G SysTems 18

Scheduling for joint processingObjective: Design and performance evaluation of scheduling solutions suitable for systems 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 the selection/configuration of the JP scheme that serves the user.

Proposed WP1 innovations:In macro-cellular networks, research is carried out to characterize when the gains related to JP CoMP are worthwhile, i.e., when the performance gain-overhead tradeoff of JP is positive, or to develop solutions that reuse the SU-MIMO scheduling technique available in LTE Release 8Fast scheduling for time reversal cooperating femtos in indoor environments. In this case, a gateway is needed to coordinate the HeNBs

CoMP users

Page 19: 02 Interference Avoidance Techniques

Advanced Radio Interface TechnologIes for 4G SysTems 19

Game theory based scheduling Objective: Design of cross-layer scheduling algorithms based on team and competitive games (distributed with different levels of channel knowledge to reduce signaling and improve scalability; low complexity). Analysis of impact on performance of 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.

Proposed WP1 innovations:To use team and competitive Bayesian games.Maximizing individual or sum throughput subject to:

Medium queue occupancy Maximum power

System to work at an equilibrium point using local system knowledge.

Page 20: 02 Interference Avoidance Techniques

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

Advanced Radio Interface TechnologIes for 4G SysTems 20

Conclusions

Page 21: 02 Interference Avoidance Techniques

Thank you

Advanced Radio Interface TechnologIes for 4G SysTems 21

Valeria D’Amico

TELECOM ITALIATelecom Italia Lab (TILAB)

Email: [email protected]