daniel c. schultz, comnets, rwth aachen university wwrf wg4 – white paper: multi-hop protocols for...

Daniel C. Schultz, ComNets, RWTH Aachen University

WWRF WG4 – White Paper:WWRF WG4 – White Paper:

Multi-hop Protocols for Relay-Multi-hop Protocols for Relay-based Deployment Conceptsbased Deployment Concepts

Editors: D.Schultz, B.Walke

ComNets, Faculty 6, RWTH Aachen University

Daniel C. Schultz, ComNets, RWTH Aachen University 2

ContributorsContributors

Name(s) Organization

D.Schultz, R.Pabst, B.Walke RWTH Aachen University

K. Navaie, H.Yanikomeroglu Carleton University

N.Johansson, K.-E. Sunell Ericsson Research

W.Zirwas Siemens


MotivationMotivation

• Relays are seen as essential part of next generation mobile radio network to allow cost efficient and fast network rollout. First concept and performance evaluations for existing system have proven the value of the concept as shown in the WWRF White Paper “Relay-based deployment “.

• The integration of relays as inherent part of the system concept is expected to increase the performance compared to the results shown in WWRF White Paper “Relay-based deployment“ at reasonable (low) node complexity


ScopeScope

• Relay-based B3G mobile radio network deployment concepts

• Layer 1-3– Physical Layer - PHY (L1)– Medium Access Control - MAC (L2)– Radio Link Control - RLC (L2)– Radio Resource Control - RRC (L3)


ObjectivesObjectives

The white paper should • provide an outline on how relaying can be

integrated in B3G systems as inherent part of it to– Optimise the capacity distribution in a given area– Cover otherwise shadowed areas– Extend the coverage of a B3G BS

• Show the traffic performance of multi-hop capable protocols to assess the protocol efficiency

• Provide an overview of the complexity of RNs


Current ContributionsCurrent Contributions

• Requirements and scope have been defined

• Multi mode reference architecture• MAC frames based approaches

– Frame in frame– Frame by frame

• RLC: Relaying ARQ frame work presented

• RRM/RRC: Outlook about resource partitioning further details needed


Table of ContentsTable of Contents

I. INTRODUCTIONA. Requirements on Multi-hop ProtocolsB. Relays in Infrastructure Based Deployment Concepts

1) Relays to extend the service range of a BS (service area size optimization)

2) Optimized Cell Capacity and Minimum Tx Power

3) Coverage of shadowed areasC. Outline

II. STATE OF THE ARTA. Protocols for central controlB. Decentralised protocols

III. REFERENCE PROTOCOL ARCHITECTUREIV. RADIO RESOURCE MANAGEMENT

A. Resource ReservationB. Mobility SupportC. Eval. of Routing and Forwarding Methods

1) Architectural and Algorithmic CharacteristicsD. Tech. Characteristics of Routing & Fwd.

1) Supporting advanced com. techniques3) Multiple access method4) Integration into other RRC functionality5) Similarity to existing standards6) Exploiting multi-user diversity

E. Resource Partitioning (new from WWRF#16 paper)

V. RADIO LINK CONTROL RLCA. Retransmission Protocols

1) Hop-by-Hop vs. End-to-End ARQ2) ARQ Framework3) Layered ARQ for error recovery4) Relay-ARQ for error recovery5) ARQ in the context of Cooperative relaying

B. Segmentation/ReassemblyC. Multi-hop Flow Management and Control (New - open for contribution)

1) Flow Set-up2) Flow control

VI. MEDIUM ACCESS CONTROL MACA. Link adaptation controlB. Resource SchedulingC. Frame Descriptor Table (new)C. Multi-user Diversity in Multi-hop Cellular Networks

1) Feeding Phase2) Delivery Phase

VII. COOPERATIVE RELAYING PROTOCOLSVIII. SPECTRUM ISSUES

A. Frequency Re-useB. Spatial diversity/Spatial Re-use

1) Tx gain vs. Rx gain between RAPsC. Interference ControlD. Coordination Across BS and RN

IX. CONCLUSION AND OUTLOOKREFERENCES


Definition of Fixed Relay-based Definition of Fixed Relay-based Deployment ConceptsDeployment Concepts

Base Station (BS)

Fixed Relay Node (FRN)d/√2

d/√

2BS

FRN UT

d

Area covered by BS

Area covered by FRN only

• L2-Relays in REC – don’t need a wired

backbone access (lowers CAPEX and OPEX)

– Full flexibility of relays (re-)positioning

• Relays support – fast network rollout, – outdoor to indoor service– Exploitation of

macrodiversity (co-operative relaying)

Capacity Optimisation

Area OptimisationCoverage of

shadowed areas

One-hop Cell


The WINNER Multi-mode Protocol ArchitectureThe WINNER Multi-mode Protocol Architecture

We can have alternatively have (1) a generic Management More flexible or(2) a Management that is specifically optimised for the mode1 and mode2 in use probably more efficient

Join

t Mod

e 1/

2 S

tack

M

anag

emen

t

Alternatives

The Multi-mode protocol architecture, facilitating transition (switching) between modes (inter-mode handover) and coexistence of modes (e.g. in relay stations connecting different modes) by way of the cross-stack management supported by the modes convergence manager of a layer or stack

RRC-s2

Gen

eric

Sta

ck M

ana

gem

ent

MAC-s2

PHY-s2 PHY-s2PHY-s2

PHY-gPHY-g

PHY-s1

PHY-gMAC-g

MAC-s1

RLC-g

control-plane

RRC-s1

RRC-g

control usermanagement

mode-switchingand

-coexistence

Configuration andinformation transfer


• Relay ARQ for high reliability and efficient retransmissions• One ARQ process with multiple multi-hop ARQ peers

– ARQ responsibility is delegated to next hop on Relay ACK (temporary responsibility)– All multi-hop peers involved in same multi-hop ARQ chain– Ultimate ARQ responsibility remains at the sender.

ARQ window only advances on Final ACK from Receiver

• Conclusion– Relay ARQ is a solution for the described problem !

Relay ARQRelay ARQ

L1

L2

L1 L1

L2

L1

L2 Relay

Sender Relay Node Receiver

L3 L3ACK

Hey, I have received this packet. But I am the final receiver. So you can now delete this packet from your buffer.

RACK

Hey, I have received this packet. But I am not the final receiver. Anyway, don’t worry, I will take care of it!


Multi-hop MACMulti-hop MAC

• In Frame Relaying:– Short delays– BS controlled

• Frame-by-Frame Relaying:– High throughput (low protocol overhead)


Identified Research AreasIdentified Research Areas

• Protocols for FDD Relaying• Relaying optimized MAC • Distributed RRM protocols for

coordination across RAPs to improve the mutual interference situation

• Protocol support for cooperative relaying

• Multi-hop flow set-up• QoS control in multi-hop links


Common GoalsCommon Goals

• Maximize Frequency Reuse• Allow efficient exploitation / fair sharing of the available

spectrum, esp. in unlicensed case• Guarantee QoS, since delay can be expected to be a crucial

issue in relay-based networks.• Minimize Multiple-Access Interference (MAI), probably making

use of advanced coordination across base stations in the system and of cooperation between base stations of different access technologies.

• Provide seamless mobility in heterogeneous networks consisting of different radio access technologies.

• Sequential coupling of different air interfaces to enable heterogeneous tandem-links.– Important either in the context of wireless connection of Base

Stations to core network or in the case of relaying in unlicensed frequency bands.

Daniel C. Schultz, ComNets, RWTH Aachen University

Contact:Daniel C. Schultz

Chair of Communication NetworksRWTH Aachen University, Faculty 6

Tel.: +49 241 8025828E-Mail: [email protected]

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