Arif Otyakmaz, ComNets, RWTH Aachen University Half- and Full-Duplex FDD Operation in Cellular Multi-Hop…

Arif Otyakmaz, ComNets, RWTH Aachen University

Half- and Full-Duplex FDD Operation in Cellular Multi-Hop

Mobile Radio Networks

Arif Otyakmaz, Rainer Schoenen

Department of Communication Networks RWTH Aachen University, Germany

FFV Workshop, 21.11.2008

1515thth FFV Workshop FFV Workshop

2Arif Otyakmaz, ComNets, RWTH Aachen University

OverviewOverviewOverview – Introduction – Duplex – System– Concept - Simulations - Conclusion

• Introduction and Motivation• Duplex Schemes in Mobile Radio

Networks• WINNER MAC frame structure• Concept for Relay Capable Combined

Full-/Half-Duplex FDD• Simulation Scenarios and Results• Conclusion


Introduction and MotivationIntroduction and Motivation

• WRC 2007 frequency bands identified for IMT-Advanced systems

• ITU-R published invitation for submission of proposals for candidate IMT-Advanced systems

• Likely candidates (among others):– 3GPP LTE-Advanced (Release 10)– IEEE 802.16m (WiMAX)– IST WINNER and Celtic WINNER+ projects

• To provide scalability and adaptivity candidate systems– are based on OFDMA– support FDD and TDD– integrate “Decode-and-Forward” layer 2 relaying for

capacity enlargement and coverage extension

Overview – Introduction – Duplex – System– Concept - Simulations - Conclusion


Duplex SchemesDuplex Schemes

• Time Division Duplex (TDD)– Able to adapt the DL and UL phases

according to the data service– Switching between DL and UL needs

guard times to avoid interference– Larger cells lead to larger guard times Practical for metropolitan area

environments• Frequency Division Duplex (FDD)

– No need for guard times due to different radio resources in DL and UL

– Not able to adapt to different data services like TDD

– Higher cost of manufacture Practical for wide area environments

• Half-duplex FDD (HFDD)– Cheaper alternative to full-duplex FDD

time

guard band

DL UL

DL

UL

guard time

frequency

TDD

FDD

time

guard band

DL

UL

frequency

HFDD



WINNER MAC Frame and RelayingWINNER MAC Frame and Relaying

“UT” “UT” “BS” “UT” “BS”“BS” “BS”

frame

“UT”

f

t

BS

UT

RN

RUT

hop1

hop2relay link

feeder link

• Relay Nodes (RN) change “task” on frame basis• “BS task” on 2nd hop: Supplying associated Remote User Terminals (RUT) on

resources assigned by the BS by means of so called “resource partitioning• “UT task” on 1st hop: “Fed” by supplying Base Station (BS)


UL

DL

duplex guardband

frame0.6912 ms

preamble0.36 ms

1 super-frame = 1 preamble + 8 frames = 0.36 ms + 8 x 0.6912 ms = 5.8896 ms

f

t

chun

k

UL

Sync

h.

RA

CH

DL

Sync

h.

BC

HB

CH

BC

H


Concept for Relay CapableConcept for Relay CapableCombined Full-/Half-Duplex FDDCombined Full-/Half-Duplex FDD

Map

Data

BS

UT Half-Duplex Group 1

RN

UL

DL

frequ

ency 2

1

1

2

2

1

1

2

2

1

1

2

2

1

1

20 21 763 54framenumber / time

UL

DL

frequ

ency 2

1

1

2

2

1

1

2

2

1

1

2

2

1

1


UL

DL

frequ

ency UT

UT

BS

BS

UT

UT

BS

BS

UT

UT

BS

BS

UT

UT

BS

BS0 21 763 54framenumber / time

UL

DL

frequ

ency 1

2

2

1

1

2

2


RemoteUT Half-Duplex Group 1



Single-Hop Scenario:Single-Hop Scenario:One BS, one FD-UT, one HD-UTOne BS, one FD-UT, one HD-UT


FDUL FD HD

UL FD HD

Saturation of full-duplex and half-duplex UT

Frame N Frame N+1

Frame N Frame N+1

Full-Duplex UT below saturation


Representative Multi-Hop ScenarioRepresentative Multi-Hop ScenarioOverview – Introduction – Duplex – System– Concept - Simulations - Conclusion

UT3

UT4

UT5

RUT6

RUT7

RUT8

BS1 RN2

hop1hop2

UT3

UT4

UT5

RUT6

RUT7

RUT8

SingleHop (SH)

FDFDD

MultiHop (MH)

HDFDDGroup 1

Group 2

Single-Hop Multi-Hop

Full-DuplexFDD

Half-DuplexFDD

Group 1

Group 2


Resource Partitioning between BS and RNResource Partitioning between BS and RNOverview – Introduction – Duplex – System– Concept - Simulations - Conclusion

BS1

time

frequ

ency

DL

UL

BS UTTaskPhase

RN267%

BS1

BS1RN267%

BS1

BS1RN2

BS1

BS1RN2

BS1

BS1RN2

BS1

BS1RN2

BS1

...

...

frame 0 1 2 3 4 5 ...

...

UT3

UT4

UT5

RUT6

RUT7

RUT8

BS1 RN2

hop1hop2

DL

UL

“BS” “BS” “BS”“UT” “UT”“UT” RN “task”


Uplink ThroughputUplink ThroughputOverview – Introduction – Duplex – System– Concept - Simulations - Conclusion

Offered total traffic [Mbit/s]

Thro

ughp

ut p

er s

tatio

n [b

it/s]

(* 1

07 )

UT3

UT4

UT5RUT6

RUT7RUT8


Thro

ughp

ut p

er s

tatio

n [b

it/s]

(* 1

07 )

UT3UT4

UT5

RUT6RUT7

RUT8

Stateless/memoryless scheduler:Round-Robin

Stateful scheduler:Proportional-Fair

UL th

roug

hput

per

stat

ion

[Mbi

t/s]

UL th

roug

hput

per

stat

ion

[Mbi

t/s]

Total offered UL cell traffic [Mbit/s] Total offered UL cell traffic [Mbit/s]

x10x10


Proportional Fair: History Weight ParameterProportional Fair: History Weight ParameterOverview – Introduction – Duplex – System– Concept - Simulations - Conclusion


Thro

ughp

ut p

er s

tatio

n [b

it/s]

(* 1

07 )

Offered total traffic [Mbit/s] P

acke

t del

ay [s

]

UT3

UT4UT5

RUT6

RUT7RUT8

x10

Total offered UL cell traffic [Mbit/s]

UL th

roug

hput

per

stat

ion

[Mbi

t/s]

Total offered UL cell traffic [Mbit/s]UL

pac

ket d

elay

[s]

• Enlarging “history weight” parameter to 0.99 leads to fairness in terms of throughput between the different UT types


ConclusionConclusionOverview – Introduction – Duplex – System– Concept - Simulations - Conclusion

• “Proof of Concept” for relay capable combined full-/half-duplex FDD

• A memoryless scheduler– leads to unfair capacity share between half- and full-duplex

UTs.– can lead to waste of / unused resources.– In multi-hop scenarios this unfairness intensifies.

• A stateful scheduler– guarantees scheduling fairness over multiple frames and so

solves before mentioned problems.– Scheduler strategy “Proportional-Fair” is sufficient.

• Multi-hop operation demands sophisticated coordination– Considering number of remote UTs already during scheduling

for first hop– Balance between “resource partitioning” for second hop and

scheduling for first hop• Cognitions directly applicable to LTE and WiMAX


Thank you for your attention !

Arif [email protected]

Arif Otyakmaz, ComNets, RWTH Aachen University Half- and Full-Duplex FDD Operation in Cellular Multi-Hop…

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