15th FFV Workshop
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
Arif Otyakmaz, ComNets, RWTH Aachen University
Overview
Overview – 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
Arif Otyakmaz, ComNets, RWTH Aachen University
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Introduction and Motivation
Overview – Introduction – Duplex – System– Concept - Simulations - Conclusion
• WRC 2007 frequency bands identified for IMTAdvanced 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
Arif Otyakmaz, ComNets, RWTH Aachen University
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Duplex Schemes
Overview – Introduction – Duplex – System– Concept - Simulations - Conclusion
frequency
guard time
• 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
UL
DL
TDD
DL
guard band
FDD
UL
time
• 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
frequency
services like TDD
– Higher cost of manufacture
 Practical for wide area environments
DL
• Half-duplex FDD (HFDD)
– Cheaper alternative to full-duplex FDD
HFDD
guard band
UL
time
Arif Otyakmaz, ComNets, RWTH Aachen University
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WINNER MAC Frame and Relaying
Overview – Introduction – Duplex – System– Concept - Simulations - Conclusion
1 super-frame = 1 preamble + 8 frames = 0.36 ms + 8 x 0.6912 ms = 5.8896 ms
preamble
frame
0.36 ms
0.6912 ms
BCH
DL
UT
BS
UL
RACH
UL Synch.
duplex guard
band
chunk
BCH
DL Synch.
BCH
f
t
f
RN
frame
“BS”
•
•
•
“UT”
“BS”
“UT”
“BS”
“UT”
“BS”
“UT”
t
RUT
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)
Arif Otyakmaz, ComNets, RWTH Aachen University
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Data
RN
Remote
UT HalfDuplex
Group 1
2
1
2
1
2
1
2
UL
2
1
2
1
2
1
2
1
framenumber / time
0
1
2
3
4
5
6
7
frequency
Map
1
DL
1
2
1
2
1
2
1
2
UL
2
1
2
1
2
1
2
1
0
1
2
3
4
5
6
7
DL
BS
UT
BS
UT
BS
UT
BS
UT
UL
BS
UT
BS
UT
BS
UT
BS
UT
framenumber / time
0
1
2
3
4
5
6
7
DL
1
2
1
2
UL
2
1
2
1
framenumber / time
frequency
BS
DL
frequency
UT HalfDuplex
Group 1
frequency
Concept for Relay Capable
Combined Full-/Half-Duplex FDD
Overview – Introduction – Duplex – System– Concept - Simulations - Conclusion
framenumber / time
0
1
2
3
4
5
Arif Otyakmaz, ComNets, RWTH Aachen University
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7
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Single-Hop Scenario:
One BS, one FD-UT, one HD-UT
Overview – Introduction – Duplex – System– Concept - Simulations - Conclusion
Saturation of full-duplex and half-duplex UT
UL
FD
Frame N
FD
HD
Frame N+1
Full-Duplex UT below saturation
UL
FD
Frame N
HD
Frame N+1
Arif Otyakmaz, ComNets, RWTH Aachen University
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Representative Multi-Hop Scenario
Overview – Introduction – Duplex – System– Concept - Simulations - Conclusion
Single-Hop
S ingleHop
(S H)
Full-Duplex
FDFDD
FDD
Half-Duplex
Multi-Hop
MultiHop
(MH)
UT3
RUT6
UT4
RUT8
Group
Group 11
UT5
RUT7
Group 22
Group
HDFDD
FDD
Arif Otyakmaz, ComNets, RWTH Aachen University
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Resource Partitioning between BS and RN
Overview – Introduction – Duplex – System– Concept - Simulations - Conclusion
Tas kP has e
BS
UT
“BS”
“UT”
frequency
UL
DL
DL
UL
BS 1
RN2
67%
BS 1
BS 1
...
“BS”
BS 1
RN2
“UT”
BS 1
BS 1
RN2
67%
BS 1
fra me 0
1
RN2
2
“BS”
BS 1
RN2
“UT”
RN “task”
BS 1
...
BS 1
...
5
...
BS 1
BS 1
3
RN2
4
Arif Otyakmaz, ComNets, RWTH Aachen University
time
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Uplink Throughput
Overview – Introduction – Duplex – System– Concept - Simulations - Conclusion
Stateless/memoryless scheduler:
Stateful scheduler:
Proportional-Fair
Round-Robin
x10
UL throughput per station [Mbit/s]
UL throughput per station [Mbit/s]
x10
Total offered UL cell traffic [Mbit/s]
Total offered UL cell traffic [Mbit/s]
Arif Otyakmaz, ComNets, RWTH Aachen University
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Proportional Fair: History Weight Parameter
Overview – Introduction – Duplex – System– Concept - Simulations - Conclusion
UL packet delay [s]
UL throughput per station [Mbit/s]
x10
Total offered UL cell traffic [Mbit/s]
Total offered UL cell traffic [Mbit/s]
• Enlarging “history weight” parameter to 0.99 leads to fairness
in terms of throughput between the different UT types
Arif Otyakmaz, ComNets, RWTH Aachen University
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Conclusion
Overview – Introduction – Duplex – System– Concept - Simulations - Conclusion
• “Proof of Concept” for relay capable combined full-/halfduplex 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
Arif Otyakmaz, ComNets, RWTH Aachen University
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Thank you for your attention !
Arif Otyakmaz
[email protected]
Arif Otyakmaz, ComNets, RWTH Aachen University
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