Distributed Resource Allocation in
OFDMA-Based Relay Networks
Christian Müller
12. Feb.2010 | Christian Müller
Outline
 Motivation Relay Networks
 Scenarios and Problems Definitions
 Distributed Resource Allocation
 Summary
12. Feb. 2010 | Christian Müller
1
Outline
 Motivation Relay Networks
 Scenarios and Problems Definitions
 Distributed Resource Allocation
 Summary
12. Feb. 2010 | Christian Müller
1
Coverage in Today‘s Cellular Networks
Coverage Problem
Base Station (BS)
wired backbone
User Equipment (UE)
12. Feb. 2010 | Christian Müller
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Coverage in Relay Networks
Coverage Problem
BS
Base Station (BS)
wired backbone
Relay Station (RS)
wired backbone
User Equipment (UE)
12. Feb. 2010 | Christian Müller
Improved Receive Power
UE
2
Capacity in Today‘s Cellular Networks
Capacity Problem
wired backbone
12. Feb. 2010 | Christian Müller
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Capacity in Relay Networks
Capacity Problem
wired backbone
12. Feb. 2010 | Christian Müller
Frequency Reuse
wired backbone
3
Outline
 Motivation Relay Networks
 Scenarios and Problems Definitions
 Distributed Resource Allocation
 Summary
12. Feb. 2010 | Christian Müller
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Considered Scenarios with Respect to Coverage and
Capacity Problem
Orthogonal Medium Access
downlink transmission
1st
3rd
2nd
12. Feb. 2010 | Christian Müller
RS
• operating in half-duplex mode
• decode, re-encode & forward
5
Considered Scenarios with Respect to Coverage and
Capacity Problem
Orthogonal Medium Access
downlink transmission
Reuse Medium Access
downlink transmission
1st
1st
3rd
2nd
12. Feb. 2010 | Christian Müller
RS
• operating in half-duplex mode
• decode, re-encode & forward
2nd
2nd
5
Resource Units
frequency
 BS & RSs:
 time division
 OFDMA (Orthogonal Frequency Division
Multiple Access)
 set of predefined beams
 power
 modulation and coding schemes
time-frequency
unit
slot
0
time
antenna gain in dB
-10
grid of beams
-20
-30
-40
-50
-60
-150 -100
-50
0
50
100
direction in degrees
12. Feb. 2010 | Christian Müller
150
resource block
6
Resource Allocation Problem
user rates depend on allocation of all
resource units
• scenario
• objective
Huge Resource Allocation Problem
• solution based on channel quality information
• duration for solution limited by coherence time
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Outline
 Motivation Relay Networks
 Scenarios and Problems Definitions
 Distributed Resource Allocation
 Summary
12. Feb. 2010 | Christian Müller
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Novel Concepts
Scenario
Orthogonal
Medium Access
Reuse Medium
Access
12. Feb. 2010 | Christian Müller
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Novel Concepts
Distributed Concept for Orthogonal Medium Access
Reuse Medium
Access
Distributed Concept for Reuse Medium Access
Scenario
Orthogonal
Medium Access
12. Feb. 2010 | Christian Müller
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Novel Concepts
Trade-off performance vs. fairness
maximize sum of user
rates subject to
minimum user rate
maximize minimum user
rate
Distributed Concept for Orthogonal Medium Access
Reuse Medium
Access
Distributed Concept for Reuse Medium Access
Scenario
Orthogonal
Medium Access
12. Feb. 2010 | Christian Müller
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Novel Concepts
Trade-off performance vs. fairness
maximize minimum user
rate
cf. thesis
cf. thesis
cf. thesis
exemplarily presented
Scenario
Orthogonal
Medium Access
maximize sum of user
rates subject to
minimum user rate
Reuse Medium
Access
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Distributed Concept for Reuse Medium Access
Assumptions
Flow of Subproblems
BS: design of grids of beams
beams applied on
time-frequency unit
RS: allocation of resource blocks
- uniformly allocated power
- fixed number of allocated
slots
bits per slot on RS-to-UE links
BS: allocation of resource blocks
12. Feb. 2010 | Christian Müller
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Distributed Concept for Reuse Medium Access
Assumptions
Flow of Subproblems
BS: design of grids of beams
beams applied on
time-frequency unit
RS: allocation of resource blocks
- uniformly allocated power
- fixed number of allocated
slots
bits per slot on RS-to-UE links
BS: allocation of resource blocks
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Design of Grids of Beams
inter-beam interference
unknown:
– current positions of UEs
– channel quality information
co-channel interference
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Design of Grids of Beams
unknown:
– current positions of UEs
– channel quality information
non-adaptive solution:
• each beam equally frequent
• equal distance
• randomly allocated to timefrequency unit
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Design of Grids of Beams
inter-beam interference
unknown:
– current positions of UEs
– channel quality information
non-adaptive solution:
• each beam equally frequent
• equal distance
• randomly allocated to timefrequency unit
RS2
RS1
co-channel interference
12. Feb. 2010 | Christian Müller
known:
+ positions of BS and RSs
+ pathloss model
+ beams
+ user distribution
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Adaptive Design
coverage area
of beam
12. Feb. 2010 | Christian Müller
metric for each combination of beams:
• determine interference based on
pathloss model and antenna gain
• average value based on coverage
area and user distribution
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Adaptive Design
coverage area
of beam
metric for each combination of beams:
• determine interference based on
pathloss model and antenna gain
• average value based on coverage
area and user distribution
hot spot
12. Feb. 2010 | Christian Müller
use beams more often where
receiving stations are expected
12
Adaptive Design
coverage area
of beam
metric for each combination of beams:
• determine interference based on
pathloss model and antenna gain
• average value based on coverage
area and user distribution
hot spot
use beams more often where
receiving stations are expected
allocate beams to time-frequency units
sequentially → best fit algorithm
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Distributed Concept for Reuse Medium Access
Assumptions
Flow of Subproblems
BS: design of grids of beams
beams applied on
time-frequency unit
RS: allocation of resource blocks
- uniformly allocated power
- fixed number of allocated
slots
bits per slot on RS-to-UE links
BS: allocation of resource blocks
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Motivation of Assumptions
co-channel
interference
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Motivation of Assumptions
Distributed Concept for Reuse
Medium Access:
• uniformly allocated power
• fixed number of allocated
slots
• design of grids of beams
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Motivation of Assumptions
pilots of BS
Distributed Concept for Reuse
Medium Access:
• uniformly allocated power
• fixed number of allocated
slots
• design of grids of beams
1.pilot phase → Signal-toInterference-plus-Noise Ratio
(SINR) estimation
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Motivation of Assumptions
pilots of RS
pilots of RS
Distributed Concept for Reuse
Medium Access:
• uniformly allocated power
• fixed number of allocated
slots
• design of grids of beams
1.pilot phase → SINR estimation
12. Feb. 2010 | Christian Müller
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Motivation of Assumptions
Distributed Concept for Reuse
Medium Access:
• uniformly allocated power
• fixed number of allocated
slots
• design of grids of beams
1.pilot phase → SINR estimation
2.SINR feedback
12. Feb. 2010 | Christian Müller
14
Motivation of Assumptions
Distributed Concept for Reuse
Medium Access:
• uniformly allocated power
• fixed number of allocated
slots
• design of grids of beams
1.pilot phase → SINR estimation
2.SINR feedback
12. Feb. 2010 | Christian Müller
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Motivation of Assumptions
SINR knowledge BS
Distributed Concept for Reuse
Medium Access:
• uniformly allocated power
• fixed number of allocated
slots
• design of grids of beams
1.pilot phase → SINR estimation
2.SINR feedback
3.allocation of resource blocks
SINR knowledge RS1 SINR knowledge RS2
12. Feb. 2010 | Christian Müller
14
Motivation of Assumptions
Distributed Concept for Reuse
Medium Access:
• uniformly allocated power
• fixed number of allocated
slots
• design of grids of beams
1.pilot phase → SINR estimation
2.SINR feedback
3.allocation of resource blocks
4.data transmission
12. Feb. 2010 | Christian Müller
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Distributed Concept for Reuse Medium Access
Assumptions
Flow of Subproblems
BS: design of grids of beams
beams applied on
time-frequency unit
RS: allocation of resource blocks
- uniformly allocated power
- fixed number of allocated
slots
bits per slot on RS-to-UE links
BS: allocation of resource blocks
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Allocation of Resource Blocks
SINR values of resource blocks
→ bits per resource blocks
Literature:
• one problem across all links
• requires knowledge of SINR
values in one point for
- all resource blocks
- all links
use SINR values locally
→ distributed allocation
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Allocation of Resource Blocks Provided by RS
•
allocate resource blocks with
objective max. min. user rate
a) non-adaptive
b) adaptive
example with 2 beams:
frequency
1st beam:
UE3
UE3
UE1
UE1
UE2
time
frequency
2nd beam:
UE1
UE1
UE2
UE2
UE3
UE1
UE3
UE2
time
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Allocation of Resource Blocks Provided by RS
•
•
allocate resource blocks with
objective max. min. user rate
a) non-adaptive
b) adaptive
RSs know bits per slot for each RSto-UE link
12. Feb. 2010 | Christian Müller
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Allocation of Resource Blocks Provided by RS
•
•
•
allocate resource blocks with
objective max. min. user rate
a) non-adaptive
b) adaptive
RS knows bits per slot for each RSto-UE link
feedback to BS
12. Feb. 2010 | Christian Müller
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Allocation of Resource Blocks Provided by BS
•
•
allocate resource blocks with
objective max. min. weighted user
rate
UE weighted by 1, RS weighted
by (number of UEs)-1
UE5
UE4
frequency
1st beam:
UE4
UE5
RS1
RS1
RS2
frequency
2nd beam:
RS1
RS2
time
RS2
RS1
UE4
RS2
RS1
time
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Allocation of Resource Blocks Provided by BS
•
•
•
allocate resource blocks with
objective max. min. weighted user
rate
UE weighted by 1, RS weighted
by (number of UEs)-1
RS is not allocated more than
required
UE5
UE4
RS1
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RS2
18
Evaluation Parameters
Value
size grids of beams
3
time-frequency units
64
number of resource blocks
192
number of slots
bits per symbol of modulation
and coding schemes
main lobe direction
channel model BS/RS to UE
channel model BS to RS
12. Feb. 2010 | Christian Müller
100
0, 0.5, 1, 2, 3, 4, 5, 6, 7, 8
0°, 30°, 60°, …, 330°
non-line of sight model
Coordinates in meter
Parameter
200
100
RS
0
BS
-100
RS
-200
-200 -100
0
100 200 300
Coordinates in meter
line of sight model
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Performance Evaluation Design of Grids of
Beams
average minimum user rate in bits/slot
120
GoB: design of
grids of beams
all-adapt.
BS: GoB, RB | RS: RB
non-adapt.
100
RB: allocation of
resource blocks
80
60
40
20
0
5
10
15
20
25
30
35
40
number of UEs
12. Feb. 2010 | Christian Müller
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Performance Evaluation Allocation of
Resource Blocks
average minimum user rate in bits/slot
120
GoB: design of
grids of beams
all-adapt.
BS: GoB, RB | RS: RB
non-adapt.
100
RB: allocation of
resource blocks
80
60
40
20
0
5
10
15
20
25
30
35
40
number of UEs
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21
Signalling RS to BS
105
Reference
Central genius approach
Distributed Concept For Reuse Medium Access
 all time-frequency
units and best
modulation and
coding scheme used
number of bits/slot
104
103
 per resource block:
- channel gain
- phase
- noise/interference
 assumption:
4 bits per value
102
101
100
1
2
3
4
5
6
7
8
9
10
number of UEs served by RS
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Outline
 Motivation Relay Networks
 Scenarios and Problems Definitions
 Distributed Resource Allocation
 Summary
12. Feb. 2010 | Christian Müller
23
Summary
 formulation of resource allocation problems in relay networks
 aiming at fair user rate allocation & high sum rate allocation
 in scenarios without & with co-channel interference
 concepts dividing problem in subproblems
 design grids of beams solved first in order to gain information about channels
 adaptive design of grids of beams according to user distribution and pathloss
 use information about channel locally and allocate resource blocks distributed
across BS and RSs
 low amount of signalling between RS and BS through bits/slot signalling
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Thank you.
12. Feb. 2010 | Christian Müller
Novel Adaptive Solutions
Maximize Sum of User Rates
Subject to Minimum User Rate
Maximize Minimum User Rate
Design of Grids of Beams
• noise
• inter-beam
interference
BS: Allocation of Resource Blocks
BS: Allocation of Resource Blocks
BS: Allocation of Power and Bits
BS: Allocation of Power and Bits
RS: Allocation of Resource Blocks
RS: Allocation of Resource Blocks
RS: Allocation of Power and Bits
RS: Allocation of Power and Bits
Allocation of Slots
• noise
• inter-beam
interference
• co-channel
interference
Allocation of Slots
Design of Grids of Beams
BS: Allocation of Resource Blocks
BS: Allocation of Resource Blocks
RS: Allocation of Resource Blocks
RS: Allocation of Resource Blocks
12. Feb. 2010 | Christian Müller
A
Motivation of Concepts
Design of Grids
of Beams
Allocation of
Resource Blocks,
Power and Bits
Allocation of Slots
12. Feb. 2010 | Christian Müller
Current information about
co-channel interference
Pathloss model and user
distribution
Joint concept for conventional
network
Entire concept for relay
networks
Central solution
Use channel knowledge
locally and define
distributed solution
Solution based on continuous
number of bits depending on
SINR
Solutions for combinational
problems
Joint solution
based on flexible number of
slots for single UE
Allocation of slots part of
the concept for multiple
RSs and UEs
B