12. Feb.2010 | Christian Müller Distributed Resource Allocation in OFDMA-Based Relay Networks...

12. Feb.2010 | Christian Müller

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

1


Coverage in Today‘s Cellular Networks

Base Station (BS)

User Equipment (UE)

wired backbone

Coverage Problem

2


Coverage in Relay Networks

Base Station (BS)

User Equipment (UE)

wired backbone

Coverage Problem

BS

UE

wired backbone

Improved Receive Power

Relay Station (RS)

2


Capacity in Today‘s Cellular Networks

wired backbone

Capacity Problem

3


Capacity in Relay Networks

wired backbone

Capacity Problem Frequency Reuse

wired backbone

3


Outline


4


Considered Scenarios with Respect to Coverage and Capacity Problem

1st

2nd

3rd

5

RS • operating in half-duplex mode• decode, re-encode & forward

Orthogonal Medium Accessdownlink transmission


Considered Scenarios with Respect to Coverage and Capacity Problem

1st

2nd2nd

1st

2nd

3rd

5

Orthogonal Medium Accessdownlink transmission

Reuse Medium Accessdownlink transmission

RS • operating in half-duplex mode• decode, re-encode & forward


Resource Units

BS & RSs: time division OFDMA (Orthogonal Frequency Division

Multiple Access) set of predefined beams power modulation and coding schemes

6

time

frequency

slot

time-frequency unit

grid of beams

-150 -100 -50 0 50 100 150

0

-10

-30

-40

-50

-60

-20

direction in degrees

ante

nna

gai

n in

dB

resource block


Resource Allocation Problem

7

user rates depend on allocation of all resource units

Huge Resource Allocation Problem• solution based on channel quality information• duration for solution limited by coherence time

• scenario• objective


Outline


8


Novel ConceptsS

cen

ario

9

Orthogonal Medium Access

Reuse Medium Access


Novel ConceptsS

cen

ario

Distributed Concept for Orthogonal Medium Access

Distributed Concept for Reuse Medium Access

9


Reuse Medium Access


Novel Concepts

maximize sum of user rates subject to

minimum user rate

maximize minimum user rate

Trade-off performance vs. fairness

Sce

nar

io

Distributed Concept for Orthogonal Medium Access


9


Reuse Medium Access


Novel Concepts

exemplarily presentedcf. thesis

cf. thesis cf. thesis

9

maximize sum of user rates subject to

minimum user rate

maximize minimum user rate

Trade-off performance vs. fairness

Sce

nar

io


Reuse Medium Access



BS: design of grids of beams

RS: allocation of resource blocks

beams applied ontime-frequency unit

BS: allocation of resource blocks

bits per slot on RS-to-UE links

- uniformly allocated power- fixed number of allocated slots

Assumptions Flow of Subproblems

10


Design of Grids of Beams

11

inter-beam interference

co-channel interference

unknown:– current positions of UEs– channel quality information



11


non-adaptive solution:• each beam equally frequent• equal distance• randomly allocated to time- frequency unit



11

inter-beam interference


RS1

RS2


non-adaptive solution:• each beam equally frequent• equal distance• randomly allocated to time- frequency unit

known:+ positions of BS and RSs+ pathloss model+ beams+ user distribution


Adaptive Design

12

coverage areaof 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


Adaptive Design

12





use beams more often where receiving stations are expected

hot spot


Adaptive Design

12





use beams more often where receiving stations are expected

allocate beams to time-frequency units sequentially → best fit

algorithm

hot spot










13


Motivation of Assumptions

14




Distributed Concept for Reuse Medium Access: • uniformly allocated power• fixed number of allocated slots• design of grids of beams

14



pilots of BSDistributed Concept for Reuse Medium Access: • uniformly allocated power• fixed number of allocated slots• design of grids of beams

1.pilot phase → Signal-to-Interference-plus-Noise Ratio (SINR) estimation

14



pilots of RSpilots of RS


1.pilot phase → SINR estimation

14




1.pilot phase → SINR estimation2.SINR feedback

14




1.pilot phase → SINR estimation2.SINR feedback3.allocation of resource blocks

SINR knowledge RS1 SINR knowledge RS2

SINR knowledge BS

14




1.pilot phase → SINR estimation2.SINR feedback3.allocation of resource blocks4.data transmission

14










15


Allocation of Resource Blocks

16

Literature:• one problem across all links• requires knowledge of SINR

values in one point for- all resource blocks- all links

SINR values of resource blocks → bits per resource blocks

use SINR values locally→ distributed allocation


Allocation of Resource Blocks Provided by RS

17

• allocate resource blocks with objective max. min. user ratea) non-adaptiveb) adaptive

UE2

UE1 UE3

time

frequency time

frequency

1st beam:

2nd beam:

UE1

UE1

UE1

UE1

UE3

UE3

UE3

UE2

UE2

UE2

example with 2 beams:



17

• allocate resource blocks with objective max. min. user rate

a) non-adaptiveb) adaptive

• RSs know bits per slot for each RS-to-UE link



17

• allocate resource blocks with objective max. min. user rate

a) non-adaptiveb) adaptive

• RS knows bits per slot for each RS-to-UE link

• feedback to BS


Allocation of Resource Blocks Provided by BS

18

UE5UE4

RS1 RS2

2nd beam:

time

frequency

1st beam: RS1

RS1

UE4

UE5

RS2

time

frequency

UE4

RS2

RS2

RS1

RS1

• allocate resource blocks with objective max. min. weighted user rate

• UE weighted by 1, RS weighted by (number of UEs)-1


Allocation of Resource Blocks Provided by BS

18

UE5UE4

RS1 RS2

• 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


Evaluation Parameters

Parameter Value

size grids of beams 3

time-frequency units 64

number of resource blocks 192

number of slots 100

bits per symbol of modulation and coding schemes

0, 0.5, 1, 2, 3, 4, 5, 6, 7, 8

main lobe direction 0°, 30°, 60°, …, 330°

channel model BS/RS to UE non-line of sight model

channel model BS to RS line of sight model

Coordinates in meter

Coo

rdin

ate

s in

met

er

BSRS

RS0

-100

-200

200

100

0-100-200 300100 200

19


100

Performance Evaluation Design of Grids of Beams

20

all-adapt.BS: GoB, RB | RS: RBnon-adapt.

number of UEs5 10 15 20 25 30 35 40

0

120

80

60

40

20

aver

age

min

imum

use

r ra

te in

bits

/slo

t

GoB: design of grids of beams

RB: allocation of resource blocks


Performance Evaluation Allocation of Resource Blocks

21

all-adapt.BS: GoB, RB | RS: RBnon-adapt.

number of UEs5

010 15 20 25 30 35 40

120

100

80

60

40

20

aver

age

min

imum

use

r ra

te in

bits

/slo

t

GoB: design of grids of beams

RB: allocation of resource blocks


1

101

103

Signalling RS to BS

22

per resource block:

- channel gain - phase - noise/interference assumption:

4 bits per value

all time-frequency units and best modulation and coding scheme used

number of UEs served by RS

100

102

104

105

num

ber

of

bits

/slo

t

2 3 4 5 6 7 8 9 10

Reference Central genius approach Distributed Concept For Reuse Medium Access


Outline


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

24


Thank you.


Novel Adaptive Solutions

Maximize Sum of User Rates Subject to Minimum User Rate

Maximize Minimum User Rate

• noise• inter-beam interference

• noise• inter-beam interference • co-channel interference


Allocation of Slots

BS: Allocation of Resource Blocks

Allocation of Slots

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

BS: Allocation of Resource Blocks BS: Allocation of Resource Blocks

RS: Allocation of Resource Blocks RS: Allocation of Resource Blocks


A


Motivation of Concepts


Allocation of Resource Blocks,

Power and Bits

Allocation of Slots

Solution based on continuous number of bits depending on

SINR

Joint solutionbased on flexible number of

slots for single UE

Central solution

Joint concept for conventional network

Current information about co-channel interference

Solutions for combinational problems

Allocation of slots part of the concept for multiple

RSs and UEs

Use channel knowledge locally and define

distributed solution

Entire concept for relay networks

Pathloss model and user distribution

B

12. Feb.2010 | Christian Müller Distributed Resource Allocation in OFDMA-Based Relay Networks...

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