Coordinated Multipoint Transmission in Femtocell Systems

Masters Thesis PresentationDepartment of Communications and Networking

Student: Utku Öztürk

Supervisor: Prof. Jyri Hämäläinen Aalto UniversityInstructor: M.Sc. Zhong Zheng Aalto University

Agenda

• Thesis• LTE Overview• Coordinated Multipoint Transmission• Femtocell Concept• Simulation Model• Performance Evaluation

Thesis

• Literature Review

• Simulator

• Implementing the new functions

• Performance tests

• Verification of the results

LTE Overview• 4G technology• Simplified Architecture• Reduced Costs• Low Power Consumption• Enhanced Data Rates• Mutliple Antenna Solutions• Increased Coverage

Coordinated MultiPoint TransmissionCoMP

• Full frequency reuse (reuse one) is highly desirable for future communication

systems so as to exploit the spectrum efficiently.

• The effects of interference is crucial if carrier frequencies of cells are the same

as in OFDMA systems. It limits the spectral efficieny mostly at cell edge.

• The main purpose is to increase the SINR of the user.

• Drawbacks: - Interference to other users

- Extra power consumption

- Additional cost

CoMP Schemes in DownlinkCoordinated Scheduling / Beamforming “Interference Mitigation Method”

Joint Processing “Improve signal quality”

Dynamic Cell Selection : Fast selection of cells Joint Transmission : Signal combining

Joint Transmission : Signals from different BSs are coherently combined at the terminal

Y1 = H11 W1 X1 + H21 W2 X2 + H31 W3 X3 + N1

X = X1 = X2 = X3

Y1 = (H11 W1 + H21 W2 + H31 W3)*X + N1

CoMP

Femtocell Concept

The need for femtocells:• Coverage• Capacity• Power

Features:• Low Power• Low Cost• Plug & Play

Ability to be connected to fixed telephony line

Inter-cell interference in Femtocell Networks

macrocell

femtocell

femtocell

femtocell

Cross-layer interferenceMacrocell FemtocellFemtocell Macrocell

Co-layer intereferenceFemtocell Femtocell

System Model Parameters ( Ref. 1 ) Assumptions

System Layout Hexagonal grid, 3 sectors per site (21 cells ), reuse 1

Propagation Scenario Macro 1 (500m ISD)

User Drop 12 users per macrocell, 4 users in the femtocell block

Carrier Frequency 2 GHz

System Bandwidth 10 MHz (48 PRBs for data)

Channel Models MBS - UE = 15.3 + 37.6 log10R + Wall Attenuation (R in meters)

FBS - UE = 38.46 + 20 log10R + Wall Attenuation (R in meters)

Antenna Pattern

MBS Antenna Amax=20 dB

Am=14dBi, Θ=70°

Omni-directional FBS Antenna

BS Transmit PowerS MBS TX power : 46 dB , FBS TX power : 10 dB

Noise Figure 8 dB

Shadowing Deviation 8 dB except among HeNBs , 4 dB for HeNBs

UE Scheduling Round Robin

Ref. 1. 3GPP TSG RAN WG4 (Radio) Meeting #51, 4-8 May 2009

System Metrics and Parameters

SINR threshold level : 0, 3, 5, 10, 15, 25 dBFBS penetration rate : 0.25, 0.50, 0.75, 1

CDF of throughput50%-ile users5%-ile users

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Throughput,kbps

CD

F of

Thr

ough

put

Comparison of SINR Thresholds with FBS penetration rate for the worst users

No Assistance

SINR Thr=3dB @FBS=0.5

SINR Thr=3dB @FBS=1SINR Thr=25dB @FBS=0.5

SINR Thr=25dB @FBS=1

0 2000 4000 6000 8000 10000 12000 14000 160000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Throughput,kbps

CD

F o

f Thr

ough

put

Comparison of SINR Thresholds with FBS penetration rate for all users

No Assistance

SINR Thr=3dB @FBS=0.5

SINR Thr=3dB @FBS=1SINR Thr=25dB @FBS=0.5

SINR Thr=25dB @FBS=1

All 4 usersThe worst user

0 100 200 300 400 500 6002000

2200

2400

2600

2800

3000

3200

3400

3600

3800Throughput Comparison for worst user

Throughput for 5%-ile users, kbps

Thro

ughput fo

r th

e 5

0%

-ile

users

, kbps

FBS = 1

FBS = 0.75FBS = 0.50

FBS = 0.25

3dB

10dB

15dB

25dB

15dB

3dB5dB

0dB

5dB

5dB

0dB3dBOutage

25dB

25dB

10dB15dB

10dB

No Assistance

0dB10dB 5dB

0dB

700 800 900 1000 1100 1200 1300 1400 1500 16006000

6500

7000

7500

8000

8500Throughput Comparison for all users

Throughput for 5%-ile users, kbps

Thro

ughput fo

r 50%

-ile

users

, kbps

FBS = 1

FBS = 0.75FBS = 0.50

FBS = 0.25

15dB

10dB15dB

25dB

25dB

3dB

0dB

25dB

3dB

3dB

0dB

0dB

5dB

5dB

15dB

10dB

No Assistance

15dB3dB

5dB

5dB10dB

0dB

10dB

6000 6500 7000 7500 8000 85002000

2200

2400

2600

2800

3000

3200

3400

3600

3800Throughput Comparison for 50 percentile

Throughput for all users, kbps

Thro

ughput fo

r w

ors

t users

, kbps

FBS = 1

FBS = 0.75FBS = 0.50

FBS = 0.25

No Assistance

0dB

3dB

10dB

0dB

0dB

5dB

5dB

0dB 3dB

25dB

25dB

15dB

15dB

25dB

5dB

10dB

3dB

10dB

25dB

10dB5dB

700 800 900 1000 1100 1200 1300 1400 1500 16000

100

200

300

400

500

600Throughput Comparison for 5 percentile

Throughput for all users, kbps

Thro

ughput fo

r w

ors

t users

, kbps

FBS = 1

FBS = 0.75FBS = 0.50

FBS = 0.25

0dB

3dB

3dB

10dB

15dB

25dB

25dB

15dB

15dB

10dB

10dB 25dB

5dBNo Assistance

10dB

5dB

3dB

0dB0dB

0dB5dB

5dB

Summary and Conclusions

• Coordination of the base stations in a femtocell network improve the

system performance in general terms

• Interference severely degrades the performance of the bad performing

users and the users having the worst throughput

• Lower SINR threshold values perform better for users in poor condition

• The increasing number of FBSs deployed in the femotcell network

increases the overall system performance as well

Thank you

Questions ?