coordinated multipoint transmission in femtocell systems
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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
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