Cell Edge Performance of
Cellular Mobile Systems
Prof. Xiaohu You
National Mobile Comm.
Research Lab.,
Southeast University
Shanghai Wireless
Comm. Research Center
Introduction
System Model
Performance Metrics
Single Cell Environment
Multicell Environment
Conclusion
ational Mobile Communications Research Laboratory, Southeast University
2 / 31
Introduction
System Model
Performance Metrics
Single Cell Environment
Multicell Environment
Conclusion
ational Mobile Communications Research Laboratory, Southeast University
3 / 31
Future mobile communication systems should
provide high data rates and mass wireless access
services over a limited spectrum bandwidth
Dramatic growth of wireless services: data,
multimedia, broadband wireless Internet
Radio spectrum becomes much more crowded than
in the past
Advanced transmission techniques improve the
spectrum efficiency
Multiantenna techniques: Diversity, SDMA
Multicarrier techniques: OFDM, GMC
ational Mobile Communications Research Laboratory, Southeast University
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Conceptual description:
― Limitations of conventional cellular architecture
― The cell-edge problem
r
Very low spectral efficiency and power efficiency at cell boundary !!!
东南大学移动通信国家重点实验室（
）
东南大学移动通信国家重点实验室（CRL@SEU）
2010年
年9月
月20日
日
第5页
页
Spectrum efficiency near the cell edge is still poor
The cell edge problem received much interests from
both academic and industry researchers. Some
countermeasures are proposed
Cell edge users suffer from large path loss
Inter-cell interference
Interference management
Cooperation：CoMP or DAS、network MIMO
But the cell edge performance, by itself, was not wellstudied in the literature
Motivation
ational Mobile Communications Research Laboratory, Southeast University
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Introduction
System Model
Performance Metrics
Single Cell Environment
Multicell Environment
Conclusion
ational Mobile Communications Research Laboratory, Southeast University
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Cellular configuration --- Collocated Antenna System
3
2
Cell-7
Cell-6
Cell-2
Cell-1
0
Cell-5
-
(0, 0)
Cell-3
Cell-4
-2
( 1, 1 )
-3
-3
-2
-
0
2
3
ational Mobile Communications Research Laboratory, Southeast University
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Cellular configuration --- Distributed Antenna System
2
( km
)
3
Cell-7
Cell-6
Cell-2
Cell-1
0
Cell-5
-
Cell-3
Cell-4
-2
( 1, 1 )
(
n,
n)
-3
-3
-2
-
0
2
3
ational Mobile Communications Research Laboratory, Southeast University
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Focus on the uplink
In each cell, the base station is assumed to be
loaded with one user
TDMA、FDMA
The composite channel fading model
Path loss : depends on the distance between the user
and the antennas of BSs
Large scale fading (shadowing) : log-normal distributed
Small scale fading : Rayleigh, Rice
ational Mobile Communications Research Laboratory, Southeast University
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Introduction
System Model
Performance Metrics
Single Cell Environment
Multicell Environment
Conclusion
ational Mobile Communications Research Laboratory, Southeast University
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Location-specific capacity
The concept of “cell edge” is based on the location
For a given channel matrix H
Conditioned on the locations
of the user and the RAU,
take expectation over other
random variables
ational Mobile Communications Research Laboratory, Southeast University
( km
)
BPU
( 1, 1 )
(
n,
n)
12 / 31
Metric 1 : The average capacity in the inscribed
circle of the hexagonal cell edge
( km
)
(√3
/2
)
( km
)
BPU
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Metric 2 : the worst case location-specific capacity in
the cell
BPU
Collocated antenna system
Distributed antenna system
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Metric 3 : the outage area
Capacity >
Capacity =
Capacity <
(km)
ational Mobile Communications Research Laboratory, Southeast University
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Introduction
System Model
Performance Metrics
Single Cell Environment
Multicell Environment
Conclusion
ational Mobile Communications Research Laboratory, Southeast University
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Large frequency reuse factor is used
Inter-cell interference is negligible
Large path loss causes performance degradation in the
cell edge
Result : Location-specific capacity in single cell
environment
ational Mobile Communications Research Laboratory, Southeast University
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Location-specific capacity with the cell
Location-specific capacity in the single cell environment (normalized SNR 0 dB)
Location-specific capacity
30
20
10
0
D
D/2
0
(2,10,1) CAS
(2,2,5) DAS
-D/2
-D
-D
-D/2
0
D/2
D
-D
ational Mobile Communications Research Laboratory, Southeast University
-D/2
0
D/2
D
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The average capacity over the inscribed circle (Metric-1)
The average capacity in the circle of radius 0.866D
20
DAS (2,2,5)
CAS (2,10,1)
18
bits/transmission
16
14
12
10
8
6
4
2
-10
-8
-6
-4
-2
0
2
4
α
Normalized SNR c*P/D (dB)
ational Mobile Communications Research Laboratory, Southeast University
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8
10
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The worst-case location-specific capacity (Metric-2)
The worst-case location-specific capacity in the single cell environment
16
DAS (2,2,5)
CAS (2,10,1)
14
bits/transmission
12
10
8
6
4
2
0
-10
-8
-6
-4
-2
0
2
4
α
Normalized SNR c*P/D (dB)
ational Mobile Communications Research Laboratory, Southeast University
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8
10
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The contour map of the location-specific capacity
DAS (2,2,5), normalized SNR 0 dB
CAS (2,10,1), normalized SNR 0 dB
D
D/2
18
12
10
-D/2
21
15
6.7
9
-D/2
10
30
9
18 15
6.
7
12
2118
12
12
12
-D
-D
15
9
12
-D/2
9
15
0
15
18
15
21
30
18
30
21
6.7
21
30
18 2
1
1821
21
30
15
18
18
21
18
15
12
15
2118
15
12
12
Location (y-axis)
1
218
9
10
15
Location (y-axis)
30
12
0
6.
7
6. 7
21
10
D/2
15
15
12
12
D
0
Location (x-axis)
D/2
D
-D
-D/2
ational Mobile Communications Research Laboratory, Southeast University
0
Location (x-axis)
6.7
D/2
-D
D
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The outage area normalize by the area of the cell (Metric-3)
The outage area normalized by the area of Cell-1
Single cell environment
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
CAS, c*P/D α = 0 dB
0.2
CAS, c*P/D α = 5 dB
0.1
DAS, c*P/D α = 0 dB
DAS, c*P/D α = 5 dB
0
5
10
15
Desired rate R
ational Mobile Communications Research Laboratory, Southeast University
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25
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Introduction
System Model
Performance Metrics
Single Cell Environment
Multicell Environment
Conclusion
ational Mobile Communications Research Laboratory, Southeast University
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The same radio spectrum is reused in all cells
Severe inter-cell interference
Large path loss
Result : Location-specific capacity in multicell
environment
ational Mobile Communications Research Laboratory, Southeast University
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Location-specific capacity with the cell
Location-specific capacity in the multicell environment (normalized SNR 0 dB)
Location-specific capacity
30
20
10
0
D
D/2
0
(2,2,5) DAS
-D/2
-D
-D
-D/2
0
(2,10,1) CAS
D/2
D
-D
ational Mobile Communications Research Laboratory, Southeast University
-D/2
0
D/2
D
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The average capacity over the inscribed circle (Metric-1)
The average capacity in the circle of radius 0.866D
12
DAS (2,2,5)
CAS (2,10,1)
11
10
bits/transmission
9
8
7
6
5
4
3
2
-10
-8
-6
-4
-2
0
2
4
α
Normalized SNR c*P/D (dB)
ational Mobile Communications Research Laboratory, Southeast University
6
8
10
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The worst-case location-specific capacity (Metric-2)
The worst-case location-specific capacity in the multicell environment
9
DAS (2,2,5)
CAS (2,10,1)
8
bits/transmission
7
6
5
4
3
2
1
-10
-8
-6
-4
-2
0
2
4
α
Normalized SNR c*P/D (dB)
ational Mobile Communications Research Laboratory, Southeast University
6
8
10
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The contour map of the location-specific capacity
DAS (2,2,5), normalized SNR 0 dB
CAS (2,10,1), normalized SNR 0 dB
D
D
1 9
16 2
16
5
6.
2130
4. 5
12
12
9
16
-D/2
6.5
16
7
-D/2
9
12
-D/2
9
2130
-D
-D
Location (y-axis)
16
9
0
30
21
16
12
9
16
12
12
6.5
3
21 0
4.5
16
21 30
21
30
16
16
12
Location (y-axis)
12
16
9
12
16
9
9
9
12
D/2
6.5
D/2
0
4.
5
5
4.
6.5
12
7
9
7
12
0
Location (x-axis)
9
4.
5
7
D/2
D
-D
-D/2
ational Mobile Communications Research Laboratory, Southeast University
5
4.
0
Location (x-axis)
D/2
-D
D
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The outage area normalize by the area of the cell (Matric-3)
The outage area normalized by the area of Cell-1
Multicell environment
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
CAS, c*P/D α = 0 dB
0.2
CAS, c*P/D α = 5 dB
0.1
DAS, c*P/D α = 5 dB
DAS, c*P/D α = 5 dB
0
4
8
12
16
Desired rate R
ational Mobile Communications Research Laboratory, Southeast University
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24
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Introduction
System Model
Performance Metrics
Single Cell Environment
Multicell Environment
Conclusions
ational Mobile Communications Research Laboratory, Southeast University
30 / 31
Cell edge effect of cellular systems was evaluated;
An analytical framework was presented
Collocated antenna system, Distributed antenna system;
Single cell environment, Multicell environment;
Three metrics were proposed to quantify the cell
edge performance
Analysis results were provided for typical system
configurations;
The theoretical results will serve as a baseline for
future work on cell edge problem and its
countermeasures.
ational Mobile Communications Research Laboratory, Southeast University
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THANKS
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