September 2013
doc.: IEEE 802.11-13/1123r0
Capacity Simulation of High Density
Indoor WLAN Systems
Date: 2013-09-16
Authors:
Name
Company
Anders Furuskär
Ericsson AB
Stephen Rayment
Ericsson AB
Leif Wilhelmsson
Ericsson AB
Submission
Address
Phone
Färögatan 6
Stockholm, Sweden
168 40
603 March Road
Kanata, ON, Canada
K2K 2M5
Scheelevägen 23
Lund, Sweden
Slide 1
email
+46 107 143 679
ander.furuskar
@ericsson.com
+1 613 254 7070
stephen.rayment
@ericsson.com
+46 706 216 958
leif.wilhelmsson
@ericsson.com
Furuskar et al, Ericsson AB
September 2013
doc.: IEEE 802.11-13/1123r0
Abstract
Preliminary results from simulation of high density
indoor WLAN systems. The static simulation is similar
to one used for cellular applications
Submission
Slide 2
Furuskar et al, Ericsson AB
September 2013
doc.: IEEE 802.11-13/1123r0
Topics
•
•
•
•
WLAN multi-cell performance aspects
Models and assumptions
Results
Summary
Submission
Slide 3
Furuskar et al, Ericsson AB
September 2013
doc.: IEEE 802.11-13/1123r0
WLAN Multi-cell Performance Aspects
• 802.11n and 802.11ac have similar physical layer
characteristics as cellular systems, e.g. LTE
– Modulation, channel coding, MIMO capabilities
• But…
• The CSMA-based MAC limits densification
– Nodes that hear each other cannot be active at the same time
– This creates a re-use in the time domain
• Operation in uncontrolled environments with external
interference will further limit performance
– Not modeled here
Submission
Slide 4
Furuskar et al, Ericsson AB
September 2013
doc.: IEEE 802.11-13/1123r0
Models and Assumptions
• IEEE 802.11n modulation and coding rates
• 2.4 or 5GHz
• Frequency reuse varied between 1 and 12 vs isolated AP
– Choose channels that maximize distance between APs that use the same
frequency
•
•
•
•
•
•
•
•
One single 20MHz carrier per AP
AP and STA power 100mW (EIRP)
CS (Carrier Sense) threshold -85dBm
2x2 MIMO in DL and UL
No external interference
File transfer traffic
75% in downlink and 25% in uplink
MAC PDU size 65KB
Submission
Slide 5
Furuskar et al, Ericsson AB
September 2013
doc.: IEEE 802.11-13/1123r0
Deployment Scenario
• An office-like building with
80x50m footprint
• Ten floors of height 3m
• Interior walls every 10m (10x10m rooms)
• Winner II propagation
– Free-space propagation with inner wall loss of 12dB, and floor loss of
17dB for first floor and 4dB for following floors
– Log-normal shadowing with standard deviation 8dB
• Subscriber density 1/16m2  250/2500 per floor/building
– ~30 subscribers per AP
• 8 APs per floor, randomly deployed per floor, all floors same
Submission
Slide 6
Furuskar et al, Ericsson AB
September 2013
doc.: IEEE 802.11-13/1123r0
Traffic Load per AP vs
Monthly Volume per User
• Subscriber density 1/16m2  250/2500 per floor/building
• 200 busy hours per month
• Traffic per subscriber and month v busy hour traffic
per floor
– Assume 10 GB per month per sub
x 250 subs per floor / 200 busy hours per month
=
27Mbps per floor or 3.4Mbps per AP
Submission
Slide 7
Furuskar et al, Ericsson AB
September 2013
doc.: IEEE 802.11-13/1123r0
Radio Characteristics
and
Performance Measurement Method
Submission
Slide 8
Furuskar et al, Ericsson AB
September 2013
doc.: IEEE 802.11-13/1123r0
AP to STA Radio Characteristics
• Good coverage
– Well above total gain of -100dB which corresponds to -80dBm received
power
100
100
90
90
80
80
70
70
60
60
C.D.F. [%]
C.D.F. [%]
• Good isolation geometry due to walls and floors
50
40
50
40
30
30
20
20
2.4GHz
5.0GHz
10
0
-110
-100
Submission
-90
-80
Total Gain (Prx-Ptx) [dB]
-70
10
0
-10
-60
Slide 9
2.4GHz
5.0GHz
-5
0
5
10
15
20
Downlik Wideband SINR (Geometry) [dB]
Furuskar et al, Ericsson AB
25
September 2013
doc.: IEEE 802.11-13/1123r0
Cell Isolation
• Propagation as a function of distance and floor
• Total loss <105dB (received power >-85dBm) some two to
three walls or floors away
2.4GHz
130
130
120
120
110
Floor 9
Floor 8
Floor 7
Floor 6
Floor 5
Floor 4
Floor 3
Floor 2
Floor 1
Floor 0
100
90
80
70
60
50
0
5
Submission
5.0GHz
140
Total Loss [dB]
Total Loss [dB]
140
10
15
20
Distance [m]
25
30
110
Floor 9
Floor 8
Floor 7
Floor 6
Floor 5
Floor 4
Floor 3
Floor 2
Floor 1
Floor 0
100
90
80
70
60
35
Slide 10
50
0
5
10
15
20
Distance [m]
25
30
Furuskar et al, Ericsson AB
35
September 2013
doc.: IEEE 802.11-13/1123r0
Cell Isolation
Received Power [dBm]
• An active AP triggers carrier sensing (>-85dBm) in 7.1
and 5.9 neighbor APs (on average) in 2.4GHz and
5.0GHz respectively -40
2.4GHz
x
• The graph shows
5.0GHz
x
-50
x
average
x
-60
received power
x
x
from neighbor APs
x
-70
in order
x
x
x
-80
x
x
of strength
x
x
x
-90
x
x
x
x
-100
x
0
2
6
4
8
10
Cell
Submission
Slide 11
Furuskar et al, Ericsson AB
doc.: IEEE 802.11-13/1123r0
Performance Measurement Method
• Cell-edge (5th percentile) and mean user throughput vs traffic load
• ‘How much can the system be loaded before user experience gets
Datarates decrease
unacceptable?’
Downlink
when load increases due to
increased interference and
more active users sharing channel
100
Downlink
80
2.4 [100%] m ean
90
80
User Throughput [Mbps]
Traffic load
70
C.D.F. [%]
2.4 [100%] 5th perc
70
60
50
40
30
60
50
40
30
20
20
Traffic load
10
10
0
0
20
Submission
40
60
User Throughput [Mbps]
80
100
Slide 12
0
0
1
2
3
4
5
6
Served Traffic per Small Cell [Mbps]
7
Furuskar et al, Ericsson AB
8
September 2013
doc.: IEEE 802.11-13/1123r0
Performance Results
2.4GHz
Submission
Slide 13
Furuskar et al, Ericsson AB
September 2013
doc.: IEEE 802.11-13/1123r0
Isolated APs, 2.4GHz, DL
• 5th percentile throughput is at most 40Mbps
• Utilization approaching 75% (CSMA efficiency)
Downlink
90
Isolated [100%] m ean
Isolated [100%] 5th perc
User Throughput [Mbps]
80
70
60
50
40
30
20
10
0
Submission
0
10
20
30
40
Served Traffic per Small Cell [Mbps]
Slide 14
50
Furuskar et al, Ericsson AB
September 2013
doc.: IEEE 802.11-13/1123r0
Reuse 3, 2.4GHz, DL
• 5th percentile throughput is at most 12Mbps
• Utilization approaching 30%
Downlink
90
Isolated [100%] m ean
Isolated [100%] 5th perc
Reuse 3 [100%] m ean
User Throughput [Mbps]
80
Reuse 3 [100%] 5th perc
70
60
50
40
30
20
10
0
Submission
0
10
20
30
40
Served Traffic per Small Cell [Mbps]
Slide 15
50
Furuskar et al, Ericsson AB
September 2013
doc.: IEEE 802.11-13/1123r0
Reuse 1, 2.4GHz, DL
• 5th percentile throughput is at most 7Mbps
• Utilization approaching 10%
Downlink
90
Isolated [100%] m ean
Isolated [100%] 5th perc
User Throughput [Mbps]
80
Reuse 3 [100%] m ean
Reuse 3 [100%] 5th perc
70
Reuse 1 [100%] m ean
Reuse 1 [100%] 5th perc
60
50
40
30
20
10
0
Submission
0
10
20
30
40
Served Traffic per Small Cell [Mbps]
Slide 16
50
Furuskar et al, Ericsson AB
September 2013
doc.: IEEE 802.11-13/1123r0
Reuse 1, 3, Isolated, 2.4GHz, UL
• Same trends as in downlink
Uplink
90
Isolated [100%] m ean
Isolated [100%] 5th perc
User Throughput [Mbps]
80
Reuse 3 [100%] m ean
Reuse 3 [100%] 5th perc
70
Reuse 1 [100%] m ean
Reuse 1 [100%] 5th perc
60
50
40
30
20
10
0
Submission
0
5
10
15
Served Traffic per Small Cell [Mbps]
Slide 17
20
Furuskar et al, Ericsson AB
September 2013
doc.: IEEE 802.11-13/1123r0
Capacity
• Maximum served traffic for cell-edge (5th percentile)
user throughput of at least 5Mbps
Downlink
Uplink
Isolated[100%
[100%]
Isolated
]
Isolated [100%
[100%]]
Isolated
Reuse33[100%
[100%]
Reuse
]
Reuse 33 [100%
[100%]]
Reuse
Reuse 1 [100% ]
Reuse 1 [100% ]
0
5
10
15
20
25
30
Served Traffic per Small Cell (at R5=5Mbps) [Mbps]
Submission
35
0
Slide 18
2
4
6
8
10
Served Traffic per Small Cell (at R5=5Mbps) [Mbps]
Furuskar et al, Ericsson AB
12
September 2013
doc.: IEEE 802.11-13/1123r0
Spectral Efficiency
• Capacity divided by total spectrum usage in used direction
– Spectral Efficiency = Capacity / (reuse * 20MHz x f)
– Downlink = 0.75 Uplink = 0.25
• Increases with tighter reuse, but still rather low
Downlink
0
Uplink
Isolated [100% ]
Isolated [100% ]
Reuse
Reuse33 [100% ]
Reuse
Reuse3 3 [100% ]
Reuse 1 [100% ]
Reuse 1 [100% ]
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
Served Traffic per Small Cell (at R5=5Mbps) [bps/Hz]
Submission
0
Slide 19
0.1
0.2
0.3
0.4
0.5
Served Traffic per Small Cell (at R5=5Mbps) [bps/Hz]
Furuskar et al, Ericsson AB
September 2013
doc.: IEEE 802.11-13/1123r0
Performance Results
5GHz
Submission
Slide 20
Furuskar et al, Ericsson AB
September 2013
doc.: IEEE 802.11-13/1123r0
Reuse 1-12, Isolated, 5GHz, DL
• Same trend as in 2.4GHz
• Slightly better than 2.4GHz due to better isolation
Downlink
80
Isolated [100%] m ean
Isolated [100%] 5th perc
70
Reuse 12 [100%] m ean
User Throughput [Mbps]
Reuse 12 [100%] 5th perc
60
Reuse 6 [100%] m ean
Reuse 6 [100%] 5th perc
Reuse 3 [100%] m ean
50
Reuse 3 [100%] 5th perc
Reuse 1 [100%] m ean
Reuse 1 [100%] 5th perc
40
30
20
10
0
Submission
0
10
20
30
40
Served Traffic per Small Cell [Mbps]
Slide 21
50
Furuskar et al, Ericsson AB
September 2013
doc.: IEEE 802.11-13/1123r0
Reuse 1-12, Isolated, 5GHz, UL
• Same trends as downlink
Uplink
80
Isolated [100%] m ean
Isolated [100%] 5th perc
70
Reuse 12 [100%] m ean
User Throughput [Mbps]
Reuse 12 [100%] 5th perc
60
Reuse 6 [100%] m ean
Reuse 6 [100%] 5th perc
Reuse 3 [100%] m ean
50
Reuse 3 [100%] 5th perc
Reuse 1 [100%] m ean
Reuse 1 [100%] 5th perc
40
30
20
10
0
Submission
0
2
4
6
8
10
12
Served Traffic per Small Cell [Mbps]
Slide 22
14
16
Furuskar et al, Ericsson AB
September 2013
doc.: IEEE 802.11-13/1123r0
Capacity 5GHz
• Maximum served traffic for cell-edge (5th percentile) user
throughput of at least 5Mbps
Downlink
Uplink
Isolated [100%
[100%]]
Isolated
Isolated [100%]
Isolated
[100% ]
Reuse12
12 [100%
[100%]]
Reuse
Reuse 12
Reuse
12 [100%]
[100% ]
Reuse 6 [100% ]
Reuse 6 [100% ]
Reuse 3 [100% ]
Reuse 3 [100% ]
Reuse 1 [100% ]
Reuse 1 [100% ]
0
5
10
15
20
25
Served Traffic per Small Cell (at R5=5Mbps) [Mbps]
Submission
30
0
Slide 23
2
4
6
8
10
Served Traffic per Small Cell (at R5=5Mbps) [Mbps]
Furuskar et al, Ericsson AB
12
September 2013
doc.: IEEE 802.11-13/1123r0
Spectral Efficiency
• Capacity divided by total spectrum usage in used direction
– Spectral Efficiency = Capacity / (reuse * 20MHz x f)
– Downlink = 0.75 Uplink = 0.25
• Increases with tighter reuse, but still rather low
Downlink
0
Uplink
Isolated [100% ]
Isolated [100% ]
Reuse 12 [100% ]
Reuse 12 [100% ]
Reuse 6 [100% ]
Reuse 6 [100% ]
Reuse 3 [100% ]
Reuse 3 [100% ]
Reuse 1 [100% ]
Reuse 1 [100% ]
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
Served Traffic per Small Cell (at R5=5Mbps) [bps/Hz]
Submission
0
Slide 24
0.1
0.2
0.3
0.4
0.5
Served Traffic per Small Cell (at R5=5Mbps) [bps/Hz]
Furuskar et al, Ericsson AB
September 2013
doc.: IEEE 802.11-13/1123r0
Next Steps
• Inter-cell carrier sensing based only on AP-to-AP
channel, need to look at STA as well
• Include hidden nodes
• Include RTS/CTS
– Currently not explicitly modeled, but no hidden nodes assumed
either
• Model more realistic modulation rate algorithms
• Model effects of more realistic AP channel selection
and placement
Submission
Slide 25
Furuskar et al, Ericsson AB
September 2013
doc.: IEEE 802.11-13/1123r0
Summary
• High capacity multi cell systems can be built with
WLAN technology (!)
• Inter-cell carrier sensing limits performance
• Possible to mitigate with more channels
• Are there more spectrally efficient solutions?
• We have a good baseline to assess enhancements
Submission
Slide 26
Furuskar et al, Ericsson AB
September 2013
doc.: IEEE 802.11-13/1123r0
References
[1] I. Siomina, A. Furuskär, and G. Fodor. A mathematical framework
for statistical QoS and capacity studies in OFDM networks, Proc. of IEEE
PIMRC ’09, Sep. 2009.
Submission
Slide 27
Furuskar et al, Ericsson AB