September 2008
doc.: IEEE 802.11-08/1132r0
Measurements of Coexistence between
802.11n 40MHz and Bluetooth SCO
Date: 2008-09-10
Authors:
Name
Company
Mohammad
Mansour
York Liu
Intel
Eldad Perahia
Intel
Submission
Address
Phone
email
mohammad.y.ma
nsour@intel.com
york.liu@intel.co
m
eldad.perahia@in
tel.com
Intel
Slide 1
Eldad Perahia (Intel)
September 2008
doc.: IEEE 802.11-08/1132r0
Abstract
Over-the-air measurements of Bluetooth SCO voice
performance in the presence of 802.11n 40 MHz link.
Results show no difference in impact to quality of
nearby Bluetooth SCO voice link due to neighboring
802.11n 40MHz link as that of 802.11n 20 MHz link
Submission
Slide 2
Eldad Perahia (Intel)
September 2008
doc.: IEEE 802.11-08/1132r0
Setup: Test Case I
•
•
•
•
Chariot Endpoint
Chariot Server/Console
Gigabit Ethernet
WiFi STA
BT Control
BT Slave
iFi
nW
11
Wired controlled network on Gigabit switch
IxChariot 6.5 traffic is managed on controlled
network
WiFi link is 2.4GHz/40MHz capable
SCO session is created over BT link with
ability to control AFH on/off.
Windows XP SP2 with Chariot endpoint is
used for all stations
Clean RF (2.40-2.48GHz) environment
verified with spectrum analyzer
Lin
k
BT Link
•
•
BT Control
BT Master
802.11n AP
Submission
Slide 3
Eldad Perahia (Intel)
September 2008
doc.: IEEE 802.11-08/1132r0
Setup: Test Case II
Chariot Endpoint
•
•
•
WiFi STA
BT1 Slave
Chariot Management
iFi
nW
Lin
k
•
Gigabit Ethernet
11
•
Wired controlled network on Gigabit switch
IxChariot 6.5 traffic is managed on controlled
network
WiFi link is 2.4GHz/40MHz capable
SCO session is created over BT1 link with
ability to control AFH on/off.
BT2 link used as an additional source of
BT Control
interference.
Windows XP SP2 with Chariot endpoint is
used for all stations
Clean RF (2.40-2.48GHz) environment
verified with spectrum analyzer
BT1 Link
•
•
Chariot Server/Console
BT Control
BT1 Master
BT2 Link
BT2 Slave
BT2 Matser
802.11n AP
Gigabit Ethernet
Submission
Slide 4
Eldad Perahia (Intel)
September 2008
doc.: IEEE 802.11-08/1132r0
Deployment Layout
• Test setup is contained
entirely in screen room.
• Lab room is a basic room
SCO BT
Devices
WiFi STA
– 15 ft x 15 ft
BT Link
Case II
WiFi AP
Submission
Slide 5
Eldad Perahia (Intel)
September 2008
doc.: IEEE 802.11-08/1132r0
Test Procedure : Case I
• Controlled network:
– All nodes are on the same network
– Chariot management traffic is on the controlled network
• Bluetooth baseline procedure:
– All WiFi nodes are powered down
– Bi-directional SCO link using HV3
• Voice traffic over SCO BT link from master to slave (~72sec standard reference wav file
transmission)
• No silence cancellation, so there is still traffic from slave to master
– MOS score calculated based on comparison of reference file sent and received file
using Opticom’s OPERA v3.5 voice quality analyzer (PESQ Algorithm).
– MOS score averaged over 5 iterations.
• Bluetooth with 802.11 traffic procedure:
– Bluetooth procedures are the same as baseline
– Add WiFi traffic for 90 Seconds
– 802.11n (max and 22mbps) traffic: 4 pairs – two per direction (Tx, Rx), high
performance throughput.scr script
– 802.11n (1 mbps) traffic: 1 pairs – one per direction (Tx, Rx), throughput.scr script
Submission
Slide 6
Eldad Perahia (Intel)
September 2008
doc.: IEEE 802.11-08/1132r0
Test Procedure : Case II
• Controlled network:
– All nodes are on the same network
– Chariot management traffic is on the controlled network
• Bluetooth baseline procedure:
– All WiFi nodes are powered down
– Bi-directional SCO link using HV3
• Voice traffic over SCO BT link from master to slave (~72sec standard reference wav file
transmission)
• No silence cancellation, so there is still traffic from slave to master
– Bidirectional voice traffic on second BT link (1 pair Tx/Rx Chariot voice) as a
source of interference.
– MOS score calculated based on comparison of reference file sent and received file
using Opticom’s OPERA v3.5 voice quality analyzer.
– MOS score averaged over 5 iterations.
• Bluetooth with 802.11 traffic procedure:
– Bluetooth procedures are the same as baseline
– Add WiFi traffic for 90 Seconds
– 802.11n (max and 22mbps) traffic: 4 pairs – two per direction (Tx, Rx), high
performance throughput.scr script
– 802.11n (1 mbps) traffic: 1 pairs – one per direction (Tx, Rx), throughput.scr script
Submission
Slide 7
Eldad Perahia (Intel)
September 2008
doc.: IEEE 802.11-08/1132r0
Test Methodology
•
•
•
•
•
•
Measurements made in accordance with test scenarios outlined in
08/971r0
Bluetooth devices comprised of two development platforms from leading
BT vendor
Bluetooth devices forming Bluetooth link separated by 1 m to model
typical distance between headset and cell phone
Bluetooth link separated from the 802.11 link by 0.5 m to model scenario
where WLAN connectivity is being using simultaneously with Bluetooth
voice call
Test measurements conducted for 802.11n 40 MHz and 802.11n 20 MHz
Test conducted with a range of 802.11 throughput
– Max throughput for each 802.11 system
– Comparable throughputs for each system to compare impact based on the same
offered load
– Minimum 802.11 throughput tested is 1 Mbps to model typical internet access
Submission
Slide 8
Eldad Perahia (Intel)
September 2008
doc.: IEEE 802.11-08/1132r0
Measurement Baseline
BT Mean Opinion Score
(MOS) - No 802.11
present
802.11n Throughput – no
BT present
Test Scenario 1
4.0
40 MHz: 155 Mbps
20 MHz: 71 Mbps
Test Scenario 2
4.0
Submission
Slide 9
Eldad Perahia (Intel)
September 2008
doc.: IEEE 802.11-08/1132r0
Test Scenario 1 – AFH off
11n 20 MHz:
44 Mbps
11n 40 MHz:
115 Mbps
BT MOS score
SCO, AFH off
4.0
3.0
2.0
BT+WiFi
2.4/40 11n
1.0
BT+WiFi
2.4/20 11n
0.0
Max TPT
22Mbps
1Mbps
11n offered load
• 802.11 traffic type: TCP
• BT link same as baseline
Submission
Slide 10
Eldad Perahia (Intel)
September 2008
doc.: IEEE 802.11-08/1132r0
Test Scenario 1 – AFH on
11n 20 MHz:
55 Mbps
11n 40 MHz:
136 Mbps
BT MOS score
SCO, AFH on
4.0
3.0
2.0
BT+WiFi
2.4/40 11n
1.0
BT+WiFi
2.4/20 11n
0.0
Max TPT 22Mbps
1Mbps
11n offered load
• 802.11 traffic type: TCP
• BT link same as baseline
Submission
Slide 11
Eldad Perahia (Intel)
September 2008
doc.: IEEE 802.11-08/1132r0
Test Scenario 2
AFH off
AFH on
11n 20 MHz
Max TPT
11n 40 MHz
Max TPT
11n 20 MHz
Max TPT
11n 40 MHz
Max TPT
BT MOS
2.6
2.4
3.9
3.7
802.11n
TPT
42 Mbps
90 Mbps
52 Mbps
105 Mbps
• BT MOS are identical to Test Scenario 1
• 802.11n throughput results degraded compared
to Test Scenario 2
Submission
Slide 12
•
•
802.11 traffic type: TCP
BT links same as baseline
Eldad Perahia (Intel)
September 2008
doc.: IEEE 802.11-08/1132r0
Analysis of Results
• All BT MOS measurements with AFH-on in the presence of
802.11n 40MHz are comparable to that of the BT baseline for both
Test Case 1 and 2
• BT MOS score improves with decreasing 802.11n offered load
with AFH-off in Test Case 1
• No measurable impact due to offered load with AFH-on in Test
Case 1
• No measurable difference between 802.11n 40 MHz and 802.11n
20 MHz with regards to BT performance
• No change in BT MOS score between Test Case 1 and 2
• 802.11n 20 MHz and 40 MHz max throughput is degraded by BT
even with AFH on
Submission
Slide 13
Eldad Perahia (Intel)
September 2008
doc.: IEEE 802.11-08/1132r0
Conclusions
• Over-the-air measurements conducted to determine
coexistence between 802.11n 40 MHz and Bluetooth
SCO voice link
• Measurements demonstrate that neighboring 802.11n
40 MHz link has no difference in impact to quality of
nearby Bluetooth SCO voice link as that of 802.11n 20
MHz link
• All BT SCO MOS measurements with AFH-on in the
presence of 802.11n 40MHz are comparable to that of
the BT SCO baseline
Submission
Slide 14
Eldad Perahia (Intel)