1. OBSS Preamble Detection
May 2013
March 2015
OBSS Preamble Detection
Date:
Authors:
Osama Aboul-Magd (Huawei Technologies)

2. March 2015
Context
In it was shown that errors on OBSS preambles were very high
Scenario 1 with 3 channels
Errors around 80-90%
In this presentation we check the probability of preamble detection in both scneario 1 and scenario 2
Qualcomm

3. Simulation Setup: Scneario 1
March 2015
Simulation Setup: Scneario 1
3 channels
Chosen to maximize distance between two apartments one 1 channel.
5 STAs per AP
1 antenna per AP & STA
Qualcomm

4. Simulation Parameters
March 2015
Simulation Parameters
Simulator Type
MAC simulator
Tx Power (AP/STA)
20/15dBm
Antenna Gain (AP/STA)
0/-2 dBi
Traffic Model
UL full buffer
BSS Bandwidth
80MHz
Noise Figure
Noise Floor
-101dBm per 20MHz
Rate Control Algorithm
single MCS chosen per link to maximize goodput
MSDU size (bytes)
1476
TXOP size
4 ms
Max Retx 10
Simulation Time (sec)
PER Curve
AWGN
Qualcomm

5. Throughput results March 2015
Preamble Detection ON for all packets
Premable Detection ON only for in-BSS packets
CCA 5%
50%
90%
Mean
-52
0.32
17.46
63.51
26.28
-62
0.83
25.38
63.95
29.89
-72
2.17
28.18
56.03
30.36
-82
24.55
70.19
32.24
-92
0.77
20.58
61.56 27
CCA 5%
50%
90%
Mean
-52
0.40
18.88
71.15
29.41
-62
0.32
26.00
70.30
31.87
-72
1.89
31.66
60.97
32.72
-82
0.89
28.63
81.53
35.83
-92
1.05
21.98
67.90
30.10
Shape of curves remains the same regardless of whether Preamble Detection is ON or OFF for OBSS packets
Note:having premable detection “OFF” for OBSS packets is like “OBSS color scheme”
Qualcomm

6. Preamble Detection Results
March 2015
Preamble Detection Results
Median number of OBSS packets detected per second is 5
Equivalent to 20ms deferral out of 1000ms (Txop=4ms)
2% of the time spent deferring due to OBSS premables.
Qualcomm

7. Preamble Detection Results cont.
March 2015
Preamble Detection Results cont.
% of successfully decoded OBSS preambles by all STAs in a BSS
Total successfully decoded preambles in BSS/Total attempted decodes of preambles in BSS
A device has an “attempted decode” of a preamble if the preamble is > -82 RSSI, and the device locks on to the preamble and tries to decode it.
 roughly 10% decode rate for OBSS premabels
Qualcomm

8. Simulation Setup: Scenario 2
March 2015
Simulation Setup: Scenario 2
“one room” 1 2 4 3 5 6 8 7 9 10 12 11 13 14 16 15 17 18 20 19 21 22 24 23 25 26 28 27 29 30 32 31
4 channels
5 STAs per AP
1 antenna per AP & STA
Qualcomm

9. Simulation Parameters
March 2015
Simulation Parameters
Simulator Type
MAC simulator
Tx Power (AP/STA)
20/15dBm
Antenna Gain (AP/STA)
0/-2 dBi
Traffic Model
UL full buffer
BSS Bandwidth
80MHz
Noise Figure
Noise Floor
-101dBm per 20MHz
Rate Control Algorithm
single MCS chosen per link to maximize goodput
MSDU size (bytes)
1476
TXOP size
4 ms
Max Retx 10
Simulation Time (sec)
PER Curve
AWGN
Qualcomm

10. Throughput results March 2015
Whether premable detection is on for OBSS packets or not, shape of curve is similar.
The ED level is the main factor affecting the shape of the tput curves
If OBSS preambles were detected, the dotted black line should match the purple curve
Qualcomm

11. Preamble Detection Results cont.
March 2015
Preamble Detection Results cont.
% of successfully decoded OBSS preambles by all STAs in a BSS
Total successfully decoded preambles in BSS/Total attempted decodes of preambles in BSS
A device has an “attempted decode” of a preamble if the preamble is > -82 RSSI, and the device locks on to the preamble and tries to decode it.
 roughly 10% decode rate for OBSS premabels
Qualcomm

12. March 2015
Conclusions
For the simulation run in scenario 1 and scneario 2, OBSS preambles are not decoded very often.
Around 10% of attempted decodes of OBSS preambles are successful
This corroborates the results found in
Could impact protocols that rely on preamble detection
Qualcomm

13. Appendix Scenario 1, reuse 1, 1DL March 2015
Same parameters as sceneario 1, reuse 3
Turning Preamble Detection ON for OBSS packets doesn’t change the shape of the tput curve. ED
No PD ED
No PD ED
No PD ED
No PD ED
No PD ED
PD ON
Qualcomm