1. doc.: IEEE 802. 11-15/0371-02-00ax
Submission M. Shahwaiz Afaqui
DSC leveraging uplink RTS/CTS control
Authors:
Name Affiliations Address Phone email
M. Shahwaiz Afaqui Technical
University of
Catalonia (UPC)
Edifici C4 Despatx 323
C/ Esteve Terrades, 7
08860 Castelldefels,
Barcelona, Spain.
+34 93 41
37218
Shahwaiz.afaqui@entel.upc.
edu
Eduard Garcia-
Villegas
Technical
University of
Catalonia (UPC)
Edifici C4 Despatx 322
C/ Esteve Terrades, 7
08860 Castelldefels,
Barcelona, Spain.
+34 93 41
37120
eduardg@entel.upc.edu
Elena Lopez-
Aguilera
Technical
University of
Catalonia (UPC)
Edifici C4 Despatx 303
C/ Esteve Terrades, 7
08860 Castelldefels,
Barcelona, Spain.
+34 93 41
37064
elopez@entel.upc.edu
July 2015

2. doc.: IEEE 802. 11-15/0371-02-00ax
Submission M. Shahwaiz Afaqui
• Context
• Simulation Environment: NS-3
• Simulation scenarios and assumptions
• Metrics used for evaluation
• Method for threshold selection to enable RTS control.
• Impact of frame size on RTS enabled DSC nodes
• Performance analysis of partial usage of RTS control
• References
• Appendix
Outline

3. doc.: IEEE 802. 11-15/0371-02-00ax
Submission M. Shahwaiz Afaqui
• IEEE 802.11ax enabled devices are expected to maintain and reduce energy consumed per
successful information bit.
• However, different amendments that are proposed to increase the efficient operation of
PHY and MAC layer would work against the aforementioned requirement.
• Since interference management is of paramount importance in dense deployments, IEEE
802.11ax aspires to intelligently utilize RTS/CTS method based on observed channel
conditions on per node basis.
• In [1], the authors highlight the possible mechanism through which an AP can control the
RTS/CTS policy for the associated stations.
• It has been shown in our previous presentations [2-3] that the use of DSC can increase
per-user throughput in dense scenarios over the cost of increase in Frame Error Rate
(FER) due to increased number of hidden nodes.
• In this submission we,
– investigate the performance of DSC,
• By utilizing intelligent RTS/CTS control method as means to mitigate the drawbacks
associated with DSC and to improve performance gains.
– recommend method to select threshold to enable RTS/CTS on each node.
– study the impact of frame size on RTS enabled DSC stations.
1. Context

4. doc.: IEEE 802. 11-15/0371-02-00ax
Submission M. Shahwaiz Afaqui
• NS-3 is a simulator for Internet systems,
– It allows the study of protocols and network performance of large-scale systems in
a controlled and scalable environment.
• Main characteristics,
– Discrete event simulator
– Packet level simulator (layer 2 and above)
– Layered architecture
– Free and open source
– Frequent updates ( latest version ns 3.23- release date 14-05-2015)
• Large number of protocol implementations and models available,
– TCP, UDP
– IPV4, IPV6, static routing
– IEEE 802.11 and variants, WiMAX, LTE
– IEEE 802 physical layer
– Mobility models and routing protocols
– Ability to design indoor, outdoor or hybrid networks
– etc.
2. Simulation Environment: NS-3

5. doc.: IEEE 802. 11-15/0371-02-00ax
Submission M. Shahwaiz Afaqui
2. Simulation Environment: NS-3
• Challenges
– dense WLAN scenario with multiple OBSS generated in NS-3 where the
simulation package is modified to,
• allow STAs to measure the energy level of received beacon frames.
• improve hybrid building pathloss model to accommodate floor
penetration losses.
– modifications /new additions made to accommodate real time operation of
DSC algorithm.
• Limitations
– MPDU aggregation is not yet mature and thus not used within these
simulations.
– IEEE 802.11ac model has not yet been developed and current results
focus on IEEE 802.11g/n..

6. doc.: IEEE 802. 11-15/0371-02-00ax
Submission M. Shahwaiz Afaqui
3. Simulation scenarios and assumptions
• Topology
– multi-floor residential building,
• 5 stories
• 2×10 apartments per story.
• Apartment size: 10m×10m×3m.
– 1 AP placed randomly in each
apartment at 1.5m height.
– channel selected randomly for each cell.
• Three channel scheme (1, 6, 11) 1/3 of
the cells share the same channel
– 5 STAs placed randomly around their
respective AP.

7. doc.: IEEE 802. 11-15/0371-02-00ax
Submission M. Shahwaiz Afaqui
• Frequency band: focused on 2.4GHz ,
• Intended to investigate the impact of DSC in a band that is more restricted in dense
environments.
• Traffic: UDP CBR uplink transmission in saturation conditions is considered,
• Worst case in terms of contention.
• Pathloss model: Hybrid Building Propagation loss model [12],
• obtained through a combination of several well known pathloss including indoor (through
walls, floors) and outdoor (urban, suburban, open).
• We simulated specific scenarios (with same STA and AP positions) with
and without utilizing the DSC and RTS/CTS control method.
• Additional simulation details are provided in the appendix.
3. Simulation scenarios and assumptions

8. doc.: IEEE 802. 11-15/0371-02-00ax
Submission M. Shahwaiz Afaqui
4. Metrics used for evaluation
• Aggregate throughput and STA’s individual throughput
• Frame Error Rate (FER)
– ratio of data frames received with errors to total data frames received.
• Fairness
– calculated according to Jain’s fairness index.

9. doc.: IEEE 802. 11-15/0371-02-00ax
Submission M. Shahwaiz Afaqui
6. Method for threshold selection to enable
RTS control
• FER of nodes used to enable and disable RTS/CTS control.
– i.e. if FER of a node is greater than RTSThrehold → enable RTS/CTS control for that
node.
• MCS0 with maximum MSDU (MAC payload) size (i.e. 2302bytes) used.
• Formula: RTSThreshold =AverageFER – N × AverageFER,
where N={-0.8, -0.6, -0.4,- 0.2, 0, 0.2, 0.4, 0.6, 0.8 }.
• Comparison done when DSC nodes enable RTS/CTS based on the aforementioned criteria.
0
2
4
6
8
10
12
14
16
%Thoughputimprovement
N=-0.8
N=-0.6
N=-0.4
N=-0.2
N=0
N=0.2
N=0.4
N=0.6
N=0.8 0
20
40
60
80
100
120
140
160
No.ofRTS/CTSenabled
STAs
N=-0.8
N=-0.6
N=-0.4
N=-0.2
N=0
N=0.2
N=0.4
N=0.6
• Approx. 14% improvement in throughput for DSC nodes utilizing RTS/CTS when N= -
0.4 (i.e. approx .137 out of 150 nodes utilize RTS/CTS ).
– N=-0.4 used in all the following experiments.
9

10. doc.: IEEE 802. 11-15/0371-02-00ax
Submission M. Shahwaiz Afaqui
7. Impact of frame size on RTS enabled DSC
nodes (1/2)
• As highlighted in previous slide, intelligent method to enable RTS/CTS control can have
multifold benefits.
• To build on the proposed argument, different frame sizes are used (i.e. 1000, 1600 and
2302Bytes) for comparative evaluation of a IEEE 802.11n networks with RTS enabled
DSC nodes (RTSDSC) with,
a. IEEE802.11n network with RTS disabled DSC nodes (NORTSDSC)
b. IEEE802.11n network with RTS disabled non-DSC nodes (NORTSNODSC)
• Approx. 55% improvement in throughput for largest frame.
• RTS control adds to benefits of DSC.
• Maximum FER improvements are achieved for small frame size.
-10
0
10
20
30
40
50
60
RTSDSC to
NORTSNODSC
NORTSDSC to
NODSCNORTS
RTSDSC to
NORTSDSC
%Throughputimprovement
1000B
1600B
2302B
-20
0
20
40
60
80
100
RTSDSC to
NORTSNODSC
NORTSDSC to
NODSCNORTS
RTSDSC to
NORTSDSC
%DecreaseinFER
1000B
1600B
2302B
10

11. doc.: IEEE 802. 11-15/0371-02-00ax
Submission M. Shahwaiz Afaqui
• In terms of fairness, RTSDSC provides substantial benefits when compared to
NORTSNODSC network.
-15
-10
-5
0
5
10
15
20
25
30
35
40
RTSDSC to
NORTSNODSC
NORTSDSC to
NODSCNORTS
RTSDSC to
NORTSDSC
%IncreaseinFairness
1000B
1600B
2302B
7. Impact of frame size on RTS enabled DSC
nodes (2/2)
11

12. doc.: IEEE 802. 11-15/0371-02-00ax
Submission M. Shahwaiz Afaqui
8. Performance analysis of partial usage of
RTS control
• As highlighted in the previous slides, RTS control method can be used as a viable
solution to reduce FER in a network.
– One of the major drawbacks of DSC scheme was the increase in FER.
– RTS enabled DSC network can overcome/improve the aforementioned problem.
• In this section, we analyze the partial usage of RTS control in DSC enabled
network.
• We propose to intelligently enable RTS/CTS,
– For large packet sizes, RTS/CTS can be beneficial.
– On the other hand, for small packets size, RTS/CTS method can be an overhead
that can lead to system performance degradation.
• The outcome of this section are also valid for AMPDU usage.
– We expect considerable improvement of DSC network utilizing RTS control with
AMPDU aggregation.
• We select N% of the nodes within a cell that have FER greater than
RTSThreshold=AverageFER – 0.4×AverageFER to enable RTS/CTS control.
12

13. doc.: IEEE 802. 11-15/0371-02-00ax
Submission M. Shahwaiz Afaqui
20% of nodes utilizing RTS Control
0
5
10
15
20
25
30
35
40
45
50
1000B 1600B 2302B
%Improvementinthroughput
RTSDSC to
NORTSNODSC
RTSDSC to
DSCNORTS
0
5
10
15
20
25
30
1000B 1600B 2302B
%decreaseinFER
RTSDSC to
NORTSNODSC
RTSDSC to
DSCNORTS
• For small frame size (i.e. 1000Bytes), utilizing small percentage of DSC enabled device
can result in increased system performance.
– In slide 3, the throughput gains achieved for RTSDSC with comparison to
NORTSNODSC were around 14%.
– However, allowing limited number of stations to enable RTS/CTS results in increase in
throughput between RTSDSC and NORTSNODSC (up to 18%.).
– On the contrary, for large frame size, the % decrease in FER is minimal.
13

14. doc.: IEEE 802. 11-15/0371-02-00ax
Submission M. Shahwaiz Afaqui
80% of the nodes utilizing RTS
0
5
10
15
20
25
30
35
40
45
50
1000B 1600B 2302B
%Improvementinthroughput
RTSDSC to
NORTSNODSC
RTSDSC to
DSCNORTS
0
10
20
30
40
50
60
70
80
90
1000B 1600B 2302B
%decreaseinFER
RTSDSC to
NORTSNODSC
RTSDSC to
DSCNORTS
14
• For the case of large number of nodes using RTS control, maximum benefits are
witnessed for larger frame sizes.

15. doc.: IEEE 802. 11-15/0371-02-00ax
Submission M. Shahwaiz Afaqui
10. References
• [1]. Sigurd Schelstraete, IEEE 802.11-15-0059, Uplink RTS/CTS Control.
• [2]. Eduard Garcia-Villegas , IEEE 802.11-15-0027, Simulation-based evaluation of
DSC in residential scenario.
• [3]. Eduard Garcia-Villegas, IEEE 802.11-15-0371, Proposal and simulation based
evaluation of DSC-AP Algorithm
15

16. doc.: IEEE 802. 11-15/0371-02-00ax
Submission M. Shahwaiz Afaqui
11. Appendix
16

17. doc.: IEEE 802. 11-15/0371-02-00ax
Submission M. Shahwaiz Afaqui
Simulation assumptions• PHY parameters
Parameters4 Values Parameters Values
Wireless Standard IEEE 802.11g and IEEE
802.11n
Packet size 1000bytes
Frequency band 2.4 GHz STA TX power 16dBm
Physical transmission
rate for IEEE 802.11n
i. 7.2Mbps Transmission gain 1dB
Channel width 20MHz Reception gain 1dB
Propagation delay
model
Constant speed
propagation delay
Noise figure 7dB
Propagation loss model Hybrid buildings
propagation loss
Energy detection threshold -78dBm
Wall penetration loss 12dB Initial CCA threshold -80dBm
Floor penetration loss 17dB Guard interval Short
Data preamble Short

18. doc.: IEEE 802. 11-15/0371-02-00ax
Submission M. Shahwaiz Afaqui
• MAC parameters
Parameters Values Parameters Values
Access protocol EDCA Retransmission attempts 16
RTS/CTS Disabled Maximum missed
beacons for re-association
10000
Association 100% STAs associated to
AP in an Apartment
Active probing Disabled
QOS Enabled Traffic model Best effort
Aggregation Disabled
• Simulation parameters
Parameters Values Parameters Values
Simulation time 25 seconds Simulations for each
hybrid case
24
Confidence interval 95% Simulations for non-DSC
network
24

19. doc.: IEEE 802. 11-15/0371-02-00ax
Submission M. Shahwaiz Afaqui
40% of the nodes utilizing RTS
• Select 40% of the nodes within a cell that have PER greater than
RTSThreshold=AveragePER – 0.4×AveragePER,
0
5
10
15
20
25
30
35
40
45
50
1000B 1600B 2302B
%Improvementinthroughput
RTSDSC to
NORTSNODSC
RTSDSC to
DSCNORTS
0
5
10
15
20
25
30
35
40
45
50
1000B 1600B 2302B
%decreaseinFER
RTSDSC to
NORTSNODSC
RTSDSC to
DSCNORTS
19

20. doc.: IEEE 802. 11-15/0371-02-00ax
Submission M. Shahwaiz Afaqui
60% of the nodes utilizing RTS
0
10
20
30
40
50
60
1000B 1600B 2302B
%Improvementinthroughput
RTSDSC to
NORTSNODSC
RTSDSC to
DSCNORTS
0
10
20
30
40
50
60
70
1000B 1600B 2302B
%decreaseinFER
RTSDSC to
NORTSNODSC
RTSDSC to
DSCNORTS
• Select 40% of the nodes within a cell that have PER greater than
RTSThreshold=AveragePER – 0.4×AveragePER,
20