= Investigating Physical Carrier Sensing in the DCF with Multiple Traffic Flows =

The purpose of the 802.11 Distributed Coordination Function (DCF) is to allow multiple flows of traffic to contend for a shared wireless medium. In this application note, we investigate how the 802.11 Reference Design behaves when subjected to multiple traffic flows. This note provides a case study on how the WLAN Experiment Framework can be used to control and analyze the performance of the 802.11 Reference Design.

== Requirements ==

To run the code provided in this note, the following requirements must be met:

 * 3 WARP v3 kits
 * [wiki:../../../Changelog#a0.91BetaRelease 802.11 Reference Design v.91 Beta]

=== Experimental Setup ===


||  [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:experimental_setup_photo.jpg, width=600)]]  ||
||  '''Experimental Setup'''  ||

We use 4 traffic flows in our experiments:
 * '''Flow 1:''' Backlogged constant bit-rate (CBR) traffic from AP to STA_1
 * '''Flow 2:''' Backlogged CBR traffic from AP to STA_2
 * '''Flow 3:''' Backlogged CBR traffic from STA_1 to AP
 * '''Flow 4:''' Backlogged CBR traffic from STA_2 to AP

 [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:experimental_flows.png, width=600)]] 

The colors in the figure above correspond to the colors used in per-flow plots below.

== Experiment 1: Enabled Physical Carrier Sensing ==

=== Experiment Details ===
 * Packet Length: 1400 byte payloads (1428 bytes OTA with MAC header and FCS)
 * PHY Rate: 18 Mbps
 * Tx Power: -5 dBm
 * Trial Duration: 300 seconds
 * Channel 1
 * Physical Carrier Sensing Threshold: 250/1023


=== Results ===


||  [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:no_cs_xput_vs_time.png, width=600)]]  || [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:no_cs_xput_hist.png, width=600)]]  ||
 ||  '''Throughput vs. Time'''  || '''Throughput Histogram'''  ||


||  [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:cs_pow_vs_time.png, width=600)]]  ||
||  '''Rx Power vs. Time''  ||

||  [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:cs_cw_vs_time.png, width=600)]]  ||
||  '''Rx Power vs. Time''  ||


||  [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:cs_coll_flow_1.png, width=300)]]  || [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:cs_coll_flow_2.png, width=300)]]  ||
||  [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:cs_coll_flow_3.png, width=300)]]  || [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:cs_coll_flow_4.png, width=300)]]  ||


||  [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:no_cs_collisions_zoom.png, width=600)]]  ||  [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:cs_1sec.png, width=600)]]  ||
||  '''Collisions (Zoomed)'''  ||  '''Collisions (1 second)'''  ||

== Experiment 2: Disabled Physical Carrier Sensing ==

=== Experiment Details ===
 * Packet Length: 1400 byte payloads (1428 bytes OTA with MAC header and FCS)
 * PHY Rate: 18 Mbps
 * Tx Power: -5 dBm
 * Trial Duration: 300 seconds
 * Channel 1
 * Physical Carrier Sensing Threshold: 1023/1023


=== Results ===


||  [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:no_no_cs_xput_vs_time.png, width=600)]]  || [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:no_no_cs_xput_hist.png, width=600)]]  ||
 ||  '''Throughput vs. Time'''  || '''Throughput Histogram'''  ||


||  [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:no_cs_pow_vs_time.png, width=600)]]  ||
||  '''Rx Power vs. Time''  ||

||  [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:no_cs_cw_vs_time.png, width=600)]]  ||
||  '''Rx Power vs. Time''  ||


||  [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:no_cs_coll_flow_1.png, width=300)]]  || [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:no_cs_coll_flow_2.png, width=300)]]  ||
||  [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:no_cs_coll_flow_3.png, width=300)]]  || [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:no_cs_coll_flow_4.png, width=300)]]  ||


||  [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:no_no_cs_collisions_zoom.png, width=600)]]  ||  [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:no_cs_1sec.png, width=600)]]  ||
||  '''Collisions (Zoomed)'''  ||  '''Collisions (1 second)'''  ||

== Resources ==

Links to the data sets and experiment scripts used to perform this study will be posted shortly.