Changes between Version 53 and Version 54 of 802.11/wlan_exp/app_notes/dcf_with_multiple_flows


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Timestamp:
Apr 22, 2014, 12:01:34 PM (10 years ago)
Author:
murphpo
Comment:

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  • 802.11/wlan_exp/app_notes/dcf_with_multiple_flows

    v53 v54  
    11= Investigating Physical Carrier Sensing in the DCF with Multiple Traffic Flows =
    22
    3 The purpose of the 802.11 Distributed Coordination Function (DCF) is to allow multiple traffic flows to contend for a shared wireless medium. In this application note we investigate how the Mango 802.11 Reference Design behaves when subjected to multiple traffic flows. This note provides a case study on how the design's experiments framework can be used to control and analyze the performance of 802.11 Reference Design nodes.
     3This application note presents results from a simple experiment using the Mango 802.11 Reference Design and its experiments framework. We use three WARP v3 nodes to build a basic 802.11 network, with one AP and two stations (STA). All three nodes contend for medium access with backlogged flows. The experiments framework enables a detailed study of the performance of each traffic flow, providing insight into the low-level behavior of the 802.11 MAC Distributed Coordination Function (DCF). As the independent variable in our experiments we modify the state of physical carrier sensing at each node.
    44
     5The primary purpose of this app note is to demonstrate the 802.11 Reference Design and its experiments framework, and to highlight the variety of experimental data which can be computed from the Tx/Rx log recorded at each node. This app note is not an exhaustive study of carrier sensing and should not be cited as such. There are [http://scholar.google.com/scholar?hl=en&q=carrier+sensing many scholarly articles] on the carrier sensing that provide a much richer theoretical background.
    56
    67=== Experimental Setup ===
    78
    8 The experiments described below used 3 Mango WARP v3 kits, each running the [wiki:../../../Changelog#a0.91BetaRelease 802.11 Reference Design (version v0.91)].
     9The experiments described below use 3 Mango WARP v3 kits, each running the [wiki:../../../Changelog#a0.91BetaRelease 802.11 Reference Design (version v0.91)].
    910
    10 Each node's RF interface was connected to an antenna with a toroidal pattern with 5dBi gain in all horizontal directions ([http://www.l-com.com/wireless-antenna-24-ghz-7-dbi-desktop-omni-antenna-4ft-sma-male-connector L-Com RE07U-SM]).
     11Each node's RF interface is connected to an antenna with a toroidal pattern with 7dBi gain in all horizontal directions ([http://www.l-com.com/wireless-antenna-24-ghz-7-dbi-desktop-omni-antenna-4ft-sma-male-connector L-Com RE07U-SM]). The antennas are positioned within line-of-sight.
    1112
    12 The nodes were indoors in a small office environment with limited mobility.
     13The nodes are indoors in a small office environment with limited mobility. The experimental network is sharing its channel with a few lightly-loaded Wi-Fi networks.
    1314
    1415||  [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:experimental_setup_photo.jpg, width=600)]]  ||
    … …  
    1617
    1718=== Experiment Details ===
    18  * Packet Length: 1400 byte payloads (1428 bytes OTA with MAC header and FCS)
     19 * Packet Length: 1400 byte payloads (1428 byte MPDUs, with MAC header and FCS)
    1920 * PHY Rate: 18 Mbps (QPSK, code rate 3/4)
    2021 * Tx Power: -5 dBm
    2122 * Trial Duration: 300 seconds
    2223 * 2.4GHz channel 1
    23  * Physical Carrier Sensing Threshold: approximately -70 dBm when enabled
     24 * Physical Carrier Sensing Threshold: approximately -70 dBm, when enabled
    2425
    2526We use 4 traffic flows in our experiments:
    … …  
    3940
    4041||    ||||=  # MPDU Tx  =||||=  # PHY Tx  =||||= # PHY Re-Tx  =||||=  # MPDU Rx  =||||=  Throughput (Mbps)  =||
    41 || Physical Carrier Sensing ||  On  ||  Off  ||  On  ||  Off  ||  On  ||  Off  ||  On  ||  Off  ||  On  ||  Off  ||
     42||= Physical Carrier Sensing =||  On  ||  Off  ||  On  ||  Off  ||  On  ||  Off  ||  On  ||  Off  ||  On  ||  Off  ||
    4243||=  Flow 1  =|| 51804|| 46883|| 65531|| 65951|| 13727|| 19068|| 51806|| 46820||  1.97|| 1.78||
    4344||=  Flow 2  =|| 51792|| 46864|| 66211|| 66090|| 14419|| 19226|| 51792|| 46794||  1.97||  1.78||
    … …  
    4546||=  Flow 4  =|| 121787|| 118609|| 147488|| 156835|| 25701|| 38226|| 121788|| 118523|| 4.62|| 4.50||
    4647
    47 Statistics:
     48Metrics:
    4849 * '''MPDU Tx''': total number of unique MAC data frames submitted to the DCF for transmission
    4950 * '''PHY Tx''': total number of PHY transmissions (includes initial transmission and all re-transmissions of all MPDUs)
    50  * '''PHY Re-Tx""": total number of PHY re-transmissions
     51 * '''PHY Re-Tx''': total number of PHY re-transmissions
    5152 * '''MPDU Rx''': total number of MAC data frames received successfully
    5253 * '''Throughput''': ratio of total number of MAC bits received and experiment duration