Changes between Version 21 and Version 22 of Internal/RunningDemos


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Timestamp:
Dec 23, 2005, 6:34:04 PM (19 years ago)
Author:
kishore
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  • Internal/RunningDemos

    v21 v22  
    1616The objective of this demo is to show the failure of current implementations of IEEE 802.11 infrastructure networks in supporting a large number (O(10)) of clients. The cumulative throughput at the access point (AP) is the measured and it is shown that beyond a certain number of clients, there is a sharp drop rather than graceful degradation. It is hypothesized that the 802.11 bit-rate adaptation algorithm is the primary culprit for this behavior - the algorithm does not differentiate between collision-based packet loss and packet loss due to poor channel conditions. It incorrectly infers collision-based loss as an indication to drop the bit-rate, resulting in the sharp drop in cumulative throughput.
    1717
    18 The demo itself consists of one receiver and 25 senders -- the start times of the senders are staggered (3-4 senders join the experiment in 10 second intervals). Traffic generated is UDP-CBR (constant bit-rate) at 1.5Mbps emulating high-quality video streaming from the clients to the AP. All the clients and the AP use 802.11a (channel 36 (5.18Ghz)) with negligible interference from other sources.
     18The demo itself consists of one receiver and 25 senders -- the start times of the senders are staggered (3-4 senders join the experiment in 10 second intervals). Traffic generated is UDP-CBR (constant bit-rate) at 1.5Mbps emulating high-quality video streaming from the clients to the AP. All the clients and the AP use 802.11a (channel 36 (5.18Ghz)) with negligible interference from other sources. The figure below provides a graphical representation.
     19
     20{{{
     21Timeline     SOURCES                                                  DESTINATION
     22                                         1.5Mbps UDP CBR on Wireless
     23Time 0       Group 1: [1,2],[1,4],[1,8] -------------------------------> [5,4]   
     24Time 10      Group 2: [2,1],[2,3],[2,5] -------------------------------> [5,4]
     25...
     26
     27Time 60      Group 7: [8,1],[8,5],[8,7] -------------------------------> [5,4]
     28
     29Time 110     Stop Group 1 senders.
     30Time 115     Stop Group 2 senders.
     31...
     32Time 140     Stop Group 7 senders.
     33}}}
    1934
    2035=== Steps to Execute Demo ===