Changes between Version 15 and Version 16 of 802.11/wlan_exp/app_notes/dcf_with_multiple_flows

Timestamp:

Apr 17, 2014, 8:07:43 AM (10 years ago)

Author:

chunter

Comment:

--

802.11/wlan_exp/app_notes/dcf_with_multiple_flows

@@ -47 +47 @@
 === Baseline: Performance of Each Flow in Isolation ===
 
-As a first cut, we establish the best-case performance for each backlogged flow by running a series of experiments with only on flow enabled at a time. To do this, we use the WLAN Experiment Framework to reset the nodes, set the PHY rate, and then start locally generated traffic from the nodes. The script used for this is provided below in the [#Resources Resources] Section.
+As a first cut, we establish the best-case performance for each backlogged flow by running a series of experiments with only on flow enabled at a time. To do this, we use the WLAN Experiment Framework to reset the nodes, set the PHY rate, and then start locally generated traffic from the nodes. The script used for this is provided below in the [#Resources Resources Section].
 
 ||  Non-Simultaneous  ||  Throughput (Mbps)  ||
@@ -73 +73 @@
 ||  ''Relative Share of Network Sum Throughput'''  ||
 
+The above figures shows the same table of data, but emphasis the relative share of the 12.77 Mbps sum throughput that each flow achieves. Here, we can see that Flows 3 and 4 each achieve about 1/3 of the overall throughput while Flows 1 and 2 have to split the remaining 1/3. This is due to the fact that the AP is burdened with sourcing two flows (Flow 1 and 2) while each STA only needs to source a single flow. The 802.11 DCF gives each of the three devices (AP, STA 1, and STA 2) a fair shot at grabbing the medium -- it does not care that one of the three nodes has more traffic it needs to send.
+
+The WLAN Experiment Framework is capable of providing ''much'' more detailed observations about the performance of the network than coarse throughput measures. Specifically, the [wiki:../../log event log] lets us observe events that occur during the experiment directly without aggregation. Given the fact that the "wireless" network in this experiment very static (RF cabling and attenuators), one might expect that the throughput values presented thus far are accurate for any arbitrarily short span of time. Using the event log, we can see this is not the case.
+
+||  [[Image(wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows/figs:connected_symmetric.png, width=600)]]  ||
+||  ''Throughput Timeline'''  ||
+
+The above figure shows the timeline of throughputs achieved by each of the four flows during the experiment with a one second rolling window average. These timelines were constructed from the event log using a technique identical to that presented in the [wiki:../../examples/txrx_log_analysis Log Analysis Example]. Furthermore the script used for this experiment is provided in the [#Resources Resources Section].
+
+=== A Simple Modification to the DCF ===
+
 == Experiment 2: Symmetric with Hidden Stations ==