Changes between Version 3 and Version 4 of 802.11/wlan_exp/app_notes/tutorial_token_mac/characterization

Timestamp:

Jul 13, 2015, 11:01:29 AM (9 years ago)

Author:

chunter

Comment:

--

802.11/wlan_exp/app_notes/tutorial_token_mac/characterization

@@ -23 +23 @@
 ||  ''Standard 802.11'''  ||  ''TokenMAC'''  ||
 
-Clearly, there are some striking differences between the operation of the standard 802.11 MAC and our TokenMAC extension. These differences are:
+Clearly, there are some striking differences between the operation of the standard 802.11 MAC and our TokenMAC extension. Two differences are:
 
 1. In the first 20 second period (annotated as "A" in the TokenMAC figure), a standard 802.11 MAC implementation is able to achieve slightly more than 14 Mbps while our TokenMAC implementation could only achieve about 8 Mbps.
 1. In the second 20 second period (annotated as "B" in the TokenMAC figure), a standard 802.11 MAC implementation achieves a sum throughput of slightly less than 14 Mbps while our TokenMAC implementation can achieve nearly 16 Mbps.
-1. In the same second 20 second period, we can see that the 16 Mbps throughput achieved by TokenMAC is due to a nearly even split of the medium between the "AP -> STA" and "STA -> AP" flow. However, it is clear that the AP's flow has a slight advantage of the STA's flow.
 
-In the following sections, we will dig deeper into each of these three observations and explain them within the context of the TokenMAC protocol.
+In the following sections, we will dig deeper into both of these observations and explain them within the context of the TokenMAC protocol.
 
 ===  1. Section A: The Zero-Contention Case  ===
@@ -49 +48 @@
 Now that both flows are active, we can see that TokenMAC is no longer "wasting" the medium like it was in the previous zero-contention case. Instead, TokenMAC alternates between the AP and the STA and allows them to send as many packets as they can during that time. Furthermore, because we lack the backoff and ACK overhead of standard 802.11, we are actually able to exceed the standard's sum throughput by a fairly wide margin (16 Mbps vs. 14 Mbps).
 
-=== 3. Section B: Fairness among the AP and STA ===
 
-We noted above that the AP's flow appears to be able to achieve slightly more than 50% of the sum network throughput while the the STA's flow appears to be able to achieve slightly less than 50%. Recall in our design modifications that prior to entering a token reservation period, a STA must complete the handshake of the token offer with its own token response. However, when the AP enters a token reservation period, no handshake is needed because it is the AP and already knows that it is now authorized to transmit. Example this extreme not-to-scale visualization:
-
-