Changes between Version 7 and Version 8 of 802.11/wlan_exp/app_notes/dcf_with_hidden_nodes

Timestamp:

Jun 23, 2015, 3:44:22 PM (9 years ago)

Author:

chunter

Comment:

--

802.11/wlan_exp/app_notes/dcf_with_hidden_nodes

@@ -8 +8 @@
 ||  '''Classic Hidden Node Topology'''  ||
 
-As we have seen in the [wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows multiflow app note], carrier sensing plays a crucial role in the DCF's ability deal with contention in a shared wireless medium. In the classic hidden node topology shown above, STA 1 can carrier sense the AP and vice versa. STA 2 can carrier sense the AP and vice versa. However, STA 1 and STA 2 are out of range of one another and cannot detect each other's transmissions. The traditional solution to this problem is the [https://en.wikipedia.org/wiki/IEEE_802.11_RTS/CTS RTS/CTS handshake]. The basic timeline of this handshake is as follow:
+As we have seen in the [wiki:802.11/wlan_exp/app_notes/dcf_with_multiple_flows multiflow app note], carrier sensing plays a crucial role in the DCF's ability deal with contention in a shared wireless medium. In the classic hidden node topology shown above, STA 1 can carrier sense the AP and vice versa. STA 2 can carrier sense the AP and vice versa. However, STA 1 and STA 2 are out of range of one another and cannot detect each other's transmissions. The traditional solution to this problem is the [https://en.wikipedia.org/wiki/IEEE_802.11_RTS/CTS RTS/CTS handshake]. The basic timeline of this handshake is as follows:
 
 1. STA 1 wishes to send a data MPDU to the AP. Since STA 2 cannot directly hear this transmission, the likelihood of a collision might be large. Instead, STA 1 "requests to send" the MPDU by sending a very short RTS frame to the AP. This transmission may still collide, but it is very short, so the penalty to lost medium time is significantly mitigated.