Using the 802.11 Reference Design: AP Application


The AP uses ETH A as its interface to the Distribution System (DS), as it is called in the 802.11 spec. Refer to the AP docs for more details. Note: ETH A defaults to using a 1Gbps speed. It will not auto-negotiate to 100 Mbps when connected to a slower Ethernet port.

In practice the ETH A interface should be connected to an Ethernet network with access to the wired network resources your experiment requires. In many experiments this means connecting ETH A to a wired network connected to the Internet, such as to a LAN port of a home router. The AP code will pass through DHCP, ARP and IP traffic from wireless client to the wired network, allowing wireless clients to receive DHCP address assignments and exchange data with Internet services.

The AP uses ETH B for interaction with the experiments framework.

User IO

Hex Displays: the AP uses the hex displays to show the number of associated stations. The displays will change in real time as stations join and leave the network. The right display also blinks slowly to indicate that the node is an AP; this helps distinguish AP nodes from STA nodes. If the BSS is Null, then "--" will be displayed.

DIP Switch: the AP uses the left-most switch to enable or disable the default BSS at boot. When the switch is up the AP's BSS will be initialized to Null (i.e. it will not transmit beacons; not respond to Probe Requests; not allow associations via wireless handshakes). The BSS can be configured and associations can still be established via wlan_exp commands.


Refer to the UART usage page for an overview of how the 802.11 design uses the UART cores on each CPU.

The normal UART output on boot of the AP application is:

----- Mango 802.11 Reference Design -----
----- v1.0 ------------------------------
----- wlan_mac_ap -----------------------

< High Framework Boot Messages - See Above >

WLAN MAC AP boot complete:
  Channel : 1
  MAC Addr: 40-D8-55-04-21-4A

Press the Esc key in your terminal to access the UART menu

The AP boot message includes the initial SSID (WARP-AP) and wireless MAC address for the node (40-D8-55-04-21-4A in this example).

Hitting the ESC key will show the AP's interactive menu:

********************** AP Menu **********************
[1] - Interactive AP Status
[2] - Print Queue Status
[3] - Print all Observed Statistics

[c/C] - change channel (note: changing channel will
        purge any associations, forcing stations to
        join the network again)
[r/R] - change default unicast rate
[s]   - change SSID (note: changing SSID will purge)
        any associations)

Option 1 will show a sub-menu with commands to reset all Tx/Rx statistics and to de-authenticate all stations.

Option 2 will show the current allocation of Tx queue descriptors among the existing Tx queues. For example, the following shows 15 packets are queued for transmission (one multicast, 5 for AID 1, 9 for AID 2):

Queue Status:
 FREE || MCAST|     1|     2|
  3159||     1|     5|     9|

During normal operation the AP will print UART messages as stations join and leave the AP's network. For example, when the first client joins the AP:

Authenticated, Unassociated Stations:

(MAC time = 404586220 usec)
|-ID-|----- MAC ADDR ----|
| 01 | F0:D1:A9:6C:86:A6 |

Authenticated, Associated Stations:

(MAC time = 404609451 usec)
|-ID-|----- MAC ADDR ----|
| 01 | F0:D1:A9:6C:86:A6 |

The first message shows the client part way through the association handshake (post authentication, pre association). The second message shows the client successfully authenticated. As more clients join and leave the BSS these node lists will grow and shrink.

Last modified 8 years ago Last modified on Mar 22, 2016, 5:28:03 PM