Changes between Initial Version and Version 1 of 802.11/wlan_exp/bss

Timestamp:

Mar 25, 2016, 11:31:17 AM (8 years ago)

Author:

welsh

Comment:

--

802.11/wlan_exp/bss

@@ +1 @@
+{{{#!comment
+[[Include(wiki:802.11/beta-note)]]
+}}}
+
+[[TracNav(802.11/TOC)]]
+
+= 802.11 Reference Design Experiments Framework Basic Service Set (BSS) =
+
+The 802.11 Reference design uses a structure to record information about a [https://en.wikipedia.org/wiki/Service_set_(802.11_network) basic service set (BSS)].  This information can be for the node's current BSS (i.e. network) or networks that the node has seen by either receiving a beacon or from [http://warpproject.org/docs/mango-wlan-exp-dev/node.html#network-scan scanning for networks].  Each node is either a member of no BSS (colloquially "unassociated") or a member of one BSS.  The following fields are recorded in the BSS information structure to describe a BSS:
+
+||=  Field Name  =||=  Description  =||
+|| bssid || BSS ID ||
+|| channel || Primary channel ||
+|| channel_type || Channel Type ||
+|| latest_beacon_rx_time || Value of System Time in microseconds of last beacon Rx ||
+|| ssid || SSID (32 chars max) ||
+|| latest_beacon_rx_power || Last observed Rx Power (dBm) ||
+|| flags || BSS flags ||
+|| capabilities || Supported capabilities of the BSS ||
+|| beacon_interval || Beacon interval - In time units of 1024 us ||
+
+
+=== Python ===
+
+The 802.11 Reference Design Experiments Framework provides methods to interact with BSS information.  In addition to the fields above, the BSS information structures in Python also contain a {{{timestamp}}} field which is the value of the MAC time in microseconds when the structure was created.  The following methods are used to interact with BSS information:
+
+  * [http://warpproject.org/docs/mango-wlan-exp-dev/node.html#wlan_exp.node.WlanExpNode.get_bss_info get_bss_info()]
+
+     This method will return the BSS information about the node's current BSS.  The value returned can be {{{None}}} if the node is not a member of a BSS.
+
+  * [http://warpproject.org/docs/mango-wlan-exp-dev/node.html#wlan_exp.node.WlanExpNode.get_network_list get_network_list()]
+
+    This method will return a list of BSS information about all the networks that the node has seen.  This list can include the node's current BSS if the node is a member of a BSS.  This list could be empty.
+
+  * '''{{{configure_bss()}}}''' for [http://warpproject.org/docs/mango-wlan-exp-dev/node_ap.html#wlan_exp.node_ap.WlanExpNodeAp.configure_bss AP], for [http://warpproject.org/docs/mango-wlan-exp-dev/node_sta.html#wlan_exp.node_sta.WlanExpNodeSta.configure_bss STA], for [http://warpproject.org/docs/mango-wlan-exp-dev/node_ibss.html#wlan_exp.node_ibss.WlanExpNodeIBSS.configure_bss IBSS]
+      
+    This method will configure the node's current BSS.  For each node type, there is a specific implementation of {{{configure_bss}}} that has different argument requirements.  See below for more details.
+
+
+
+=== Configuring the BSS ===
+
+A node requires a minimum set of information to be a member of a BSS. The minimum set of information is:
+   * BSSID: 48-bit MAC address
+   * Channel: logical channel for Tx/Rx by BSS members
+   * SSID: variable length string
+   * Beacon Interval: time between TBTTs in units of TUs (not required by STA)
+
+A node's current BSS can be populated by default in C, by active scanning, or by wlan_exp.  The DIP switch on the WARP v3 node can be used to control the default BSS at boot (see [http://warpproject.org/trac/wiki/802.11/Usage/UserIO user I/O documentation] for each MAC project).
+
+'''Arguments:'''
+
+ * {{{bssid}}}: depends on node type; {{{None}}} means wipe BSS state; {{{False}}} means no change
+  * '''AP''': must be node's wireless MAC address
+  * '''STA''': must be BSSID of BSS with which to associate
+  * '''IBSS''': must be valid locally-administered BSSID (use [http://warpproject.org/docs/mango-wlan-exp-dev/wlan_exp_util.html#wlan_exp.util.create_locally_administered_bssid create_locally_administered_bssid()] utility to create locally-administered BSSIDs from MAC addresses)
+ * {{{ssid}}}: string; {{{None}}} means no change
+ * {{{beacon_interval}}}: integer in ![10, 65534]; {{{None}}} means no beacon Tx; {{{False}}} means no change
+ * {{{channel}}}: Integer channel index; {{{None}}} means no change
+ * {{{ht_capable}}}: Does the node advertise HT processing capabilities; {{{None}}} means no change
+
+=== Changes to code from 802.11 Reference Design v1.4 ===
+
+  * '''Replaces:'''
+    * {{{node.set_channel()}}}: New method [http://warpproject.org/docs/mango-wlan-exp-dev/node.html#wlan_exp.node.WlanExpNode.set_radio_channel set_radio_channel()] only affects hardware, not BSS
+    * {{{node_ap.get/set_ssid()}}}: Use {{{get_bss_info()}}} as getter
+    * {{{node_ap.get/set_beacon_interval()}}}: Use {{{get_bss_info()}}} as getter
+    * {{{node_sta.set_association()}}}
+    * {{{node_ibss.join()}}}
+    * {{{util.create_bss_info()}}}
+
+  * '''Affected:'''
+    * {{{node.reset()}}} has new arguments:
+      * {{{bss=bool}}}: nullifies the node's BSS state but does not remove any entries from the BSS information list; wipes station_info list
+        * {{{n.reset(bss=True)}}}, unlike {{{n.configure_bss(bssid=None)}}}, shall produce the following OTA transmission:
+          * For AP, a deauthentication frame to each associated station
+          * For STA, a disassociation frame to its AP
+          *  For IBSS, nothing. {{{n_ibss.reset(bss=True)}}} == {{{n_ibss.configure_bss(bssid=None)}}}
+      * {{{network_list=bool}}}: wipes the node's list of overheard BSS information, excluding the bss_info entry for the node's current network (if any)
+      * Removed arguments {{{associations=bool}}}, {{{bss_info=bool}}}
+    * {{{node.reset_all()}}} includes {{{(bss=True, network_list=True)}}}
+
+
+=== Example: Configuring BSS ===
+
+
+{{{#!python
+# Setup a new network with 1 AP, 1 STA
+#     - Assumes that both nodes started with no default BSS (i.e. 
+>>> n_ap.configure_bss(ssid='My Network', beacon_interval=100, channel=6, ht_capable=True)
+>>> n_ap.get_bss_info()
+{'bssid': AP_WLAN_MAC_ADDR, 'ssid': 'My Network', 'beacon_interval': 100, 'channel': 6, 'ht_capable': True, ...}
+
+>>> n_sta.get_bss_info()
+None
+
+>>> n_ap.add_association(n_sta)
+
+>>> n_sta.get_bss_info()
+{'bssid': AP_WLAN_MAC_ADDR, 'ssid': 'My Network', 'beacon_interval': 100, 'channel': 6, 'ht_capable': True, ...}
+
+# Update the beacon interval
+>>> n_ap.configure_bss(beacon_interval=250)
+>>> n_ap.get_bss_info()
+{'bssid': AP_WLAN_MAC_ADDR, 'ssid': 'My Network', 'beacon_interval': 250, 'channel': 6, 'ht_capable': True, ...}
+
+# Query STA before it receives a new beacon
+>>> n_sta.get_bss_info()
+{'bssid': AP_WLAN_MAC_ADDR, 'ssid': 'My Network', 'beacon_interval': 100, 'channel': 6, 'ht_capable': True, ...}
+
+# Query STA after it receives a new beacon
+>>> time.sleep(250*1024*1e-6)
+>>> n_sta.get_bss_info()
+{'bssid': AP_WLAN_MAC_ADDR, 'ssid': 'My Network', 'beacon_interval': 250, 'channel': 6, 'ht_capable': True, ...}
+
+# Retune both nodes by adjusting the BSS channel
+for n in [n_ap, n_sta]:
+    n.configure_bss(channel=7)
+
+# Disable AP beacon Tx
+>>> n_ap.configure_bss(beacon_interval=None)
+}}}
+
+=== Example:  Changing Channel ===
+
+
+
+{{{#!python
+# No command arguments, no response payload
+my_node.send_user_command(CMDID_USER_MYCMD, args=None)
+}}}
+
+
+=== Example:  Adjusting Beacon Interval ===
+
+{{{#!python
+# No command arguments, no response payload
+my_node.send_user_command(CMDID_USER_MYCMD, args=None)
+}}}
+
+
+=== Example:  Scanning for Networks ===
+
+{{{#!python
+# No command arguments, no response payload
+my_node.send_user_command(CMDID_USER_MYCMD, args=None)
+ args=[ARG0 ARG1])
+}}}
+
+
+