User`s guide

Aironet Wireless Communications, Inc. 7-54 Confidential and Proprietary
the PC4500/4800 is not currently associated to an access point. The packet will be transmitted
when the PC4500/4800 does finally associate, or will be removed from the queue when the
transmit lifetime expires for the packet whichever occurs first.
Station IBSS Operation
In IBSS mode, also referred to as adhoc mode, the PC4500/4800 will scan for an appropriate
wireless network and then join that network by synchronizing to the hopping pattern (if enabled).
If the PC4500/4800 fails to find an appropriate network within the desired interval, it will form a
new network; it may be the first station to be turned on. In IBSS mode, all stations must be in
range of each other station to communicate with them.
Access Point Operation
In access point mode, the host must receive and transmit management and data 802.11 packets.
The host must also receive PS-POLL control packets. In this mode, the PC4500/4800 provides
only part of the access point operation; the host must provide a some of the functionality. Access
point operation is supported for both "root" access points and "repeater" access points. (A repeater
is an access point that registers to another access point to extend the range of a cell.)
In access point mode, it is recommended that the 802.3 headers be disabled for efficiency. The
access point must deal with 802.11 headers in any event.
Wireless LAN Monitor Operation
In the monitor mode, the PC4500/4800 will scan for the appropriate network and then synchronize
to the hopping pattern (if enabled) and begin passing receive packets to the host. In monitor
mode, the host is not allowed to transmit.
Three modes of operation are supported for the wireless monitor:
wireless monitor for a single BSS
wireless monitor for any BSS
LAN monitor
The wireless monitor mode is intended for monitoring the wireless traffic as is. 802.11
management, control and data packets will all be passed to the host. 802.3 headers can be
disabled. In wireless monitor mode, the packet payload is always passed through “as is”
regardless of the setting of the payload type field. The single BSS mode limits received packets to
the current BSSID.
The LAN monitor mode will only pass up data packets. In this case 802.3 headers should be used.
This mode is useful for looking for upper layer protocol problems on the wireless LAN.
Packet Header Type
The transmit and receive packets always have an 802.11 wireless LAN protocol header. An
optional 802.3 header, with destination and source addresses, is also available. The 802.3 header
can be disabled for receive packets by setting the HeaderType bit the ReceiveMode field of the
General Configuration. The 802.3 header can be disabled for transmit packets by setting the
HeaderType bit in the TxControl field of the transmit FID.
For station mode, the preferred operation is with 802.3 headers, since the station need only receive
and transmit data packets. For access point mode, 802.11 headers must be used. Disabling the
802.3 header allows for more efficient reading and writing of 802.11 packets since the host does
not have to read or write the 802.3 header bytes.