User`s guide

Aironet Wireless Communications, Inc. 7-66 Confidential and Proprietary
Power Save Operation
Several levels of power save are implemented in the PC4500/4800:
PSP Should be used in the cases where small amounts of data are intermittently transferred
(example = a handheld scanner used to read bar codes and use the information to query a
database)
Fast-PSP Can be used in the cases where large amounts of data are intermittently transferred. Will
result in a more efficient use of battery as well as effecting a quicker data transfer.
(example = pen based unit which updates information on a screen by screen basis)
In both the above modes, the user may enter values for the following parameters which
will affect the amount of time that the PC4500/4800 wakes to check for pending data:
ListenInterval, FastListenInterval, ListenDecay, FastListenDelay, SleepForDTIMs.
In addition, if the network supports any of the MAGIC Packet or WAKE-ON-LAN
functions, the user may configure the PC4500/4800 to ignore all traffic until an
appropriate wake-up frame is received.
Also available is a Host Sleep command (can be used in conjunction with all modes)
which is used to inform the PC4500/4800 that the host is not available. This feature
allows the PC4500/4800 to power down the host interface which results in the lowest
power save mode.
The PC4500/4800 product line offers the user many alternatives which can be used to conserve power
when operating in a battery powered environment. The parameters are implemented in such a fashion as to
define consistent power save operation and definition from the client perspective. This allows the client to
roam between access points which may have different operating parameters while maintaining the same
power consumption characteristics.
The parameters affecting power save operation are described in detail below.
ListenInterval = value in kusec used to set the maximum time that the client will wait before waking
to listen for DTIM frames. This value is currently limited to be no more than 2 minutes. (This
value is rounded to the nearest integer beacon interval as set on the current access point.)
FastListenInterval = value in kusec used to set the current listen interval to be used immediately after
a receive operation. (This value is rounded to the nearest integer beacon interval as set on the
current access point and can be no greater than the ListenInterval.)
ListenDecay = integer number of times to cycle using the current listen interval value before doubling
the value. (The starting point is the FastListenInterval value)
FastListenDelay = value in kusec used to set the time to wait after a data transmit before resuming the
power save operation. At the completion of this time, the FastListenInterval is started. This
parameter is not used in Fast-PSP operation.
SleepForDTIMs = boolean parameter where 0 indicates to the psp client that it must wake for ALL
DTIMs and for any beacons for which the ListenInterval will expire before the next expected
DTIM. A nonzero value indicates that the psp client will wake only for beacons specified by
the ListenInterval (this means that broadcast and multicast traffic may be missed).
In order to achieve maximal power saving in power save mode, some cooperation is required from the host.
If the PC4500/4800 is aware that it will not be accessed by the host, it can achieve additional power saving.
To achieve this, a Host Sleep command is issued by the host to the PC4500/4800. After issuing this
command, the host must not access any PC4500/4800 registers until the host "awakens" the PC4500/4800.
The PC4500/4800 will maintain the wireless network connection to receive any pending traffic. If any
valid packets are received, then an interrupt will be generated to the host as normal. To service a receive