2-16 Advanced Power Management
MX2 Reference Guide Revision A MX2A137REFGD
Appendix C includes bar codes that provide settings as low as 2 seconds
for the backlight auto-off timer. You can also use the PM.COM utility to
set the timeout.
Power Management at the Radio Card
To conserve battery life, the radio card has an inactivity sleep mode. The
sleep mode is automatically engaged when a certain period of time has
elapsed since the computer has sent or received data over the network.
Once the card is asleep, it can be awoken by an access point attempting
to send data to it. The time before sleeping is calculated by adding the
Inactivity_min and Inactivity_sec parameter settings.
Note: Do not set an inactivity timeout on an RF MX2 being used as a
master station. If the unit goes to sleep, you will lose all
communication with your network.
The access point buffers packets that are to be sent to the MX2s. A
dozing radio card will receive a sync message and wake-up list from the
Access Point every 400 ms. The AP adds a media access control (MAC)
address to the wake-up list each time a send attempt fails. (The access
point buffers the packet and adds the MAC address of the MX2 to its
wake-up list.)
If a MX2 detects that it is on the wake-up list, the radio card exits doze
mode and enters receive mode. Once the radio card wakes up to receive
the packet, it stays awake for all future sends until the inactivity timeout
expires. This is why it is important to have the inactivity timeout as low
as possible. The advantages of a higher timeout value is that the radio
card will remain in Receive mode for longer periods of time; network
throughput may be better because the unit will not have the delay of
coming in and out of doze mode or of waiting for the wake-up list to see
if there are any packets.
Generally, in the types of environments that the radio card will be used
in, the user should strive for maximum power management. Most MX2
RF applications will not be expecting asynchronous network traffic, and
it is doubtful that throughput differences due to power management will
be noticeable with these types of applications. Always set the
Inactivity_min parameter to 0, and set the Inactivity_sec
parameter as low as possible (preferably to 1). Never set
Inactivity_sec to 0, as that turns off the power management
completely, and the card will always stay in receive mode.
