User's Manual

Datalogic Scanning, Inc
959 Terry Street
Eugene, Oregon 97402
Page 37 10/23/2009
Revision X2
bucket works.
The firmware also stops conditional scanning for this period when it receives an inquiry or when the last
connection has just ended, returning the firmware to the idle state. Conditional scanning is never performed
in the connected state.
Key Name Key
Number
Type Default Setting
PSKEY_CONDITIONAL_SCAN_BUCKET_BOTTOM 0x0110 int8 -10
This value provides a clip on the minimum level of the leaky bucket used to manage the power use of the
conditional scan. The closer this value is to zero, the less a history of radio inactivity will matter when
deciding whether to conditional scan.
See the description of PSKEY_CONDITIONAL_SCAN_BACKOFF_LEVEL for a description of the
leaky bucket mechanism.
Key Name Key
Number
Type Default Setting
PSKEY_CONDITIONAL_SCAN_BUCKET_BACKOFF_LEVEL 0x0111 int8 10
When using conditional scan, if the radio environment is busy, performing the conditional scan plus the
ordinary page/inquiry scan will use more power than conditional scan alone. To turn off conditional scan
when the radio environment is busy, the LM uses a leaky bucket filter.
The bucket level is incremented by 1 whenever the conditional scan detected a radio source, and
decremented by an amount which depends on the scan window and interval when the conditional scan did
not detect a radio source. The decrement amount is calculated to keep the level at zero at the percentage
chance of radio activity where conditional scanning uses an equal amount of power to not conditional
scanning. When the level rises above zero, it is becoming inefficient to conditional scan. When the level
goes below zero (possible as the level is a signed value), it is more efficient to conditional scan than not to.
When the bucket level reaches the value of this key, conditional scanning is disabled for the period of time
given by PSKEY_CONDITIONAL_SCAN_BACKOFF_TIME
. It is then re-enabled with the bucket level
set back to zero.
Key Name Key
Number
Type Default Setting
PSKEY_CONDITIONAL_SCAN_BACK_TO_BACK_OPTIMISE 0x0112 bool TRUE
When page scan and inquiry scan have the same interval, to save power we arrange to do the scans back to
back, with inquiry scan first and then page scan. When this key is true, if the inquiry scan was a conditional
scan and the conditional scan heard nothing, the following page scan is not performed. Conversely, if the
inquiry scan was a conditional scan and heard something, the following page scan is never a conditional
scan, but always an ordinary page scan. This key is best used when the scan window is short compared to
the scan interval.
When this key is false, the conditional scanning from page and inquiry are not coupled in this way,
although both still contribute to the leaky bucket which decides whether to conditional scan.
This key only has an effect if conditional scan is enabled using
PSKEY_CONDITIONAL_SCAN_ENABLE
.