Opticon ESL - Manual (Page 20)

Opticon ESL
DEMO KIT
User Manual
20
5.4.1. Associate interval
When an ESL is not connected to any base station it will automatically start looking for
nearby base stations. Since searching for base station consumes a relative large amount of
power it will not continuously search, but only once every couple of seconds. The associate
interval determines the time (in seconds) between two associating attempts of an ESL. The
default associate interval is currently 15 seconds.
Please note that ESLs consume much more power while not being connected to a base
station than when they‟re connected, so it‟s strongly recommended to never turn off the
base stations once a
network of ESL‟s is operating. If ESLs are not being used for a long
period of time the associate interval can best be set to a much longer interval like 300
seconds. For an even longer period of time, removing the batteries might be the best
option.
The
amount of power that is being consumed by the ESL, when it‟s not connected to any
base station is also strongly related to the number of RF channels it is configured to search
for base stations. More information about the configuration of the „Scan Channels‟ can be
found in chapter 5.4.5.
5.4.2. Poll Info Ratio
The poll info ratio determines how often ESLs will automatically send their current status
and settings to the base stations. By default the ESLs will transmit this information once
every 40 polls, so a ratio of 1:39.
The status and information of an ESL is also requested immediately by opening the
settings dialog of an ESL by right clicking on the ESL. This will cause the base station to
request the settings the next time this ESL polls for data.
The poll info ratio is set to a relative high value, because settings and status usually don‟t
vary a lot and because sending settings and status information uses more bandwidth and
consumes more power than regular polls for data.
5.4.3. Poll Interval
The poll interval specifies the interval (in seconds) at which the ESL sends a poll for data to
the base station. This parameter is the most significant configuration of an ESL since it
strongly determines the response time of an ESL (how fast is an image displayed) as well
as the battery life time.
By default the ESLs poll every 15 seconds once they‟re connected to a base station. This
means that to response time of an ESL can be anywhere in between 0 to 15 seconds
(unless the poll doesn‟t arrive at the base station due to interference).
The poll interval greatly influence the battery life time, so lowering it is not recommended.
For example, changing the poll interval from 15 seconds to 5 seconds will roughly double
the power consumption and thereby shorten the battery life time by a factor of 2.
An advantage of making the poll interval bigger is the reduction of the used bandwidth per
ESL, making it possible to connect more ESLs to a single base station.