Generally, yes, anchors are not optimized for power consumption as they expect to be listening mostly all the time and expect to have unlimited power.
It takes very careful protocol design to build such a system where both sides, tags and anchors, can be off significant amounts of time. Such a system suffers from the potential they don’t hear each other. Then, even if they do, you have to set up a means to schedule both sides so they awake and hear each other in the future. With clock drift and other issues, this becomes a very non trivial project which takes very careful protocol design.
The real issue here is that receive power on the DW1000 is so high, about 400 mW. So the major requirement is to be in receive as little as possible. Ciholas is working on such systems now, wireless anchors which operate for long periods on batteries. They are best used in places with high install costs, or temporary installs, and with systems that have fairly low capacity requirements. If you end up using full air time capacity, then anchors are on most of the time and the battery is gone.
Another issue with battery anchors is that eventually somebody has to charge or swap the batteries. Anchors are usually mounted up high for best performance, so this isn’t trivial in many cases.
That is possible. You’d need a sufficiently large battery to work overnight and to bridge cloudy days. In cold climates, snow can cover the array for a long period of time.
Some numbers: estimate anchor uses about 15 WH per day (10 WH for the DW1000, rest of system about 5 WH). Battery should be about 6 times that number to bridge a week, so 100 WH or so. Solar array should recharge battery in 6 solid hours, so about a 15 to 20 watt panel. That is about 30 to 40 cm square panel, so not small, but not huge. So, seems doable. Does add some extra install steps and requires the anchor sites have good sun visibility.
Wireless anchors are on everyone’s hot list, but when the battery servicing burdens and capacity limitations become evident, it soon becomes apparent that wired anchors are preferred in most permanent and professional installations.
Mike Ciholas, President, Ciholas, Inc
3700 Bell Road, Newburgh, IN 47630 USA
+1 812 962 9408