That was one of the features I was thinking about for my EvDashPc!
I was working on a design for a remote control for an airbag system and
was looking into ZigBee on the 915Mhz range. (868mhz in europe)
There is always a trade off of range vs data rate and most sites
concentrate on explaining the 2.4 ghz range which is only 10 to 100
meters. (the lower freq have longer range for the power but less data rate.)
At the lower frequencies, you can get a mile of range. (for when
charging at the mall or work) Some car alarms already send to the fob on
your key ring, so I know it is do-able.
http://www.sensorsmag.com/articles/0603/14/main.shtml
http://en.wikipedia.org/wiki/ZigBee
ZigBee is low power,low range, low cost, small footprint and low
overhead. So it works well with the micro in the keyfob.
These guys get the range vs freq and power issue, you can see they are
using 1200m with the 900mhz band for their example.
http://www.edn.com/article/CA6442439.html
I was working on a design for a remote control for an airbag system and
was looking into ZigBee on the 915Mhz range. (868mhz in europe)
There is always a trade off of range vs data rate and most sites
concentrate on explaining the 2.4 ghz range which is only 10 to 100
meters. (the lower freq have longer range for the power but less data rate.)
At the lower frequencies, you can get a mile of range. (for when
charging at the mall or work) Some car alarms already send to the fob on
your key ring, so I know it is do-able.
http://www.sensorsmag.com/articles/0603/14/main.shtml
http://en.wikipedia.org/wiki/ZigBee
ZigBee is low power,low range, low cost, small footprint and low
overhead. So it works well with the micro in the keyfob.
These guys get the range vs freq and power issue, you can see they are
using 1200m with the 900mhz band for their example.
http://www.edn.com/article/CA6442439.html
