I am exploring the world of RTLS system and trying to produce one on my own. I chose 433Mhz frequency for its penetration capabilities and I produced a PCB mounting CC430 TI family MCU-transceiver, two quarter-length PCB antennae to reduce heading problems in RSSI measurements and a 250mA battery. Right now the tag is transmitting a 30 bytes packet (using the SimpliciTi communication protocol from TI) with 0dBm every minute at 1.2kbaude data rate. The receivers use pretty much the same circuitry except that they mount a half length dipole rubber duck antenna and they are wired at the power line.
The beacon sent by the tag serve for a reliable trilateration in a 30 meters range indoor with sporadic and slim (10 cm) concrete walls
My experiments show that the battery gets completely drained just after 3 days of transmitting a beacon every minute, which is probably due to the extremely low data rate used (which I suspect it has an impact on the readings' accuracy due to small fading phenomenon and multipath).
I would like to have some advice on best practices for extending battery life in an RF application such as the one I described without compromising too much the accuracy of the RSSI readings and suggestions on how and what instruments I can employ to test such drainage. The desired battery life for the tag is 6 months.