ISM Band Systems: Power Consumption, Usability and Economics

Abstract

This thesis describes research into a specific area of Industrial Scientific and Medical (ISM) band applications that employ a central control panel to send broadcast information to the units in a system. One example of this is fire safety systems. The focus is on how battery life, reliability and usability of such a system may be improved through different mechanisms. The case study application is a system of radio controlled fire door holders.

Following a review of the current literature and a look at the considerations of designing a wireless network, a comparison is made of two radio transceivers, each of which operates in a different frequency band. Testing is performed with both, and a choice made as to which to use in system implementations and further research.

Results from the first system implementation quantify communications and circuitry improvements that increase battery life through improved receiver sensitivity and communications resilience.

The second system implements a narrowband system, as well as improving unit displays for information output and system troubleshooting. Results from it show a further increase in receiver sensitivity and techniques developed to improve timing to reduce on-time, so reducing power consumption further.

The third implementation employs frequency hopping techniques along with further advances in timing. Enhanced display manager techniques add to the usability of the system.

Beyond this, more recent chip technology is used with algorithmic changes in small test units to assess how further improvements can be made in terms of battery life.
A ten-fold improvement in battery life compared to the original implementation is shown to be possible when comparing the narrowband and wideband systems. Further improvements are described employing the latest chip technology.