Ultra-low energy consumption
Many IoT applications terminals will be powered by batteries leading to the need for low energy consumption. All LPWAN technologies operating in licence exempt spectrum are low power but Weightless uses a number of techniques to offer best in class power consumption performance and consequently very long battery life. Overall energy consumption is a factor of both the power used during transmission and the amount of the time that the transmitter is active - the duty cycle. Weightless uses GMSK and offset-QPSK modulation schemes which deliver optimum power amplifier efficiency. Offset-QPSK modulation is also inherently interference immune and using spread spectrum for improved link quality in busy radio environments minimises the required transmit power. The low transmit power of 17dBm means that terminals can operate from coin cell batteries. Adaptive data rate also permits minimal transmit power for nodes with a cleaner signal path to the base station so maximising battery life. And since a terminal device will nearly always spend a very large proportion of the time in an idle state, the power consumption in this mode becomes critical. Weightless consumes less than 100µW when inactive.