Radio-triggered Wake-ups with Addressing Capabilities for Extremely Low Power Sensor Network Applications

Sensor network applications are generally characterized by long idle durations and intermittent communication patterns. The traffic loads are typically so low that overall the idle duration energy consumption dominates. Low duty cycle MAC protocols are used to reduce the idle duration energy consumption. However, lowering down the duty cycle in favour of energy consumption results in increased latency, which makes it undesirable for many applications. In this paper, we propose radio triggered wake-up with addressing capabilities (RTWAC) that allows suppressing the idle duration current consumption. Our solution consists of an external low-cost hardware wakeup circuit attached to the microcontroller of a sensor node. The sensor node stays in the sleep mode with its normal communication radio turned off. In order to communicate with a sensor node, a special kind of out-of-band modulated wakeup signal is transmitted. The modulated signal contains data that enables to distinguish between differently addressed nodes in order to avoid undesired node wake-ups. Furthermore, we augment this solution to a MAC protocol running on the normal radio on the sensor node in an advantageous way to achieve high energy gains and low latency for data communication.