Signaling in sensor networks for sequential detection

Abstract

Sequential detection problems in sensor networks are considered. The true state of nature/true hypothesis is modeled as a binary random variable $H$ with known prior distribution. There are $N$ sensors making noisy observations about the hypothesis; $\mathcal{N} =\{1,2,\ldots,N\}$ denotes the set of sensors. Sensor $i$ can receive messages from a subset $\mathcal{P}^i \subset \mathcal{N}$ of sensors and send a message to a subset $\mathcal{C}^i \subset \mathcal{N}$. Each sensor is faced with a stopping problem. At each time $t$, based on the observations it has taken so far and the messages it may have received, sensor $i$ can decide to stop and communicate a binary decision to the sensors in $\mathcal{C}^i$, or it can continue taking observations and receiving messages. After sensor $i$'s binary decision has been sent, it becomes inactive. Sensors incur operational costs (cost of taking observations, communication costs etc.) while they are active. In addition, the system incurs a terminal cost that depends on the true hypothesis $H$, the sensors' binary decisions and their stopping times. The objective is to determine decision strategies for all sensors to minimize the total expected cost.