  We propose a simple yet efficient scheme for a set of energy-harvesting
sensors to establish secure communication with a common destination (a master
node). An eavesdropper attempts to decode the data sent from the sensors to
their common destination. We assume a single modulation scheme that can be
implemented efficiently for energy-limited applications. We design a
multiple-access scheme for the sensors under secrecy and limited-energy
constraints. In a given time slot, each energy-harvesting sensor chooses
between sending its packet or remaining idle. The destination assigns a set of
data time slots to each sensor. The optimization problem is formulated to
maximize the secrecy sum-throughput.
