Distributed decision fusion using a random access channel

We study a binary decision fusion scheme which employs a common channel for detector-DFC communication. Unlike most parallel fusion schemes, which use a dedicated communication channel between every local detector (LD) and the data fusion center (DFC), our scheme uses a single shared, time-slotted communication link for all LDs to transmit decisions to the DFC. Two window-based methods are presented for managing traffic over this channel. The first allows simultaneous messages to collide. The DFC uses the statistics of the channel states (i.e., the number of successful transmissions, idle slots, and collisions during a specified time period) to make its global decision. The second method uses a simple collision resolution algorithm (CRA), similar to slotted-ALOHA with dynamically updated retransmission probability. With this scheme, the DFC makes its decision based on data transmitted successfully within a specified time window. Over-all performance of the systems are presented and compared. Simple rules are developed for assessing the conditions under which each one of the schemes is preferred.