Accounting for Reliability in Unacknowledged Time-Constrained WSNs

Wireless sensor networks typically consist of nodes that collect and transmit data periodically. In this context, we are concerned with unacknowledged communication, such as where data packets are not confirmed upon successful reception. This allows reducing traffic on the communication channel—neither acknowledgments nor retransmissions are sent—and results in less overhead and less energy consumption, which are meaningful goals in the era of the Internet of Things. However, packets can be lost, and hence we do not know how long it takes to convey data from one node to another, which hinders any form of real-time operation and/or quality of service. To overcome this problem, we propose a medium access control protocol, which consists of transmitting each packet at a random instant but within a specified time interval from the last transmission. In contrast to existing approaches from the literature, the proposed medium access control can be configured to meet reliability requirements—given by the probability that at least one data packet reaches its destination within a specified deadline—in the absence of acknowledgments. We illustrate this and other benefits of the proposed approach based on detailed OMNeT++ simulations.