Feedback-Aided Coded Random Access via Replica Spacing

In this paper, new coded random access schemes for massive IoT, capable of accommodating a non-instantaneous feedback from the receiver, are developed. The proposed schemes are based on the introduction of waiting slots between any two consecutive replicas transmitted by the same active device. The waiting window can be exploited by the device to receive acknowledgment messages that, otherwise, would consume uplink resources with a consequent performance degradation. The achievable performance of the developed schemes is investigated, by analysis and simulation, over a realistic wireless channel model and realistic signal processing at the base station, showing negligible losses with respect to previously proposed coded random access systems with idealized instantaneous feedback.