Buffer-Aided Cooperative Space-Time Line Code for Relay-Assisted IoT Networks

We propose a novel buffer-aided cooperative space-time line code (B-CSTLC) technique for 6G internet-of-things (IoT) networks comprising a single source node (SN), a single destination node (DN), and multiple relay nodes (RNs) equipped with a single buffer. We assume all communicating nodes have a single antenna to ensure low-complexity implementation in wireless IoT systems. In the proposed scheme, multiple RNs receive and decode signals broadcast by the SN, and those that successfully decode the signals simultaneously transmit space-time line-coded (STLC) signals to enhance the effective channel gain. The buffers in RNs further provide opportunities to optimize channel conditions, with packet delay constrained by a maximum delay time. We analytically evaluate the performance of B-CSTLC in terms of outage probability and average packet delay. Extensive simulations confirm that the analytical results align closely with Monte Carlo simulations. Moreover, the proposed B-CSTLC technique significantly outperforms existing buffer-aided cooperative phase steering and buffer-aided best relay selection techniques in outage probability performance.