  For data collection scenarios in the Industrial Internet of Things, wireless
communication provides a cost-effective and easy-to-deploy alternative to wired
networks. The main focus lies on energy efficiency and reliability, as many
devices are battery operated. IEEE 802.15.4 DSME enhances reliability by
acknowledging each packet individually, imposing an overhead for each
transmitted packet, and increasing energy consumption. In networks with little
interference, it may be beneficial to aggregate the acknowledgments for
multiple nodes and broadcast them in a compressed format to all nodes in the
neighborhood. The IEEE 802.15.4 2012 standard describes such a group
acknowledgment scheme which, however, disappears in later iterations of the
standard. This paper compares different group acknowledgment schemes and
proposes a novel group acknowledgment scheme with the goal to examine whether
group acknowledgments constitute a viable alternative to regular
acknowledgments in reliable data-collection scenarios. Our analysis suggests
that apart from a few cases, GACKs do not constitute a valid alternative to the
direct acknowledgement of data packets.
