  In the Internet-of-Things (IoT), random access is employed for devices to
share a common access channel in packet transmission with low signaling
overhead. Although a retransmission strategy is necessary for packet collision
resolution, it might be prohibitive for some devices due to energy and
complexity constraints. In this paper, we consider a novel relay-aided random
access (RARA) scheme where re-transmissions are carried out by relay nodes, not
devices. Thanks to multipacket reception with multiple copies of collided
signals forwarded by relay nodes, a receiver is able to recover multiple
collided packets simultaneously in RARA. As a result, devices of limited
complexity and energy source can enjoy reliable transmission using RARA, and
the throughput can approach 1 with a large number of relay nodes.
