On the Benefits of Network-Level Cooperation in Millimeter-Wave Wireless Networks

Relaying techniques for millimeter-wave wireless networks represent a powerful solution for improving the transmission performance. In this work, we quantify the benefits in terms of throughput and delay for a random-access multi-user relay-assisted millimeter-wave wireless network, in which both the destination and the relay have multi-packet reception capabilities. We consider a full-duplex cooperative relay and two possible transmission techniques: fully directional and broadcast. In the former, the source nodes transmit a packet either to the relay or to the destination, whereas, in the latter, the nodes transmit to both the destination and the relay in the same timeslot by using a wider beam with lower beamforming gain. Moreover, we consider the effects of the beamforming alignment phase, that occurs every time a node changes the destination node, and the inter-beam interference at the receiver. We show the optimal transmission scheme (i.e., broadcast or fully directional) with respect to several system parameters, e.g., positions, number of the nodes, and beamforming alignment duration. As expected, a fully directional transmission is not always beneficial, but broadcasting and relaying can improve the performance of the transmission. Moreover, we show the effect of the duration of the alignment phase on both the throughput and the delay.