On the Benefits of Network-Level Cooperation in Millimeter-Wave Communications

Abstract

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 delay and throughput for a random-access multi-user millimeter-wave wireless network, assisted by a full-duplex network cooperative relay. The relay is equipped with a queue for which we analyze the performance characteristics (e.g., arrival rate, service rate, average size, and stability condition). Moreover, we study two possible transmission schemes: fully directional and broadcast. In the former, the source nodes transmit a packet either to the relay or to the destination by using narrow beams, whereas, in the latter, the nodes transmit to both the destination and the relay in the same timeslot by using a wider beam, but with lower beamforming gain. In our analysis, we also take into account the beam alignment phase that occurs every time a transmitter node changes the destination node. We show how the beam alignment duration, as well as position and number of transmitting nodes, significantly affect the network performance. We additionally discuss the impact of beam alignment errors and imperfect self-interference cancellation technique at the relay for full-duplex communications. Moreover, we illustrate the optimal transmission scheme (i.e., broadcast or fully directional) for several system parameters and show that a fully directional transmission is not always beneficial, but, in some scenarios, broadcasting and relaying can improve the performance in terms of throughput and delay. Index TermsMillimeter-waves, network cooperative relaying, beam alignment, random access networks, directional communications.cooperative full-duplex relay that is equipped with a queue. We analyze the impact of directional communications by evaluating two possible transmission schemes: broadcast (BR) and fully directional (FD). Using the former, the UEs transmit simultaneously to both the mmAP and the relay by means of wider beams at lower beamforming gains, whereas, with the FD scheme, the UEs transmit either to the mmAP or to the relay by using narrow beams. Moreover, we take into account the beam alignments that occur every time the transmitters change receiver and scheme. A. Related WorkSeveral works have been proposed for evaluating the benefits of relaying techniques in mmwave communications, e.g, [25]- [34]. In [25], the authors propose a physical layer analysis of cooperative communications for frequencies above 10 GHz and evaluate the outage probability of several multiple access protocols, combining techniques, and relay transmission techniques.The study shows that the use of relays drastically improves the coverage probability and the correlation between the source-relay and relay-destination links can be exploited to improve the performance. The authors of [26], [27] use stochastic geometry to show the improvements in the signal-to-interference-plus-noise ratio (SINR) distribution and coverage probability for a mm-wave cellular network...

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