Optimal Relay Probing in Millimeter-Wave Cellular Systems With Device-to-Device Relaying

• Published in: IEEE transactions on vehicular technology Vol. 65; no. 12; pp. 10218 - 10222
• Main Authors: Wei, Ning, Lin, Xingqin, Zhang, Zhongpei
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.12.2016; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Array signal processing; Data communication; Device-to-device (D2D) communications; Mathematical model; millimeter wave (mmWave); Millimeter waves; network connectivity; optimal stopping; Receivers; Relay; relay selection; Relaying; Relays; Throughput; Transmitting antennas
• ISSN: 0018-9545; 1939-9359
• DOI: 10.1109/TVT.2016.2552239

Millimeter-wave (mmWave) cellular systems are power limited and susceptible to blockages. One promising approach to increasing mmWave connectivity and range is to use relays. Device-to-device (D2D) communications open the door to the vast opportunities of D2D relaying for mmWave cellular systems. In this paper, we study how to select a good relay for a given source-destination pair in a two-hop mmWave cellular system, where the mmWave links are subject to random Bernoulli blockages. In such a system, probing more relays could potentially lead to the discovery of a better relay but at the cost of more overhead. We find that the throughput-optimal relay probing strategy is a pure threshold policy: The system can stop relay probing once the achievable spectral efficiency of the currently probed two-hop link exceeds an optimized threshold. We further characterize the optimal spectral efficiency threshold via a fixed-point equation.