Energy-Efficient Decoupled Access Scheme for Cellular-Enabled UAV Communication Systems

This article proposes a decoupled access scheme with enhanced energy efficiency (EE) for cellular networks serving a mix of randomly distributed ground and areal users. While unmanned aerial vehicles (UAVs) benefit from line-of-sight (LOS) dominant channels with their serving base-stations (BSs), their omnidirectional antennas could cause high interference to ground users (GUEs). To overcome this, a downlink (DL) and uplink (UL) decoupled (DUDe) access scheme is proposed in which the UAVs’ control and nonpayload communication links are separated from the high-capacity data links by connecting to different BSs and transmitting over different frequency bands in the UL and DL directions. The GUE-BS channels are also decoupled in tandem to minimize interference. Moreover, as battery life is a major constraint for UL transmissions, an optimal low-complexity power allocation algorithm—based on fractional programming and successive convex approximation—is proposed for optimizing the EE of this DUDe scheme. Our numerical results demonstrate that the proposed scheme can achieve several times higher sum-rates in both UL and DL directions than its coupled benchmark counterparts. Moreover, it will be shown that in addition to improving the GUE sum-rate by 15%, the devised power allocation algorithm achieves twice higher GUE EE than conventional fractional power control.