Joint Position and Resource Optimization for Multi-UAV-Aided Relaying Systems

Abstract

Unmanned aerial vehicles (UAVs) can enhance the overall performance of terrestrial communication systems due to their high possibility of the line of sight (LoS) links and on-demand deployments. The advantages of the UAV position optimization now attract attentions from researchers to study the cooperation among static UAV relays. In this paper, we study a relaying system, where multiple UAVs establish a cooperative UAV relay network to help some transmitters (Txs) communicate with their corresponding receivers (Rxs) by employing orthogonal frequency division multiple access (OFDMA). We maximize the paired Tx-Rxs' minimum rate through solving a non-convex, information causality constraints involved problem by optimizing the UAV relays' locations, nodes' powers, and bandwidth allocations together. An iterative algorithm is proposed by using block coordinate descent (BCD) and successive convex approximation (SCA) methods. Moreover, we also propose a new position initialization method, discuss some special cases of our problem to show some insights for future works, and prove the convergence of our algorithm. Simulations show the effectiveness of our proposed algorithm, some interesting trade-offs about the optimized UAVs' locations, and the influence of available resources.

On UAV Selection and Position-Based Throughput Maximization in Multi-UAV Relaying Networks

“…For the simulation, it is assumed that P AUi /σ 2 = P UiB /σ 2 = γ NF dB. We set the value of frequency f = 2GHz, while the value of path loss exponent whose value lies between 2 and 4 is a = 2 [25], [27], [35]. Furthermore, the distance between GU A to GU B is set as 1200m [25].…”

“…The utilization of multiple conventional relays in wireless networks has been widely studied in literature [20]- [23]. However, utilizing multiple UAVs as relays in future generation wireless networks is still required to be explored, and some of the current works [24]- [27] have discussed multiple UAV based relaying. In [24], [25], the performance of multi hop single link and multiple dual hop links between a pair of transmitter and receiver using same number of UAVs have been studied and compared for both amplify-and-forward (AF) and decode-and-forward (DF) relaying protocols.…”

“…In case of DF relaying, performance analysis has been performed for best-of-worse (BoW) UAV selection strategy considering independent and identically distributed (i.i.d) small scale fading channels. While in [27], placement optimization and resource allocation have been studied (neglecting small scale fading and selection strategy) for a system where multiple UAVs act as relay to serve several GUs pair. To the best of author's knowledge, to date no work has analyzed the performance of multiple UAV based relaying network for independent and non identically distributed (i.n.i.d) small scale fading channels (which is a more practical scenario in terrain conditions).…”

UAV Swarm Intelligence: Recent Advances and Future Trends

“…From the perspective of UAV communication and network, the relevant mission parameters, data requirements of the network, and the applicability o the existing technology that can support aerial networks are summarized [99]. The main problems of current communication layer research include communication architecture [100]- [102], communication, networking technology [103]- [110], airbase station technology [111]- [117] and security communication technology [118]- [126]. The minimum number of upper-layer unmanned aerial vehicles is theoretically proved by a closed-form coverage boundary, and the average delay and average link delay are verified by numerical simulation.…”

“…At the same time, due to the high probability of line-of-sight (LOS) link and on-demand deployment, the UAV can improve the overall performance of the ground communication system. Chen Q et al studied a relay system in which multiple UAVs established a UAV relay network through orthogonal frequency division multiple access (OFDMA) to help some transmitters communicate with corresponding receivers [103]. In a cellular network composed of drones, each drone can sense and transmit data from multiple tasks to the base station.…”