Owing to the explosive expansion of wireless communication and networking technologies, cost-effective unmanned aerial vehicles (UAVs) have recently emerged and soon they will occupy the major part of our sky. UAVs can be exploited to efficiently accomplish complex missions when cooperatively organized as an ad hoc network, thus creating the well-known flying ad hoc networks (FANETs). The establishment of such networks is not feasible without deploying an efficient networking model allowing a reliable exchange of information between UAVs. FANET inherits common features and characteristics from mobile ad hoc networks (MANETs) and their sub-classes, such as vehicular ad hoc networks (VANETs) and wireless sensor networks (WSNs). Unfortunately, UAVs are often deployed in the sky adopting a mobility model dictated by the nature of missions that they are expected to handle, and therefore, differentiate themselves from any traditional networks. Moreover, several flying constraints and the highly dynamic topology of FANETs make the design of routing protocols a complicated task. In this paper, a comprehensive survey is presented covering the architecture, the constraints, the mobility models, the routing techniques, and the simulation tools dedicated to FANETs. A classification, descriptions, and comparative studies of an important number of existing routing protocols dedicated to FANETs are detailed. Furthermore, the paper depicts future challenge perspectives, helping scientific researchers to discover some themes that have been addressed only ostensibly in the literature and need more investigation. The novelty of this survey is its uniqueness to provide a complete analysis of the major FANET routing protocols and to critically compare them according to different constraints based on crucial parameters, thus better presenting the state of the art of this specific area of research.

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Routing in Flying Ad Hoc Networks: Survey, Constraints, and Future Challenge Perspectives

Addressing disasters in smart cities through UAVs path planning and 5G communications: A systematic review

This letter studies a variant of the multi-player reach-avoid game played between intruders and defenders with applications to perimeter defense. The intruder team tries to score by sending as many intruders as possible to the target area, while the defender team tries to minimize this score by intercepting them. Finding the optimal strategies of the game is challenging due to the high dimensionality of the joint state space. Existing works have proposed approximation methods to reduce the design of the defense strategy into assignment problems, however, they suffer from either suboptimal defender performance or computational complexity. Based on a novel decomposition method, this letter proposes a scalable (polynomial-time) assignment algorithm that accommodates cooperative behaviors and outperforms the existing defense strategies. For a certain class of initial configurations, we derive the exact score by showing that the lower bound provided by the intruder team matches the upper bound provided by the defender team, which also proves the optimality of the team strategies.

Cooperative Team Strategies for Multi-Player Perimeter-Defense Games

Cooperative control for multi-player pursuit-evasion games with reinforcement learning

A path planning strategy is developed for the coordinated multiple unmanned vehicles(UAVs).Firstly,an initial path from the projection start position to the target position can be devised by constructing a Voronoi diagram based upon the locations of the threats.Then the initial path is discretized for adjustment and smoothing.At last the desirable paths to the target are obtained by simulating the dynamic chain in a potential field.The result for multiple vehicles is a set of smooth and flyable paths with equal length that reduces exposure to threats.The simulation result shows that this strategy woks well and makes it possible for the simultaneous arrival of UAVs formation at the target.

Trajectory Planning for Coordinated Rendezvous of Unmanned Air Vehicles

In this article an $N$ -pursuer versus $M$ -evader team conflict is studied. This article extends classical differential game theory to simultaneously address weapon assignments and multiplayer pursuit-evasion scenarios. Saddle-point strategies that provide guaranteed performance for each team regardless of the actual strategies implemented by the opponent are devised. The players’ optimal strategies require the codesign of cooperative optimal assignments and optimal guidance laws. A representative measure of performance is employed and the Value function of the attendant game is obtained. It is shown that the Value function is continuously differentiable and that it satisfies the Hamilton–Jacobi–Isaacs equation—the curse of dimensionality is overcome and the optimal strategies are obtained. The cases of $N=M$ and $N>M$ are considered. In the latter case, cooperative guidance strategies are also developed in order for the pursuers to exploit their numerical advantage. This article provides a foundation to formally analyze complex and high-dimensional conflicts between teams of $N$ pursuers and $M$ evaders by means of differential game theory.

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Multiple Pursuer Multiple Evader Differential Games

We consider a general pursuit-evasion differential game with three or more pursuers and a single evader, all with simple motion (fixed-speed, infinite turn rate). It is shown that traditional means of differential game analysis is difficult for this scenario. But simple motion and min-max time to capture plus the two-person extension to Pontryagin’s maximum principle imply straight-line motion at maximum speed which forms the basis of the solution using a geometric approach. Safe evader paths and policies are defined which guarantee the evader can reach its destination without getting captured by any of the pursuers, provided its destination satisfies some constraints. A linear program is used to characterize the solution and subsequently the saddle-point is computed numerically. We replace the numerical procedure with a more analytical geometric approach based on Voronoi diagrams after observing a pattern in the numerical results. The solutions derived are open-loop optimal, meaning the strategies are a saddle-point equilibrium in the open-loop sense.

The Multi-pursuer Single-Evader Game A Geometric Approach

A scenario is considered where a coastline or border is coming under attack by two aircraft. The maritime border is guarded by a faster defender bent on intercepting both aircraft in sequence. A differential game is formulated where the defender sequentially pursues both aircraft and tries to capture them as far as possible from the border. The two aircraft cooperate and try to minimize their combined distance to the border at the moment when each one is intercepted by the defender. In this paper, the regular solution of this differential game is obtained and the game’s singular surfaces are identified.

Strategies for Defending a Coastline Against Multiple Attackers

In this paper an N-pursuer vs. M-evader team conflict is studied. The differential game of border defense is addressed and we focus on the game of degree in the region of the state space where the pursuers are able to win. This work extends classical differential game theory to simultaneously address weapon assignments and multi-player pursuit-evasion scenarios. Saddle-point strategies that provide guaranteed performance for each team regardless of the actual strategies implemented by the opponent are devised. The players' optimal strategies require the co-design of cooperative optimal assignments and optimal guidance laws. A representative measure of performance is proposed and the Value function of the game is obtained. It is shown that the Value function is continuous, continuously differentiable, and that it satisfies the Hamilton-Jacobi-Isaacs equation - the curse of dimensionality is overcome and the optimal strategies are obtained. The cases of N=M and N>M are considered. In the latter case, cooperative guidance strategies are also developed in order for the pursuers to exploit their numerical advantage. This work provides a foundation to formally analyze complex and high-dimensional conflicts between teams of N pursuers and M evaders by means of differential game theory.

In this paper, we extend the well-studied results of the two-pursuer, single-evader differential game to any number of pursuers The main objective of this investigation is to exploit the benefits of cooperation amongst the pursuers in order to reduce the capture time of the evader Computational complexity is a chief concern as this problem would need to be solved in an online fashion, eg, in the case of autonomous unmanned aerial vehicles A new geometric approach to solving the game is introduced and analyzed, which changes the problem of optimizing over continuous domains to a discrete combinatoric optimization While past efforts at solving multiple pursuer problems have suffered from the curse of dimensionality, the geometric algorithms put forth here are shown to be scalable Categorization and removal of redundant pursuers is the primary means by which scalability is achieved The solution of this problem serves as a stepping stone to more complex problems such as the M-pursuer N-evader differential game

Alexander Von Moll

Papers

Multiple Pursuer Multiple Evader Differential Games

The Multi-pursuer Single-Evader Game A Geometric Approach

Strategies for Defending a Coastline Against Multiple Attackers

Multiple Pursuer Multiple Evader Differential Games

Pursuit-evasion of an Evader by Multiple Pursuers