The recent progress in unmanned aerial vehicles (UAV) technology has significantly advanced UAV-based applications for military, civil, and commercial domains. Nevertheless, the challenges of establishing high-speed communication links, flexible control strategies, and developing efficient collaborative decision-making algorithms for a swarm of UAVs limit their autonomy, robustness, and reliability. Thus, a growing focus has been witnessed on collaborative communication to allow a swarm of UAVs to coordinate and communicate autonomously for the cooperative completion of tasks in a short time with improved efficiency and reliability. This work presents a comprehensive review of collaborative communication in a multi-UAV system. We thoroughly discuss the characteristics of intelligent UAVs and their communication and control requirements for autonomous collaboration and coordination. Moreover, we review various UAV collaboration tasks, summarize the applications of UAV swarm networks for dense urban environments and present the use case scenarios to highlight the current developments of UAV-based applications in various domains. Finally, we identify several exciting future research direction that needs attention for advancing the research in collaborative UAVs.

翻译：近年来，无人飞行器技术的显著进步极大推动了无人机在军事、民用及商业领域的应用。然而，建立高速通信链路、灵活控制策略以及开发高效的无人机集群协同决策算法所面临的挑战，限制了其自主性、鲁棒性和可靠性。因此，协同通信日益受到关注，使得无人机集群能够自主协调与通信，从而在更短时间内以更高效率与可靠性合作完成各项任务。本文对多无人机系统中的协同通信进行了全面综述。我们深入讨论了智能无人机的特性，以及其实现自主协作与协调所需的通信与控制要求。此外，我们综述了多种无人机协作任务，总结了无人机集群网络在密集城市环境中的应用，并通过用例场景展示了无人机应用在各领域的最新进展。最后，我们指出了若干值得关注的未来研究方向，以推动协作无人机领域的进一步发展。