Automatic repeat request (ARQ) schemes, and in particular hybrid-ARQ (HARQ) schemes, which jointly adopt forward error correction (FEC) and ARQ, are essential to provide reliable data transmission in wireless communications systems. However, the feedback from the receiver to the transmitter and the retransmission process used in ARQ incurs significant cost in terms of power efficiency, throughput, computational power and delay. Unfortunately, such drawbacks can limit their applications to several current and emerging technologies. More specifically, the increasing number of wireless users has create spectrum scarcity, relying on small-size batteries create power constraints, deployment of real-time applications boost the demand for ultra-low delay networks, and the ultra-small low-cost Internet of Things (IoT) devices has limited signal processing and computation capabilities. Consequently, extensive research efforts have been dedicated to overcome the limitations inherent in HARQ. This survey paper provides an extensive literature review of the state-of-the-art HARQ techniques and discusses their integration in various wireless technologies. Moreover, it provides insights on advantages and disadvantages of particular ARQ types and discusses open problems and future directions.

中文翻译：

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无线通信系统和标准中的混合自动重传请求 (HARQ)：当代调查


自动重复请求(ARQ)方案，特别是联合采用前向纠错(FEC)和ARQ的混合ARQ(HARQ)方案对于在无线通信系统中提供可靠的数据传输至关重要。然而，从接收器到发射器的反馈以及ARQ中使用的重传过程在功率效率、吞吐量、计算能力和延迟方面产生显着的成本。不幸的是，这些缺点可能会限制它们在几种当前和新兴技术中的应用。更具体地说，无线用户数量的增加造成了频谱稀缺，依赖小尺寸电池造成了功耗限制，实时应用的部署推动了对超低延迟网络的需求，以及超小型低成本物联网的需求。物联网 (IoT) 设备的信号处理和计算能力有限。因此，广泛的研究工作致力于克服 HARQ 固有的局限性。本调查论文对最先进的 HARQ 技术进行了广泛的文献综述，并讨论了它们在各种无线技术中的集成。此外，它还提供了对特定 ARQ 类型的优点和缺点的见解，并讨论了未解决的问题和未来的方向。