In distributed device-to-device (D2D) communications, no common reference time is available and the devices must employ distributed synchronization techniques. In this context, pulse-based synchronization, which can be implemented by distributed phase-locked loops is preferred due to its scalability. Several factors degrade the performance of pulse-based synchronization, such as duplexing scheme, clock skew and propagation delays. Furthermore, in distributed networks, devices should be aware of the synchronization status of others in order to initiate data communications. To address these prevailing issues, we first introduce a half-duplex timing-advance synchronization algorithm wherein each device alternates between being a transmitter and receiver in their exchange of synchronization pulses at each clock period. Based on this algorithm, we propose a novel fully-distributed pulse-based synchronization protocol for half-duplex D2D communications in 5G wireless networks. The protocol allows participating devices to become aware of the global synchronization status, so that they can complete the synchronization process ideally at the same time and proceed to data communication. In simulation experiments over multi-path frequency selective channels, the proposed synchronization protocol is shown to outperform a benchmark approach from the recent literature over a wide range of conditions, e.g., clock skew, number of devices, and network topology.

中文翻译：

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半双工D2D通信的基于脉冲的分布式同步协议

在分布式设备到设备（D2D）通信中，没有可用的公共参考时间，并且设备必须采用分布式同步技术。在这种情况下，由于其可伸缩性，因此可以通过分布式锁相环实现的基于脉冲的同步是首选。多种因素会降低基于脉冲的同步性能，例如双工方案，时钟偏斜和传播延迟。此外，在分布式网络中，设备应该知道其他设备的同步状态，以便启动数据通信。为了解决这些普遍存在的问题，我们首先介绍一种半双工定时提前同步算法，其中每个设备在每个时钟周期交换同步脉冲时在发送方和接收方之间交替进行。基于此算法，我们为5G无线网络中的半双工D2D通信提出了一种新颖的基于完全分布式脉冲的同步协议。该协议允许参与的设备了解全局同步状态，以便它们可以在理想情况下同时完成同步过程并进行数据通信。在多径频率选择性信道上的仿真实验中，所显示的同步协议在广泛的条件下（例如时钟偏斜，设备数量和网络拓扑）表现出优于最新文献的基准测试方法。这样他们就可以在理想的情况下同时完成同步过程并进行数据通信。在多径频率选择性信道上的仿真实验中，所显示的同步协议在广泛的条件下（例如时钟偏斜，设备数量和网络拓扑）表现出优于最新文献的基准测试方法。这样他们就可以在理想的情况下同时完成同步过程并进行数据通信。在多径频率选择性信道上的仿真实验中，所显示的同步协议在广泛的条件下（例如时钟偏斜，设备数量和网络拓扑）表现出优于最新文献的基准测试方法。