Developing low-power wide-area network (LPWAN) solutions that are efficient to adopt, deploy and maintain are vital for smart cities. The poor quality-of-service of unlicensed LPWAN, and the high service cost of LTE-M/NB-IoT are key disadvantages of these technologies. Concatenating unlicensed with licensed LPWANs can overcome these limitations and harness their benefits. However, a concatenated LPWAN architecture will inevitably result in excess latency which may impact users' quality-of-experience (QoE). To evaluate the real-life feasibility of this system, we first propose a concatenated LPWAN architecture and experimentally measure the statistics of end-to-end (E2E) latencies. The concatenated delay margin is determined by benchmarking the latencies with different LPWAN architecture schemes, namely with unlicensed IoT (standalone LoRa), cellular IoT (standalone LTE-M), and concatenated IoT (LoRa interfaced with LTE-M). Through extensive experimental measurement campaigns of 30,000 data points of E2E latencies, we show that the excess delay due to LPWAN interfacing introduces on average less than 300 milliseconds. The proof-of-concept results suggest that the latency for concatenating unlicensed LPWAN with cellular IoT is negligible for smart city use cases where human perception and decision making is in the loop.

中文翻译：

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将非授权LPWAN与蜂窝物联网连接的延迟：一项实验性QoE研究

开发有效采用，部署和维护低功耗广域网（LPWAN）解决方案对于智慧城市至关重要。这些技术的主要缺点是，未经许可的LPWAN的服务质量较差，而LTE-M / NB-IoT的服务成本较高。将未许可的产品与许可的LPWAN并置可以克服这些限制并发挥其优势。但是，级联的LPWAN架构将不可避免地导致过多的延迟，这可能会影响用户的体验质量（QoE）。为了评估该系统的实际可行性，我们首先提出了一个级联的LPWAN架构，并通过实验测量了端到端（E2E）延迟的统计信息。通过使用不同的LPWAN架构方案（即无执照的IoT（独立的LoRa））对延迟进行基准测试来确定级联的延迟余量，蜂窝物联网（独立的LTE-M）和级联物联网（LoRa与LTE-M接口）。通过对30,000个E2E延迟数据点进行广泛的实验测量，我们发现LPWAN接口所导致的额外延迟平均不到300毫秒。概念验证的结果表明，对于无人值守的决策的智能城市用例而言，将无许可证LPWAN与蜂窝物联网连接的等待时间可以忽略不计。