Minimum Throughput Maximization in LoRa Networks Powered by Ambient Energy Harvesting
Minimum Throughput Maximization in LoRa Networks Powered by Ambient Energy Harvesting
复制标题
DOI：
10.1109/icc.2019.8761478
复制
发表时间：
2019-05
期刊：
影响因子：
--
通讯作者：
Fatma Benkhelifa;Zhijin Qin;J. Mccann
中科院分区：
文献类型：
--
作者：
Fatma Benkhelifa;Zhijin Qin;J. Mccann
在本文中，我们研究了低功耗广域网（LPWAN）中的上行传输，其中用户通过从周围环境中收集的能量自供电。我们展示了它们在支持各种物联网（IoT）应用方面的潜力，重点关注远程（LoRa）网络，其中LoRa用户使用收集的能量通过不同的传播代码将数据传输到网关。具体来说，我们通过联合优化LoRa用户的扩频因子（SF）分配、能量收集（EH）时间和发射功率来研究LoRa用户的吞吐量公平性优化问题。首先，通过检查用户之间的各种冲突排列，我们得出了LoRa用户之间数据包冲突时间的一般表达式，该表达式取决于SFs和EH持续时间要求。然后，在回顾之前的SF分配工作之后，我们开发了两种类型的算法，要么确保公平的SF分配，要么为LoRa用户提供有目的的“不公平”分配方案。我们的研究结果揭示了三个新的发现。首先，我们证明了为了最大化最小率，不公平SF分配算法优于其他方法。其次，考虑到同时用户之间数据包冲突的推导表达式，我们现在能够提高LoRa用户的最小速率的性能，并表明它可以免受不同sf用户之间发生的sf间干扰。也就是说，不完美的SF正交性对最小速率性能没有影响。最后，我们观察到co-SF干扰是吞吐量性能的主要限制，而不是能源短缺。
In this paper, we investigate the uplink transmissions in low-power wide-area networks (LPWAN) where the users are self-powered by the energy harvested from the ambient environment. Demonstrating their potential in supporting diverse Internet-of-Things (IoT) applications, we focus on long range (LoRa) networks where the LoRa users are using the harvested energy to transmit data to a gateway via different spreading codes. Precisely, we study the throughput fairness optimization problem for LoRa users by jointly optimizing the spreading factor (SF) assignment, energy harvesting (EH) time duration, and the transmit power of LoRa users. First, through examination of the various permutations of collisions among users, we derive a general expression of the packet collision time between LoRa users, which depends on the SFs and EH duration requirements. Then, after reviewing prior SF allocation work, we develop two types of algorithms that either assure fair SF assignment indeed purposefully ‘unfair’ allocation schemes for the LoRa users. Our results unearth three new findings. Firstly, we demonstrate that, to maximize the minimum rate, the unfair SF allocation algorithm outperforms the other approaches. Secondly, considering the derived expression of packet collision between simultaneous users, we are now able to improve the performance of the minimum rate of LoRa users and show that it is protected from inter-SF interference which occurs between users with different SFs. That is, imperfect SF orthogonality has no impact on minimum rate performance. Finally, we have observed that co-SF interference is the main limitation in the throughput performance, and not the energy scarcity.