Multi-Hop LoRa Networks Enabled by Concurrent Transmission
Multi-Hop LoRa Networks Enabled by Concurrent Transmission
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DOI：
10.1109/access.2017.2755858
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发表时间：
2017-01-01
期刊：
影响因子：
3.9
通讯作者：
Morikawa, Hiroyuki
中科院分区：
文献类型：
--
作者：
Liao, Chun-Hao;Zhu, Guibing;Morikawa, Hiroyuki
在本文中，我们致力于构建一个高效的多跳网络的基础上的sub-GHz低功耗广域技术。具体来说，我们研究了LoRa（一种可以提供几公里户外覆盖的物理层标准）和并发传输（CT）（一种最近提出的可以显着提高网络效率的多跳协议）的组合。本文的主要贡献有三个方面。1)由于CT通过允许同步分组冲突来增强网络效率，因此需要仔细检查物理层接收器在这种分组冲突下的性能以确保网络可靠性。我们首先广泛评估了LoRa接收机在CT下的性能，以验证LoRa是否兼容CT。具体地说，我们发现，由于时域和频域的能量扩散效应，LoRa是强大的数据包碰撞造成的CT。2)我们进一步发现，通过在中继分组之间引入定时偏移，可以进一步提高CT下的接收机性能。鉴于此，我们提出了一种定时延迟插入方法，偏移CT方法，在数据包之前添加随机定时延迟，同时防止定时偏移在多跳网络上发散。3)我们进行了概念验证实验，以证明基于CT的LoRa多跳网络的可行性和所提出的偏移CT方法带来的性能改善。
In this paper, we strive to construct an efficient multi-hop network based on the sub-GHz low power wide-area technology. Specifically, we investigate the combination of LoRa, a physical-layer standard that can provide several-kilometer outdoor coverage, and concurrent transmission (CT), a recently proposed multi-hop protocol that can significantly improve the network efficiency. The main contributions of this paper are threefold. 1) Since the CT enhances the network efficiency by allowing synchronized packet collisions, the performance of the physical-layer receiver under such packet collisions needs to be carefully examined to ensure the network reliability. We first extensively evaluate the LoRa receiver performance under CT to verify that LoRa is compatible to CT. Specifically, we find that, due to the time-domain and frequency domain energy spreading effect, LoRa is robust to the packet collisions resulting from CT. 2) We further find the receiver performance under CT can be further improved by introducing timing offsets between the relaying packets. In view of this, we propose a timing delay insertion method, the offset-CT method, that adds random timing delay before the packets while preventing the timing offset from diverging over the multi-hop network. 3) We conduct proof-of-concept experiments to demonstrate the feasibility of CT-based LoRa multi-hop network and the performance improvement brought by the proposed offset-CT method.