Abstract
LoRa (Long Range) is a long-range communications capacity with chirp spread spectrum modulation. It has been developed for Internet of Things (IoT) applications for long-distance and low power consumption. Some authors proposed LoRa protocols such as LoRaWAN, LoRaBlink, DQ-LoRa and the multi-hop LoRa network with linear topology; however, these protocols have disadvantages. In this paper, we propose a minimized latency multi-hop LoRa network protocol that is collision-free with low latency to improve on the disadvantages. First, in the proposed protocol, tree topology is constructed by exchanging packets between LoRa nodes and the sink node. During this period, a timeslot and channel are assigned to each tree link, over which LoRa nodes communicate with their parent node and which is collision-free with its neighbor nodes. After the tree construction period, LoRa nodes start data transmission using the timeslot and channel that they have already been assigned to in the tree construction period. We developed the proposed protocol in a LoRa node prototype using the MultiTech mDot module, and we conducted experiments at Ulsan University. The results show that the proposed protocol provides high reliability, parallel transmissions, a minimized number of timeslots assigned for all the links in the network, a minimized packet size, and low latency.
Highlights
LoRa is a new Internet of Things (IoT) network technology for long-range, low data rates and low power consumption [1,2,3,4]
We consider the Low Power Wide Area Network (LP-WAN), which consists of one sink and several sensor nodes for tree topology
Mechanism, in which all nodes in the network are assigned timeslot and channel to communicate to the parent node or child node, which is collision-free with the neighboring node in the tree construction period
Summary
LoRa is a new Internet of Things (IoT) network technology for long-range, low data rates and low power consumption [1,2,3,4]. Some studies work on improving high reliability and low latency of multi-hop network, such as DeAMON [9], DiSCA [10], PC-LLF [11], CLLF [12], SCSMA [13], SSMADBTC [14], DEDAS-MC [15,16], Multi-hop LoRa linear protocol [8]:. Data transmission is performed progressively, starting with the nodes at the highest level and proceeding to those at level 2 (the lowest sending level) This protocol employed RTS and CTS control messages; it is not suitable for very low bandwidths such as LoRa. In this paper, we propose a minimized latency multi-hop LoRa protocol for monitoring and controlling applications over long-distance and low power consumption. In the tree construction period, the proposed protocol assigns collision-free cells to neighbor nodes using distributed aggregation scheduling, which eliminates all collisions when transmitting data; the reliability of data transmission is high.
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