A Two-Hop Real-Time LoRa Protocol for Industrial Monitoring and Control Systems

Abstract

A single-hop LoRa (Long Range) network suffers from a limitation in coverage caused by high signal attenuation when deployed in industrial areas, which often include wireless unfriendly zones (WUZs). Thus, some end nodes in WUZs may fail to transmit data to the gateway (GW). This paper proposes a reliable two-hop real-time LoRa protocol in which the nodes in WUZs transmit data to another node that relays the received data to the gateway for reliable transmission. The proposed protocol allocates transmission slots to nodes with different data transmission periods, so the nodes not only achieve high reliability but also meet time constraints or periods for delivering data to a gateway. In this case, 1-hop nodes (one hop away from GW) may consume more energy than 2-hop nodes (two hops away from GW). For energy balancing, the protocol uses a data aggregation approach to minimize the number of transmissions. We show by analysis that the proposed protocol can support up to 200 nodes using a single-channel GW when every node sends one packet with a payload of 30 bytes within 17 seconds, and 30% of the nodes are 2-hop nodes. In addition, we show by experiment that the proposed protocol can achieve high reliability in data transmission. INDEX TERMS two-hop LoRa network, energy balancing, relay, real-time scheduling, reliable transmission

Numerical and Experimental Characterization of LoRa-based Helmet-to-UAV links on Flat Lands

“…Helmet-UAV off-body links for SaR [13], [14] Terrestrial links for mountain SaR [8] Localization and tracking [15] Emergency communications [9] Remote health monitoring [16] Extend the SMS coverage to unconnected areas [10] Human activity recognition [17] Industrial monitoring [11] UAV communications for swarm configurations [18] Wireless underground sensor networks [12] Recovery of incapacitated UAVs [19], [20] Smart cities…”

Performance Analysis of a Two-Hop Relaying LoRa System

“…It should be noted that, the proposed system performs selection strategy using the protocol described in [17], which can select the best relay by examine the link quality (i.e., SNR) when constructing the parent-child tree between nodes and gateway during network initialization.…”

“…Since the multi-relay architectures are developed to boost the performance of the system [12], [13], there are some progresses in applying relaying communication to LoRa networks via advanced protocol design [14]- [17]. To construct a robust multihop LoRa network, a combination of the LoRa physical-layer standard with concurrent transmission protocol was proposed in [14].…”

“…Moreover, a synchronous LoRa mesh protocol was proposed in [16] to improve transmission quality and reduce packet error for underground applications. By considering the link quality between end nodes and the gateway, a two-hop real-time LoRa protocol was devised in [17], which assigns nodes to different data transmission periods, providing a reliable and energyefficient scheme.…”

Cooperative Relaying in LoRa Sensor Networks

“…Relaying in LoRa networks and its potential benefits are reported in [3]- [8]. Uncoded forwarding is employed in [3]- [7]. In the coded relaying scheme of [8], multiple relays employ random linear network coding to combine received sensor messages before sending.…”