Multi-Hop LoRa Network Protocol with Minimized Latency

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.

LoRaWAN Mesh Networks: A Review and Classification of Multihop Communication

“…The research in [25] proposed a full protocol solution over LoRa physical layer, including TDMA access, collision avoidance, synchronization, and routing mechanism to provide a low latency solution. The authors deployed end-devices on a university campus to do the tests.…”

“…Ebi et al [27] Router-Device Single Yes No Relay-Gateway Multi Haubro et al [29] Router-Device Single Yes Yes Lee and Ke [23] Router-Device Single No Yes Liao et al [18] Router-Device Single Yes Yes Lundell et al [19] Router-Device Single Yes Yes Mai and Kim [25] Router-Device Single Yes Yes Sartori et al [28] Router-Device Single Yes Yes Sisinni et al [31] Relay-Gateway Multi No No Sisinni et al [32] Relay-Device Multi No Yes Tanjung et al [35] Relay-Device Single Yes Yes Weiwei Zhou and Wang [34] Relay-Device Single Yes Yes Zhu et al [26] Router-Device Single Yes Yes…”

“…Router-Device (Figure 7a) -Smart Building -Industrial -Improve connection -Access to power supply -Multiple barriers scenario Abrardo and Pozzebon [21] Anedda et al [20] Bor et al [17] Dias and Grilo [24] Haubro et al [29] Lee and Ke [23] Liao et al [18] Lundell et al [19] Mai and Kim [25] Sartori et al [28] Zhu et al [26] Router-Gateway (Figure 7b) -Smart Farm -Smart City -Connect remote areas -Concentrate data traffic Dwijaksara et al [30] Router-Device Router-Gateway (Figure 7c) -…”

“…Many authors have proposed multihop solutions for LoRaWAN [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ], where some devices act as relays to other devices. The forwarding mechanism is a crucial choice for a multihop LoRaWAN, as it may affect the performance of the network, in terms of throughput, reliability, latency, and energy consumption.…”

Opportunistic and On-Demand Network Coding-Based Solutions for LPWAN Forwarding

“…This topology requires time synchronization, such as time division multiple access, to synchronize Transmission and Reception between the parent and its children. Similarly, the authors in [ 13 , 14 , 28 ] also propose a solution that requires a parent to forward a packet and time synchronization to avoid a collision. However, both approaches will pressure the parents because they have to listen and forward several packets from their children.…”