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.
Recently, duty-cycle MAC protocols with pipelined-forwarding and routing-integrated features such as P MAC and PRI-MAC were proposed for efficient communication in terms of power consumption and end-to-end delay in Wireless Sensor Networks (WSNs). However, they remain unnecessary idle listening time at each cycle and their handshake mechanism introduces unnecessary delay at each hop. In this paper, we propose a new cross-layer duty-cycle MAC protocol, called RP MAC (Reduced Pipelined-forwarding) protocol, which improves performance by reducing idle listening time and control overhead. In RP-MAC, the RTS/CTS handshake procedure in the pipeline is shortened by taking advantage of ACK mechanism. A relaying node overhears the A CK message from its potential senders instead of listening to RTS. Right after receiving the data successfully, the relaying node just needs to listen to the CTS without sending the RTS. The simulation results using Qualnet show that RP-MAC achieves significant improvement in comparison with PRI-MAC in terms of energy consumption and end-to-end delivery latency.
Abstract. Long Range (LoRa) communication is known as new technology communication for Internet of Things (IoT). LoRa technology offers a very compelling mix of long range, low power consumption and secure data transmission. Networks system using this technology can provide coverage that is greater in range compared to that of existing cellular networks. By multi-hop communication, we argue that LoRa is potentially very useful for the monitoring system for wide area with long distance. In this paper, we propose a protocol with multi-hop communication for linear network including network constructing period and data operating period using LoRa. The experimentation performed in the university area shows a delivery reliability of above 90%
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