LoRaWAN-Based Adaptive MACs for Event Response Applications

Abstract

Low Power Wide Area Networks have emerged as a leading communications technology in the field of Internet of Things sensor and monitoring networks. In such networks, uplink traffic is characterized as a combination of periodic data reports and event-triggered alarm reports. When an many devices detect an event in a short timespan, a burst of concurrent transmissions can occur, leading to a surge of collisions, and thus severe data delivery performance degradation. In this paper, a hybrid random/scheduled access strategy is proposed for mitigating the impact of traffic-triggering events on network performance. Under periodic report traffic the LoRaWAN standard Class A protocol is in effect, but after an event a TDMA scheme is applied. Three implementations of this strategy are described. The first is a pair of novel MACs for LoRaWAN, allowing (a) synchronization of end devices with the network using the event detection as a crude synchronization point, and (b) the dynamic scheduling of groups of devices. The other two implementations build upon a single-hop and a two-hop previously proposed LoRaWAN-based wake-up architectures, respectively. The above approaches are validated and studied through extensive simulation. The results show improved packet delivery ratio over the Class A MAC. The effect is more prominent as the event propagation velocity increases. The proposed approach also surpasses LoRaWAN in energy per delivered bit for high event propagation velocities. Finally, the novel protocol has a lower hardware and deployment complexity than the wake up radio based alternatives, at the cost of higher energy consumption.

Adaptive Spatial Scheduling for Event Traffic in LoRaWAN Networks

“…In [7,17], the authors propose that traffic caused by events could be handled through a hybrid random access/TDMA MAC protocol, where the TDMA is activated only in response to an event, in order to allocate appropriate limited-contention resources for the delivery of event-report frames. The advantage of this approach is that under normal traffic no overhead is imposed on the network, or only minimal when using wake-up receivers, and the mechanism is only activated for end devices that detect the event.…”

“…More specifically, in [7], three implementation mechanisms for TDMA over LoRaWAN are mentioned, a two-hop wake-up receiver mechanism, based on [18], a single-hop wakeup receiver mechanism, based on [19], and a novel mechanism taking advantage of the approximate implicit node synchronization caused by the event. Assuming that all event reports are important, using a TDMA-based method achieves a higher frame delivery ratio than using plain LoRaWAN, and for this reason, it is more energy efficient per delivered bit.…”

“…In order to define a model that delimits arbitrary spatial sections, an overall area of effect of an event is defined in terms of smaller components [7]. Let Ψ 1 , Ψ 2 , .…”

“…2. The paper introduces an extension to the spatially and temporally correlated event traffic model of [4,7], where spatially anisotropic events can be generated. 3.…”

An Environment-Aware Adaptive Data-Gathering Method for Packet-Level Index Modulation in LPWA

“…However, as the event or the change in the monitored environment occurs, a lot of sensors recognize it and then access the channel, simultaneously. The packet collisions frequently occur and thus it is quite difficult to gather the sensing data [ 12 ]. In addition, LPWAs have the limitation of a data transmission duty cycle to secure a time for other systems to gain access.…”