A Survey on the Viability of Confirmed Traffic in a LoRaWAN <s> C. INDUSTRIAL <s> The emerging Internet of Things (IoT) is getting closer to reality every day, with standards and protocols tailored to specific applications. Although some technologies follow a ‘make once, fit all’ approach, others are designed for specific applications such as smart-metering where the devices are often stationary with low jitter and throughput requirements. ETSI is already working towards a new standard for such applications, having specified a Specification Group to study what they call Low Throughput Networks (LTN) and propose a communications standard. In the meantime industrial solutions have entered the market such as, among others, Sigfox's and OnRamp Wireless technologies and LoRaWAN. Although this may lead to fragmentation of the IoT, they are worth examining to gain insights from their innovations and approaches to solving problems that are common in IoT technologies, and more specifically, security, energy management and resource constrains. This paper examines the wireless technologies of LoRaWan, Sigfox and OnRamp Wireless, the emerging leaders in IoT smart metering applications. These have so far not been studied in any peer-reviewed paper. Furthermore we discuss the suitability of Low Throughput Networks for certain applications and how the above technologies would work in such scenarios. <s> BIB001 </s> A Survey on the Viability of Confirmed Traffic in a LoRaWAN <s> C. INDUSTRIAL <s> The emergence of low-cost connected devices is enabling a new wave of sensorization services. These services can be highly leveraged in industrial applications. However, the technologies employed so far for managing this kind of system do not fully cover the strict requirements of industrial networks, especially those regarding energy efficiency. In this article a novel paradigm, called Low-Power Wide Area Networking (LP-WAN), is explored. By means of a cellular-type architecture, LP-WAN–based solutions aim at fulfilling the reliability and efficiency challenges posed by long-term industrial networks. Thus, the most prominent LP-WAN solutions are reviewed, identifying and discussing the pros and cons of each of them. The focus is also on examining the current deployment state of these platforms in Spain. Although LP-WAN systems are at early stages of development, they represent a promising alternative for boosting future industrial IIoT (Industrial Internet of Things) networks and services. <s> BIB002 </s> A Survey on the Viability of Confirmed Traffic in a LoRaWAN <s> C. INDUSTRIAL <s> Low-power wide area networking technology offers long-range communication, which enables new types of services. Several solutions exist; LoRaWAN is arguably the most adopted. It promises ubiquitous connectivity in outdoor IoT applications, while keeping network structures and management simple. This technology has received a lot of attention in recent months from network operators and solution providers. However, the technology has limitations that need to be clearly understood to avoid inflated expectations and disillusionment. This article provides an impartial and fair overview of the capabilities and limitations of LoRaWAN. We discuss those in the context of use cases, and list open research and development questions. <s> BIB003 </s> A Survey on the Viability of Confirmed Traffic in a LoRaWAN <s> C. INDUSTRIAL <s> The proliferation of embedded systems, wireless technologies, and Internet protocols have enabled the Internet of Things (IoT) to bridge the gap between the virtual and physical world through enabling the monitoring and actuation of the physical world controlled by data processing systems. Wireless technologies, despite their offered convenience, flexibility, low cost, and mobility pose unique challenges such as fading, interference, energy, and security, which must be carefully addressed when using resource-constrained IoT devices. To this end, the efforts of the research community have led to the standardization of several wireless technologies for various types of application domains depending on factors such as reliability, latency, scalability, and energy efficiency. In this paper, we first overview these standard wireless technologies, and we specifically study the MAC and physical layer technologies proposed to address the requirements and challenges of wireless communications. Furthermore, we explain the use of these standards in various application domains, such as smart homes, smart healthcare, industrial automation, and smart cities, and discuss their suitability in satisfying the requirements of these applications. In addition to proposing guidelines to weigh the pros and cons of each standard for an application at hand, we also examine what new strategies can be exploited to overcome existing challenges and support emerging IoT applications. <s> BIB004 </s> A Survey on the Viability of Confirmed Traffic in a LoRaWAN <s> C. INDUSTRIAL <s> Among the Low-Power Wide Area technologies available today, LoRa is one of the most successful, as it enables robust long-distance low-power communications in the unlicensed sub_GHz Industrial, Scientific and Medical band. A number of solution providers and network operators show much interest in this technology for Industry 4.0 applications. In addition, LoRa represent a promising candidate for boosting future Industrial Internet of Things networks and services. However, the current standardized LoRaWAN Medium Access Control (MAC) protocol over LoRa does not fully cope with the requirements of industrial networks, in particular as far as the scheduling of real-time data flow is concerned. To overcome this limitation, this paper proposes Industrial LoRa, a novel medium access strategy for LoRa that enables the implementation of industrial wireless networks for Industrial Internet of Things and Industry 4.0 applications. The paper describes the proposed MAC scheme and the advantages it provides. A simulative assessment shows the performance of the proposed approach in a realistic scenario that is compliant with the requirements of soft real-time applications in Industry 4.0. <s> BIB005 </s> A Survey on the Viability of Confirmed Traffic in a LoRaWAN <s> C. INDUSTRIAL <s> Low-power wide-area network (LPWAN) technologies enable Internet of Things (IoT) devices to efficiently and robustly communicate over long distances, thus making them especially suited for industrial environments. However, the stringent regulations on the usage of certain industrial, scientific, and medical bands in many countries in which LPWAN operate limit the amount of time IoT motes can occupy the shared bands. This is particularly challenging in industrial scenarios, where not being able to report some detected events might result in the failure of critical assets. To alleviate this, and by mathematically modeling LPWAN-based IoT motes, we have derived optimal transmission policies that maximize the number of reported events (prioritized by their importance) while still complying with current regulations. The proposed solution has been customized for two widely known LPWAN technologies: 1) LoRa and 2) Sigfox. Analytical results reveal that our solution is feasible and performs remarkably close to the theoretical limit for a wide range of network activity patterns. <s> BIB006 </s> A Survey on the Viability of Confirmed Traffic in a LoRaWAN <s> C. INDUSTRIAL <s> The Internet of Things (IoT) addresses a huge set of possible application domains, requiring both short- and long-range communication technologies. When long distances are present, a number of proprietary and standard solutions for low power wide area networks are already available. Among them, LoRaWAN is a candidate technology supported by many network operators. This paper discusses the possible role of LoRaWAN for the IoT. First, the LoRaWAN technology is assessed experimentally through a set of laboratory and on-field tests, to characterize it from the link-level viewpoint; then, a system-level analysis is performed through simulation, to evaluate the capacity of an LoRaWAN gateway and a multigateway network to serve a large area. Finally, the results are discussed considering a broad set of use cases. <s> BIB007 </s> A Survey on the Viability of Confirmed Traffic in a LoRaWAN <s> C. INDUSTRIAL <s> Low power wide area networks (LPWANs) are suitable for many applications that require low energy consumption, support for a high number of nodes, and large coverage range. Long range (LoRa) is one of the most successful LPWAN technologies, as it enables robust long-distance low power communications and it is proven to be effective in Internet of Things (IoT) applications, such as environmental monitoring and smart metering. LoRa is also promising for Industrial IoT scenarios, but its adoption is impaired by the relevant standardized medium access control protocol, LoRaWAN, that does not offer support to real-time data flows. For this reason, this article proposes RT-LoRa, a medium access strategy for LoRa that provides support for real-time flows, thus enabling the implementation of LoRa-based LPWAN for Industrial IoT applications. This article describes RT-LoRa, presents a simulative assessment in a realistic Industrial IoT scenario and provides some guidelines for the configuration of an RT-LoRa network. <s> BIB008
One of the major areas in which the IoT is expected to play a major role is in industrial settings, hence the term Industrial Internet of Things (IIoT) was coined. The deployment of low-cost connected devices is seen to pave the way forward to productivity improvements and cost savings across manufacturing and supply chains BIB002 . Industrial settings can have harsher requirements than other IoT deployments areas and deployment must be economically viable BIB004 . The use of LoRaWAN in an industrial setting is up for debate as whilst the technology offers good scalability, range and security it might not meet a specific use case's jitter, delay or bandwidth requirements BIB001 . The protocol was not designed with delay in mind, and even for small 10 byte long packets sent using the fastest LoRaWAN data rate available, the transmission time required would be 20 ms. This delay would be too high for real-time operations such as closed-loop control but suitable for most other operations BIB003 , BIB004 . For industrial settings with real-time requirements, alternatives to the use of LoRaWAN as the MAC layer have been developed. Examples of this are RT-LoRa ( BIB008 ) and Industrial LoRa ( BIB005 ) which aims to optimise message latency. Industrial settings vary greatly from crowded factories in cities with lots of radio interference to wide-open areas such as open-pit mining. The number of devices would also differ from thousands of devices down to potentially only one hundred. The network might also be split between a majority of devices that periodically sent measurements and a few devices whose packets are critical to be received BIB004 . In such a scenario, it would be beneficial to only deploy one network servicing both needs rather than deploying two networks. In industrial settings, the fact that the protocol supports confirmed traffic is especially useful as LoRaWAN devices would commonly be used to monitor equipment BIB006 . During normal operations, non-critical data such as temperature would be transmitted for use in fault prevention strategies. Critical faults, such as a breakdown or measured values outside of acceptable operating ranges can be sent as confirmed traffic, to make sure a manufacturing line can be halted. A LoRaWAN supports confirmed uplink and downlink traffic and its viability in industrial settings will in part depend on the power sources available. Battery-powered devices will necessitate the use of LoRaWAN Class A, whilst devices with grid power can use the power-intensive but lower delay Class C. An industry in which the IoT can play a significant role is Smart agriculture. This sector traditionally had limited monitoring and automation options but as land and water become scarce better ways to farm as needed BIB002 . Animal tracking is a use case where LoRaWAN is starting to feature in strongly, with commercial applications such as mOOvement's cattle tracker already available  . The technology is highly suited for this type of use case due to its excellent coverage capabilities in rural areas BIB007 . Most of the animal's movement can be sent without requiring acknowledgements, however, once an animal breach geo-fences due to e.g. theft, confirmation of the animal's location becomes important. Similarly, when technology is used to enable precision agriculture, most of the sensor measurements can be sent as unconfirmed messages. Only the devices that enable the automation elements on a smart farm, such as irrigation pumps, need to make use of acknowledgements to ensure proper operation.