sensors Review State of the Art in LP-WAN Solutions for Industrial IoT Services Ramon Sanchez-Iborra * and Maria-Dolores Cano Departamento de Tecnologías de la Información y las Comunicaciones, Universidad Politécnica de Cartagena, Cartagena 30202, Spain; [email protected] * Correspondence: [email protected]; Tel.: +34-968-325-953 Academic Editor: Gonzalo Pajares Martinsanz Received: 25 February 2016; Accepted: 9 May 2016; Published: 17 May 2016 Abstract: 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. Keywords: Low-Power Wide Area Networks (LP-WAN); Machine-to-Machine (M2M) communications; Industrial Internet of Things (IIoT); Internet of Things (IoT); wireless sensor networks 1. Introduction Machine-to-Machine (M2M) networks and Industrial Internet of Things (IIoT) services are two key enabling approaches for future industrial networking [1]. As reflected from the forecast investments predicted in the IIoT field [2], the advent of low-cost, always-connected devices opens new and exciting opportunities involving many stakeholders from a wide range of sectors. Deploying well-structured and easily-accessible M2M networks will facilitate having a precise control over the production or company’s installations, which could be translated into a smart strategy for saving logistic costs [3]. As an example, new services such as real-time event processing or 24/7 access to tracking information will be introduced into the supply chain. Having a thorough monitoring system deployed all along the manufacturing and supply chain allows enriching the complete value chain with precious information, minimizing losses against unexpected events, and hence improving both business processes and the information exchange among stakeholders (Business-to-Business (B2B) networks) [4]. In this case, smart metering (water, oil, etc.), goods and facilities monitoring, or smart farming are good examples of areas of activity for M2M/B2B networks. M2M networks can be seen as a revamp of the widely-deployed Wireless Sensor Networks (WSN); we could also think that most of the aforementioned applications are already covered by this well-studied approach. It is true that we have survived so far with the existing WSN classic solutions such as ZigBee, Bluetooth, or even WiFi (short-range technologies), but the main point of industrial M2M networks is the huge increase in the number of devices composing them and the notable widening of the covered areas. Global device connections are estimated to be about 28 billion Sensors 2016, 16, 708; doi:10.3390/s16050708 www.mdpi.com/journal/sensors Sensors 2016, 16, 708 2 of 14 Sensors 2016, 16, 708 2 of 14 2020 (Figure 1) [5]. 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