Computer Communications 111 (2017) 41–55 Contents lists available at ScienceDirect Computer Communications journal homepage: www.elsevier.com/locate/comcom Neighbor discovery for industrial wireless sensor networks with mobile nodes Sergio Montero * , Javier Gozalvez, Miguel Sepulcre UWICORE, Ubiquitous Wireless Communications Research Laboratory, Universidad Miguel Hernández de Elche (UMH), Elche Alicante, Spain a r t i c l e i n f o Article history: Received 7 June 2016 Revised 2 March 2017 Accepted 11 July 2017 Available online 12 July 2017 Keywords: Industrial wireless sensor networks IWSN WirelessHART ISA100.11a IEEE 802.15.4e Mobility Neighbor discovery Factories of the future Industry 4.0 Industrial wireless communications Industrial wireless networks a b s t r a c t Industrial wireless sensor networks can facilitate the deployment of a wide range of novel industrial applications, including mobile applications that connect mobile robots, vehicles, goods and workers to industrial networks. Current industrial wireless sensor standards have been mainly designed for static deployments, and their performance significantly degrades when introducing mobile devices. One of the major reasons for such degradation is the neighbor discovery process. This paper presents and evaluates two novel neighbor discovery protocols that improve the capability of mobile devices to remain con- nected to the industrial wireless sensor networks as they move. The proposed protocols exploit topology information and the nature of devices (static or mobile) to reliably and rapidly discover neighbor devices. This is achieved in some cases at the expense of increasing the number of radio resources utilized and the energy consumed in the discovery process. The proposed solutions have been designed and evaluated considering the WirelessHART standard given its widespread industrial adoption. However, they can also be adapted for the ISA100.11a and IEEE 802.15.4e standards. © 2017 Published by Elsevier B.V. 1. Introduction Industrial Wireless Sensor Networks (IWSNs) can help reduce the cost and time needed for the installation and maintenance of cables and machinery, enhance the flexibility and reconfigurability of a factory, and facilitate the introduction of healthcare solutions [1,2]. Current IWSNs mainly focus on static deployments and de- vices, but there is a growing interest in utilizing IWSNs for con- necting mobile subsystems or devices. For example, NAMUR (User Association of Automation Technology in Process Industries) has established a "Mobile Automation" working group (WG 4.15) to study fields of application for wireless technologies and mobile ap- plications in process automation. Current IWSN standards include WirelessHART [3], ISA100.11a [4] and IEEE 802.15.4e [5] for industrial automation and control applications. Despite their differences, both standards share some fundamental wireless technologies and mechanisms [6], e.g. a cen- tralized network management to provide the reliability and latency levels required by industrial applications. IWSNs still face signif- * Corresponding author. E-mail addresses: smontero@umh.es (S. Montero), j.gozalvez@umh.es (J. Goza- lvez), msepulcre@umh.es (M. Sepulcre). icant challenges to ubiquitously guarantee the reliability and la- tency requirements of industrial applications, in particular when considering mobile nodes (robots, vehicles, goods, people, etc.). In fact, the mechanisms defined in WirelessHART for joining, discov- ering, scheduling or routing are currently not optimized for scenar- ios where mobile devices would require permanent network con- nectivity. So, even if WirelessHART considers the use of handheld devices, these handheld devices can only communicate with the attached device and cannot maintain network connectivity as they move. In this context, studies such as [7,8] have highlighted the need to design new mechanisms that reduce the time required to discover neighbor devices and the time to reconfigure the network before mobile nodes can be integrated in existing WirelessHART networks. Mobility management mechanisms are also necessary for mobile devices to remain connected to the network [9]. Such connectivity is also significantly influenced by the Neighbor Dis- covery Protocols (NDP) [10]. Devices utilize the NDPs to discover their one-hop neighbors. Adequate NDPs are necessary to reduce the probability of mobile devices to lose network connectivity and minimize the time to discover neighbors in case the connectivity is temporarily lost. It is important to highlight that the discovery pro- cess can only be executed by devices that have previously joined the network. As a result, the NDPs are independent of the process followed by devices to join the network. http://dx.doi.org/10.1016/j.comcom.2017.07.004 0140-3664/© 2017 Published by Elsevier B.V.