# A Mechanism for Reliable Mobility Management for Internet of Things Using CoAP
## 1 Introduction  
In recent years, the Internet of Things (IoT) technology is being increasingly applied to diverse application areas including healthcare monitoring, disaster management, and vehicular management. IoT has been playing an essential role ever since it appeared, which covers from traditional equipment to general household objects [1] and has been attracting the attention of researchers from academia, industry, and government in recent years. The Internet of Things (IoT) is an information network of physical objects (sensors, machines, cars, buildings, and other items) that allows interaction and cooperation of these objects to reach common goals [2]. The IoT will play a key role for building cyber-physical systems for complex industrial applications [3]. Traditional wireless sensor networks are usually being developed using static sensor nodes. However, the applications in IoT environments may require mobility of their nodes for maintaining the Internet connectivity without any need of gateways [4]. There have been proposed lots of Internet Protocol (IP) mobility management protocols, including those standardized by the Internet Engineering Task Force (IETF) such as Mobile IP version 6 (MIPv6) [5] and its variants such as Hierarchical MIPv6 (HMIPv6) [6] and Proxy MIPv6 (PMIPv6) [7]. Unfortunately, most standard IP mobility management protocols may be unsuitable for IoT environments [8]. This is because IoT environments are often constructed with unreliable wireless sensor networks in which hundreds of mobile sensor nodes may be connected to each other. Furthermore, these mobile sensor nodes typically have constrained characteristics in processing capability and electric power. On the other hand, most standard mobility management protocols such as Mobile IPv6 and its variants typically have high signaling overhead owing to tunneling and binding operations and areconsiderably complex, thereby incurring high processing overhead [8]. The signaling and processing overhead can result in excessive power consumption during movement of power-constrained IoT sensor nodes. Furthermore, these standard mobility management protocols do not address the characteristics of a constrained wireless network, such as a limitation in packet size, high packet loss ratio, and sleep mode operation. Under unreliable constrained wireless networks for IoT environments, the loss of the signaling message may frequently occur [9]. MIPv6 and its variants do not consider this situation. Consequently, as a constrained device moves around different wireless networks, its IP connectivity may be frequently disrupted and power can be drained rapidly. This can result in the loss of important sensing data or the large delay for time-critical IoT services such as healthcare monitoring and disaster management. [PERSON] et al. [10] recently proposed a power-aware mobility management scheme for IoT communication. However, their work focused on the optimal selection of an access point for the next available network by considering the energy consumption of a particular application during handover. They did not consider the high energy consumption due to signaling and processing overhead during the handover operation. [PERSON] and [PERSON] [11] propose a network-based mobility protocol for an IP sensor network. However, their work focuses on reducing the signaling cost, without considering the latency for the time-critical services such as healthcare monitoring and disaster recovery. [PERSON] et al. [12] proposed the use of a dual-overlay network structure for IP mobility. Their works introduce a second overlay network where the identity-to-location association is stored, but the introduction of a second overlay network structure may lead to an increase in binding update cost as the number of sensor nodes increases. [PERSON] et al. [13] presented a resource mobility scheme for service continuity in an IoT environment.