**3.1. Smart homes**

architecture, a distributed, interoperable architecture was proposed for IoT to address the scalability issues without degrading the QoS for the realization of IoT notion [30]. In [30], the authors propose three layers of IoT infrastructure: (1) virtual object layer (VOL), (2) composite virtual object layer (CVOL), and (3) service layer (SL). The base structure "IoT daemon" of the distributed architecture consists of the functionalities of the three layers which are object virtualization, service composition and execution, and service creation and management. Based on the processing power and memory, every object hosts its own IoT daemon. Various applications are unified by using the three layers of IoT daemon. VOL digitally represents the properties and functionalities of each object. However, to perform a task, multiple objects work in collaboration. Thus, during runtime, composite virtual object (CVO) is created as a mash-up of VOs corresponding to the task. To create a mash-up, potential VOs should be identified, which is done at the CVOL. With the aid of uniform representation of objects (virtual object (VO)), addition of new objects to the IoT network does not degrade QoS because all the devices are connected with distributed architecture. Also, there are scalability issues due to the increase of network elements (NEs) in the Internet. Compensating the scalability issues with a service-oriented path computation element (S-PCE) instead of conventional host-oriented PCE was proposed by Barbosa C. Souza et al. in [31]. The performance evaluation confirmed that the proposed model supports more network elements than host-oriented PCE by comparing

Interoperability is another major concern with regard to IoT, since various types of devices are connected to each other via IoT. Hence, IoT should facilitate services to all these devices regardless of the type, as interoperability is a necessity. By adhering to standardized protocols, this can be achieved to a certain level at the network and application levels. Due to ambiguous interpretations of the same protocol, achieving interoperability is challenging. So, by avoiding such ambiguities, interoperability of IoT would become more realistic. In [32], a solution to address IoT resources using Web protocols via IoT hubs has been proposed. Thus, the interoperability challenges are reduced to data formats and presenting hub catalogues.

In IoT, most of the devices are mobile devices, which make the IoT scenario more complex. So, IoT applications need to deliver services by considering the mobility factor as well. There are available standard management protocols, that is Mobile IPv6 (network layer) and TCP migrate (transport layer), to facilitate mobility issues in IoT. However, these standards are too complex to be used in IoT nodes. For constrained devices in IoT, a CoAP-based mobility protocol (CoMP) was proposed [33]. Moreover, to ensure mobility, a group mobility management (GMM) mechanism is shown to be promising [34]. In this context, the leader machine does mobility manage-

Precision is another one of the most important challenges that need to be addressed in many smart IoT environments such as transportation, healthcare, and unmanned aerial vehicular networks, where devices and systems are connected globally. Compliance with stringent requirements becomes central to the health and safety of the machine operators, machines, and related businesses when dealing with precision machines that can fail if the timing is 1 ms. Available bandwidth and network latency are the key factors that can affect the precision of distributed IoT delay-sensitive mission-critical environments. Therefore,

ment for the group of machines that are grouped according to mobility patterns.

results obtained and the logs of DNS servers [31].

110 Telecommunication Networks - Trends and Developments

In [35], for detecting a fault in the software defined network (SDN)-based smart home environment, a cloud-based home solution was proposed. To find the faulty location in an IoT-based smart home environment, four social relationships are defined, namely, IoTService, IoTphysical space, IoTNetwork, and IoTIoT. An SDN controller makes a status graph that contains information on each home IoT to resolve the dependencies by collecting information from the packets passing through SDN switches, and the stateless protocol is used by Webbased services, which are not made for long-term sessions.
