# A Web of Things-Based Emerging Sensor Network Architecture for Smart Control Systems
## 2 Related Work  
The WoT provides cost effective and fast services with high-speed connectivity integrating heterogeneous wireless networks technologies. Similarly, the introduction of 5G technology will boost the communication among smart objects as well as will satisfy the high data rate requirements. Moreover, the always-connected services problem is significantly addressed by the macro and femtocell technologies that are widely used in enabling network connectivity for indoor communications. However, the integration of WoT in such heterogeneous technologies is still a challenging job. The smart objects are mainly controlled through a sensor which is operated on batteries. Thus, enabling energy-aware communications in such environments must be based on energy-efficient protocols [15; 16]. The z-wave short range wireless technology was introduced in [17] to address the home automation in an energy efficient and cost effective way. However, the z-wave technology does not specify the interoperability with the Internet protocols. Therefore, a dedicated gateway is required to translate the z-wave protocol format into an acceptable format for the Internet protocols [17]. A similar work has been done by the KNX protocols by translating the messages down from transport layer up to the application layer using a dedicated gateway. However, z-wave technology is mainly based on ZigBee technology which suffers highly from crowded frequency and compatibility issues, thus, making it less effective for constrained smart objects. Keeping these issues in mind, researchers have proposed several techniques and paradigms to establish seamless communication among smart objects. Thus, the motto of the WoT is to design a generic and well-established architecture to provide ubiquity connectivity between the objects and the Web [7; 18]. A major breakthrough was made by [PERSON] et al. by in integrating smart objects with the Web using REST architecture with the HTTP protocol [19]. However, they did not consider the topology and localization of sensor nodes in integrating the smart things with the Web [20; 21]. Similarly, several other protocols have been used for specific purposes such as Extensible Pessaging and Presence Protocols (XMPP) for short and instant messaging and so on. However, HTTP is the de facto protocol mainly used for RESTful applications. Moreover, it is also considered as a sub-optimal protocol for smart objects and specifically those objects which operate on batteries. The HTTP protocol always relies on a long header format to establish TCP communication and also a request/response structure which requires high memory and processing time. Therefore, these issues make HTTP a poor match for the constrained oriented applications [13]. In order to address the aforementioned issues in HTTP protocols, the IETF develop a constrained RESTful group (CORE). The primary task of CORE is to design a constrained oriented structure for CoAP. The main functionality of COAP is to transfer the data from smart objects in a WoT environment with the least possible power and processing [22]. CoAP also supports a limited set of REST requests such as GET, POST and DELETE. Moreover, the caching of resource and device discovery is also carried out using the above requests method. The CoAP mainly uses UDP protocol for transmission. However, the reliability is achieved through a built-in retransmission mechanism. In general, CoAP has many advantages over HTTP in the case of using it for constrained oriented applications [23; 24]. The major advantages among those are given below:  
1. A UDP protocol along with a header length of 10-20 bytes reduces the delay and battery consumption. 2. The asynchronous push services enable the smart objects with the functionality of sending information of its state change. The smart objects remain in asleep state until and unless it has to send data. Thus, reducing the power consumption. 3. A minimum number of REST requests reduces the complexity of the system.