Analysis of Green IoT

Internet of Things (IoT) is an idea and theory of connecting billions of devices and enable them to exchange a massive amount of information. Green IoT visualize the theory of IoT with improved energy efficiency. The overview of Green IoT and the challenges that were faced due to the excessive usage of energy hungry IoT devices were given initially. The research of energy efficiency in IoT had been presented extensively in this paper. Authors presented some challenges, existing works, opportunities, and future directions of green IoT.


Introduction
The blending of renewable energy and expansion of energy use are both critical enablers of sustainable energy transitions and climate change. IoT is increasing globally and its network infrastructure consisting of various devices, e.g. actuators, sensors, and other appliances which are physically embedded objects and having the capability of sensing, processing, and communicate information over the network. Modern inventions like the Internet of Things (IoT) offer an extensive application in the energy sector, i.e., in transmission and distribution, energy supply, and demand. A numerous amount of sensing devices, processing elements, and communication technologies are involved in the growth and expansion of any IoT based system. A copious amount of sensing devices, processing elements, and communication technologies are included in the growth and development of any IoT based system even though sensing and processing devices operate on battery; they must be efficient in providing high performance. Furthermore, the communication devices must be capable of providing an uninterrupted connection for the QoS of the system. Due to IoT, physical objects are seamlessly integrated into the information network where they can become active participants in business processes [1]. Hence, enabling information transmission about their status, neighboring environment, production, and maintenance processes with scheduling, and much more. However, many severe issues still got to be addressed and both technological, also as social knots, got to be united before the vision of IoT becomes a reality. The main issues are to accomplished full interoperability between interconnected devices and the way to supply them with a high degree of smartness by enabling their behavior while ensuring trust with security, and privacy of the users and their data [2].On the other hand, increase in energy prices, rising ecological awareness, and changing  3  The processing layer plays the role of a middleware layer as it collects the information from a transport layer. The layer is responsible for eliminating extra information that has no meaning and extracts useful information. However, it also tackles the IoT a significant amount of data that is responsible for its performance.  The processing layer can be affected by exhaustion [9], and malware [10] causes to disturb the performance of IoT.  The business layer has an intended behavior of an application and behaves like a manager of a whole system. It is responsible for managing and controlling applications, business, and profits models of IoT. It can determine creation, storage, and changing of information. Common problems that business layer faces are logic attack [11] and zero-day attack [12,13] Different layers of IoT architecture discussed in this paper is presented in Table 1.  [53] Compact sensing Complicated task scheduling Network layer [54,55] Game theory, Multihop Inflexible service due to compact positioning Application layer [56,57,58] WCCFS, MQTT No limitations

Green IoT technology
Green IoT (Internet of Things) mainly aims on the energy efficiency in the IoT. Green IoT decreases the effects of greenhouse produced [59]. Different scientific solutions for Green IoT proposed by researchers are discussed in this paper and all these strategies details and summaries. For structure execution of Green IoT, some work is proposed in [60]. Additionally, Green IoT may be executed by using Green Cloud Computing [61], [62], Green Datacentres [63], Green Sensor Networks [64] and Green RFIDs. Details of these are discussed in this section. We must tackle the energy resources in large scale by IoT. The more we solve this problem efficiently, the more effective will be the IoT. Green IoT generally has technologies like Green Cloud Computing [65], Green RFID [66], Green WSN [67], Green Machine to machine [68] and Green Data Centers [69].
 Green Cloud Computing: Green cloud computing system based on technologies like communication and networking both and have a service like IaaS, PaaS, and SaaS. In green structure of IoT, software and hardware are employed in such a way that helps to reduce energy consumption.  Green Data centers: They are employed in a system for storage, handling and for processing all types of data.  Green RFID Tags: RFID tags can store information and data of small intensity which are linked altogether. One type of RFID tag is active tags that are designed with built-in batteries for non-stop transmission of their own signal and another type is passive tags that don't have any battery source in it and they can only store energy from the reader. To accomplish the objective of green RFID, numerous research efforts have been done shown in Table 2.  [70] 2017 Size reduction of nondegradable material using RFID [71] 2014 Removal of overhearing issue in active RFID [72] 2013 Low cost RFID tags was designed [73] 2012 Algorithm was designed to energy efficient active tags [74] 2011 APS algorithm was designed based on energy efficiency for variable slot lengths The summary of the methods for enhancing the energy of different components in several layers is presented in Table 3.

Green IoT techniques based on software
Techniques like data centers can be vital for attaining energy efficient IoT network. e-CAB, which is a policy-based design, proposed by a researcher in [84] utilize an Orchestration Agent (OA) in a system based on Client-Server model, that is accountable for management of data centres. A context aware sensing platform (C-MOSDEN) proposed in [85], uses selective sensors to attain energy efficiency which decreases the energy consumption and causes some small overheads.

Green IoT techniques based on hardware
Many energy utilizations models in IoT concentrates on hardware modifications but classification of an objects in an IoT system can help it to make green network. RFID is an important part of IoT so, enhancement of an active RFID was discussed in [86] and development of passive RFID in [87], Wireless Identification and Sensing Platform (WISP) can lead to a more energy efficient system in IoT discussed in [88]. The summary of hardware-centric solutions for enhancing the energy is presented in Table 4.

Table 4. Summary of hardware-based solutions in IoT Reference Functions
Advantages [89] LoRa Lowers the power consumption and enhances the range [90] Dual-core processor Enables the system to run in low voltage state [91] RAM arrangement Helps to attain energy efficient low voltage [92] RAM arrangement Helps to connect internet via IPv6 using thermal aware RAM

Green IoT techniques based on policies
Strategies and policies based on the real time data obtain from IoT devices can save energy. Different phases of planning policies for attaining energy efficiency are supervising, information management, feedback of user, and automation of system. Automation of systems can help in identification of resident's location in a building for energy efficiency purpose.

Applications of IoT
IoT transforms our life daily activities and scenarios in intelligent decisions so that they improve our lifestyle. Some of the application are discussed below:  IoT in Energy: A joint research initiative of the ETH Zurich and the University of St. Gallen in Switzerland, named The Bits to Energy Lab, started a project that has developed a smart water meter that provides feedback on water consumption directly at individual showerheads or faucets. The device captures temperature, flow rate, and derives the amount of water extracted, energy used, and carbon dioxide emitted. Upgradation of energy usage awareness is under research by researchers at the Swedish Institute of Computer Science. [14]  IoT in logistics, Retail, and supply chain management: Logistics and supply chain management have its advantages. Tracking of items by smart shelves, monitoring of stocks through RFID tags and fast payment solutions, tracking of supply chain and status monitoring of pharmaceutical products with sensors, tracing of food and ingredients across the supply chain, all are now possible through IoT.  IoT in Information security: The Spanish Ministry of Science funded the advanced research on information security and privacy project (ARES) which are working to bring security to the information society. It is the focus in on three application scenarios, that is, Securing critical information infrastructures, universal computing with an emphasis on RFID and W.S.N., safe electronic and digital commerce and content distribution (ARES, 2012). The Institute of Information Systems at the Humboldt-Universitat zu Berlin is working on P2P discovery from RFID-based information production -SHARDIS  Food Supply Chains (F.S.C.): IoT also has its impacts on the supply chain of food business industry. Real-time tracking from farms to consumer possible using IoT. Paper [15] proposes the value-centric business-technology joint design framework. A business-oriented model for F.S.C. using IoT which can enhance food security and can collect the production data.  [16] is developed for IoT where large scale operations are lifting the potential of IoT in supply chain management.  IoT in Garments: An innovation E-Thread [17] gives the idea of collecting data from clothes. It helps in collecting real-time data for tracking activities of a patient without using any extra device.  Smart Cities: A smart city is a city of connecting physical infrastructures, social infrastructures, I.C.T. infrastructures, and business infrastructures [18]. A city can be smart through a large distribution of IoT (especially through communications of machine-to-machine and human-tomachine). W.S.N.s, the sensing-actuation arm of the IoT, Digital Skin that is seamlessly integrated into urban infrastructure. The generated information is shared across platforms and applications to develop a (C.O.P.) Common Operating Picture of the city [19].  Smart Health: A Wireless Body Area Network (WBAN) which is a technology that is formulated on a low-cost wireless sensor network is designed for the convenience of monitoring systems in residential places, hospitals, residential and other work environments [20]. WBAN sensors can be placed inside or outside of the human body and are light weighted having a small battery in the wearable form. The sensors then communicate using technologies like ZigBee, CoAP, 6LowPAN, etc. Through these sensors patient's blood flow, blood pressure, blood P.H. level, the temperature of the body can be analyzed.

Previous working of researchers on IoT
In this section, the critical literature review of the researchers proposed models and there working in the field of energy efficiency and IoT are presented. Table 5 discusses and highlights the findings. Green IoT focuses on energy efficiency concepts. It mainly approaches in IoT is to reduce the greenhouse effect. Ku et al. proposed an energy-efficient smart energy system IoT technology. This service efficiently collects energy resource information in the home. The research should add a feature of enabling a system to continue with its operations even when there is a failure in one part of the system [21]. Miorandi et al. provided an overview of the issues and challenges of IoT technology. It also presented some technique and application fields of IoT. but it lacks in showing Green IoT system model. [22] Chaouch et al. proposed a system based on Energy Management Scheme by using machine-tomachine communication that can reduce extra energy consumption. The researcher emphases the whole system mainly on HVAC. [23]. Kumar et al. introduced a harvesting system based on an IoT system. This system is not considered as an energy efficient. [24].  7 Shaikh and Zeadally discuss the extensive review of harvest energy in W.S.N. where it focused on energy harvesting techniques for generating energy for W.S.N. in different ambient environments. Some issues and challenges focusing on miniaturised generic harvesters that still need to be addressed are identified [27]. Srinivasan et al. introduced a system of energy conservation by using two schemes in it. The whole system was designed to calculate the efficiency of energy conservation. The proposed system is workable in different environments, including large scale industries. In addition, the proposed system is not matching the nature of the IoT [28]. Suresh et al. proposed an energy-efficient solution using IoT that can save the energy mechanism as compared to old mechanisms helping to decrease the energy consumption of sensor nodes using only W.S.N. [29]. Akkaya et al. showed a survey of buildings and its infrastructure based on IoT system. Past papers with some working in HVAC, sensors, were also discussed in it. Its focus was on the point of implementing proper systems in HVAC with energy efficiency. [30] Choi et al. proposed a low-cost renewable energy monitoring system. This system is constructed for an open IoT platform including Arduino, Raspberry Pi. There is a bit inaccuracy in result findings by the system. [31]. Alaudin et al. proposed a system based only on a real-time monitoring device using IoT. [32]. Tcarenko et al. introduced a system design which can modify the energy consumption rate. The whole design is based only for mobiles [33]. Salman et al. proposed an IoT infrastructure deployment for smart homes. He represented his research as a survey for government, regulators and IoT firms. His research was only for cameras and sensors and transmission of information up to kilobytes only. [34] 7. Challenges Green IoT technologies will play a significant part in energy-efficient technology. Numerous severe problems need to be addressed. Right here, author summarize them and spotlight the key issues that want further attention.
 Green Infrastructure: Offering electricity-efficient infrastructure for it is taken into consideration a vital issue closer to greening. However, due to the complexity of deploying significantly new infrastructure, this location of research is less focused and requires in addition to attention.  Green Security and QoS: Execution of algorithms puts the extra load on IoT devices causes the excess consumption of energy and power. In the case of green IoT, safety and security are on high priority. Along with the security, we need to check out excellent mechanisms that consider both strength consumption and the required QoS [48]  Green IoT Architectures for IoT: IoT architecture is nevertheless below standardization. The committees of standardization are trying to allow links between heterogeneous networks and other devices with huge varieties. The mission is to consider protocols as an energy-efficiency while executing their other tasks.  Green Communication: Green IoT has many essential elements, and one of them is communication which is under several issues and challenges. Some of them are mentioned in Table 6: Power controlling Algorithm are designed to control QoS and make power schemes effective. More researchers working is needed to create a common architecture for IoT so that it helps in acquiring more generic results for energy efficiency.
• Eco-friendly material for the enhancement of sensors needs to be comprehensively investigated. • There is a need for a thorough research to set up policies and strategies for establishing awareness among the providers and users for efficient implementation of IoT solutions.

Future directions
Green IoT will change our future and can make it greener and healthier in both economically and environmentally. The research work done recently in realizing the gap in green IoT are mostly focusing on Green IoT services, integrated RFIDs, energy-efficient models and planning, and localization. Hence, researchers need to find solutions for following fields mention in Figure 2:

Conclusion
In conclusion, several possible solutions to overcome the limitations of Green IoT in a specific area is presented in Table 7. UAV is an essential element to replace a massive number of IoT devices, especially in controlling traffic and agriculture, which will help in energy efficiency and to limit pollution.

3.
Sensor-cloud is an emerging technology in green IoT integrating W.S.N. and mobile cloud and is under investigation by (SNaaS) services. 4.
M2M transmission functions to reduce strength use and hazardous emissions. Machine automation lengthens must be minimized in case of congestion and should take immediate steps on the spot. 5.
Radio frequency energy harvesting plays a vital role in energy balancing for supporting green communication between IoT devices must be taken into consideration.
Authors have tried their best to explain all the significant challenges of energy efficiency in the IoT network, and different solutions have been critically estimated. The author discusses various components of an IoT system with visualization tools that can be employed for different smart applications in the energy sector, from buildings to smart cities, agriculture, and health. The author also reviews the application of IoT in the energy supply chain under different levels, including smart cities, smart buildings, and intelligent transportation, smart grids and discuss few of the challenges in the energy sector as well. The author also highlights solutions for a few challenges, i.e., Green IoT as future directions of research and blockchain.