Internet of Things (IoT), is a new expansion of Information Technology and promising concept that acquiring popularity in every application and field. The Internet of Things transforms the real physical objects and their status into intelligent virtual objects. The converted virtual form or sensed information can be acquired, checked, modified and connected for controlling the object or related things. In IoT, anything, anywhere, anytime can be communicated. In this perspective, this review paper addresses IoT concepts through review of scholarly research papers, professional discussions with experts and online databases. Current IoT technologies, protocols and models are studied, discussed and presented.
Internet of Things, IoT, RFID,, Cloud, Reference Model
Now a day the Internet is accessible by everyone and reached everywhere in the world, and is touching individual life in incredible ways. New connectivity area with very wide reach, with a variety of appliance, will be connected to the internet. Forwarding towards the age of the “Internet of Things” ( IoT) To day nearly in all fields all objects are in connected network and internetwork. The connected network includes an object which may be living and non-living. In every application, IoT plays a vital role. The applications may be healthcare, industry, smart office, smart home, and smart parking etc. In IOT the data is collected with the help of sensors. The collected data stored and shared with the help of internet for further processes. This data or information or status is very useful to take decisions on a situation and act on it. The control of machine, object or a situation is possible from anywhere, with a virtual appearance of the object.
Definition of IOT:
IoT can be defined as "Internet of Things envisions a self-configuring, adaptive, complex network that connected things to the Internet through the use of standard message protocols. These connected things have a physical or virtual presentation in today’s world of digital, sensing capability, a programmability feature, and can be uniquely identified. The presentation contains all the information of the things. The data about things can be captured and communicated. The service through the use of interfaces and is made available anywhere, anytime, and for anything." 
IoT reference model
Abbildung in dieser Leseprobe nicht enthalten
FIGURE 1: IoT reference model (cisco 2014)
IOT reference model contains broadly seven layers. Researchers have a different opinion about a number of reference layers it varies from 3 to 7.
Physical Devices and Controllers
This layer has physical devices like sensors for sensing and assembling information about the surroundings which senses some physical parameters or identifies other smart objects in the environment.
In connectivity layer, communications, and processing executed by existing networks. This layer includes connectors like RJ45, ModBus, USB or wireless connectivity.
The objective of computing layer is for mainly analyzing of data and data formation. Data prepared by encoding, decoding and summarizing for and transformation. This layer is also known as edge computing.
Data storage and data functionality are handled in this layer. This considers type of data, processing of data, higher level application data compatibility, combining of data and storage type. In the area of huge Data backend Hadoop, HBase, MongoDB, and Cassandra can be adding for data storage.
The data abstraction layer receives data sent by device stored at data accumulation layer need to send to an endpoint to use for the application. The collected data is in many different formats as collected from different sources; need to convert in the same format suitable to a higher-level application. Data indexed, normalized and providing appropriate authentication and authorization for security.
Application (Reporting, Analytics, Control)
The application layer main objective is information interpretation and Software for interactions with previous data abstraction level. Simple communications applications can be handled like Mobile Applications are based on device data, business, programming patterns, and software stacks, operating systems, mobility, application servers, hypervisors, multi-threading, multi-tenancy, etc
Collaboration and Processes (Involving people and business processes)
The information generated in IOT yields to accomplish in this layer by handover to end user and processes. They use applications and associated data for their specific requirements. Sixth layer Applications layer gives the right data, at the right time, so they can do the right thing. People must be able to communicate and collaborate, sometimes using the traditional Internet, to make the IoT useful. 
Wireless IoT Communication Protocols
IoT involves smart devices available in the entire region and networked them as personal wireless network locally and worldwide through the Internet. wireless communication technologies required for connectivity. Some main protocols are Bluetooth, Wi-Fi, ZigBee, Z-Wave and RF Link. In IOT implementation Communication Technologies utilized by IoT devices are summarized below:
This ZigBee standard defines the physical and Medium Access Control layers for cheap wireless networks . The physical layer Zigbee functions are channel selection, link quality, energy measurement and channel assessment. For the network and the application layer, ZigBee standard is applicable. The network layer provides routing over the internet, specifying different network topologies: star, tree, peer-to-peer and mesh. In the application layer provides a framework for distributed application development and communication. Zigbee is used in agriculture and food industry, additionally used in a smart home, automation, security, and medical monitoring. 
ii. RF Links
RF communication modules data rates are quite low ranges up to 1Mpbs and also need an Internet-enabled gateway that will provide access to the devices for making a complete IoT network. The Radio Frequency Identification (RFID) technology has been initially introduced for identifying and tracking objects with the help of small electronic chips, called tags. RFID has been originally categorized as the enabling communication power for the Internet of Things, due to its low cost, high mobility, and efficiency in
identifying devices and objects. Despite RFID is very common for device identification and some information exchange 
Bluetooth (IEEE 802.15.1) is a wireless protocol for short-range communication in wireless personal area networks (PAN) as a cable replacement for mobile devices. It uses the 2.4 GHz radio bands to communicate at 1 Mb per second between up to seven devices. Bluetooth is low-powered devices to use for small data like health or tracker. When connectivity is initiated Bluetooth comes into action from sleep mode and conserves power. It uses a method of frequency-hopping spread-spectrum (FHSS) communication, transmits data over different frequencies at different time intervals. Bluetooth uses a master-slave-based MAC (medium access control) protocol [6-8]
The 6LoWPAN is Wireless PAN with low power, large-scale network and supports IPv6. It is a connection-oriented technology in which router forwards the data to its next hop to the 6LoWPAN gateway which is connected to 6LoWPAN with the IPv6 domain and then forwards the data to its respected device correctly. With IPv6 we have enough address space to identify all the things in the world. In IP based network standard protocols (HTTP, TCP/IP) are directly applied to sensor nodes just as they do with traditional web servers out there on the Internet .
Z-Wave protocol architecture is low power consuming mostly used in home automation, security and light commercial environment. It has an open communication protocol. The main purpose of Z-wave is a reliable mesh network, message passing from a control unit to one or more nodes in the network. Z-wave have two types of devices, one is poll Controllers which send commands to the slaves, the second type of device, which replies to the controller to execute the commands .
vi.Wi-Fi Wireless fidelity
Wireless fidelity is known as Wi-Fi, with the IEEE 802.11x standards, common way to connect devices wirelessly to the Internet. Laptop, Smartphone, and Tablet PC are equipped with Wi-Fi interfaces and talk to a wireless router and provide two-way accesses to the Internet. The Wi-Fi standard family allows establishing a wireless network on short distances. Wi-Fi has series types of networks of IEEE 802.11 and IEEE security extension. The Wi-Fi group is working on an unlicensed spectrum of 2.4 GHz band. WIFI consumes more power. [13-14]
Abbildung in dieser Leseprobe nicht enthalten
Figure 2 source: IOT research EU
MQTT - Message-Queue Telemetry-Transport
It is a publish subscribe based lightweight messaging protocol for use in conjunction with the TCP/IP protocol. This provides an embedded connection from applications to a middleware’s on one side. on the other side connection from networks to communications, The system consists of three main components: publishers, subscribers, and an agent. MQTT enters in sleep mode once data transmission complete.
- Quote paper
- Ajit Singh (Author), 2018, Internet of Things Reference Model and Wireless IoT Communication Protocols, Munich, GRIN Verlag, https://www.grin.com/document/489811