Internet of Things: A Review on Technologies, Architecture, Challenges, Applications, Future Trends

Published Online April 2017 in MECS

• I.    Introduction

  World Wide Web (1990’s) and Mobile Internet (the 2000’s) had consequential corroborated the way how people communicate. However, with an evolution in technology, the cataclysm of Internet has stepped into a new phase ‘Internet of Things-The next generation technology’.

Internet of things (IoT) provides a communication platform supporting person to person (P2P), Machine to Machine (M2M) and Person to Machine (P2M) interactions. Thus, IoT reckons to ‘Accumulate and Ubiquitous’. Fig. 1 shows Accumulate and Ubiquitous IOT.

Internet of Things- A prominent paradigm in the field of IT has a nominal intervention of humans, it is a network where miscellaneous things like animals, plants, vehicles, appliances, buildings dialogue information via the internet. IoT makes our surroundings smart by exploiting RFID tags, sensors, mobile phones, spime, Internet protocols, and wired or wireless communication technologies. The authors in [8] deployed Bluetooth Low Energy (BLE) technology for energy efficient smart homes. Tabish et al. [54] used 6LoWPAN to remotely monitor patient’s health.

IoT has been included in first six ‘Disruptive Civil technologies’ list by US National Intelligence Council(NIC) [85]. NIC also envisions IoT to be present in everything be it furniture, paper, food packages or anything by 2025. By 2020, CISCO gauge to approximately 50 billion IoT objects. In 1999, Kevin Ashton first coined the term ‘Internet of Things’.

Fig.1.Accumulate and Ubiquitous IOT

Gubbi et al. define IoT as:

“ Interconnection of sensing and actuating devices providing the ability to share information across platforms through a unified framework, developing a common operating picture for enabling innovative applications. This is achieved by seamless ubiquitous sensing, data analytics and information representation with Cloud computing as the unifying framework [3]. ”

IoT sensors enable things (real/physical) to anticipate, sight, perceive and conduct jobs as living things do. For example, a wristband with embedded sensors monitor your sleeping and waking time and set an alarm accordingly, this wristband can then convey a message to the bath tub to start warming water and can even communicate to the coffee maker to prepare coffee. Thus, IoT cannot only sense things but it can also control and actuate things.

Things can be uniquely identified by assigning Identification through IPv6 addressing. Current IPv4 have the capability to address only 4.3 billion devices whereas IPv6 has an address space ranging from 2 to 128^th power devices that count to trillions of devices. With Unique identification, things can be easily located, recognized and controlled via the internet. IoT is considered essential in performing everyday activities. It can connect, Monitor heterogeneous things around us, locate things present around the globe, automatically manage and control things .

Deploying IoT in our daily activities can the increase quality of life and can even help in the growth of the economy. By 2025, approximately 2-3 billion people will access the internet also economic growth caused by IoT is estimated to be in the range of $2.7 trillion to $6.2 trillion [55]. Table 1 shows various application areas and the percentage they have an impact on economic growth. From this Medical Care is found to benefit economic growth at the most followed by Manufacturing then Electricity.

Table 1. Percent of Economic Growth Caused By Deploying Iot in Various Application Arenas

APPLICATION ARENAS	PERCENTAGE
Medical Care	41%
Manufacturing	33%
Electricity	7%
Metropolitan Infrastructure	4%
Safety	4%
Resource Extortion	4%
Agriculture	4%
Vehicles	2%
Retail	1%

With IoT, many multinational software companies have switched to the physical world. For instance, Google collaborated with a thermostat company to create its mark in providing smart world/homes. IBM also leveraged IoT for traffic management and provides solutions for smart Grids. Various other companies such as Facebook, Apple envision IoT as its future technology.

IoT has a high significance in our day to day life. It has its vision in business, working and domestic domains such as assisted living, e-healthcare, industrial manufacturing, automation, management, smart transportation and abundant. In [8] [28] IoT is deployed for energy efficient smart Homes and Appliances, [33] deploys Arduino to monitor Air quality. Industry manufacturing processes are made efficient and more economic decisions are made with IoT [36] [27]. In [39] an author proposed an approach to control traffic congestions as well as provides smart car parking. IoT has its application in making green, safe and secure cities [31] [34].

Section II describes various components required for the functioning of IoT devices and various IoT technologies. These technologies include RFID which is the first hardware embedded in IoT devices, its main functionality is automatic identification, authentication, and tracking; Near Fields communication (NFC) - A wireless communication technology is capable of sharing data within the range of 10 cm; ZigBee is another communication technology based on IEEE 802.15.4; 6LowPAN – An IoT communication technology that adequate IPv6 packets to IEEE 802.15.4 specification and provides multi-hop delivery. This section further reviews the applications where these technologies have been utilized. Section III highlights IoT’s system Architecture. Section IV describes various application layer protocols and their comparison. Section V reviews proposals devised for various IoT complications such as energy efficiency, cost efficiency, availability, security, scalability, reliability. Section VI addresses application areas leveraged by IoT. Section VII highlights future research trends. Section VIII associates Big Data with IoT and Section IX concludes the paper.

• II.    Component Prerequisite for Internet of Things

This section describes various components required for the functioning of IoT devices and various IoT technologies. These technologies include RFID which is the first hardware embedded in IoT devices, its main functionality is automatic identification, authentication, and tracking; Near Fields communication (NFC) - A wireless communication technology is capable of sharing data within the range of 10 cm; ZigBee is another communication technology based on IEEE 802.15.4; 6LowPAN – An IoT communication technology that adequate IPv6 packets to IEEE 802.15.4 specification and provides multi-hop delivery. IoT exploits RFID tags, NFC, sensors, smart bands, and wired or wireless communication technologies to build smart surroundings, smart Homes, quick-witted intelligence in medical care, ease of Transport, and more.

There are three components that are required for proper functioning of IoT. These are:

• 1)    Hardware and technologies – It incorporates sensors, actuators and other embedded devices and technologies.

• 2)    Middleware – It comprises of repository and data analytic tools.

• 3)    Display – It comprises of some presentation tools required for user interaction.

Fig. 2 shows various components that sum to IoT.

Fig.2. Various Components of IoT

This section expounds IoT components as follows:

• A.    Hardware

Hardware associated with IoT collects required data from the surroundings. IPv6, RFIDs, NFC, BLE, ZigBee, 6LowPan, WiFi, LTE (Long Term Evolution) are some enabling technologies that gather IoT data.

Radio Frequency Identification (RFID)

RFID is first technology that exists from the time when the concept of IoT was found in late 90’s. RFID is a hardware embedded in the device; its main functionality is automatic identification, authentication, and tracking. RFID consists of passive RFID tags and active RFID readers. Passive RFID tags do not operate on batteries and it conveys ID to the active RFID readers. Active RFIDs are associated with the battery and it initiates communication. Healthcare, supply chain management, automatic recycling are some applications of RFIDs.

Near Field Communication (NFC)

Near Fields communication (NFC) is a wireless communication technology that has the capability of sharing data among electronic devices within the range of 10 cm. NFC works at a high frequency of 13.56 MHz and up to 424 Kbps of the data rate. Smart transportation, IPv6 packet transmission are some application areas where NFC technology is leveraged.

ZigBee

ZigBee is another communication technology based on IEEE 802.15.4. It was standardized in 2003 later was revised in 2006. ZigBee provides high-level communication among IoT devices with coverage of 10100m. It also has its proficiency in monitoring, authentication but does not guarantee QoS. It is a costeffective technology and consumes less energy, so it can be deployed in electric meters, wireless light switches, industrial tools that require short-range data transfer. Applications include Smart Homes, Super Market and more.

Bluetooth low energy (BLE)

Bluetooth low energy (BLE) as the name suggests is a wireless technology that is proficient in reducing power consumptions, thus increasing the lifespan of devices. BLE uses shorter wavelength, operates in the range of 100m but have 15 times lower latency than traditional Bluetooth. It follows a master-slave approach. Almost all Smartphones are leveraging this technology to a greater extent. BLE is coherent in consuming energy as compared to ZigBee. Applications include Data transmission, Home appliances, Vehicle to Vehicle communication and more.

6LowPan

IPv6 over low-power wireless personal area network (WPANs) abbreviated as 6LowPAN is an IoT communication technology that adequate IPv6 packets to IEEE 802.15.4 specification. In 2007, IETF 6LowPAN working group follow this standard.

6LowPAN foreshortens transmission overhead by performing comparisons. It also supports multi-hop delivery [86] and is capable of providing security and protection in IoT environment. It operates in the range of 10-30 m. The datagram of 6LowPAN incorporates 4 types of 2 bit headers. 00 represents ‘No Header’ and jettison all those packets that discard to 6LowPAN. 01 typify to ‘Transmit Header’. This Header accomplishes multi-casting and constricts IPv6 header. 10 represent ‘Reticulation addressing’. It is capable of identifying IEEE 802.15.4 packets. 11 represent fragmentation. Applications include Intrusion detection system, Healthcare.

Table 2 illustrates Attributes of Technologies used in Internet of Things.

Table 2. Attributes of Technologies used in Internet of Things

Technology	Proficiency	Data Rate	Range	Applications
RFID	Authentication , Monitoring, Identification, Information Management	Up to 640 kbps	1-10m	HealthCare[17], Supply    chain Management [56], Automotive Recycling Industry[57], Object Tracking[58], warehouse management[59]
NFC	communicatio n, Security	106 - 424 kbps	≤  10 cm	Smart Transportation [60], Electronic Lock[61],IPv6 packet transmission[62]
6LowPan	Protection and Security	20 250 kbps	10-30 m	Intrusion Detection System [63], HealthCare[64]
BLE	communicatio n, Reduce power consumption	1 mbp s	100 m	Data transmission [65], Home appliances [66], Smart Home[8]
ZigBee	communicatio n, monitoring	20 250 kbps	10 100 m	Smart Home[67], Super Market[68]

• B.    Middleware

In order to aid repository and data analytics, a centralized system is a must. IoT paradigm results into the creation of abundant data. This data must be stored efficiently and intelligently in order to perform actuation and smart observations. A centralized system provides reliability. The data so generated by IoT can be stored in a cloud-based repository.

• C.    Display

Display components of IoT consist of those tools that provide user interaction with the scenario. Since most users of IoT are non-technical, it becomes a necessity to develop devices that are easy to operate and from which user can have maximum benefit from. Devices such as smart phones, smart tablets, 3D screen etc. fall under this category.

• III.    IoT System Architecture

IoT system architecture has the ability to perform interoperability among heterogeneous assets around us. Considering the aforementioned fact, the architecture of IoT should be flexible layered [1]. As there is no commonly accepted IoT architecture, authors proposed various architectures, few among them are SoA based architecture proposed by Atzori et al. [2] and five-layered architecture [86].

Applications

Service

Composition

Service

Management

Object Abstraction

Objects

(a)

BUSINESS LAYER

APPLICATION LAYER

CoAP, MQTT: XMPP, DDS, AMQP

SERVICE MANAGEMENT LAYER

OBJECT ABSTRACTION LAYER

OBJECTS PERCEPTION LAYER

(b)

Fig.3. (a) SoA (Service Oriented Architecture) [2] (b) Five Layered Architecture.

A brief introduction to the five layers of IoT system architecture is as follows:

• A.    Objects or assets layer (Perception layer)

The lowest layer of IoT architecture is responsible for gathering data from the surroundings wielding sensors and actuators. It is proficient in identifying location, monitoring room temperature and humidity, recording vehicle acceleration and more. It digitizes the sensed data and communicates to the object abstraction layer.

• B.    Objects Abstraction layer

Through various communication technologies counterpart RFID, ZigBee, 6LowPAN, WiFi, 3G/4G, BLE etc. this layer act as a bridge to transfer incoming digitized data from objects layer to the service management layer. This layer is also responsible for cloud computing functionalities [87].

• C.    Service Management layer

It is a middleware layer that after identifying the names and address provides service to its requestors. It is the layer with the help of which IoT is capable of connecting with heterogeneous things.

• D.    Application layer

The Application layer is associated with delivering services to the customers. For instance, it can give the acceleration of the vehicle as well as an exact location of the vehicle. Various application domains include Smart Home, Smart Grid, Intelligent Transport, Smart Factory, Quick-witted HealthCare intelligence and more. Application layer incorporates CoAP (Constrained Application Protocol), AMQP (Advanced Message Queuing Protocol), DDS (Data Distribution Service), MQTT (Message Queue Telemetry Transport), XMPP (Extensible Messaging and Presence Protocol) protocols. These protocols are discussed in next section.

• E.    Business layer

The Business layer also named as management layer manages all layers, activities, and service of IoT. It incorporates certain graphs, flowcharts, and models based on the data acquired from the application layer. This layer is capable of making effective decisions for big data analysis.

• IV.    Protocols associated with Application Layer of IoT

The Application layer of IoT system architecture furnishes user services by following certain rules and procedures called Application layer protocols. These protocols include:

CoAP (Constrained Application Protocol).

MQTT (Message Queue Telemetry Transport).

XMPP (Extensible Messaging and Presence Protocol).

AMQP (Advanced Message Queuing Protocol).

DDS (Data Distribution Service).

Among these CoAP and MQTT are most disseminate protocols. A detailed description of these protocols is discussed as follows:

• A.    Constrained Application Protocols (CoAP)

CoAP is a retransmission protocol that features request and response messaging. It was standardized by Internet Engineering Task Force (IETF) constrained Restful environment. CoAP was basically designed for resource constrained devices like WSN (Wireless Sensor Networks). The main functionality of CoAP is monitoring, controlling remote devices as well as guarantying message delivery. CoAP leverages HTTP commands GET, POST, PUT and DELETE for interactions between client and server. It relies on UPD (User Datagram Protocol).

CoAP is divided into two sub-layers namely message sub-layer and request/response sub-layer. The former ensures reliable communication based on exponential back off and later deals with REST communications.

CoAP is proficient in providing Datagram transport layer security (DTLS) that provides privileged message communication, minimizing communication overhead and monitoring resources by utilizing publish/subscribe mechanism. Confirmable, Non-Confirmable, Acknowledgment (Piggybacked) and Separate Response are four types of CoAP messages. CoAP has a 32 bit message format. Fig. 4 shows CoAP message format. It incorporates CoAP version (V), Transaction Type (T), OC (Option Count), Code and Message ID (M ID) in header field followed by Token, Options and Payload fields.

Various Application domains where CoAP is utilized are personal HealthCare Systems [9], Resource Sharing [10], Congestion Control [13], and Security [37].

• B.    Message Queue Telemetry Transport(MQTT)

MQTT is a lightweight messaging protocol that supports machine to machine communication. It relies on TCP. In comparison to CoAP, MQTT has higher throughput but lower Latency [88]. It was developed by IBM in collaboration with Arcom in 1999 and later was standardized as OASIS in March 2013.

MQTT utilizes Publish/Subscribe messaging mechanism and provides SSL (Service Socket Layer) encrypted link between client and Broker.

It has 3 QoS levels:

• 1)    Fire and Forget – Fire the message and Forget i.e. no acknowledgment is received.

• 2)    Delivered at least once – Message is delivered at least once and for each delivery acknowledgment is received.

• 3)    Delivered exactly once – In order to guarantee message delivery, 4-way handshake procedure opts.

The Client-Server of MQTT comprises of 3 elements:

• 1)    Subscriber.

• 2)    Publisher.

• 3)    Broker.

Every server in this architecture is referred to as broker. Client subscribes to a topic generated by the publisher. The Publisher on the other hand forwards the generated topic to the broker. For Instance, Consider three clients A, B, and C. Here Client A is a Publisher that publishes a topic ‘air humidity’ and Client B and C subscribes to this topic. Now, whenever Client A publishes the value of air humidity says 49 then the intermediate broker gives access of this value to all the subscribed Clients.

Fig.5. Publisher/ Subscriber MQTT Architecture

The message format of MQTT consists of four bytes header, 1-4 bytes length, variable length header and variable length message payload. Fig. 6 shows MQTT message format.

0      1      2         3 4            5           6                 7

Message Type	UDP	QoS	Retain
Remaining Length
Variable Length Header
Variable Length Message Payload

Fig.6. MQTT Message Format

Applications include medical information sharing [21], power meters, observations and more.

• C.    Extensible Messaging and Presence Protocol (XMPP)

XMPP is an XML, TCP based Messaging protocol that was invented by Jaber open Source community to ensure SSL confidential message communication. It became an IETF instant messaging standard in 2002.

XMPP has its applications in social networking such as multi-user chat, video/voice calling and more. It is a platform independent protocol, have no QoS support and supports Publish/Subscribe and Request/ Response.

Two or more users exchange data in the form of XML Stanza. XML stanza is cleaved into 3 components.

• 1)    Message – it identifies source and destination address, type and IDs.

• 2)    Presence – it notifies updates to the customers.

• 3)    Info/query – It pairs sender and receiver.

  Shows XML Stanza of XMPP [1].