Comparison Of Wireless Communication Standards For Cyber Physical Systems And IoT

Factors Used to Compare Wireless Communication Technologies

Introduction

The design of cyber-physical systems is more and more   dependent on wireless networks, sensors and actuators that are connected together by IoT technology.  Cyber Physical Systems (CPS) can include smart grids, autonomous car systems, process control systems, robotics automatic avionics and more [1]. Cyber Physical Systems (CPS) commonly contains both physical and a cyber-systems. The physical system is controlled by a system of networks comprising of some device sensors with wireless, computing and communicating abilities called a cyber-system.  CPS focuses on physical systems, and triggering actions to improve the behaviour of a physical environment so that it can work much more correctly and better [2].  The success of CPS system largely depends on efficient latency, throughput, range and low energy consumption of the connected devices. Wireless networking technologies are used with CPS to provide the design and platform for CPS. Understanding wireless networks principles and standards is thus important for effective CPS. This report compares several wireless communication standards applied in the design of CPS in relation to specific measures.  It also seeks to evaluate examples of wireless communication standards for CPS and IoT. Additionally, it evaluates wireless network performances and suggests the best wireless standard to implement CPS.

Wireless communication technologies can be compared using several factors including the following:

Communication spectrum

All wireless technologies used varied communication spectrums.  They are widely implemented for the infrared range (IR), radio frequencies (RF) and as transmission media. They operate in different wave bands and hence have frequencies that cannot interfere with each other. Many wireless technologies use radio spectrums of between 30MHz and 30 GHz because they are not affected by the curvature of the earth and only require moderately sized antennas [3] . Communications spectrums for wireless systems are assigned in licensed frequency bands and differ according to country and region.

Modulation techniques  

Modulation refers to the process of converting data into transmission signals. Wireless signals originally only had a single carrier frequency called Amplitude Modulation (AM), used for AM radio. They were followed by Frequency Modulation (FM) and Digital Modulation for mobile systems. Other modulation techniques for wireless include Multiple Input Multiple Output (MIMO). The type of modulation affect the communication spectrum. Multicarrier modulation is currently being used by many wireless standards. It divides transmitted bits into very many streams and send them over multiple sub channels [3]. 

Medium access control mechanism

For medium access control, wireless standards use Time Divisions Multiple Access (TDMA) which assigns time allocations to frequency between   sender and receiver channels, Code Division Multiple Access (CDMA) which sends wireless signals over a wide band, and Frequency Division Multiple Access (FDMA) which allocates a frequency to a sender and receiver transmission channels.

UHF RFID and NFC

Network topologies

A network topology refers to the physical arrangement of devices in a network. Different wireless standards implement different topologies. Both ZigBee and Z-Wave implement Mesh network device arrangement. Others including Bluetooth and Bluetooth low energy adopt a scattered device arrangement. The arrangement is based on whether a network has a hub or is working in a peer to peer fashion.

UHF RFID and NFC

Ultra High Frequency (UHF) Radio Frequency Identification (RFID) is a wireless communication protocol which uses electromagnetic signals to pinpoint and track object tags that containing electronic information [4].  This technology therefore allows items to be uniquely identified using radio waves. On the other hand, Near Field Communication (NFC) is a technology that facilitates communication between two electronic devices when they are close to each other.  NFC is a specialized subcategory of the RFID technology that operates at 13.56 MHz frequency.  Both RFID can be used in cyber physical systems with NFC designed enable a secure form of exchange of data [5]. Active RFID systems have demonstrated great potential for connecting and building highly interrelated physical information systems [6].  NFC technology is also used to facilitating peer-to-peer communication among devices in cyber physical systems.

	RFID	NFC
Operating Distance	Can transmit beyond several meters	Limited 10cm(4 inches)
Frequency	13.5 MHz	13.5MHz
Use	Wide range of use	Needed when security is required

ZigBee and  Z-Wave

Both ZigBee and Z-Wave are popular wireless technologies for smart devices home automation. Today, ZigBee technology is used to serve as a sensing and control wireless standard for cyber physical systems in residential, commercial, and industrial areas. ZigBee connects network devices in a mesh arrangement so that information can be transmitted from one device to the other until it reaches the network hub without the need for high-power transmitters.  ZigBee requires very little power and devices can last for a long time with one set of batteries or use no batteries at all. 

Like ZigBee, Z-Wave is a wireless standard for home automation that is implemented for automated heating, lighting, security, appliances, and smart devices. Its original use was to help users remotely control and monitor their home smart devices. A Z-Wave network hub serves as the network home controller and allows wireless communication between more 230 devices.  

Both use mesh topologies to connect sensor devices that can communicate signal across each other and back to the hub. Additionally, they use AES 128 encryption for security.  However, ZigBee can handle high data rates since it operates in 2.4 GHz range whereas Z-Wave uses 908 MHz’s ZigBee can only transmit 35 feet compared to Z-wave 100 feet [7]. Below is the summary of the comparison between ZigBee and Z-Wave.

	ZigBee	Z-Wave
Operating Distance	35 feet	100 feet
Hub	Requires hub	Requires Hub
Topology	Mesh	Mesh
Data Rate	40- 250 kbps	9.6 – 100 kbps
Max Network Devices	65,000	232
Frequency	915MHz/ 2.4	908/ 916 MHz
Security	AES-128 symmetric encryption	AES-128 symmetric encryption

ZigBee and Z-Wave

Bluetooth and Bluetooth Low Energy (BLE)

Both classic Bluetooth and Bluetooth Low Energy (BLE) are wireless networking protocols designed to transmit data among devices that are near each other through radio transmissions with frequencies of 2. 4 – 2. 48 GHz but use separate channels [8]. The technologies are used in stationary and mobile devices for connecting devices high security. Bluetooth Low Energy is an improved version of Bluetooth and has very low energy consumption, low cost and enhanced range [9].  BLE can be very effective for cyber physical systems since applications can run on battery for close to 5 years and is always inactive until a connection is initiated.  Both are good for sensors that require to exchange small amounts of data frequently. Below are summarized features for Bluetooth and BLE.

	Bluetooth	Bluetooth Low Energy (BLE)
Frequency	2400–2480 MHz	2400 MHz
Frequency Channel	79 1-MHz	40 2-MHz
Energy Consumption	High energy  consumption (1 Watt)	Low energy consumption (0.01–0.50 Watt)
Security	56 to 128 bit security  layer	128 bit Advanced Encryption Standard
Operation distance	100m	100m
Topology	Scatternet	Scatternet

Cellular Systems

Cellular systems represent a wireless communication technology where strategically located cells with low-power radio antennas exchange data over a wide area. Cells are interconnected through a central exchange and their identity, location and frequency is managed by several cells without interrupting transmission.  Cellular systems are becoming an integral part for cyber physical systems [10].  They provide network coverage for devices and sensors on the move, support more connections, and reduce power consumption. They can be used for personal, public,  industrial, and home automation including  smart metering, lighting, livestock breeding, waste management,  environment monitoring, irrigation and more.

IEEE 802.11P

IEEE 802.11p is a wireless communication technology and a modified version of IEEE 802.11. It is used to provide wireless access for vehicular communication systems [11]. The standard included 802.11 enhancements that are needed to sustain Transportation Systems and applications. It facilitates data transmission amongst vehicles and roadside infrastructures and uses a frequency band of   5.9 GHz.

Low-Power Wide Area Networks

LP-WANs are low-cost networks designed for applications that require limited data exchange. They implement long-lasting battery-powered sensors. Unlike the wireless standards discussed above which are costly to design and maintain, LP-WANs include low cost hardware  and installation, long-lifetime  battery life, provide secure communications, and offer interoperability, and easy deployment [12]. 

In my opinion, Low Powered Area Network wireless standard will be a major standard for cyber physical systems across the globe. They provide low cost hardware and network installation. LPWA consume the lowest energy compared to other standards.   Other wireless technologies are therefore limited in terms of energy consumption. Additionally, cyber physical systems will be required to serve a diverse range of industries from health, manufacturing to automotive, and increasingly cover a wide range of applications and deployment scenarios.  Short range wireless technologies including Bluetooth, ZigBee, BLE, Z-Wave and the rest  cannot work effectively and hence  cannot ensure good connectivity.

Bluetooth and Bluetooth Low Energy

Benefits of LPWANs over other wireless standards

• Low energy consumption with devices lasting over 10 years after system charge
• Sends small amounts of  optimized data
• Low device costs
• Requires only a few stations/bases to operate
• Easy to install
• Covers both long and short distances
• Provides authentic networks
• Sufficient network coverage and penetration 

Conclusion

Technology is growing tremendously. There’s increased growth of Cyber Physical systems and technologies such as IoT are progressively growing. More and more devices need to be connected to others for easy and fast data migration. As a result, it is important to seek and understand available wireless connecting options necessary for such systems for successful designs, operations, maintenance and sustainability.  From the report, it is clear that there are many wireless communication standards that can be used to accommodate growing technology innovations including computer networks. Wireless technologies is one of the fastest growing sectors of the communication industry. Cellular systems have expanded significantly in the last decade with cellular devices becoming an integral tool for both personal and business related operations. Additionally, wireless local area networks have replaced cabled networks at home and for businesses. Many new applications such as Low Powered Wide Area Networks (LPWA) have developed in order to enable low cost network installation and low cost power consumption. Many innovations including wireless sensor networks, automated factories, smart devices, smart home, smart farming, and telemedicine all require wireless communication for growth and sustainability. Internet of Things and cyber Physical Systems will continue to require stable and low power consumption wireless technologies as wireless communications will increasingly be required to support information exchange between devices and people in the coming decades. Since there are many wireless standards, and each has varying frequency bands, communication spectrum, modulation frequency and each may support a different topology, it is important to first understand the cyber system and physical system architecture in order to design, install and implement a suitable wireless technology to achieve maximum network performance optimality.   

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