The Internet of Things (IoT) is about connecting sensors, controls, and intelligent systems to a common platform rich with pooled resources and an open market of software and hardware tools. Though many of the applications and services emerging from IoT concepts are app, cloud, and software-based, the reality is that at many levels IoT applications rely on physical connections and wireless communications. Many of these data and power connections use RF connectors and cables along with a range of wireless technologies, and these trend is likely to only continue has high-speed data, enterprise networking, and industrial IoT applications take advantage of flexibility and ruggedness of various forms of RF connectivity.
Though much of the buzz around the Internet of Things (IoT) involves new commercial devices and applications, the essence of this new wave of technology is connecting previously unconnected sensor, actuator, and control systems through the internet. This trend applies to consumer, commercial, enterprise, and industrial systems where control/interfacing and communication, if possible, was done through dedicated systems without the accessibility or open community development typical of internet technologies. A key enabling technology for this capability is RF connectivity, either through RF transmission lines or wireless communications. RF connectivity is used in virtually every hardware element within the IoT Stack, from device hardware, communications systems, the cloud/enterprise systems, and to end-user web/mobile applications.
The goal of this article is to discuss the prevalence and details of the RF connectivity technologies with IoT applications. This discussion will include an overview of RF connectivity technologies and where these technologies appear throughout the IoT Stack.
Within the IoT Stack, Sensors, Actuators, Device Hardware, Communication Network, Web/Mobile Applications, and Enterprise Systems all may rely on RF connectivity, be it through transmission lines or wireless communications.
1. Peripherals: Sensors, Actuators, Control
2. Device Hardware: Communication Modules
3. Device Firmware
4. Communication Systems: Long-haul Network Infrastructure, In-building Network Infrastructure,Wireless Communications
5. Software Platforms
6. Web/Mobile Applications
7. Enterprise Systems
8. Industrial Systems
RF Connectivity Overview
There are two main methods of using electromagnetic energy in the RF portion of the spectrum for IoT applications. As IoT applications typically use RF energy in the frequencies below 6 GHz, the methods of RF connectivity include transmission lines and one-way, two-way, and wireless networking. The types of RF transmission lines commonly seen with IoT are RF coaxial cables and connectors (cable assemblies), as well as stripline (microstrip) transmission lines. Generally, stripline transmission lines are used within device enclosures and on PCBs to more efficiently conduct RF energy between hardware modules and within specialized connector interfaces. RF coaxial cable assemblies are used in a wide range of applications, and at every level of the IoT Stack:
RF Coaxial Cable Assembly Use Case List
- Connecting modules within device or enclosure
- As part of complex multi-pin connector assemblies used in industrial/enterprise systems or test and measurement
- As a low-loss and interference resistant connection between sensors/actuators/control systems and communication devices
- Connecting wireless modules to antennas
- In high-speed digital applications as high fidelity interconnect
- Long-haul networking applications
- In-building networking applications
- Extensively used with cellular networking, wireless networking, and wireless broadcast systems
- Within mobile devices and computer systems with wireless networking and communication modules
Wireless RF connectivity is the other main use of RF technologies with IoT, and has enabled an enormous number of IoT applications that would otherwise be infeasible if transmission lines or other wired interconnect were used. Wireless RF connectivity allows for IoT devices and systems to be placed and installed in mobile applications, modular systems, and in spaces that would otherwise pose cost, complexity, or operation challenges for wired connections. Wireless communications systems rely on a variety of non-proprietary and proprietary wireless communication standards.
RF Connectivity through the IoT Stack
RF connectivity technologies enable either high quality signal transmission resistant to interference, or highly flexible, low power, and mobile operation, depending on if RF transmission lines or wireless communication systems are used. Hence, RF connectivity is highly useful throughout the IoT Stack, mainly with connectivity device and peripheral hardware, wireless networking and communications, and with enterprise and industrial systems.
Device and Peripheral Hardware
IoT Peripherals, specifically sensors, actuators, and controllers, are often installed on or near key areas where they acquire information or perform a function. The use cases for IoT peripherals is growing and can include, sensing temperature/humidity or other environmental information, activating a door lock or security access, controlling a motor or powering an accessory, or many untold future applications. In each of these cases, and likely with future IoT use cases, the fidelity of the sensor information and control signals can be extremely important. As the threat of electrical interference is increasing with the electrification and boom of electronic systems, protecting sensitive IoT peripherals and ensuring critical data and control signal communications is a high priority.
RF coaxial cable assemblies are often chosen as a solution to providing DC power and communication for remote IoT peripherals, as coaxial cables are able to handle low and medium power loads and can allow for communication of high bandwidth signals. The shielded nature of RF coaxial assemblies helps to prevent the intrusion of interfering signals, and also prevents security threatening signal leakage common to other high speed signal technologies, such as ethernet. As RF coaxial cable assemblies are used in extreme applications, such as military and aerospace, there are viable options for rugged interconnect certified for virtually all applications. RF coaxial assemblies can also be purchased and installed at relatively low expense, and come in a wide range of sizes and types.
For example, there are large and rugged RF coaxial assemblies that can handle kilowatts of signal energy, as well as very small and lightweight coaxial assemblies that are commonly used within device enclosures to connect modules. Hence, many IoT wireless modules are connected to internal hardware using either stripline or coaxial transmission lines. There are many low-profile surface mount technology (SMT) coaxial connectors that work with push-type connections, and don’t require torquing to achieve a good electrical connection.
Wireless Communications for IoT
In some instances, there are IoT peripherals and devices distributed throughout and environment where physical connections aren’t desirable. In these cases, wireless RF connectivity is often used. Much like the diverse nature of the internet, there are also a variety of wireless standards commonly used with IoT applications, either for point-to-point, point-to-multipoint, or wireless networking. Among these standards are proprietary low-power wide area (LPWA) network standards, medium/short range wireless standards useful for IoT applications, and cellular network standards viable for select IoT applications.
Wireless Standards Common to IoT:
1. Low-Power Wide Area (LPWA) Networks: Long-Range (LoRa), SigFox, Ingenu, Weightless
2. NB-IoT: Medium/Short Range IoT Wireless Network Technology: Zigbee/IEEE 802.15.4, Thread, Bluetooth, Z-Wave, Wi-Fi, WirelessHART, RFID/NFC
3. Cellular 4G/5G: 4G LTE, 5G Sub-6 GHz, 5G Millimeter-wave
Overview of Wireless IoT Standards
Generally, wireless standards useful for IoT are between several hundred megahertz and below 6 GHz, with the exception of NFC/RFID which use frequencies in the tens of megahertz for ultra-short range communication and identification. The 2.4 GHz ISM band is commonly used by several wireless standards, including IEEE 802.11 (WiFi), IEEE 802.15, Bluetooth, Zigbee, and others. Future wireless standard may include TV White Space (TVWS) frequencies in the range around 400 MHz to over 700 MHz, such as IEEE 802.11af, as TVWS relatively low frequencies allow long range communication at comparably low power levels.
The main considerations when selecting a wireless standard are the cost, range, power, infrastructure, module size, networking type, interference, licensing, and certification. Wireless RF connectivity, due to its emission properties, is heavily regulated in each major country, the FCC regulates wireless emissions and RF spectrum usage in the United States. Hence, consideration and expert resources must be leveraged to ensure proper operation of wireless communications technology, though pre-certified wireless communication and networking modules are becoming increasingly available for IoT applications.
Enterprise and Industrial IoT (IIoT)
Enterprise IoT systems and IIoT applications present a unique opportunity for RF connectivity technologies. The extreme environmental and ruggedness requirements of Industrial applications, and the noise and interference immunity requirements of Enterprise networking and communications systems are readily met with available RF coaxial cable assembly technologies. As machine-to-machine (M2M) and Industry 4.0 technologies are adopted, more industrial systems will opt for high-speed digital and RF connectivity options for low-latency real-time control, monitoring, and communications. Though some of these industrial applications will opt for wireless RF connectivity for large areas and remote communications, such as oil and gas, mining, and agriculture applications, in-factory and facilities based technologies will likely benefit from the installation of fixed RF coaxial assemblies for more reliable and interference resistant communications supporting critical use cases.
Conclusion
The era of IoT is just emerging in consumer, enterprise and industrial applications. The potential for enhanced awareness, efficiency and communications are just starting to be realized by early IoT pioneers. These innovators are also learning an age old lesson of communications, that quality communications are reliant on RF connectivity, either through transmission lines or wireless systems. As IoT adoption and applications increase, so will the use of RF coaxial cable assemblies and wireless networking and communications technologies.
