The adoption of communication technologies in manufacturing has evolved over several decades, with protocols such as Ethernet/IP, EtherCAT, and Profinet continuing to serve as a backbone for time-sensitive automation and control applications. Today however, the increasing prevalence of sensors connected via the industrial internet of things (IIoT) to provide information for data-driven applications like predictive maintenance are now driving the need for a complementary communications infrastructure.

What is needed is wireless instrumentation that can be retrofitted without interrupting functioning processes while satisfying demanding industrial requirements. Recognized for their unique advantages in terms of range, power, and costs, Low Power Wide Area Networks (LPWAN) will soon become the standard industrial IoT connectivity infrastructure covering the entire facility and supporting a multitude of uses cases, from simple temperature monitoring in the manufacturing plant to condition monitoring, energy consumption tracking, and worker safety.

IIoT Sensor Networks on the Factory Floor

The manufacturing sector is constantly looking for innovative approaches to increase productivity and reduce costs. Installation of numerous sensors on shop floors provides informative data about the status of critical asset and machinery, as well as the production environment, to improve control over plant operations. For example, air pressure sensors help monitor and maintain optimal pressure levels to prevent dust infiltration in the manufacturing facility, thereby securing product quality in pharmaceutical and microelectronics industries. Vibration sensors recording excessive movement of motors and pumps may suggest possible mounting defects, shaft misalignment, and bearing wear that require proactive responses. Ultimately, the potential for IIoT in manufacturing facilities is boundless.

Coupled with a powerful analytics platform, sensor networks provide inputs that enable condition monitoring and analysis of past equipment failures to detect causes and anticipate fault probability. This enables planning around predictive maintenance and timely replenishment of spare parts based on asset condition to minimize costly downtime and production losses. Unnecessary manual inspection of various machinery components can also be eliminated, saving labor costs.

While industrial Ethernet and classical fieldbus technologies are best suited for real-time automation and process control, they can be cost-prohibitive and too cumbersome when connecting huge numbers of sensors for remote monitoring to the cloud. Thanks to ease of installation and expansion, wireless industrial IoT connectivity solutions have been increasingly implemented in production environments to provide an additional layer for efficient sensor communication. Industry-grade robustness, the ability to integrate massive end-points across the entire factory, network longevity, low power requirements, and cost-efficiency are leading requirements for wireless networks.

Low Power Wide Area Networks

Incorporating a family of technologies that utilize sub-GHz bands (e.g. 868MHz in Europe and 915MHz in North America) to transmit low-throughput messages, LPWAN can support the communication of vast battery-operated sensor arrays over long distances. Most traditional LPWA networks operate in the unlicensed ISM (industrial, scientific, and medical) bands, with the exception of a few cellular-based LPWA technologies such as Narrow Band IoT (NB-IoT).

LPWAN addresses major drawbacks of short-range radio technologies (e.g. Wi-Fi, Bluetooth) and cellular connectivity in large-scale IIoT deployments. With a range varying from a few to more than 10 km and deep indoor penetration, LPWAN enables effective sensor communication in remote and underground industrial complexes, and fills other cellular coverage gaps. For example, sensors can be installed at previously unfeasible and challenging positions, or even in hazardous areas. A battery life of more than 10 years considerably simplifies battery replacement and recharging.

Less complex waveforms of LPWAN technologies reduce transceiver design complexity, allowing for comparatively low device costs. Wide area coverage in combination with one-hop star topology reduces the requirement for expensive infrastructure (i.e. gateway) and power consumption of endpoints, as opposed to mesh topology in short-range networks with their relaying functionality. Thanks to low device and infrastructure costs along with low subscription fees, LPWAN can be deployed at a fraction of the capital and operating expenditures of wireless alternatives.

A Critical Examination of Existing LPWAN: Quality-of-Service and Standardization

Existing LPWA networks, however, have their downsides, too. Quality-of-Service problems and the lack of standardization encountered by the majority of unlicensed solutions threaten to limit their industrial application, where carrier-grade reliability is a prerequisite.

Operating in the increasingly congested ISM bands, unlicensed LPWA networks expose interference vulnerability and co-existing weaknesses. Technologies employing an ultra-narrow band technique like Sigfox utilize a very long transmission time of about 6 seconds. The chance that another system also sends telegrams at the same time is relatively high, thus increasing the probability of collision and loss of data. Considering the high electromagnetic interference in factory settings, this can greatly diminish network performance. Long on-air time also has a significant impact on power consumption and imposes higher battery requirements. In addition, the number of transmissions is also limited by duty cycle regulations that defined the relationship between on-air time and silent time.

LoRa adopts a spread spectrum modulation scheme to increase data rate and shorten on-air time. During a transmission, the system changes the frequency, resulting in a frequency ramp that occupies much broader bandwidth compared to a narrow band approach. In real-world installations, LoRa networks are very sensitive to interference caused by their own system. Increased traffic within a LoRa network causes an overlay of different telegrams, making it impossible for the receiver to separate them, thereby leading to data loss. Consequently, overall system capacity is confined and system scalability is limited. The use of different spreading factors resulting in different frequency ramps aims to achieve higher network capacity, but introduces other negative effects like different range and data rate for different spreading factors. This requires more effort for network management.

The existence of many proprietary protocols in a fragmented unlicensed LPWAN landscape introduces another major concern for businesses. Proprietary technology such as LoRa entails the problem of vendor lock-in that restricts customers’ innovation capability and flexible reaction to future technological changes. In general, the lack of standardization poses a significant barrier to worldwide IIoT scalability due to reliability and interoperability issues.

Using licensed spectrum, cellular LPWAN like NB-IoT surpass the co-existence and standardization problems experienced by unlicensed counterparts, offering higher quality-of-service. However, it is worth noticing that NB-IoT entails comparatively higher device costs, lower power efficiency, and insufficient coverage (“white spots”) typical of all cellular and operator-based networks. The additional requirement of SIM cards with data volume limits makes these systems more complex and more expensive to deploy and contrary to common perception, cellular technologies do not offer a worldwide solution for IIoT or M2M communication. 

A global standard for robust LPWAN in industrial applications

Answering the call for industrial-grade, worldwide interoperable LPWAN, mioty which leverages Telegram Splitting – Ultra Narrow Band (TS-UNB) technology, has been developed and approved as a global ETSI standard for low throughput networks (TS 103 357). Employing a unique communication method wherein transmission of a telegram (data packet) is divided into short radio-bursts (sub-packets), mioty satisfies other critical network features in IIoT deployments:

• Robustness and Quality-of-Service: Due to very short “on air” time of sub-packets, interference and collision probability are considerably reduced, guaranteeing high network robustness, even in the congested license-free spectrum. Signal strength through physical interference like concrete walls, steel, and rebar obstructions typical in complex industrial settings, is also maximized. Low-bandwidth and short channel occupation make the system extremely “friendly” to other co-existing radio networks. Forward error correction further enables successful data retrieval even if up to 50 percent of sub-packets are lost during transmission.
• High scalability: Providing maximum spectral efficiency, LPWA networks using mioty can scale to handle up to 1.5 million daily messages from thousands of sensors in a single network, without degrading range and connection quality.
• Worldwide compatibility and vendor-independent protocol: As an open standard, accepted worldwide, the protocol can be supported on a global scale and implemented on any commodity, off-the-shelf hardware. The standardized protocol offers end users better investment security and trouble-free, companywide deployments across their global facilities.

Outlook – A New Spectrum of Industrial IoT Use Cases 

Adding carrier-grade robustness, scalability, and compatibility to established long-range, low-power and low-cost attributes of LPWAN, the new industrial IoT connectivity standard mioty, unlocks multiple use cases in manufacturing settings beyond industrial automation:

• Factory-wide environmental sensors including air pressure, temperature, and humidity, can be deployed to monitor and control optimal ambient conditions for various processes like painting, gluing and drying, etc.
• Health parameters and operating surroundings of innumerable remote assets (e.g. motors, valves, pumps, tanks, etc.) can be effectively tracked to curtail manual tasks and enable predictive maintenance leveraging analytical models.
• Wearables transmitting workers’ health and activity status, coupled with environmental sensors (e.g. gas, heat, air quality, etc.), can identify “out-of-tolerance” incidents to enhance worker safety.
• Energy consumption across various areas of the production complex can be monitored with wireless smart meters to detect power waste sources and improve energy efficiency.
• Digitized management of critical building facilities (e.g. elevators, smoke detectors, intrusion alarms, etc.) enhances security and safety.

As we look ahead, robust industrial IoT connectivity technologies that meet the new ETSI TS-UNB Standard are poised to add a new IIoT infrastructure for cost-efficient, reliable sensor communication in factory settings.