Comparison of several mainstream wireless technologies in the Industrial Internet of Things

Large-scale production scenarios involve a large number of equipment, production application systems, workers, and products. A stable, high-speed, and easy-to-manage wireless network is an essential requirement.

Wireless communication technologies for the Industrial Internet of Things are mainly divided into two categories: one is short-distance communication technologies such as ZigBee, WiFi, and Bluetooth; the other is LPWAN (low-power Wide-Area Network), which is low-power wide-area network communication technology. LPWAN is further divided into two categories: one is technologies such as LoRa and SigFox that work in unlicensed spectrum; the other is 2/3/4G cellular communication technologies supported by 3GPP that work in licensed spectrum, such as EC-GSM, LTE Cat-m, NB-IoT, etc.

Different wireless technologies differ in networking, power consumption, communication distance, security, etc., and therefore have different applicable scenarios. For example, Sub-1GHz technology is suitable for applications with long transmission distances, battery power, and robustness; Bluetooth is suitable for high speed, more information transmission, and control via mobile phones; Thread, Wi-Fi and other technologies also have their own advantages and applicable scenarios.

Wireless connectivity in Industry 4.0 application scenarios

It is worth noting that new wireless technology standards are also emerging. For example, as an extension and supplement to traditional WiFi technology, Wi-Fi HaLow can provide a unique combination of security, long distance, low power consumption and highly optimized wireless connection, which greatly improves the management efficiency of factory automation.

Performance comparison of different wireless technologies in the Industrial Internet of Things

Transmission rate and distance of different wireless technologies in the Industrial Internet of Things

Reception efficiency and distance of different wireless technologies in the Industrial Internet of Things

The following are some common wireless technologies in the industrial Internet of Things: ZigBee, Bluetooth, Lora, NB-IoT, Sigfox, and the latest WiFi Halow technology.

ZigBee Technology

ZigBee was formally proposed in 2003 to make up for the shortcomings of Bluetooth communication protocol, such as high complexity, high power consumption, short distance, and small network scale. The name comes from bees, which rely on flying and "zig" (buzzing) wings to communicate with their companions about the location of pollen, thus forming a communication network in the group.

ZigBee can operate in three frequency bands: 868MHz~868.6MHz, 902MHz~928MHz and 2.4GHz~2.4835GHz. The last frequency band is universal worldwide and has 16 channels. It is a free and application-free radio frequency band. The transmission rates of the three frequency bands are 20kbps, 40kbps and 250kbps respectively.

ZigBee is a low-cost, low-power, low-power short-range wireless communication standard. It is a wireless network specification designed for low-rate sensors and control networks and has the following characteristics:

• Low power consumption: ZigBee devices are very power-efficient due to their low transmission rate, 1mW transmission power, and sleep mode. It is estimated that a ZigBee device can last for 6 months to 2 years with only two AA batteries, which is far beyond the reach of other wireless devices.
• Low cost: The initial cost of a ZigBee module is around $6, and it is estimated that it will soon drop to $1.5-2.5, and the ZigBee protocol is free of patent fees.
• Low complexity: The size of the ZigBee protocol is generally between 4 and 32KB, while Bluetooth and WiFi are generally over 100KB.
• Short latency: The communication latency and latency for activating from a dormant state are very short, with a typical latency for searching for devices of 30ms, a latency for activating from a dormant state of 15ms, and a latency for accessing a channel for an active device of 15ms. Therefore, ZigBee technology is suitable for wireless control applications that have strict latency requirements (such as industrial control applications, etc.).
• Large network capacity: A star-structured ZigBee network can accommodate up to 254 slave devices and one master device. Up to 100 ZigBee networks can exist simultaneously in one area. A network can have up to 65,000 nodes connected, and the network composition is flexible.
• Reliable: A collision avoidance strategy is adopted to reserve dedicated time slots for communication services that require fixed bandwidth, avoiding competition and conflicts in sending data. The MAC layer adopts a fully confirmed data transmission mode, and each data packet sent must wait for the receiver's confirmation information. If there is a problem during the transmission process, it can be resent.
• Security: ZigBee provides a data packet integrity check function based on a cyclic redundancy check (CRC), supports authentication and authorization, and uses the AES-128 encryption algorithm. Each application can flexibly determine its security attributes.

Although ZigBee has the advantages of low power consumption, low cost, low rate, high capacity, and long battery life, it also has disadvantages, namely poor anti-interference, short communication distance, and the ZigBee protocol is not open source.

Bluetooth Technology

Bluetooth technology was first developed in 1994 by telecommunications giant Ericsson. It is the simplest and most convenient way to conduct short-distance wireless communication between two devices, and can achieve short-distance data exchange between fixed devices, mobile devices and building personal area networks. Bluetooth technology is widely used in mobile devices such as mobile phones and PDAs, PCs, GPS devices, and a large number of wireless peripherals (Bluetooth headsets, Bluetooth keyboards, etc.).

Bluetooth uses frequency hopping technology, and the communication frequency band is 2.402GHz~2.480GHz. So far, 10 versions have been updated, namely Bluetooth 1.0/1.1/1.2/2.0/2.1/3.0/4.0/4.1/4.2/5.0, and the communication radius extends from a few meters to hundreds of meters.

Compared with the previous Bluetooth 4.2 or even older versions, Bluetooth 5.0 has the following features:

• Faster transfer speed: The upper limit of the speed is 2Mbps, which is twice that of the previous 4.2LE version.
• Longer effective distance: The effective distance is 4 times that of the previous version. Theoretically, the effective working distance between Bluetooth transmitting and receiving devices can reach 300 meters.
• Navigation function: More navigation functions have been added. It can be used as an indoor navigation beacon or similar positioning device. Combined with WiFi, it can achieve indoor positioning with an accuracy of less than 1 meter.
• More transmission functions: With the addition of more data transmission functions, hardware manufacturers can create more complex connection systems through Bluetooth 5.0, such as Beacon or location services.
• Lower power consumption: Power consumption is greatly reduced, and people no longer have to worry about standby time when using Bluetooth.

The main advantages of Bluetooth technology are that it does not rely on external networks, has fast speed, low power consumption, and high security. As long as you have a mobile phone and smart device, you can maintain a stable connection and connect wherever you go. Its disadvantages are that it cannot directly connect to the cloud, the transmission speed is relatively slow, the networking ability is relatively weak, and there are few network nodes, which is not suitable for multi-point control.

LoRa Technology

LoRa is an ultra-long-distance, low-power wireless transmission solution based on spread spectrum technology developed and promoted by Semtech in the United States. It provides users with a simple system that can achieve long distance, long battery life, and large capacity, thereby expanding the sensor network. Currently, LoRa mainly operates in the global free frequency band, with an operating frequency of 915MHz in the United States, 868MHz in Europe, and 433MHz in Asia. Its typical range is 2km to 5km, and the longest distance can reach 15km, depending on the location and antenna characteristics.

LoRa technology has the following characteristics:

• Low power consumption: The communication distance can reach 15 kilometers, the receiving current is only 10mA, and the sleep current is 200nA, which prolongs the battery life.
• Large capacity: It can cover about 2 kilometers in densely built urban environments, and up to 10 kilometers in less dense suburban areas.
• Supports ranging and positioning: LoRa's distance measurement is based on the signal's air transmission time, and positioning is based on the measurement of the spatial transmission time difference between multiple points (gateways) and one point (node). The positioning accuracy can reach 5m (assuming a range of 10km).

Therefore, LoRa technology is very suitable for IoT applications that require low power consumption, long distance, large number of connections, and positioning tracking, such as parking, vehicle tracking, smart industry, smart cities, smart communities, etc.

The disadvantages of LoRa are slow transmission rate, communication frequency band susceptible to interference, chip supply is monopolized by Semtech, the bottom-level development cycle is long, and the network mechanism of self-organizing network is relatively complex. Therefore, most companies are reluctant to study LoRa technology and prefer to buy modules for direct use.

NB-IoT Technology

NB-IoT (Narrowband Internet of Things) technology originated from a British startup company Neul (acquired by Huawei in 2014), focusing on the low-power and wide-coverage Internet of Things (IoT) market.

Instead of using the full 10MHz or 20MHz bandwidth of standard LTE, NB-IoT uses 180kHz-wide resource blocks consisting of 12 15kHz LTE subcarriers, with data rates ranging from 100kb/s to 1Mb/s.

NB-IoT uses licensed frequency bands and can be deployed in three ways: in-band, guard band or independent carrier, and coexist with existing networks.

As a technology applied to low-rate services, NB-IoT has the following advantages:

• Low power consumption: NB-IoT sacrifices speed in exchange for lower power consumption. It uses a simplified protocol and a more appropriate design, which greatly improves the standby time of the terminal. The standby time of some NB terminals is said to be up to 10 years!
• Low cost: Compared with LoRa, NB-IoT does not need to rebuild the network, and the radio frequency and antenna can basically be reused. Low rate, low power consumption and low bandwidth also bring low-cost advantages to NB-IoT chips and modules, and the module price does not exceed US$5.
• Massive connections: In the case of the same base station, NB-IoT can provide 50 to 100 times more access than existing wireless technologies. One sector can support 100,000 connections, low latency sensitivity, ultra-low equipment cost, low equipment power consumption and optimized network architecture.
• Wide coverage: NB-IoT has strong indoor coverage. In the same frequency band, NB-IoT has a gain of 20dB over the existing network, which is equivalent to increasing the coverage area by 100 times.

Although NB-IoT has many advantages, its low-speed data transmission, privacy and security, and IT system conversion time will limit its development.

Sigfox Technology

Sigfox is a wireless network built by the French company Sigfox using ultra-narrow band (UNB) technology. It is both a wireless technology and a network service.

Sigfox operates in the ISM bands of 868MHz and 902MHz, consuming very narrow bandwidth or power consumption.

Sigfox radios use a technique called ultra-narrowband (UNB) modulation to occasionally transmit short messages at a low data rate, with a maximum message length of 12 bytes, and a node can transmit up to 140 messages per day. Due to the narrow bandwidth and short messages, in addition to its 162dB link budget, it can also achieve a long transmission distance of several kilometers. For burst applications that only need to send small, infrequent data, Sigfox is an excellent choice.

The downside of Sigfox is that data sent back to the sensor/device (downlink capability) is severely limited and signal interference can also be a problem.

HaLow Technology

Unstable connection, low efficiency, and intermittent time periods have always been headaches for WiFi technology.

HaLow is a new version of WiFi suitable for industrial IoT applications. Codenamed 802.11ah, it enables WiFi to be applied to more places, such as small-sized, battery-powered wearable devices. It is also suitable for deployment in industrial facilities and applications in between.

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HaLow uses the 900MHz frequency band, which is lower than the current WiFi 2.4GHz and 5GHz bands, and is more suitable for small data loads and low-power devices. The United States uses the unlicensed band of 902MHz to 928MHz, and other countries use similar bands below 1GHz. Although most WiFi devices can only achieve a maximum coverage range of 100m under ideal conditions, HaLow can reach up to 1km with the right antenna, with stronger signals and less susceptible to interference. HaLow is said to have a transmission distance twice that of standard 2.4GHz WiFi and a stronger ability to penetrate walls.

HaLow is not suitable for fast data transmission or web browsing (which has little impact on IoT devices). In addition, 900MHz is an unlicensed frequency band and is susceptible to interference.

Comparison of Industrial IoT Wireless Technology Parameters

Which technology will win?

According to the latest report from market research firm IHS Markit, among low-power wide-area network wireless technologies, LoRa and NB-IoT are far ahead, with the LTE-M version of 4G cellular technology ranking third, followed closely by Sigfox.

IHS Markit predicts that NB-IoT and LoRa are expected to account for 86% of all LPWAN links by 2023. 2023 will be a competition between the two technologies, with more private networks adopting LoRa and NB-IoT mainly used in public networks.

It is worth mentioning that HiSilicon, a subsidiary of Huawei, is currently the leading supplier of NB-IoT chips, 90% of which are deployed in China; the second largest NB-IoT chip supplier is Taiwan's Mediatek, and the third largest supplier is China's Unisoc.

Sigfox, on the other hand, relies mainly on the support of a venture capital company to become a global IoT operator and maintain its proprietary technology. According to a survey report by IHS Markit, Sigfox shipped less than 9,000 modules in 2017, ranking third in market share, far behind LoRa and NB-IoT. IHS Markit predicts that Sigfox's annual sales are expected to grow 10 times by 2021, but it will still rank behind LoRa and NB-IoT.

At the same time, the Bluetooth Alliance and the Wi-Fi Alliance have both used their own tricks. The improved signal coverage of Bluetooth 5.0 is said to cover the entire apartment, which is comparable to the data transmission distance of a home WiFi router. HaLow combines the advantages of previous WiFi technology and Bluetooth.

In the Industrial Internet of Things, customer needs are rich and diverse, and a single technology cannot solve all customer problems. Different wireless technologies compete with each other, but also complement each other, because in the future of the Industrial Internet of Things, no one communication technology can dominate the world.