What is Passive IoT Technology?
Passive IoT technology, as the name implies, is the IoT without a source.
The source is the power and energy source. We often talk about the passive optical network (PON), and passive wavelength division (WDM), all involving passive.
Passive is not connected to an external power supply, without batteries. Passive IoT technology is not the network passive, but the end node passive.
In other words, the network does not change, and the end-node devices are connected to the network, without power lines and built-in batteries.
In fact, the so-called passive, not the end node does not use electricity, but a different way to get electricity (energy).
The passive IoT technology that is now hotly debated is mainly the IoT based on wireless magnetic energy capture technology.
In other words, passive IoT technology refers to IoT technology where the IoT terminal captures and collects energy by collecting radio waves emitted from the network side.
What are the technical Challenges of Passive IoT?
As we all know, RFID is a very mature technology. the most critical point for RFID to work properly is that the distance between the tag and the reader is very close.
The farther the distance, the lower the density of electromagnetic energy, and the more difficult it is to obtain energy.
RFID belongs to the inductive coupling, the shape of the antenna is a coil, the transmission of electromagnetic energy is completed in the induction field area, and the distance is very short.
In fact, RFID is a passive IoT technology.
Now, on the basis of RFID, passive IoT technology hopes to further extend the passive interconnection based on Wi-Fi, Bluetooth, 3G, 4G, and even 5G communication technologies.
Wi-Fi and Bluetooth work at a much greater distance than RFID, and 3G/4G/5G even further. This is not an induction field, but a radiation field.
Radiation field using antenna technology, mainly dipole antenna or microstrip antenna. Want to be in the radiation field, with the help of these antennas to complete the transmission of electromagnetic energy is extremely difficult.
What are the typical characteristics of passive IoT?
Energy oscillation passive IoT technology node energy is no longer a single static trend from high to low because the energy comes from the environment, it will present a dynamic state of sometimes high and sometimes low.
Node imbalance there is randomness and instability in energy acquisition in passive IoT technology nodes, and the energy distribution in the whole network may not be balanced, which will also lead to differences in each node.
Energy Constrained
Passive IoT technology acquires energy in different ways and the collected environmental energy is very weak, typically at the nano-watt (nW) to micro-watt (μW) level, and is affected by the node’s power storage capacity.
Connectivity vulnerability
The network connectivity of passive IoT technology is directly affected by the energy of each node. When the energy of some nodes falls below a certain level, these nodes become isolated, resulting in a disconnected network. Due to the oscillatory nature of energy, the network connectivity is fragile, intermittent, and difficult to maintain all the time.
The biggest advantage of Passive IoT is that it does not require batteries at all.
While NB-IoT changes batteries every 10 years (ideally), passive IoT technology does not need them for life. This not only reduces the labor cost of battery replacement but also reduces the cost of battery components.
For the current general-purpose UHF RFID tags, the price can do 20-30 cents. NB-IoT module, the price is about a dozen, and the difference are tens of times.
Second, no batteries, which is conducive to environmental protection. Although a single battery is very small, the scale of the number of hundreds of billions, the environmental impact should not be underestimated.
Third, there is no battery, and the size of the terminal can be further reduced. For example, RFID is a small patch, that will greatly benefit the terminal design.
In short, passive IoT technology is a very good development idea. However, to take this road really through, we may still need a long time.
The Internet of Everything is the ultimate ideal of the IoT industry. IoT Analytics statistics show that there are currently 12.3 billion active IoT terminals worldwide, and it is expected that the number of IoT terminals will exceed 27 billion in 2025.
To achieve more terminal interconnection, it is not enough to rely on NB-IoT, LoRa, and other LPWAN technologies.
In the face of a complex communication environment, changing terminal form, and networking communication costs, how to further improve terminal coverage becomes a key point affecting the rapid development of the IoT industry.
With the surge in the number of connections, the power consumption of IoT terminals, and signal interference resistance issues become an important direction for technological breakthroughs, and the concept of passive IoT derived from RFID technology is hot now.
Passive IoT technology refers to the IoT terminal network nodes without an external energy source, but the use of access to environmental energy for energy supply IoT technology, this type of technology is regarded as the key to achieving the vision of 100 billion interconnections.
Research on passive IoT relies on these three types of underlying technologies.
The first is environmental energy harvesting.
Passive IoT technology tag-side devices do not rely on batteries or power lines for power, but rather by capturing energy from the environment and converting it into electrical energy for use. The sources of energy can include light, heat, kinetic energy, RF, etc.
Solar energy is currently the highest conversion efficiency program, electromagnetic waves in a single frequency band under the energy conversion efficiency can reach 50%, in the multi-band complex scenario only 1 ~ 2%, temperature difference thermal energy capture on the use of environmental requirements, the conversion efficiency is less than 10%.
The second is low-power computing.
Passive IoT terminal operation available energy is limited, which determines the power consumption requirements of the driver circuit or chip used for computing can not be too high, the current mature application of low-power computing MCU chip general power consumption in the μW level.
Finally, it relies on low-power communication backscattering to achieve data communication.
Passive IoT terminals are often based on low-power proximity and low-rate communication technology, relying more on backscattering to reflect the received RF signal to transmit data.
Currently, in a critical period of passive technology innovation, the IoT Institute of China Mobile Research Institute believes that the evolution path of passive IoT technology can be divided into three stages: single-point passive 1.0, networked passive 2.0, and cellular passive 3.0.
Traditional RFID applications take point-to-point proximity read-write integrated architecture, there is a strong self-interference and mutual interference problems, mainly in the field of fast-moving goods, and storage.
New networked passive 2.0 technology to take the send and receive separated system, support network deployment, solve the problem of interference enhance the acceptance distance, to a certain extent expand the RFID application scenario.
The 3.0 stage, can further take advantage of the cellular network, the use of base stations to expand the communication distance, for a wider range, and more complex scenarios of networking application needs, such as the full lifecycle management of assets to provide the possibility.
Such as 2021 Huawei proposed a 5.5G passive IoT solution concept, through the cellular network to RFID support scenarios transmission distance from 10 meters level to expand the level of 100 meters, cutting off the dedicated reader, so that the terminal to the cellular network node for self-back transmission.
With zero power consumption, small size, and other advantages, passive IoT can be in industrial sensors, intelligent transportation, smart logistics, smart storage, smart agriculture, smart cities, energy fields, and other industrial IoT fields as well as smart wear, smart home, medical care, and other consumer IoT fields have a wide range of application prospects.
Typical scenarios such as industrial sensor field to achieve industrial automation, environmental sensing, security monitoring, and other scenarios applications, need to arrange a large number of sensor nodes in complex and dangerous environments, low cost, low power consumption, tiny size is the basic requirement for communication devices in this field, passive IoT can extend the life cycle of sensor nodes and reduce maintenance costs through energy harvesting and backscattering and other technologies.
Another example is the logistics and warehousing, super retail industry to intelligently manage a large number of non-expensive items, giving the items the ability to network and communicate.
The use of passive IoT technologies in frequently operating scenarios can save a lot of hardware costs, power supply costs, and human management costs, significantly improving the efficiency of logistics and warehousing management.
Major passive IoT technologies: RFID alone accounts for tens of billions, and associated technologies are still emerging.
In terms of technical maturity, passive IoT technologies can be divided into two categories: mature applications represented by RFID and NFC, and theoretical research lines powered by the collection of Wi-Fi, Bluetooth, 5G, LoRa, etc. for energy.
6 types of passive IoT technology analysis, hundreds of billions of connections who is the best answer?
RFID-based passive IoT
RFID technology is the most familiar and widely used passive IoT technology, and its principle is very simple.
When the RFID tag is close to the reader, it receives the RF signal from the reader, generating an induction current and gaining energy.
Through the collected energy, the tag sends information through the built-in antenna to realize communication with the reader.
As a passive IoT underlying core technology, RFID technology is used in warehouse logistics, smart retail, smart manufacturing, garment management, smart medical, air transportation, and other industries that require identification and management of thousands of hundreds of industries, these huge numbers of physical terminals can become a hundred billion IoT coverage nodes.
According to AIoT Star Chart Institute statistical analysis, in 2021, only UHF RFID global shipments reached about 23 billion, plus low-frequency and high-frequency, the total global shipments of passive RFID that year is close to 30 billion.
With the cost advantage, RFID is a hundred billion passive IoT technology today’s optimal solution, but there is also a small amount of transmission data storage, compared to Bluetooth, NFC, 5G technology, and cell phone interaction is poor limitations.
Different scenarios need to combine other passive IoT technologies to meet the application space.
NFC-based passive IoT
NFC (Near Field Communication technology) is a short-range high-frequency wireless communication technology, which is a variant of high-frequency RFID technology and can realize contactless data exchange within 10cm of the device.
Unlike RFID, NFC is a highly integrated single chip, relatively expensive, mainly used for high-security information transmission scenarios, and commonly used in traffic, access control, cell phone payment, and other functions.
Bluetooth-based passive IoT
BLE low-power Bluetooth we are no stranger to, without power supply can also complete the sensing, storage and communication of passive Bluetooth low-power sensor tag have also been successfully marketed, the tag by collecting the surrounding radio frequency energy to power it, and with the help of these energies to send the tag unique identification code data and sensor readings.
Wi-Fi-based Passive IoT
Researchers at the University of Washington developed a Passive Wi-Fi technology in 2016, Passive Wi-Fi passive nodes transmitting 1Mbps and 11Mbps consume only 14.5μW and 59.2μW respectively, enabling a 30m return distance and even a certain ability to penetrate walls.
The design principle of this solution is similar to the RFID chip, using the backward reflection communication technology of RF signal, when the nearby Wi-Fi router transmits a relatively high-power RF signal, the passive IoT node absorbs the RF signal and modulates the antenna reflection coefficient to transmit the sensor information.
Passive IoT based on 5G/6G cellular
According to Wang Tao, President of Huawei ICT, a large number of current IoT applications are based on passive connections, and improving the recognition rate, coverage, and positioning accuracy of passive IoT through networking technology is the future direction of evolutionary innovation for 5G/6G networks.
The cellular signal is one of the most widespread wireless RF signals in the environment. There are two core difficulties in realizing passive, the first is how to obtain energy, and the other lies in how to realize long-distance back transmission, especially the latter is more difficult to maintain efficient communication.
Passive terminal through a variety of ways to obtain energy is very weak, the return path is too long, and the signal will quickly decay.
The most advanced technology at the laboratory stage can already achieve the collection of 5G RF energy in specific frequency bands within a range of 180 meters, collecting about 6 μW of power.
LoRa and NB-IoT-based Passive IoT
LoRa, NB-IoT, and other LPWAN terminals themselves take low power consumption as the core technology, and passive is the upgrade direction of power consumption research.
In 2021 Murata Japan and Nowi collaborated to launch a reference platform for battery-free LoRa solutions, using Murata’s LoRa modules coupled with Nowi’s energy harvesting power management (PMIC) chips to supply energy.
Most of these passive solutions are customized cooperation between module manufacturers and energy chip companies to launch modules compatible with LoRa/NB-IoT modules, using linear spread spectrum technology to enhance the backhaul capability, and with the help of a reflection modulation system to achieve a permanent energy supply.
All the above new passive technologies, many in the laboratory research stage, but also such as the Bluetooth program have begun to be put into commercial use.
Once the large-scale commercial application, passive IoT technology can not only optimize resource allocation and improve efficiency, but even have a disruptive impact on the organization and industrial form of the industrial environment.
Passive IoT Technology Outlook
In the evolution of passive IoT technology, zero-power communication and passive are key and long-term goals, although the current commercial solutions beyond RFID are still immature due to the development of communication technology, commercial cost, and customization of application scenarios.
However, a number of innovative companies based on PV, Bluetooth, Wi-Fi, LoRa, NB-IoT, and 5G for research have emerged at home and abroad, gradually establishing an ecology to carry low-power passive connectivity networks in more applications.
The following are a few visions for the development of passive IoT technologies.
Richer passive tag functions
The current passive tags have a single function, and there is an urgent need to develop passive tags that integrate identification, sensing, positioning, communication, and other multi-functional functions so that they can be widely used in manufacturing, storage, logistics, medical and health care industries in the future.
More mature open source and cost-saving technologies
Backscatter technology is currently in the early stages of commercialization, and its communication distance, throughput, and security are not yet perfect, and the scenarios in which it can be applied are relatively limited.
In the future, to realize more mature and large-scale commercial applications of passive IoT, three directions are needed to enhance energy utilization, improve system communication efficiency, and upgrade safety and security mechanisms.
Unified common protocol standard
Passive IoT technology, as a new communication technology, is expected to be the next generation communication network technology standard with 6G deep integration, becoming plus a more intelligent and efficient communication standard.
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