IoT: History
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Subjects: Computer Science, Artificial Intelligence | Engineering, Environmental
Contributor:
Zbigniew Watral

This entry presents the problems of powering wireless sensor networks operating in the structures of the Internet of Things (IoT). This issue was discussed on the example of a universal end node in IoT technology containing RFID (Radio Frequency Identification) tags. The basic methods of signal transmission in these types of networks are discussed and their impact on the basic requirements such as range, transmission speed, low energy consumption, and the maximum number of devices that can simultaneously operate in the network. The issue of low power consumption of devices used in IoT solutions is one of the main research objects. The analysis of possible communication protocols has shown that there is a possibility of effective optimization in this area. The wide range of power sources available on the market, used in nodes of wireless sensor networks, was compared. The alternative possibilities of powering the network nodes from Energy Harvesting (EH) generators are presented.

  • Internet of Things
  • Energy Harvesting

1. Signal Transmission in IoT Networks

In the case of signal transmission in the IoT network, the most popular solution is the Wi-Fi standard–IEEE 802.11, which is available for most devices found both in everyday use and in industrial solutions. The currently exercised standards are 802.11a, 802.11b, 802.11g, 802.11n, 802.11ac, and more recently, 802.11ax. The band used is not licensed, and the only limitation is EIRP radiation power, which, for example, for the 2.4 GHz band, is 100 mW. In practice, we encounter standards that differ in the range of frequencies used: ISM: 1–6 GHz, 5 GHz, 2.4 GHz, and the WiGig IEEE 802.11ad standard, which operates in the 60 GHz band [1][2][3]. Each of these standards differs in transmission speed and potential range.
The second very popular type of communication in the short-range area (PAN–Personal Area Network) is a family of standards defined in IEEE 802.15.1 [1], known as Bluetooth. This standard distinguishes three classes of devices with different ranges in open space (100 m, 10 m, and 1 m). In practical solutions, the most common standard is Bluetooth 4.0 + LE (Low Energy), which is characterized by very low energy consumption and a range of up to 100 m in the open area.
Another means of communication harnessed for IoT networks is mobile telephony. We distinguish five basic standards: GPRS (General Packet Radio Service), EDGE (Enhanced Data rates for GSM Evolution), HSDPA (High-Speed Downlink Packet Access), LTE (Long Term Evolution), and 5G. These standards provide IP connectivity through the infrastructure of the mobile operator. Apart from the obvious advantages of this type of communication, there is one major disadvantage of the necessity to use the services of a commercial operator.
An interesting and widespread means of communication in IoT networks is LoRaWAN (Long Range WAN) technology. The LoRaWAN technology has been designed to meet four very important requirements for IoT: minimum electricity demand, large network capacity, long-range and low-cost end devices. The main advantages of the LoRaWAN technology when applied to IoT are additionally the possibility of self-building own infrastructure, high security of transmitted data, and high resistance to interference. As for the disadvantages, in Poland, these are mainly low data transfer speeds, and that publicly available networks currently do not cover a large area of the country [4].
Many practical solutions apply two relatively popular wireless communication protocols, Z-Wave and ZigBee. Z-Wave is a wireless protocol with a mesh topology used to connect many devices into one network. The number of intermediary nodes in transmission is four, which allows the creation of a wireless network with a range five times greater than the range of the connection between the control panel and Z-Wave devices. This solution has one major advantage—it enables the construction of a network of sensors in a way that does not interfere with the construction infrastructure of the facilities [5].
As with Z-Wave, the ZigBee network also uses a mesh topology, with all its advantages. The ZigBee specification uses the IEEE 802.15.4 [6][7] standard, which defines the wireless transmission method. A typical structure of a Z-Wave network consists of three basic blocks: a coordinator (ZigBee Coordinator), whose task is to collect data and is a connection point for other devices; a router (ZigBee Router) ensuring data transmission from end devices to the coordinator; the end device (ZigBee End Device), which sends data to the router to which it is connected. Data sent over the network is encrypted with the symmetric AES algorithm with a key length of 128 bits. The main advantages of this technology are the relatively high level of data security and the low cost of devices. As far as the disadvantages are concerned, experts mainly mention low data transfer speed and low network capacity.

2. RFID—Universal End Node in IoT Networks

RFID tags are one example of a universal end node in IoT technology. RFID is a term for a system based on transponders used for radio identification of objects. The history of RFID technology dates back to World War II. The IFF (Identification, Friend or Foe) system, invented in Great Britain for identifying aircraft, is considered the predecessor of RFID. An early version of RFID was the predecessor of the EAS (Electronic Article Surveillance) system, introduced in the 1960s. Magnetized strips of metal attached to the products were detected by a detector at the exit of the store, similar to today’s anti-theft systems. The first RFID device, or radio transmitter with memory, was patented in 1973, in the United States, by Mario Cardullo. It was a passive tag powered by an electromagnetic signal with 16-bit memory. In 1973, the Freyman brothers demonstrated a system operating at 915 MHz, which is still used today by most UHF chips. The first fully functional RF identification system was TIRIS, introduced by Texas Instruments in the 1970s and is still operational today. Miniaturization, enhanced tag memory, and the addition of various new functionalities (e.g., measurement of temperature, humidity, and GPS) have enabled newer and newer applications [8][9].
RFID tags consist of three basic parts, an electronic system responsible for data storage and processing, as well as creating a radio signal; an antenna for receiving and sending signals; a housing, which can be in the shape of a plastic card, a thin adhesive foil, or a capsule. There are several types of RFID tags (RFID chips): active, passive, and semi-passive [9][10]. Figure 1 shows examples of passive and active RFID tags.
Energies 14 02417 g003 550
Figure 1. (a) RFID tags (TAGS), (b) passive, and (c) active [11].
The main feature of active RFID circuits is the presence of a power source that powers the RFID chip with an integrated antenna. Thanks to the antenna being powered by an internal battery, the signal sent to the reader is stronger than in other types of systems, which results in greater efficiency and accuracy of data transmission, better resistance to interference (e.g., electromagnetic or environmental), and an increased reading range up to 100 m. The disadvantages of this type of solution are larger sizes, price, and shorter operation time.

This entry is adapted from the peer-reviewed paper 10.3390/en14092417

References

  1. Sieczkowski, K. Jednoukładowe komputery SBC w zastosowaniach IoT. In Wybrane Aspekty Internetu Rzeczy w Zastosowaniach Metrologicznych; Wojskowa Akademia Techniczna: Warsaw, Poland, 2020; pp. 59–92.
  2. IEEE802.11ad. Available online: (accessed on 31 March 2021).
  3. IEEE 802.15.1. Available online: (accessed on 31 March 2021).
  4. Wiszniewski, Ł. Wykorzystanie technologii LoRaWAN w bezprzewodowych systemach IoT. In Wybrane Aspekty Internetu Rzeczy w Zastosowaniach Metrologicznych; Wojskowa Akademia Techniczna: Warsaw, Poland, 2020; pp. 29–58.
  5. Z-Wave Alliance. Available online: (accessed on 31 March 2021).
  6. Wiszniewski, Ł. Suitability of LoRaWAN Technology for the Development of Maritime Applications. Task Q. 2018, 22, 4.
  7. Park, C.; Chou, P.H. Ambimax: Autonomous energy harvesting platform for multi-supply wireless sensor nodes. In Proceedings of the 3rd Annual Communications Society on Sensor and Ad Hoc Communications and Networks, Reston, VA, USA, 25–28 September 2006; Volume 1, pp. 168–177.
  8. Ashton, K. That ‘internet of things’ thing. RFID J. 2009, 22, 97–114.
  9. Michalski, A.; Watral, Z. Internet Rzeczy—Narzędzie współczesnej metrologii. In Wybrane Aspekty Internetu Rzeczy w Zastosowaniach Metrologicznych; Wojskowa Akademia Techniczna: Warsaw, Poland, 2020; pp. 9–28.
  10. Tagi RFID—Zbliżeniowe Chipy Radiowe, PWSK. 2020. Available online: (accessed on 12 November 2020).
  11. RFID Technologies. Available online: (accessed on 31 March 2021).
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