What are wireless IoT sensors

Internet of Things (IoT)

There are already various studies and white papers on the topic of IoT cloud services and edge technologies that deal with the use of the technologies and provide assistance for decision-makers. The leading technology providers of IoT cloud services, including Amazon, Google, IBM, Microsoft and SAP, unfortunately leave it up to the user how his IoT devices should reach these cloud services in the first place. Only the large telecommunications providers often bundle their networks and cloud services, which they obtain from other technology providers, into complete IoT offers. Of course, these telcos try to push their own wireless technologies in licensed frequency ranges, as these licenses were often a costly future investment.

In addition, there are also some technologies in the unlicensed frequency bands. In Europe, the 868 MHz band is of particular interest here. After wireless IoT connectivity was identified as one of the most important IoT trends in 2018, customer inquiries about the comparison and the right choice of wireless technologies have increased. Reason enough to give some guidance.

IoT wireless technology: "speed" is not the most important thing!

The table in the Analyst View “The IoT trends in 2018” first gives a good overview. Now, however, the technologies should be viewed directly in relation to one another. There are three groups:

1. Cellular technology

These are exclusively licensed frequency bands that are known from smartphones and are operated exclusively by Telcos. The various technologies have developed on 900, 1800 and 2100 MHz in recent years. The focus was always primarily on the bandwidth of the smartphone, but not on the energy consumption of the IoT device or good penetration into buildings. Nevertheless, these technologies are still relevant for many IoT cases today.

  • GPRS (General Packet Radio Service) comes from the 2G era of mobile networks. With transmission rates of up to 55 Kbit / s, it is still a good alternative, especially in rural areas, for example to connect a heating system or a pumping station of the municipal water supply to the network. As with all mobile radio technologies, the disadvantages are, of course, the costs of a SIM card, which are particularly high compared to the bandwidth.

  • EDGE (Enhanced Data Rates for GSM Evolution) started on 2G and is also available on many 3G networks. It reaches bandwidths of up to 290 Kbit / s.

  • HSPA (High Speed ​​Packet Access) even reaches up to 7 Mbit / s on 3G in some networks. However, some telcos have immediately concentrated on HSPA +. With over a billion devices connected via HSPA worldwide, it is one of the mainstream technologies on cellular networks.

  • HSPA +, the further development of HSPA, a 3G network can theoretically reach up to 28 Mbit / s. If you really need this bandwidth for an IoT application, we recommend that you look specifically at the telcos' expansion plans. Today HSPA + is also used on LTE-4G networks and further development in HSPA + Advanced is already being planned.

  • LTE 4G (Long Term Evolution, 4th generation), today delivers realistic bandwidths of 30-50 Mbit / s. With the 5G plans and HSPA + Advanced, for example, bandwidths of up to 3 Gbit / s could be possible.

  • LTE 5GIn addition to the higher bandwidths, significantly lower latencies or completely new communication topologies are possible. Here, for example, peer-to-peer communication should be mentioned. With 5G, two autonomous vehicles could exchange data directly with each other, even if no cell phone mast is currently available!

2. Low Power Wide Area (LPWA) technology

This is the great innovation, especially for IoT devices that have to live with a battery supply. LPWA is the collective term for a wide variety of technologies. These initially share licensed frequencies with the representatives NB-IoT or LTE-M and the non-licensed frequency bands with the well-known examples Sigfox or LoRaWAN. All LPWA technologies are optimized for IoT use cases. This means that IoT devices can couple into these networks with significantly less energy.

  • Sigfox In the 868 MHz range, it focuses on use cases that require a very small bandwidth but good coverage of the country and good penetration depth into buildings. The costs are very low and the performance of approx. 600 bits per second is sufficient to bring simple sensor status updates into the network. A firmware update over the air is, however, unrealistic even for small controllers. Sigfox is unfortunately a proprietary technology.

  • LoRaWAN on the other hand is a much more open standard that is driven by the LoRa Alliance (lora-alliance.org). Since LoRaWAN is in the non-licensed area of ​​863 - 870 MHz in Europe, it is particularly interesting for smart city solutions or larger industrial plants that do not want to get involved in an OPEX model with a Telco, but rather the infrastructure want to roll out yourself. Telcos are also rolling out LoRa in some countries. With LoRa you can achieve bandwidths of up to 50 Kbits / s. If you combine this with broadcast protocols, you can wirelessly refuel large quantities of devices with new firmware.

  • Narrowband IoT (NB-IoT) and LTE-M are very similar and both are in the licensed frequency range. These are reduced LTE specifications that are designed to save energy on the IoT device and prioritize accessibility, especially building intrusion, higher than bandwidth and latency. NB-IoT does this on additional frequencies right next to the cellular frequencies, while LTE-M runs the stripped-down protocol directly on the same frequencies. As a result, LTE-M can only be rolled out with software updates in many LTE infrastructures, while NB-IoT requires corresponding LTE hardware for Telco. In Germany, NB IoT is Deutsche Telekom's focus offer.

3. Building networks

In buildings, in addition to wired networks such as Ethernet, KNX, etc., mainly WiFi, Bluetooth and Zigbee are used. There are also a lot of other wireless “field technologies” that are used either in the smart home environment or in the industrial environment.

  • Wifi is known on the 2.4 GHz or 5 GHz frequency and realistically delivers bandwidths of up to 100 Mbit / s and more in the future. Especially small and inexpensive controllers like the ESP8266 from Espressif have made WLAN attractive for IoT devices. The ranges and building penetration are intentionally modest in order to avoid conflicts and overreaches.

  • Bluetooth also works very close to WiFi at 2.45 MHz and has developed closer and closer to WiFi in its possible bandwidths. In the professional field, Bluetooth is much more interesting than WiFi, especially for new types of mesh topologies.

  • Zigbee works in Europe on the 868 MHz band and focuses on applications with less bandwidth than Wifi and Bluetooth. That is why it is very popular for networking smart buildings within the building. Even controllers with very little power can achieve good response times and ranges. Due to the lower frequency, the building penetration is better than with WiFi and Bluetooth.

This small overview of the most important IoT wireless technologies can help with the question of which wireless technology you should embed your sensors and actuators or more complex IoT devices into. Power supply and range play the most important role. But the decision as to whether to use a telco service on a licensed frequency band such as Deutsche Telekom's NB-IoT service or an unlicensed frequency band must also be made. For a municipality that wants to network hundreds of street lights, its own LoRa network over ten years may be cheaper than an NB-IoT subscription with Telco.

The decision whether to move inside or outside of buildings is also very important. While a street lamp needs a LoRa connection, Zigbee or Bluetooth is more practical for an office lamp. Innovative manufacturers of controllers and wireless components such as Telit already offer “combo” modules. For example, Bluetooth and LoRa radio protocols are housed on 19x15mm. Only the software decides which one is used or whether both technologies are "on" at the same time. This enables manufacturers to cover more volumes with fewer product variants. The Telit radio controller shown has a current consumption of only 2µA in standby. For example, you can already build smoke detectors that run safely for 10 years on a battery.