Wireless Networks Introduction
The purpose of this chapter is to give an overview of some of the many wireless technologies. What is global? When is a license required? How fast is a given solution?
ISM Frequency Bands
Some frequency bands were originally declared to be outside the - typically licensed - telecommunications bands. They were meant for ISM - Industrial/Science/Medical. This could be ovens, garage door-openers, motion detectors and much more. Today they are a very important part of the IoT.
- 433 MHz ISM 10 mW - worldwide. Duty cycle must be very small and FCC rules out repeated transmissions. Limited remote control OK.
- 868-869 MHz ISM - Region 1 (CEPT - Mainly Europe)
- 902-928 MHz ISM - Region 2 (FCC - Mainly North America)
- 2.4 GHz ISM - Worldwide. The only truly free worldwide global band. Only 100mW in region 1 (mainly Europe).
- 5.x GHz ISM - almost worldwide (not China). Indoor only in some sub-bands and detection of weather radar in region 2 in others.
Due to the above frequency allocations, some technologies that are basically the same all over the world, use e.g. 868-869 MHz in US and 902-928 MHz in Europe.
Bandwidth
As you move towards the higher frequencies, the transmission bandwidth goes up. The downside is that the range goes down.
The LPWAN technologies generally offer very limited bandwidth, to preserve energy as well as sharing the spectrum in large areas with many other users. Cellular on the other hand offers high bandwidth. With Cellular the range is not long - especially in cities. This however, can be a benefit as the same frequency band can be "reused" - not so far away. This means that there is a need for many "base-stations" for cellular, which is easy to see from the many antennas in the cities. Especially 5G offers high bandwidth and low latency. Contrary to older cellular technologies 5G also offers slower rates that allows the mobile units to use low bandwidth and little power.
Note that LAN = Local Area Network, PAN = Personal Area Network, LPWAN is Low-Power Wide Area Network. Cellular is the classic Mobile radio.
Wireless Technologies - comparison
In the following table some numbers are given. They depend on a lot of things, so don't take them too serious.
| Infrastructure | Type | Frequency | Bandwidth | Latency | Remarks |
|---|---|---|---|---|---|
| LAN (/PAN) | BLE | 2.4 GHz | ~10 Mbps | Low | Freq Hopping -> Robust for interference. |
| LAN | WiFi | 2.4/5 GHz | ~300 Mbps | Low | Wideband n*20 MHz - n in [1,2,4,8]. See also WiFi - the letters |
| LAN | WiFi Halow | 900 MHz | ~50 Mbps | Low | Long range & low bandwidth due to low frequency |
| LAN (/PAN) | Zigbee | 868/915 MHz + 2.4 GHz | ~100 kbps | Low | Mesh |
| LAN | Z-wave | 868/908 MHz | ~100 kbps | Low | Licensed Technology |
| LAN | Thread | 2.4 GHz | Low | Mesh. Directly IPv6 routable. | |
| LAN | M-bus | 169/433/868 MHz | Low | Standard for remote reading of utility meters (gas, water, electricity) | |
| LPWAN | LoRa | 433/868/915 MHz | ~10 kbps | High | Semtech owns the technology, but you can build your own network |
| LPWAN | Sigfox | 869/9xx MHz | ~100 bps | High | Licensed Operators - subscription worldwide Uplink 140 messages/day Downlink 4 messages/day |
| Cellular | NB-IoT | Many | ~ 100 kbps | Low | Licensed Operators. NB = Narrowband. Competes with LPWAN |
| Cellular | LTE-M | Many | ~1 Mbps | Medium | Licensed Operators. Classic Mobile/Cellular |
| Cellular | 5G | Many | ~1 Mbps | Low | Licensed Operators. Future Mobile/Cellular |
When you are using a licensed band with a 3'rd party operator there is obviously a price in the form of a subscription and/or cost per message. In many cases the larger issue is that each country his its own operator. This means a lot of administration if you want to create a global product. Sigfox is an exception here, because they offer a global subscription.
eSIM cis the modern way of getting global subscription in e.g. NB-IoT or 5G.
The LAN-based solutions - like Wi-Fi, BLE etc. - are typically free to use. When used in a larger IoT-solution they do however, require gateways. If the LAN technology supports IP it makes it easier to integrate.
Wired Networks
For now this website has more content on wireless networks than on wired networks. This is mainly because a large part of Embedded Software for the IoT goes very deep into Ethernet and the TCP/IP stack. However, pages like Ethernet Transmission Delay and Python and Scapy relate to Ethernet. Scapy may also be used with WiFi, and several of the network-relevant pages are agnostic to the physical layer.