“The devil is in the details” best describes IoT. Computing will vanish, says Walt Mossberg. And the public and data scientists gush with optimism at the thought of 20 billion to 50 billion connected IoT devices emitting an endless stream of data.
Getting the billions of devices connected will be no small task. The thought of all the IoT applications of all that data is nothing less than seductive. Cities will self-regulate motor vehicle and public transportation saving commuters hours of travel time. Sensors will alert us (and doctors) when mom is not keeping to her pharmaceutical regimen.
And all these IoT devices will give context to people’s daily lives. Lights dimming or illuminating to match our mood or actions, refrigerators will warn that we have either eaten too much or not exercised enough before opening the door. Our designer glasses with integrated Microsoft Hololens technology will project the most salient context of the moment at that location.
IoT, ambient intelligence, ubiquitous networks, cyber-physical networks, all names for the same thing assume devices made of microcontrollers, sensors, and communications will be placed or built into everything everywhere transmitting data between devices and the cloud. But engineering an unconstrained complex system that matches these expectations for IoT is not engineering but magic.
Communications is the constraint in IoT design. One size does not fit all applications. The characteristics of a robust communications layer, frequency band, maximum signal rate, nominal range, cryptography, network type, and coexistence mechanisms point that it is not magic but a lot of systems design and engineering to build application-specific communications to interconnect these devices.
A look at eight existing and developing IoT communications methods should not dissuade optimism, but should inspire an appreciation for the engineering task undertaken to deliver on the promises of IoT data from everything everywhere. They understand the devil in the details of matching throughput, range and power efficiency for all the IoT applications imagined and yet to be imagined.
ZigBee (IEEE 802.15.4): The granddaddy of IoT communications, was conceived of in the 1990s and specified in 2005. A self-organizing ad-hoc digital wireless mesh radio network design, Zigbee is designed low cost, lower power applications. The Zigbee specification is licensed for commercial use through a paid membership in the Zigbee Alliance.
- Data Rate: 250kbps
- Range: 10-100m
- Frequency: 2.4GHz
Bluetooth LE: The evolution of today’s Bluetooth LE (BLE), began shortly after Zigbee. BLE is ubiquitous, found in fitness trackers, headsets, mobile devices, beacons, healthcare devices, etc. is designed for low power, low cost and small size capable of operating on battery power for months or years. A commercial license to the BLE specification is available through paid membership in the Bluetooth Special Interest Group.
- Data Rates: 125 2 Kbps – 2 Mbps – 2 Mbps
- Range: 50-150m (Smart/BLE)
- Frequency: 2.4GHz
Z-Wave: Z-Wave is a proprietary wireless mesh network (limited to four hops) designed for residential automation and control. The radio chips, fabricated by Sigma Designs, are designed to be powered creating the mesh network and with a sleep mode for battery applications that do not forward packets. About 1,700 products applied to controlling HVAC, security systems, home cinema and light switches. The specification is maintained by the Z-Wave Alliance, an association of product brands using Sigma’s chips.
- Data Rates: 9.6/40/100Kbps
- Range: 30 – 40m
- Frequency: 900MHz
Near Field Communication (NFC): NFC evolved from radio-frequency identification (RFID) first specified in a patent in 1983. In IoT as an extended user interface between a smart device for peer or passive device to securely read or write. Most applications in IoT are to simplify devices for secure connection to other networks, control and to collect data from sensors not connected to another IoT network. The NFC specification can be licensed from the NFC Forum through purchase or membership.
- Data Rates: 100 – 420Kbps
- Range: 10cm
- Frequency: 13.56MHz
HomePlug: HomePlug is a family of standards for data communications over existing electrical wiring infrastructure with a modulated non-interfering data signal. Using existing infrastructure and by definition powered, HomePlug provides connections between any powered IoT devices. HomePlug Green PHY is the most often cited IoT application in smart grids to turn equipment and appliances on or off to match peak power generation loads and time of day pricing, reading power meters. HomePlug is a public domain IEEE standard.
- Data Rates: 3.8 – 14 Mbps
- Range: NA
- Frequency: NA
Wi-Fi: One of the oldest communications methods, Wi-Fi (802.11) dates to 1997. The cost of Wi-Fi components has been driven down by volume. It fits in IoT communications in areas where devices need to be simultaneously paired and/or send and receive over a routable topology. Throughput is much greater than BLE for example but power consumption is four times greater. Wi-Fi is finding its way into home IoT applications for interconnecting powered devices and as gateways to controllers or to the cloud.
- Data Rate: 600 Mbps
- Range: Approximately 50m
- Frequencies: 2.4GHz and 5GHz bands
6LowPAN and Thread: Thread uses 6LoWPAN (short for IPv6 over Low power Wireless Personal Area Networks) to route packets over a low-power, low-speed IPv6 network like any traditional IP mesh network. 6LoWPAN, the link, and physical layer is a draft IETF standard. Thread is an effort of over 50 companies, including Google and Samsung, to standardize the network and transport layers. Thread and 6LoWPAN seem to be an effort to apply IPv6’s expanded address space compared to IPv4 to stitch very large IoT networks together with cloud applications.
- Data Rate: NA
- Range: NA
- Frequency: 2.5GHz
Sigfox: Sigfox is a proprietary technology that enables communication that uses a low-power signal that passes freely through solid objects. Devices can be very low power, but deployment will require a carrier to deploy base stations to carry and route the traffic.
- Data Rates: 10-1000bps
- Range: 30-50km
- Frequency: 900MHz
These eight examples are not all the IoT communications alternatives. A few more could easily have been added. One size network does not fit all IoT applications. More networking technologies will come on the scene as engineers try to match specifics of cost and performance. The constraints of bandwidth, range and power efficiency will remain tightly tied to the application.
And none of the alternatives address real-time control that will require 5G networks, which carriers are just beginning to prototype in test beds. Though there are competing communications methods listed, most are different enough that a specific IoT application will narrow most choices to one or two choices.