Most IoT systems assume there will be some form of connectivity. But what happens when there isn’t any Bluetooth, WiFi or cellular connectivity? R2D2, the adorable robot from Star Wars, may have the answer with the bird-like noises he used to communicate.
How can sensors share data when connectivity isn’t available? How can IoT devices be designed to last longer without being recharged? How can legacy equipment be retrofitted affordable to communicate with other devices?
Most IoT devices communicate through either a Bluetooth, WiFi, LoRaWAN, SIGfox or cellular connection. The mode chosen is determined by the size of the payload to be transmitted, distance to be traversed, and the power available to the transmitting device. Walls, other electronic equipment and conflicting radio signals also influences the selection of the protocol to be used. What’s needed is that can work in ‘noisy’ environments and work with very little power.
Bluetooth operates at 2.4 GHz with a range of under 33 feet while WiFi works at 2.4 GHz and has a range of around 60 feet depending on obstructions. Audio signals work at much lower frequencies around 20 to 20,000 Hz. Audio signals can traverse over 500 feet using simple speakers and microphones that require very little power. The amount of data that can be transmitted with audio signals, however, is much less than with Bluetooth and WiFi.
Background
A chirp is a signal in which the frequency increases (up-chirp) or decreases (down-chirp) with time. Data is encoded through modulation/demodulation. The data is encoded into a series of pitches and tones on the sending device, and then decoded on the receiving device. Chirps maybe audible, or silent (ultrasound) to minimize noise pollution.
Chirping is peer-to-peer that doesn’t require connections to ‘the cloud’. It’s ideal for broadcasting data in a ‘one to many’ network configuration to devices as sound travels in all directions. Devices don’t even need a prior ‘handshake process’ before they can exchange data.
The benefits of chirping
IoT sensors have to conserve power so they can work for extended periods without recharging. They have to communicate with other sensors and devices that are installed later without requiring reconfiguration. Chirping handles these constraints, and also has other benefits:
- The data to be transmitted is encoded by generating a new signal whose properties are determined by the data to be transmitted, and does not require an existing audio signal.
- The information to be transmitted is encoded and decoded in real-time, without any external resources that might require a network connection.
- It’s ideal for small, dynamic payloads such as a network of sensors and gateways. It isn’t designed for mission critical IoT applications with large data payloads such as industrial gear.
Consumer applications
Consider a home monitor that’s designed to connect through a home WiFi network. What happens when the customer is trying to install it is having problems as it can’t connect to the WiFi network? It’s difficult for a remote technician to troubleshoot the device as they can’t check the status of the device. But with ‘chirping’ capability built into the home monitor it’s possible to have the customer simply hold their phone near the device and the support technician could query the status of the home monitor through chirp sound signals.
Shuttl is a popular Indian bus service. Passengers can easily show that they have a valid ticket by sending a chirp signal from their phone to the conductor, instead of having manually present a ticket. This improves the passenger experience and reduces the workload for bus conductors. It even works when there is no cellular or WiFi connectivity on the bus. "Detecting authorized boarding is extremely important for us from a safety standpoint. Unlike a regular bus, where a conductor checks whether someone has bought a ticket, we were looking to completely automate it making manual intervention obsolete," said cofounder Deepanshu Malviya.
Using Chirp in IoT devices
Chirp is a data-over-sound communications firm whose technology is embedded in IoT devices and sensors. It allows data to be encoded on a sending device before being transmitted, over the air, to a receiving device, or group of devices where it is decoded. IoT devices with a speaker can emit ‘Chirps’ and others with a microphone and a small amount of processing power can receive and decode them.
Chirp is integrated through a software development kit (SDK). These SDKs work on different technology platforms including iOS, Mac OS, Android, Windows UWP, JS, Web Browsers, Python, Arduino, Raspberry Pi and Linux. This allows sensors to connect with a range of devices. Chirps can be generated on-device with dynamic data, or recorded as an audio file for later playback – like a sonic barcode.
Chirp enables IoT applications without connectivity as the Shuttl bus service demonstrates. As R2-D2 might say, “beep-boop-bleep-boop.” In other words, go ahead and add chirping capability to your IoT devices. It works.