Almost a year ago we talked about IoT, Internet of Things, which is the technology that allows us to transmit data from and commands to our smart water meters in real-time. IoT is a network of devices connected via the Internet, with a hub that can analyze the aggregated data. The IoT endpoints can be a person, an animal, a home, a farm, a building, or a whole city. But in all cases these things “talk” to each other without any human intervention via an IoT protocol.
There are different protocols for the different layers in an IoT architecture and in this post we take a look at just a few of them.
The Correct Protocol for the Right Device
The first IoT devices were fairly simple applications. For these early devices, such as the “smart” Coca Cola vending machine that transmitted the number of bottles left and their temperature, a simple HTTP connection was all that was necessary. Wi-Fi and Bluetooth are still two of the most popular protocols for simple IoT networks.
For today’s smart buildings and smart cities, however, you need a more robust protocol. These more advanced IoT systems have a three-level architecture comprised of devices, gateways and the data system. The data moves across these levels to various applications to create the “smart” effect.
Different protocols are used to meet the different needs of each connection. For example, a device-to-gateway connection has different protocol requirements than the connection between a gateway and a data system. The choice of protocol must consider a whole array of requirements, from gateway computing ability to security needs, network capacity and data traffic.
Another important factor in deciding which protocol is needed is the type of network connecting the devices. The different network types are determined primarily by device size and the distance between devices. For example, nano-networks have a small number of devices in close proximity, each no larger than a few millimeters. These networks are often used in military and healthcare related deployments. A LAN (Local Area Network) connects larger devices in a defined locality, such as a building. And a WAN (Wide Area Network) is used for a very large geographic area that can include different types of terrain and networks such as LANs, MANs (Metropolitan Area Networks) and smaller networks. 
The Most Popular IoT Protocols for Three Different Layers
- Constrained Application Protocol (CoAP) is used to communicate between constrained devices with limited CPU, memory and power resources, such as sensors/actuators—often within constrained networks that have limited and unpredictable bandwidth.
- Message Queue Telemetry Transport Protocol (MQTTP) has been around since 1999. This protocol allows many different devices and many different networks to communicate across great distances through a common server.
- Advanced Message Queueing Protocol (AMQP) supports verbal communication with devices, like Alexa or Siri.
- Data Distribution Services (DDS) is a protocol with different layers for the devices sending information versus the devices receiving and reading this information. DDS supports a stable, real-time and scalable exchange of data. 
Communication Transport Protocols
There are many Communication Transport protocols to choose from depending on the range, frequency and data rate required.
- Bluetooth and Wi-Fi are both low cost protocols but very limited in their range, which is just a few hundred feet.
- LoRa has a range of up to 3 miles and a relatively slow data rate that uses very little power. NB-IoT, on the other hand, has a slightly larger range and a faster data rate but uses more power than LoRa. In addition, since NB-IoT transmits via cellular band, it is much more costly than LoRa, which transmits over the Internet.
- Cat-m has a high data rate, which is essential in real-time data transfer, and has the ability to receive verbal communication.
- 2G/3G cellular band protocols are very fast, work over great distances and are very costly.
- Multicast Domain Name System (mDNS) is used when you have a small network without a local name server.
- Physical Web uses a Bluetooth low energy beacon that allows you to see a list of URLs that are being broadcast in the network.
- Universal Plug and Play (UPnP) is a set of protocols that allows different devices on a network to seamlessly find each other and share data.
The Final Note
Though many IoT devices seem simple, there are many layers of hardware and software and each layer has its own protocol requirements and possibilities. When we design our meters, we keep in mind all of the different requirements that will best serve our customers—data transfer, connectivity, speed, reliability, and security.
 Natallia Sakovich,IoT protocols and connectivity options: an overview ,2019
 Data Flair, What is the Internet of Things?, May 11, 2019
 Simon Ford, IoT Standards and Protocol, October 2019