Machine to machine communication (m2m) is the term that identifies the space enveloping the collection of devices, services and the value chain required to allow the interconnection of electronic apparatus, typically but not always wirelessly. Another characteristic of m2m communication is that this interconnection enables primarily automated communication between distant, remote machines and one or more layers of central management applications. It provides for real-time monitoring and control without the need for human intervention.
In the wireless m2m space, there are two major classes of interconnections: short range and wide area. The predominant wide area technology applies embedded cellular modules to connect remote devices to the internet or application servers. Think of embedded cellular modules as cell phones for machines or cell phones without the display and keyboard. A cellular module includes many of the same features that you would find in a cellular handset, including voice and data communication, and is ideal for embedded applications.
Short range is not too dissimilar from wide area. It applies embedded short range wireless modules in a wide range of protocols and frequencies according to application type and regional spectrum regulatory constraints. These modules operate in the license-free ISM frequency, typically in the bands of 169, 433, 868, 915 MHz, and 2.4 GHz. They are available in standard air-interface protocols such as wireless M-Bus and ZigBee as well as other proprietary technologies.
Cellular and short range modules connect with an application using AT commands or RIL drivers, typically through a UART or USB connection.
The figure above shows how an m2m application works to connect home utility meters, allowing them to communicate automatically to the various utility consumer billing systems. Information from the meters goes over short range communication, through a hub which bridges the local connection to the cellular network and to the central management system. All arrows point both ways indicating that in this typical m2m application the central management system can poll individual meters.