This blog series is an extension of an earlier released blog, “IoT Wireless Standards in a Nutshell”. This post focuses more on the basic background of IoT systems architecture and network categories. Future blogs will cover more detailed information about network topologies and IoT protocols, standards, and wireless communication technologies.
IoT System Architecture
Generally, IoT devices connect with other devices in a network in three basic ways. They either connect with other devices directly, connect to IoT gateways that then connect with outside networks, and are IoT gateways that provide communication and networking service between IoT devices and external networks.
Device-to-device (D2D)
IoT device-to-device (D2D) communications can be performed in a variety of ways. Some IoT devices are capable of directly communicating with other IoT devices via wireless communication, such as with Bluetooth or Zigbee mesh networks. Other types of IoT devices communicate over a LAN to other devices, and hence use the current LAN networking infrastructure as a basis for their communication. A common example of D2D communications is a smartphone communicating voice and data via Bluetooth to a wireless headset. This can be either as a one-way link in the case of music, or a two-way link in the case of a two-way voice call or the use of headset control buttons.
There are a variety of instances of current and predicted IoT D2D communications. Some of these communications are like mesh networking, which relays wireless communications using a mesh of several IoT nodes, or as direct high-speed and narrow-beam, such as with proposed vehicle-to-vehicle (V2V) communications for autonomous vehicles. The length, throughput, latency, range, power efficiency, directionality, security, frequency, bandwidth, and other performance factors and specifications for D2D communication depends largely on the standard and application the communication is used for.
There is a whole class of D2D communications for industrial machinery, environmental sensors, security systems, and etc. that are generally targeted for municipal, transportation, energy, and industrial applications where machines intercommunicate directly in order to coordinate, a technology known as machine-to-machine (M2M) communications. Hence, the diversity of application requirements for D2D communications have spawned a variety of technologies with various capabilities and objectives. In some cases, IoT devices are battery powered, or otherwise powered by limited power sources, such as solar, vibration, energy harvesting, and other means of energy acquisition. In these cases, an IoT device will likely be designed to operate with minimal power use, and thus rely on low-power wireless communications that are only activated as necessary.
Device-to-gateway (D2G)
A device-to-gateway (D2G) communication is used to transfer communications from the D2D network to an external network. A gateway is an IoT device that facilitates this transfer. Typically, IoT gateways contain hardware that enables a gateway to communicate over the same network, wireless or wired, as the IoT devices they are designed to complement, and hardware that enables communication to internet or data services, such as Ethernet using internet protocols. For example, many mesh networking systems often employ the gateway as an end-node as well as another node in the system in the case of inter-network communication.
Gateways are commonly capable of IP-based communications, where many D2D communications use different forms of device identification. Using different forms of communication for D2D and gateway-to-internet (G2I) is also a method of enhancing security, as avoiding IP-based communication can make accessing D2D networks externally more challenging.
Gateway-to-Internet (G2I) or Gateway to Data Infrastructure
G2I, or gateway to data infrastructure, is the communication from the IoT gateway to outside networks, such as the internet and cloud services. Often, service providers will have methods of connecting a gateway to a secure data service using the internet and secure communication methods, such as secure TLS-tunneling. In some cases, gateways are capable of communicating with a variety of cloud services, and enable interoperability between a variety of cloud-based services. This could include voice command platforms, such as Google Assistant and Amazon Alexa, and various control technologies, such as Philips Hue Bridge or Samsung Smartthings.
Though often called “Hubs”, IoT gateways are a critical component in an IoT systems accessibility and security. Many IoT gateways are built with enhanced security features to protect IoT devices and networks from malicious activity, such as snooping and hacking. In some cases, IoT devices in a network are also gateways, or capable of performing gateway functions, in the case of a gateway failure there may be built in redundancy. Also, many IoT gateways and networks are designed to relay all communications through a “Hub”, such as with start network typologies. If a gateway is compromised, then often the entire IoT network can be compromised, which is leading to more significant investigation of security measures that allow for accessibility as well as security.
