Gateways offer an elegant means for simplifying the networking of “things.” Gateways effectively mitigate the great variety and diversity of devices by consolidating data from disparate sources and interfaces and bridging them to the Internet. The result is that individual nodes don’t need to bear the complexity or cost of a high-speed Internet interface in order to be connected. But gateways are not created equal. What follows is a brief overview of the three main types of IoT gateways.
Simple Gateways
There are several ways to implement an IoT gateway, depending upon the application. Two common approaches are a simple gateway and an embedded control gateway. Both provide consolidated connectivity by aggregating data from multiple end points. In general, a simple gateway organizes and packetizes the data for transport over the Internet. It is also responsible for distributing data back to end points in applications where two-way communications is advantageous or required.
Note that a gateway is different from a router. A router manages similar traffic, and it connects devices that share a common interface. For example, the devices that connect to a home router all use IP. In contrast, because a gateway functions as a bridge, it must be able to route different types of traffic, aggregate data from varying communication interfaces and convert these streams to a common protocol for access across the WAN.
Some devices might use IP natively while others might use PAN-based protocols like Bluetooth, ZigBee or 6LoWPAN. Nodes that are simple sensors may need to be connected to an ADC to convert their raw analog voltage to a digital value before transport. An embedded control gateway extends the functionality of a simple gateway by providing processing resources and intelligence for handling local applications. This can take the form of shared processing resources where the gateway performs tasks that would otherwise occur on nodes.
Embedded Control Gateways
An embedded control gateway can evaluate and filter sensor data as well as implement high-level management tasks. After evaluating and filtering sensor data, a gateway could determine whether a critical threshold has been passed. If so, it could then trigger an alarm that is passed up through the network to alert an appropriate manager.
Having an intelligent embedded control IoT gateway can reduce the complexity – and cost – of end points. Depending upon the application, this can result in significant system savings. Consider a security system with an array of sensors to which it connects. Consolidating processing, such as sensor data filtering, in the gateway enables nodes to leverage a shared resource, making each node simpler as well as lower in cost.
The same holds for enabling connectivity. IP is a complex protocol to implement with relatively high overhead for more simple IoT nodes. Instead, simple nodes can connect to a PAN using a wired connection like I-squared-C (I2C) or a wireless interface like Bluetooth. The gateway also connects to the PAN and then bridges each connection to an IP-based WAN interface like Wi-Fi or Ethernet. In both of these cases, savings include lower processing, memory and power requirements. Nodes can therefore be less expensive as well as more efficient. When these savings are spread across a network, they add up quickly.
End points that have to house their own intelligence and WAN connectivity require more complex architectures. Using a consolidated or shared architecture, the cost of each end point can be substantially reduced, more than making up for any increase in gateway cost through volume savings. Reducing the complexity of nodes also reduces overall power consumption for applications where nodes have limited battery life or operate on energy harvesting sources.
Intelligent Gateways
Distributed intelligence also accelerates the implementation of new applications. Consider smart appliances that use time-of-day information from the utility meter to operate off peak hours to reduce energy costs. Implementing this intelligence at the node level requires the washer, dryer and dishwasher to be able to communicate with the utility meter. When each appliance comes from a different company, the interface to use this feature will likely differ, creating interoperability issues. In addition, to take advantage of this feature, consumers would need to buy new appliances.
Enabling intelligence in a gateway addresses both interoperability issues on a local level while minimizing the changes required to connect appliances. Rather than require full intelligence in each appliance, the gateway can provide the base intelligence for all devices. This also has the advantage of consolidating management of new features for consumers; rather than needing to figure out and integrate each new appliance as it enters the home, the consumer only needs to understand how to manage the gateway.
An intelligent gateway also better addresses the issues that arise from connecting disparate nodes, compared to users manually connecting each device or appliance to the Internet. For many applications, an intelligent gateway can eliminate the need for a dedicated onsite management or control end point. For example, with an integrated LCD controller, a gateway can support a user interface so users can directly interact with nodes.
Alternatively, an intelligent gateway can provide a web-based user interface – accessible through a PC, tablet or smartphone – to allow users to easily access additional built-in applications. This enables the gateway to serve as a flexible and dynamically programmable onsite control point. This in turn lowers the cost of installation of new systems as well as enables third parties to introduce new technology and devices with a significantly lower cost of entry. Finally, a gateway can serve as a fabric between co-located nodes when Internet access is lost or temporarily interrupted. This ensures robust local connectivity without the cloud, thus increasing the reliability of the local network to maintain its intended functions.
So, what do you think: how intelligent should an IoT gateway be? Simple, complex or intelligent. Tell us what you think. Share you experiences.
To learn more about IoT Gateway Design Considerations or the use of TM4C12x MCUs in enabling IoT gateway applications, please download the attached document by Texas Instruments called "Building a Gateway for the Internet of Things," which was the source of information for this document.