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Sub-GHz wireless for long range IoT connectivity

Posted: 03 Dec 2014 ?? ?Print Version ?Bookmark and Share

Keywords:Internet of Things? IoT? MCU? Wi-SUN? ZigBee?

The term Internet of Things (IoT) has gained enormous popularity with the explosion of wireless sensor networks, smart meters, home automation devices, and wearable electronics. The IoT spans long-range outdoor networks such as the smart grid and municipal lighting, as well as shorter-range indoor networks that enable the connected home and residential security systems.

Numerous companies have introduced innovative solutions for the IoT market that provide security, status, and other convenient services. A connected system architecture comprises a number of wireless nodes ranging from simple remote control devices to complex wireless networks featuring a gateway to connect to the Internet. These networks can also provide localized system intelligence and cloud services as shown in figure 1. In this article, we will discuss low-power, long-range wireless connectivity in the widely used sub-GHz band.

 Connected system

Figure 1: Connected system architecture.

Choosing the right wireless solution
MCUs and wireless ICs are primary building blocks of an IoT system. MCUs used in connected device applications typically offer a wide selection of memory and peripheral options. The choice of wireless ICs (transceivers, transmitters, and receivers) is an equally important, or even more important, complex decision. Choices include sub-GHz devices running mostly licence-free proprietary protocols and a plethora of 2.4GHz devices based on standards such as ZigBee, Bluetooth Smart, and Wi-Fi. There is no one-size-fits-all solution when it comes to choosing the optimal wireless protocol for a given IoT application. Each wireless option has pros and cons, and the application, such as a gateway or a battery-powered end node, drives the selection of the right connectivity technology.

Proprietary sub-GHz protocols and the open ZigBee standard are among the most commonly used wireless protocols for applications that require a combination of energy efficiency, long battery life (5-15 years depending on the battery), and extended range for remote sensor nodes (figure 2).

 Sensor node

Figure 2: Sensor node architecture.

Bluetooth provides very short-range, point-to-point connectivity for smart phones and tablets without additional wireless infrastructure. Wi-Fi is the most widely used protocol for bandwidth-intensive applications such as video streaming and wireless hot-spot connectivity. The sub-GHz band is ideal for long-range, low-power, and lower data rate applications such as smoke detectors, door and window sensors, and outdoor systems such as weather stations, smart meters, and asset tracking.

Sub-GHz wireless connectivity
Sub-GHz technology is an ideal choice for wireless applications requiring long range and low power consumption. Narrowband transmissions can transmit data to distant hubs, often several miles away, without hopping from node to node. This long-range transmission capability reduces the need for multiple expensive base stations or repeaters.

Proprietary sub-GHz protocols allow developers to optimise their wireless solution to their specific needs instead of conforming to a standard that might put additional constraints on network implementation.

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