Wireless System-on-Chip (SoC) for IoT sensors

Building electronic circuits within a system-on-chip (SoC) has benefits such as improving compatibility and efficiency while reducing space requirements and speed of development. In IoT, including the wireless technology in the SoC helps to overcome implementation challenges such as network incompatibility, integration, and reliability issues.

Edge devices or sensors without inbuilt wireless connectivity often require additional and expensive hardware to connect to the wireless networks. For example, sensors using the Bluetooth, Zigbee or Zware must be paired with a smartphone or other form of gateway for them to connect to the servers or the Cloud. This increases implementation costs, power requirements, and complexity.

On the other hand, a sensor with a wireless-enabled SoC overcomes most of the network compatibility and integration challenges. This makes it easier and cheaper to connect to other external networks in addition to reduced complexity, cost, and energy consumption.

Network and power challenges when deploying IoT

The majority of IoT sensors rely on wireless connectivity that allows them to be part of larger networks. But more often, there are many types of networks and protocols in the IoT ecosystem. When it comes to connecting different sensors using various protocols and network technologies such as ZigBee, Wi-Fi, cellular, Bluetooth, etc., the deployment may face some incompatibility challenges. Others may require additional hardware or complex configurations to connect them to the edge, cloud, or on-premise servers.

Also, the devices rely on battery power in addition to limited processing, storage, and memory resources. Because of nature, location, and size of the endpoint devices such as the sensors, deploying and maintaining them in remote and far locations is usually a challenge and can be very expensive. In particular, powering the devices is usually a challenge.

For this reason, manufacturers should aim at producing easy to deploy devices that last for several years without requiring battery replacement or any form of maintenance. Ideally, this calls for a self-contained unit that operates for thousands of hours from a single battery.

Building blocks of a wireless IoT SoC

Integrating wireless capability involves combining analog, digital, mixed-signal, and RF circuits into one IC. The main components of a typical ultra-low-power wireless SoC, such as the GS1011, are:

• Digital baseband processor
• Applications processor
• On-chip SRAM memory
• On-chip flash memory
• Connectivity such as 802.11b radio
• Media access controller (MAC)
• Power management

Wireless connectivity

Chip manufacturers are producing SoCs with different types of inbuilt network connectivity technologies. These conform to various commonly used wireless protocols such as Bluetooth, ZigBee, Wi-Fi, etc. Most often, the exact components may differ from one manufacturer to the other and depending on the type of network protocol in the target application. Also, some SoCs integrate separate hardware to speed up the encryption process, therefore improving security.

The above building blocks represent an ultra-low-power, Wi-Fi SoC chip that supports 11Mbps data rates. This has the ability to support high bandwidth IoT applications. While such a chip and some others only support one type of protocol or network, some manufacturers are producing SoCs with several different types of networks. These have the ability to support more than one network protocol and are therefore more flexible.

A typical multiple wireless SoC chip is the Redpine Signals RS9113 which supports WLAN (802.11n), Zigbee (802.15.4–2006) and Bluetooth version 4.0. A sensor or device using this SoC can connect directly to any of the three networks without additional components.

Power management

The energy efficiency of IoT sensors is critical due to the limited power sources. Generally, the devices at the edge are physically small and installed in remote locations with no power. As such, they have to rely on batteries, which are in most cases very small due to space constraints. With thousands of devices installed in remote locations, running wires to power them or replacing batteries is practically impossible or very expensive. Optimizing the designs improves the efficiencies, hence extending the battery lives to last for several years.

Most often, the low power wireless SoC for IoT applications are optimized for the battery-operated sensors such as those used in the smart thermostats, smart door locks and others. The SoC with inbuilt wireless connectivity features usually employs power-saving algorithms that allow them to use only a few microamperes, hence extending the battery life further.

Consideration when selecting a wireless SoC

There are a few considerations when selecting the SoC IoT chip for certain applications. These include power consumption, the physical size of the device, data throughput, latency, etc.

However, the three most critical issues are the range, data rate, and power. These parameters are somehow interrelated since the data rate and range depend on the protocol.

In any application, the SoC must have the correct wireless protocol, similar to what the IoT application and network are using. Consequently, this will influence the data rate and range.

Although the distance depends on the protocol, the IoT system designer must also pay attention to the available space and possible battery energy to adequately power the RF module and other components in the chip. Basically, there must be enough power to enable the device to achieve the desired range.

In a typical application, the factors that determine the SoC power requirements are the efficiency of its RF part, the sensitivity of the receiver, as well as the energy consumption by the other components.

There may be other issues to consider when working with SoC. In practice, mixing the digital and analog circuits creates some challenges. To ensure reliability and performance designers often make some trade-offs such as working at lower transmit power and receiver sensitivity.

These trade-offs vary according to the application area and manufacturer. As such, there is no one-size-fits-all solution and one must look for a SoC component that best satisfies the critical areas of the application.

Conclusion

Today, most manufacturers are building low power SoC devices with integrated wireless capabilities. This helps to address most of the network incompatibility issues while providing flexibility in the system design. When used in an IoT application, these SoC features enables direct connection to wireless networks, extended battery life, lower implementation cost, ease of integration as well as accelerated deployments.