How to choose the right IoT wireless technology

Wireless connectivity is a key part of IoT end-node design. Important and popular connectivity methods in the IoT include Bluetooth Low Energy, Bluetooth Mesh, Zigbee, Thread, Z-Wave, Wi-Fi, and various proprietary protocols using the Sub-1GHz.

IoT devices have many application scenarios that require a variety of connectivity capabilities. For example, Wi-Fi is commonly used for Internet Protocol (IP) cameras and devices that stream content; Bluetooth is ideal for deploying a variety of smart home devices and other applications; and Zigbee, Thread, Z-Wave, and Bluetooth Mesh support large-scale interoperable networks of devices (e.g., smart lighting, energy monitoring, and home security systems).

Each wireless protocol has unique features and functions, and choosing the right protocol depends on the needs of the end product. Understanding how to use and adapt to the broader ecosystem will help you make decisions and help address issues related to energy efficiency, performance, security, interoperability, scalability, and interference with other RF sources.

Bluetooth

Bluetooth is a popular and ubiquitous protocol that has continued to evolve. Its first official specification was published by the Bluetooth SIG in 1999. What started as a mobile headset and streaming voice/audio data protocol has evolved into a powerful and energy-efficient wireless technology, and Bluetooth Low Energy (Bluetooth LE) is popular in power-sensitive IoT end-node applications.

The Bluetooth Low Energy (Bluetooth LE) specification supports extremely low power operation. To ensure reliable operation in the 2.4GHz, it employs a robust frequency-hopping spread spectrum approach that allows data to be transmitted over 40 channels. With the release of Bluetooth 5.0 enhancements, Bluetooth Low Energy offers great flexibility for IoT designs, including multiple physical layer (PHY) options, data rates from 125kbps to 2Mbps, multiple power levels (from 1mW to 100mW), and multiple security options, even up to government level security.

Bluetooth Mesh, introduced in mid-2017, adds another mesh networking option to the IoT. Bluetooth Mesh networks enable many-to-many device communication and are ideal for creating IoT solutions (where tens, hundreds, or even thousands of devices must reliably and securely communicate with each other). Bluetooth Mesh devices are ideal for smart home (see Figure 1), lighting, beacon, and asset tracking applications. For example, in retail merchandising and asset tracking, Bluetooth Mesh technology simplifies the deployment and management of beacons. By combining low-power Bluetooth (Bluetooth LE) with mesh networking, new functionality and value can be introduced to IoT devices, such as connected lighting that can also be used as beacons or beacon scanners.

Bluetooth - How to choose the right IoT wireless technology

Figure 1: Bluetooth Mesh can provide multiple devices communication for IoT environments such as smart homes

Zigbee

First standardized by the Zigbee Alliance in 2004, Zigbee runs on top of the IEEE 802.15.4 physical radio specification and has lower power consumption compared to Bluetooth and Wi-Fi. It is widely used in home automation and industrial mesh networks due to its mesh topology and proven scalability, which can easily support networks with more than 250 nodes.

The combination of low power consumption and “self-healing” scalability makes Zigbee unique. Using 802.15.4 MAC/PHY with short packet lengths, a 16-channel Direct Sequence Spread Spectrum (DSSS) modulation scheme, and MAC layer mechanisms for message fault handling, Zigbee can operate within a low power envelope. In addition, the output transmitter power can be configured for power-saving mode, especially in centralized networks that use adjacent battery-powered “routing nodes” for relaying messages. This optimized approach to handling mesh routing functions allows for relatively low memory resource requirements, requiring less than 160kB flash and typically 32kB RAM. This provides application developers and consumers with a lower cost and ultimately a more economical solution.

The Zigbee Alliance also standardizes application configurations, called cluster libraries, to simplify the development of standard products, such as light bulbs and occupancy sensors. As shown in Figure 2, the generic Zigbee application layer for IoT is called Dotdot, a common standard application language that can be used for smart devices to communicate in any network (e.g. Thread).

ZigBee dotdot - How to choose the right IoT wireless technology

Figure 2: Dotdot provides a common application layer for the IoT

Thread

Thread is the latest wireless technology to emerge for the Internet of Things, offering IP-based mesh networking and advanced security. Founded in 2014, the Thread Group released the Thread specification in July 2015 and continues to improve it. Thread builds on existing standards (including IEEE 802.15.4) and adds network and transport layer Thread builds on existing standards (including IEEE 802.15.4) and adds special design specifications for the network and transport layers. Like Zigbee, Thread operates in the 2.4 GHz and can form a robust, self-healing mesh network of up to 250 nodes.

Thread supports low power consumption, low cost, mesh scalability, security, and IP address. Similar to Zigbee, it translates some of the complex processing in the vicinity of the mesh into static memory “lookup tables”, while also keeping transmission/routing resources relatively low so that it can run on low-cost embedded devices (less than 185kB Flash and 32KB RAM). Achieving this goal works primarily through software, which is why Thread solution and stack providers pride themselves on developing and delivering robust solutions implemented on host chips (typically wireless MCUs or SoC devices). As flash memory becomes cheaper and integrated circuits (ICs) integrate more memory, the Thread stack’s need for low/medium memory capacity allows the chip to integrate more RF components (such as inductor matching networks). This allows developers to move away from complex RF engineering.

Z-Wave

Z-Wave® technology is an open, internationally recognized International Telecommunication Union (ITU) standard (G.9959). It is one of today’s leading wireless smart home technologies, with more than 2,700 certified interoperable products worldwide (see Figure 3). Z-Wave is managed by the Z-Wave Alliance, supported by more than 700 companies worldwide, and is a key enabler of smart living solutions for home security, energy, hospitality, office, and light commercial applications. enabler. Z-Wave technology was developed in 1999 by Zensys, a Copenhagen-based startup that was later acquired by SigmaDesigns in December 2008 and most recently acquired by Silicon Labs in April 2018.

z wave - How to choose the right IoT wireless technology

Figure 3: More than 700 companies worldwide use Z-Wave in over 2,700 certified interoperable products

One of the main attractions of Z-Wave is that it offers to mesh networking in the sub-1GHz, avoiding the sometimes-crowded 2.4 GHz industrial, scientific and medical (ISM) band, the band used by most other standards-based IoT protocols.

Interoperability and backward compatibility are the key principles of the Z-Wave technology concept. This outlook has attracted many fans in the device manufacturing and ecosystem space and has been the backbone of the Z-Wave Alliance’s success. The Alliance is dedicated to certifying Z-Wave product interoperability as well as expanding marketing opportunities for its members.

Wi-Fi 802.11b/g/n

Wi-Fi is built on the IEEE 802.11 specification used for local area networks. It primarily addresses the need for higher bandwidth IP networks for homes and businesses. Like many wireless IoT technologies, Wi-Fi operates in the 2.4 GHz. It has now been extended to support the 5GHz to address the challenges of achieving higher data rates and avoiding interference from other licensed 2.4GHz technologies.

Key considerations for Wi-Fi include IP networks, bandwidth, and power. Because they typically lend themselves to high bandwidth, high power, and complex supporting software, Wi-Fi-based designs tend to be more expensive than other IoT technologies. Wi-Fi requires larger, more complex RF components and more embedded computing resources for network processing. However, if you need data rates over 10Mbps and direct access to the Internet, then Wi-Fi is the ideal choice for you.

Looking ahead, we can expect Wi-Fi to continue to evolve with the IoT, which may mean lower power consumption, faster speeds, and a combination of hardware/software solutions that can coexist in both the 2.4 GHz band (e.g., Bluetooth and 802.15.4) and the 5 GHz band (e.g., cellular networks).

Proprietary Sub-1GHz

For low data rate applications such as industrial sensing, sub-1GHz networks operating below 1GHz have several advantages over the more powerful and feature-rich 2.4GHz protocol. The transmission range is where the main advantage of sub-1GHz networks lies. Narrowband transmissions can transmit uninterrupted for a kilometer or more, transmitting data to remote hubs without the need for more complex mesh software to implement inter-node hops. In addition, the sub-1GHz band is less crowded compared to ISM 2.4GHz.

However, in some regions, the available sub-1GHz channels are limited, making it impossible for developers to build a global solution with a single architecture. Another related disadvantage is that sub-1GHz radio wave regulations vary from country to country, and duty cycle restrictions may limit the transmission time of an application.

Overall, the sub-1GHz network wins in terms of transmission distance but lacks the standardization of the 2.4GHz protocol we mentioned before.

Multi-protocol connectivity

Thanks to a combination of hardware and software engineering across the industry, we have seen a rapid growth in wireless MCUs and SoCs that support multiple wireless protocols. These multi-protocol devices open up new IoT capabilities and application scenarios, such as simplified device deployment and Bluetooth beacons on other networks.

Multi-protocol SoCs can also take advantage of the convenience of a smartphone or tablet to perform over-the-air (OTA) updates to deployed devices and provide an easy way to add new protocols, such as low-power Bluetooth, to products with legacy proprietary protocols.

Advanced multi-protocol, multi-band SoCs from a wide range of vendors now offer greater flexibility and design options for developers seeking to increase wireless connectivity while simplifying their end-node designs.