Wireless connection is a key part of the IoT terminal node design. Important and popular connection methods in the Internet of Things include low-power Bluetooth Low Energy, Bluetooth Mesh, ZigBee, Thread, Z-Wave, Wi-Fi, and various proprietary protocols with SUB-GHz band.
Internet of Things equipment has many application scenarios, which requires a variety of connection capabilities. For example, Wi-Fi is usually used in Internet Protocol (IP) cameras and transport streams; Bluetooth is ideal for deploying various smart home equipment and other applications; ZigBee, Thread, Z-Wave and Bluetooth Mesh support large-scale Interoperable equipment networks such as intelligent lighting, energy monitoring, and home security systems, etc.).
Each wireless protocol has unique features and features, and the correct protocol depends on the needs of the final product. Understand how to use and how to adapt to more ecosystems, will help your decision and help solve problems related to energy efficiency, performance, security, interoperability, upgradeability, and other RF source interference.
Let us take a look at these common connection methods.
Bluetooth
Bluetooth is a popular and universally existing agreement and has been continuous development. Its first official specification is released by Bluetooth Sig in 1999. Initially been a streaming voice / audio data protocol, it has been developed into powerful and energy-saving wireless technology, while low-power Bluetooth LE is popular in power-sensitive Internet of Things terminal node applications. .
The low-power blueburst specification supports extremely low power operations. In order to ensure reliable work within the 2.4 GHz band, it uses a powerful frequency hop spreading method that can transmit data on 40 channels. With the release of Bluetooth 5.0 enhancement, low-power Bluetooth provides great flexibility, including multiple physical layer (PHY) options, 125 kbps to 2 Mbps data rate, multiple power levels ( From 1 mW to 100 mW), as well as a variety of security options, even government-level security.
The Bluetooth Mesh launched in the middle of 2017 added another network options for the Internet of Things. The Bluetooth Mesh network implements multi-to-multi-device communication, which is ideal for creating an Internet of Things solutions (where dozens, hundreds or thousands of devices must communicate with each other). Bluetooth Mesh equipment is ideal for smart home (see Figure 1), lighting, beacon, and asset tracking applications. For example, in retail sales and asset tracking, Bluetooth Mesh technology simplifies the deployment and management of beacons. By combining low-power bluebearing with a mesh network, new features and value can be introduced into an Internet of-connected devices, such as internet lighting, can also be used as a beacon or beacon scanner.
ZigBee
ZigBee was first standardized by the Zigbee Alliance in 2004, which is running on the IEEE 802.15.4 physical radio specification, with lower power consumption relative to Bluetooth and Wi-Fi. Due to its network topology and verified scalability, it is easy to support more than 250 nodes, so it is widely used in home automation and industrial mesh networks.
The combination of low-power and "self-repair" scalability make ZigBee unique. ZigBee can run within the low power packet with a MAC layer mechanism for a short packet length 802.15.4 mac / phy, a 16-channel direct sequence spread spectrum (DSSS) modulation scheme and the MAC layer for message fault. In addition, the output transmitter power can be configured to power saving mode, especially in a centralized network of relay messages using adjacent battery power supply "routing nodes". This optimization method for processing mesh routing enables relatively low memory resources, only less than 160 kb flash memory and typical 32 KB of RAM. This provides a lower cost chip and ultimately economical solution for application developers and consumers.
The ZigBee alliance also specifies the application configuration, called cluster libraries to simplify the development of standard products (such as bulbs and occupancy sensors). As shown in FIG. 2, a universal ZigBee application layer for foundation is referred to as Dotdot, which is a common standard application language that can be used for communication in any network (e.g., Thread).
Thread
Thread is the latest wireless technology that the Internet of Things provides IP-based network and advanced security. THREAD Group was established in 2014, which released the Thread specification in July 2015 and continuously improved it. Thread is based on existing standards (including IEEE 802.15.4), and add special design specifications for the network layer and the transport layer. Like ZigBee, Thread operates in a 2.4 GHz band, which can form a powerful, self-repairable mesh network consisting of up to 250 nodes.
Thread supports low power, low cost, mesh scalability, security, and IP addressing. Similar to ZigBee, it converts some of the complex processing of the grid into a static memory "lookup table" while maintaining transmission / routing resources to run on low cost embedded devices (less than 185 kb flash memory and 32) KB RAM). This goal is mainly through software, which is why the Thread solution and protocol provider are proud of developing and providing a powerful solution implemented on a host chip (usually wireless MCU or SOC device). As flash memory becomes cheaper, and integrated circuit (IC) integrates more memory, the Thread protocol stack makes the chip to integrate more RF components (such as inductive matching networks) for low / medium memory capacity requirements. This allows developers to get rid of complex RF projects.
Z-Wave
Z-Wave® technology is an open, internationally recognized international telecommunications alliance (ITU) standard (G.9959). It is one of the leading wireless intelligent home technology today, with more than 2,700 certified interoperable products worldwide (see Figure 3). Z-WAV is managed by the Z-Wave Alliance, and has supported more than 700 companies around the world. It is a key active for home security, energy, hotel, office and light commercial application intelligent living solutions. Z-Wave Technology was developed by ZENSYS in 1999, ZENSYS is a start-up company headquartered in Copenhagen, which later was acquired by Sigma Designs in December 2008, recently received by Silicon Labs in April 2018.
One of the main attractions of Z-WAVE is that it provides a network network in the SUB-GHz band, avoiding the 24 GHz industry, science and medical (ISM) band, which is most other standard IoT protocols. In the frequency band used.
Interoperability and backward compatibility are key principles of Z-Wave technical concept. This prospect has attracted many fans in manufacturing and ecosystem fields, and becomes a pillar of the Z-Wave alliance. The Alliance is committed to certifying Z-Wave products interoperability and expanding the marketing business opportunities for members.
Wi-Fi 802.11b / g / n
Wi-Fi is built on the IEEE 802.11 specification for the local area network. It mainly solves the needs of families and companies for higher bandwidth IP networks. Like many wireless termination technology, Wi-Fi works in the 2.4 GHz band. It currently extension to support for 5 GHz bands to deal with higher data rates and avoid other grades of 2.4 GHz technology interference.
Wi-Fi main considerations include IP networks, bandwidth and power. Since they are usually suitable for high bandwidth, high-power and complex support software, Wi-Fi-based design is often more expensive than other Internet of Things. Wi-Fi requires larger, more complex RF components and more embedded computing resources for network processing. However, if you need more than 10 Mbps data rate and directly access the Internet, Wi-Fi is your ideal choice.
Looking forward to the future, we can expect Wi-Fi to continue to develop with the Internet of Things, which may mean lower power consumption, faster speeds and can be in 2.4 GHz bands (such as Bluetooth and 802.15.4) and 5 GHz bands (such as Bluetooth and 802.15.4) and 5 GHz For example, a cellular network coexisting hardware / software solution combination.
Proprietary SUB-GHZ
For low data rate applications such as industrial sensing, Sub-GHz networks below 1 GHz have some advantages than the more powerful and rich 2.4 GHz protocol. The transmission range is the main advantage of the SUB-GHz network. Narrow-band transmission can be transmitted or farther away from uninterrupted, transmitting data to a remote hub without having to more complex mesh software implementation nodes. In addition, the SUB-GHz band is not so crowded relative to ISM 2.4 GHz.
However, in some areas, available SUB-GHz channels are limited, which makes developers unable to construct a single architecture global solution. Another associated disadvantage is that SUB-GHz radio waves are different from country, and duty cycle limits actually limit the transmission time of the application.
Overall, the SUB-GHz network won in transmission distance, but lacks standardization of the 2.4 GHz protocol mentioned earlier.
Multi-protocol connection
Due to the combination of hardware and software engineering across the industry, we have seen wireless MCUs and SOCs supporting multiple wireless protocols in rapid growth. These multi-protocol devices have opened new Internet of Things features and application scenarios (see Figure 4), such as simplifying device deployment and Bluetooth beacons on other networks.
Multi-protocol SOC can also utilize a smartphone or tablet's convenience, and the deployed device is disconnected (OTA) update, and provides a simple way to add new protocols (such as low power Bluetooth) to have The products of traditional proprietary protocols.
Advanced multi-protocols from many suppliers, multi-band SOC now provides greater flexibility and design choices for developers seeking to increase wireless connection while simplifying their terminal node design.
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