Seven Wireless Standards for IoT Devices

Comparison of Some Protocols

Zigbee is similar to Bluetooth, a low-power, low-data-rate, short-range self-organizing wireless network that supports mesh network topology, using the IEEE 802.15 WPAN specification. It provides data rates of 250 kbps, 40 kbps, and 20 kbps, and operates within a range of 10 to 100 meters. A Zigbee mesh network can contain up to 65,000 devices, which is twice the number supported by Bluetooth LE.

Zigbee was conceptualized in 1998, standardized in 2003, and revised in 2006. The name Zigbee comes from the waggle dance of bees, and its trademark is owned by the Zigbee Alliance, which is responsible for maintaining and publishing the Zigbee standard. According to information on its website, there are hundreds of millions of devices using Zigbee technology worldwide.

Zigbee is very popular among IoT device manufacturers, providing most of the basic functions (connectivity, range, security) that users need, and as an open industry standard, it allows interoperability with any Zigbee-certified device. The biggest complaint from OEM manufacturers is the cost of joining the alliance, certification, and the lack of an open GPL license, as OEMs must become members of the alliance to use its technology.

Zigbee is primarily used in home automation applications, such as smart lighting, smart thermostats, and home energy monitoring. It is also commonly used in industrial automation, smart metering, and security systems.

Z-Wave is similar to ZigBee, a low-cost, low-power, high-reliability, network-friendly short-range wireless communication technology based on radio frequency. The structure of Z-Wave is a source-routed mesh network, where all devices connect to a central hub, usually a router or gateway. The network itself consists of three layers that work together to ensure all devices can communicate simultaneously. The radio layer defines how signals are exchanged between the network and radio hardware, while the network layer determines how to control the exchange of data between nodes and devices. Additionally, the application layer assigns messages to specific applications to perform tasks such as turning on lights.

Z-Wave operates in the frequency band of 908.42MHz (USA) ~ 868.42MHz (Europe), using FSK (BFSK/GFSK) modulation, with a data transmission rate of 9.6 kbps, and an effective coverage range of 30m indoors and over 100m outdoors, suitable for narrowband applications.

Z-Wave technology is designed for residential, lighting commercial control, and status reading applications, such as metering, lighting and appliance control, HVAC, access control, and theft and fire detection. Z-Wave can convert any standalone device into a smart network device, allowing for control and wireless monitoring. Z-Wave technology was originally designed for the smart home wireless control field. It transmits using a small data format, and a 40kb/s transmission rate is sufficient. Compared to other similar wireless technologies, it has a relatively low transmission frequency, a relatively long transmission distance, and a certain price advantage.

Similar to Zigbee, LoRaWan is a proprietary technology defined and controlled by the non-profit LoRa Alliance. The main difference is that Zigbee is a short-range IoT protocol designed to tightly connect multiple devices, while LoRa focuses on wide area networks.

LoRa is particularly suitable for long-distance communication, and its modulation method greatly increases communication distance compared to other communication methods. It can be widely used in various situations for long-distance low-rate IoT wireless communication, such as automatic meter reading, building automation devices, wireless security systems, industrial monitoring and control, etc. It features a small size, low power consumption, long transmission distance, and strong anti-interference capability, and the antenna gain can be adjusted according to actual application needs.

The LoRaWAN network architecture is a typical star topology, where the LoRa gateway acts as a transparent relay connecting terminal devices and servers. The gateway connects to the server via standard IP, while terminal devices communicate with one or more gateways in a single hop, and all nodes can communicate bidirectionally. LoRa gateways and modules form a star network, while LoRa modules can theoretically form a point-to-point polling network, but the polling efficiency is much lower than that of a star network. The gateway can achieve multi-channel parallel reception, handling multiple signals simultaneously, greatly increasing network capacity.

LoRa Network Composition

However, as the number of LoRa devices and networks increases, there will be some spectral interference among them.

LTE-M is a cellular technology designed to meet the needs of IoT or machine-to-machine communication applications. LTE-M is a wireless system for mobile telecommunications operators, supported by industry associations GSMA and 3GPP standard organizations. One of the main advantages of LTE-M is its potential for global connectivity, and it is the only system suitable for long-term tracking of moving objects. GSMA states: “This technology can improve indoor and outdoor coverage, support a large number of low-throughput devices, low latency sensitivity, ultra-low device costs, and low power consumption network architecture.”

Since LTE-M operates through cellular networks, it can be used to monitor, control, and receive information from IoT devices in transportation vehicles (such as trucks, trains, ships, etc.). When LTE networks are unavailable, the system can fall back to WCDMA (3G) or GPRS/EDGE (2G) to maintain connectivity.

LTE-M also provides positioning services based on cellular base station positioning, eliminating the need for satellite-based systems like GPS or Galileo. This feature can save significant costs for OEMs that need to equip their devices with basic positioning systems.

However, the biggest advantage of LTE-M is security. Devices connected to cellular networks require a SIM chip, which can be embedded in the circuit board and pre-configured in the factory with keys and signatures. Once the embedded keys for the SIM card are configured, these keys cannot be modified without physical access to the device.

SIM is a secure module that can provide NSA Suite B AES-256 encryption and authentication.

Another advantage of LTE-M is that it can maintain connectivity even during power outages. Since it connects to cellular networks, it does not require access points (APs); as long as the IoT device’s battery is functioning, it can remain connected.

This is why cellular-based IoT connectivity is widely used in critical applications such as power grids, home and office security, and fleet management.

The only issue with LTE-M is its high cost. To use this system, operator services must be ordered, and each connected device requires a SIM card.

NB-IoT is built on cellular networks, consuming about 180kHz of bandwidth, and can be directly deployed on GSM networks, UMTS networks, or LTE networks to reduce deployment costs and achieve smooth upgrades.

NB-IoT focuses on the low-power wide-area IoT market, a new emerging technology that can be widely applied globally. It has characteristics such as wide coverage, many connections, low rate, low cost, low power consumption, and optimized architecture. NB-IoT uses licensed frequency bands and can be deployed in-band, guard band, or standalone carrier modes, coexisting with existing networks.

NB-IoT has four main characteristics: first, wide coverage, which will provide improved indoor coverage; under the same frequency band, NB-IoT can provide a gain of 20dB compared to existing networks, equivalent to a 100-fold improvement in coverage area; second, it supports a large number of connections, with NB-IoT able to support 100,000 connections in a single sector, supporting low latency sensitivity, ultra-low device costs, low power consumption, and optimized network architecture; third, lower power consumption, with NB-IoT terminal modules having standby times of up to 10 years; fourth, lower module costs, with enterprises expecting the cost of a single connection module to be no more than $5.

IEEE 802.11af (White-Fi) and IEEE 802.11ah (HaLow) both use previously licensed spectrum and do not interfere with traditional Wi-Fi signals in the 2.4 GHz and 5 GHz bands, nor do they interfere with 2G and 3G cellular networks. Some spectrum shares with certain LTE channels used in the USA.

White-Fi utilizes the digital dividend released when broadcast television transitioned to digital terrestrial television and when some previous UHF channels ceased operation. In the USA and Europe, there are different regulations regarding the use of digital dividend spectrum, and connected devices need to regularly search for available frequencies.

HaLow extends Wi-Fi into the 900 MHz band, enabling low-power connections required for applications such as sensors and wearable devices. Since this frequency can be used for basic communication without charge, HaLow is the preferred Wi-Fi standard for IoT.

The biggest issue with HaLow is the lack of unified unlicensed spectrum globally: HaLow operates at 900 MHz in the USA, 850 MHz in Europe, and 700 MHz in China, with many countries having no operating spectrum at all.

Due to the characteristics of the low frequency band, these two technologies are not suitable for high-speed or high-capacity data transmission. However, they can be used to provide connectivity for a large number of deployed devices.

HaLow can provide data rates as low as 150kbps.

For the next generation of low-power devices, connections below 1 GHz are also crucial, as their battery life typically needs to last for several years. This battery performance is essential for the billions of sensors and monitoring devices deployed in cities around the world.

HaLow also offers some power-saving features, such as Target Wake Time (TWT) and Traffic Indication Map (TIM), allowing IoT devices to communicate at selected intervals to save battery power.

In 2017, IEEE introduced another Wi-Fi standard for IoT: 802.11ax (later officially renamed WiFi 6). Compared to HaLow, 802.11ax has the advantage of using the 2.4 GHz and 5 GHz bands, making it more suitable for local range IoT.

In terms of security, Wi-Fi lacks the security elements and hardware encryption provided by SIM cards on cellular networks. However, to deploy hundreds or thousands of wireless sensors over a large area, White-Fi and HaLow can provide low-cost connectivity and good performance.

If you are looking for a low-cost solution for close-range connections for non-critical devices, then Zigbee, Z-Wave, or White-Fi may be the best choice. Zigbee’s DotDot software will help you develop solutions compatible with other Zigbee devices, provided you join the Zigbee Alliance.

For long-distance applications, LoRaWan, LTE-M, or NB-IoT are the best choices. LTE-M is the most powerful and secure, and it is supported by cellular networks, but it may also be the most expensive. It guarantees global connectivity and can be used for freight and fleet management.

For local medium networks that do not require positioning services or NSA级 security, LoRa is a good solution.

Therefore, the choice of which solution to use depends entirely on your needs, and users can choose the best option based on their actual situation.

Original link:

https://iot.eetimes.com/top-wireless-standards-for-iot-devices/

Editor: Bian Xiaobai, Da Lian Fei Fei Cat