How to Quickly and Effectively Implement Wi-Fi HaLow IoT Networks

Technical Overview: Distributed Internet of Things (IoT) networks often require greater range, building penetration, device capacity, and energy efficiency than conventional Wi-Fi can provide. IEEE 802.11ah Wi-Fi HaLow addresses these needs using sub-1 gigahertz (GHz) operation, scalable channel bandwidths, and power-management features. This article explains the principal network trade-offs and introduces Quectel FGH100M modules for implementing HaLow connectivity. It compares the FGH100MABMD and FGH100MAAMD variants, outlines their regional certifications and data rates, and presents the FGH100MAAM2 development board. It also reviews host interfacing, power supplies, antenna routing, electrostatic discharge protection, modulation settings, receiver sensitivity, transmit power, and link-budget considerations in practical designs. (Overview courtesy of ChatGPT)

Connected Internet of Things (IoT) devices for industrial, building, smart city, and agricultural applications can place significant demands on wireless networks. For example, conventional Wi-Fi provides high data rates and familiar network connectivity, but range and penetration can limit reliable performance when devices are spread across large buildings, industrial sites, outdoor areas, or other challenging environments. Many long-range wireless technologies can extend coverage but may come at the cost of much lower data rates and require adopting a less well-known network architecture.

Wireless protocols such as IEEE 802.11ah (Wi-Fi HaLow) can extend coverage while supporting useful data rates, low-power operation, and many connected devices. Still, designing RF interfaces remains complex and resource-intensive, adding cost and delaying time-to-market.

This article discusses the challenges wireless IoT device designers face, including trade-offs among range, data rate, power consumption, and device capacity. It then introduces compact IEEE 802.11ah Wi-Fi HaLow solutions from Quectel and shows how to use them to quickly implement distributed IoT connectivity.

Why IoT networks have different wireless requirements

Conventional IEEE 802.11-based Wi-Fi freed computers from wired network ports in homes and offices, where high bandwidth for browsing, streaming, and large data transfers is important. Here, Wi-Fi coverage scales by adding access points (APs), usually routers operating in the 2.4, 5, or 6 gigahertz (GHz) bands.

Industrial IoT presents a different scenario. For example, sensor nodes may be scattered across a manufacturing facility, each monitoring equipment operating conditions or collecting data from production processes. These devices typically send very little data and are designed to run for long periods without maintenance.

The same pattern appears in smart buildings, where sensors may be located in basements, stairwells, and ceiling voids, often behind metal surfaces or thick concrete walls that attenuate the signal. In outdoor settings, such as smart city infrastructure, devices may be hundreds of meters from the nearest gateway, causing additional signal loss.

Adding APs addresses part of the problem, but each one may require a new Ethernet connection and, if Power over Ethernet (PoE) is unavailable, a separate power supply. On a large industrial or agricultural site with equipment spread over long distances, scaling this infrastructure can be challenging. Battery-powered sensors introduce another constraint: frequent radio activity or higher transmission power shortens battery life, increasing maintenance needs.

While long-range wireless technologies have been developed to address some of these challenges, they also have limitations, particularly when applications require native Internet Protocol (IP) support and sufficient data throughput.

How Wi-Fi HaLow supports long-range IoT networks

Wi-Fi HaLow operates in sub-1 GHz bands and is based on the IEEE 802.11ah standard, which retains IEEE 802.11-based networking and enables distributed devices to communicate through a compatible AP using standard IP networking (Figure 1). This makes Wi-Fi HaLow a useful technology for expanding existing industrial IoT networks.

Figure 1: Wi-Fi HaLow uses IEEE 802.11ah APs to connect distributed IoT devices to standard Internet infrastructure. (Image source: Seeed Studio)

With this network infrastructure, IEEE 802.11ah provides several features that make it well suited for building large-scale, long-range IoT networks:

• Sub-1 GHz operation: Free-space path loss is lower than at higher Wi-Fi frequencies, extending the potential communication range. Sub-1 GHz communications also penetrate many common building materials better, making them well suited for urban and indoor networks.
• Channel bandwidth and modulation: IEEE 802.11ah supports channel bandwidths of 1, 2, 4, 8, and 16 megahertz (MHz), enabling scalable data transmission that matches application requirements. Orthogonal frequency-division multiplexing (OFDM) enables efficient use of the available channel bandwidth, while different modulation and coding schemes (MCS) allow devices to balance data rate and communication robustness. Combined with IEEE 802.11ah's media access control (MAC) mechanisms, these features help many devices share the same wireless network.
• Network access management: Wi-Fi HaLow association identifiers can theoretically support up to 8,191 stations (i.e., devices) per AP. Although this does not reflect real-world simultaneous network capacity, it provides a framework for associating thousands of devices with a single AP, potentially reducing the need to divide a large deployment, such as smart building management infrastructure, into smaller network cells.
• Power management: Target Wake Time (TWT) allows compatible devices to schedule when they communicate with the network, enabling battery-powered sensors to enter low-power or sleep modes between transmissions. This can help prolong battery life and reduce routine maintenance, though actual savings depend on operating current and how often the application needs to send data.

These features allow Wi-Fi HaLow to serve devices under very different radio conditions within a larger IoT network. The challenge for designers now is implementing the Wi-Fi HaLow RF interface. This requires RF expertise to meet performance and regulatory requirements, including those covering electromagnetic compatibility (EMC). Developing this expertise in-house or hiring consultants can add cost and time.

Wi-Fi HaLow modules for space-constrained designs

One solution is to use off-the-shelf HaLow modules to simplify and accelerate the design process. For example, the Quectel FGH100M Wi-Fi HaLow modules (Figure 2) provide designers with a practical starting point for implementing IEEE 802.11ah connectivity. Integrating wireless functionality into a compact module reduces required RF development and lets designers focus on the broader application.

Operating at 850 MHz to 950 MHz, the modules support 1 MHz, 2 MHz, 4 MHz, and 8 MHz channel bandwidths, depending on regional regulations, and are available in a 13.0 mm × 13.0 mm × 2.2 mm LGA package. They are well suited for space-constrained designs such as IoT sensors mounted in industrial machinery or existing urban infrastructure that require a range up to 1 km.

Figure 2: FGH100M Wi-Fi HaLow modules come in a compact LGA package and suit IoT applications requiring a range up to 1 km. (Image source: Quectel)

These deployment conditions are further supported by a wide operating temperature range of -40°C to +85°C. With AP and station (STA) operating modes, the FGH100M modules offer flexible field configuration. WPA3 and AES encryption provide network security, which is important because each additional node increases the potential attack surface.

Quectel offers two FGH100M module variants that allow designers to match data throughput and regional requirements to each application. For installations requiring higher data rates, the FGH100MABMD supports a maximum physical-layer (PHY) data rate of 32.5 megabits per second (Mbits/s). This module is FCC certified for the United States.

Alternatively, the FGH100MAAMD is CE certified for the European market and provides a maximum PHY data rate of 3.3 Mbits/s. Although lower, this throughput suits many sensor applications that report periodically.

For development and debug, Quectel also offers the FGH100MAAM2 development board for the FGH100MAAMD, allowing designers to evaluate operating configurations before committing to a custom design.

Practical Wi-Fi HaLow implementation

When building an IoT sensor node, it is important to consider how the device interfaces with surrounding components and how channel bandwidth and MCS selection affect data rate, link budget, and communication range. The FGH100M modules require a main power supply of 3.0 to 3.6 volts (3.3 volts, typical) with a separate I/O supply of 1.8 to 3.6 volts from the host, which communicates with the module via SPI or SDIO (Figure 3).

Figure 3: A typical FGH100M host connection includes the supply rails, SDIO or SPI interface, control lines, and external antenna port. (Image source: Quectel)

In addition to the supply rails and the SDIO or SPI bus, the host uses dedicated WAKEUP_IN, BUSY, and RESET_N lines to control the module. The WAKEUP_IN and BUSY lines support power-saving operation, helping to extend the operating life of battery-powered sensor designs.

The RF signal is routed to a single antenna port for connection to an external antenna. For this interface, Quectel reference designs recommend routing RF traces at a controlled 50 ohm (Ω) impedance and reserving an electrostatic discharge (ESD) protection component with a junction capacitance no greater than 0.05 picofarads (pF).

Once the FGH100M module is integrated, its channel configuration must be set to match the application requirements. At MCS 0 on a 1 MHz channel, which may suit smaller data packets such as temperature readings, the FGH100MABMD has a typical transmission power of 21 decibels referenced to 1 milliwatt (dBm) and a receiver sensitivity of -108 dBm. This provides a theoretical link budget of 129 decibels (dB) before antenna gains and losses.

However, if MCS 0 on an 8 MHz channel is used for more demanding communications, such as image data from a motion-triggered agricultural monitoring camera, the sensitivity drops to -98 dBm. With a transmission power of 20 dBm, this yields a theoretical link budget of 118 dB. The 11 dB difference shows that wider communication channels can reduce the available link budget, potentially affecting range or reliability.

The achievable communication range also depends on propagation losses, including free-space path loss of approximately 91.5 dB at 1 km for 900 MHz, as well as attenuation caused by walls, surrounding machinery, and other obstacles.

Conclusion

Distributed IoT networks for industrial, building, smart city, and agricultural applications often need to communicate over distances that conventional Wi-Fi cannot reliably cover without additional infrastructure. IEEE 802.11ah Wi-Fi HaLow extends network coverage while maintaining useful data rates and supporting large numbers of connected devices. Using Quectel FGH100M modules, designers can quickly and effectively implement a HaLow-based design.