Wi-Fi HaLow

While much of the recent news about Wi-Fi is around the new 6GHz standard, another specification has recently been released that has the potential to have a big impact in the Internet of Things (IoT) world. This is the 802.11ah specification or Wi-Fi HaLow. Released by the Wi-Fi Alliance in 2017, it is best described as “sub-GHz long-range Wi-Fi”.

The original Wi-Fi as well as many other popular radio protocols (802.15.4, ZigBee, Bluetooth) operate in the 2.4GHz band (2.400 to 2.4835GHz) because the requirements for operating in that band are standardized around the globe. This means that a company can make one product and sell it all over the world. It may have to be tested in each country, but if it passes in one then it will pass in the others because the rules are all the same. The downside of this band is that as the frequency gets higher, the range gets shorter.

For better range, operating in a band below 1GHz is preferable. But there is no single harmonized frequency band for global operation. There are two bands that allow these kinds of transmissions that cover most of the countries. First is the 900MHz / 915MHz band (902-928MHz) that is allowed in North, South and Central America. Australia and New Zealand support most of this band. The other band is the 868MHz band (863 to 870MHz). This is defined by the European Union and is supported by virtually all of Europe and most Middle Eastern countries that have a national spectrum plan.

Wi-Fi HaLow takes the features that have made Wi-Fi one of the most successful wireless protocols and brings it into these lower frequency bands. It fills a gap by offering much better range than Bluetooth and IEEE 802.15.4 radios while offering much better data throughput than protocols like ZigBee, Thread and LoRa. The radios have a higher peak power usage, but a much shorter on time. So total energy usage is lower than other LPWAN protocols.

Wi-Fi HaLow fills a gap in the IoT radio options of medium range and high data rate.

When evaluating a radio solution for an application, there are some primary metrics that are considered: range, data throughput and power consumption / battery life / battery size, scalability / node count, ease of installation and operation, security, and cost. The articles available from the links at the end of this document go into some detail about each of these, so a summary is presented here.

Range

Range and signal penetration is one of the first considerations for IoT radios. The actual range in a particular environment depends on several factors. Getting an apples-to-apples comparison of different systems without actually going into the field and testing them side-by-side is notoriously difficult. Most companies perform a calculation for “free space” operation using the Friis transmission equation. This includes the transmitter output power, receiver sensitivity, frequency of the signal and the antenna gains of the receiving and transmitting antennas. In addition to these factors, the environment plays a major role in system range. It is very difficult to generalize this impact. Anything between the two antennas will have an impact. Conductive objects like metal walls and equipment degrade the signal more than wood and sheetrock or trees and shrubs. Higher frequency transmissions have shorter range just by the physics or electromagnetic propagation, but also tend to interact with the environment more. Much more can be said about this, but that is another article.

Even though the environment of operation is such a big part of realized range, the difficulties in modeling its impact mean that most radio system manufacturers calculate the free space range for marketing purposes. The figure below shows a calculated range comparison between HaLow and LoRa and traditional Wi-Fi (802.11n) using published performance values.

LoRa is about 3.5 times the range of HaLow 1MHz channel performance, which is not surprising. This is the main feature of LoRa and is the basis for its name (Long Range). Both BLE and 802.11n were about 500m, which is comparable to the longest range for 802.15.4 radios (ZigBee, Thread). HaLow was over 3 times further at 1.71km.

In a real-world test, Newracom compared the range of an IP video camera sending data over 2.4GHz Wi-Fi (802.11n) and Wi-Fi HaLow. The results were that the HaLow link was able to send the video over 6 times further than the traditional Wi-Fi. The video of their testing is here.

Likewise, Silex Technologies conducted a real-world test and achieved 1Mbps at over 1 mile range. Their article is here. In both cases, the use of higher gain antennas could increase the range or data throughput within that range.

HaLow fills a gap between the Personal Area Network (PAN) systems of 802.15.4, Bluetooth and Wi-Fi and the Wide Area Network (WAN) of LoRa and cellular technologies. It offers longer range than PAN systems and much higher data rates than LoRa within that range.

Power Consumption

Power consumption is another of the major considerations for IoT radios. This directly impacts battery size and life and any ability for energy harvesting. IMEC Research Group conducted a study to compare the energy consumption of several sub-GHz technologies. The details can be seen in the study, but the comparison calculated the number of bits that can be transmitted using 1 Joule of energy. The figure below shows the results.

Wi-Fi HaLow is far more efficient than the other protocols. Newracom also conducted a study using the Silex SX-NEWAH module that is based on the Newracom NRC7292 SoC with a front-end amplifier module. Power consumption is shown in the figure below.

The time required to send 25kb in each technology is shown below.

The time required by LoRa is so much greater than BLE, Wi-Fi or HaLow that it throws off the scale for the other technologies. The second figure removes LoRa so that the other technologies can be better compared. Using these two metrics, the bits per Joule can be calculated.

As can be seen from the data, BLE, HaLow and Wi-Fi are all more efficient than LoRa, so are better choices unless the application requires the range.

HaLow is more efficient than BLE except at the higher ranges that BLE can’t reach.

The IMEC Research Group study also calculated the battery life for a 500mAh battery using the various technologies.

As can be seen, HaLow outperforms the other technologies. Newracom’s testing showed similar results.

The takeaway from this is that LoRa is best used for applications that need very long range and send very small amounts of data infrequently. If the range requirements are within 1 to 1.5km, HaLow offers a much better solution in terms of power and data throughput.

HaLow has a much higher peak current consumption than other common technologies, but it is for a much shorter duration. The battery used on a long-range HaLow-enabled device needs to be able to supply these pulse currents. They will not be able to operate on small coin cell batteries, but will be fine on larger cells and lithium packs.

However, the transmit power on the HaLow radio can be turned down to greatly lower power consumption. For applications that need lower power instead of greater range, the narrow band communication and sub-gigahertz frequencies enable a 0dBm output HaLow device to provide similar coverage to a 2.4Ghz 802.11b device transmitting at 17dBm. This can enable ultra-low power applications to operate with HaLow on small coin cell batteries.

Scalability

The number of nodes that can be supported by each gateway / boarder router / access point is a concern because it speaks to infrastructure costs. Supporting higher node counts lowers installation costs. Most IoT systems can intelligently manage 250 to 350 nodes. HaLow has the theoretical ability to support over 8,000 nodes with one access point. Newracom has tested over 1,000 devices on one access point, showing the capabilities of the technology.

Security

Wi-Fi has led advances in security over the years and HaLow benefits from this experience. Wi-Fi HaLow uses WPA3 and Wi-Fi Enhanced Open, the highest level of security developed for the latest Wi-Fi generation.

Ease of Installation

Installation of devices into the network will likely vary based on the application, but Wi-Fi HaLow offers several mechanisms developed specifically for IoT applications. IoT devices generally do not have screens, so the installer cannot look up SSIDs and enter passwords. New methods include QR codes, NFC tags or downloading device information from the cloud. The Wi-Fi Alliance has created Wi-Fi CERTIFIED Easy Connect™ as an option, but not required its use. This allows product developers to implement a method that makes sense for the application.

Cost

Wi-Fi HaLow is a brand-new technology with few options on the market at the moment. As such, it is at the top of the cost curve. While chips and modules are currently more expensive than any of the entrenched technologies, as second-generation chips hit the market and with mass market adoption, Wi-Fi HaLow will compete on costs.

Conclusion

Wi-Fi HaLow offers a fantastic new option for IoT applications. A medium range and high data rate radio fills a in the wireless technology options. Most technologies are focused on sending small amounts of data over a fairly short range using a little power as possible. HaLow provides the option of sending more data over a longer range. At Nexcomm Systems we believe that this will have a large impact in the Industrial market.

Vibration sensors on industrial machinery are a great example use case for Wi-Fi HaLow. They produce Mb of data in seconds that needs to be sent to a high-performance gateway or cloud server for analysis. The high data throughput allows this data to be transmitted quickly enough to have many sensors on each access point, which lowers the infrastructure costs. Further, the lower frequency offers greater penetration in industrial environments. With high data rates and long range, Wi-Fi HaLow will find a home in many IoT applications.

Nexcomm Systems has integrated the Silex SX-NEWAH module that is based on the Newracom NRC7292 SoC into our Nexus gateways to offer rugged, industrial cellular access points. In addition, we have integrated it into some SensePoint nodes to offer sensor hubs for traditional wired sensors and serial interfaces for existing controllers, drives and PLCs. Contact us for more information.