Can this Wi-Fi reach a kilometer away? Maybe…

Unlike most entries in this blog, I have not actually purchased or received the products mentioned. The purpose of this post is to give you a heads up on a Wi-Fi standard that was promulgated in 2017 and is now at the point of becoming a commodity item with some great potential. I will be getting some HaLow products in the future, so watch this space for updates on things worth buying to get your own HaLow network on the air. —Ya’akov

At the fall, 1999 COMDEX show in Las Vegas I was chairing a panel on the future of wireless networking attended by a few companies with competing standards. Each hoped theirs would prevail, of course. Also at the show was an obscure group with a 10x10 booth and a table. It was the “Wi-Fi Alliance” and one could be forgiven for being confused about just what they were selling.

There were no products on display, just some brochures. But the person manning the booth (whose name, regrettably, is lost to the fog of personal history) was very enthusiastic. What Wi-Fi Alliance was selling was—interoperability. Two years earlier, IEEE 802.11-1997 was promulgated describing the MAC (Medium Access Control), and PHY (Physical) layers for an IEEE 802 (variable frame size networks) standard for “WLAN” (Wireless Local Area Network).

The six companies that formed the alliance did it to promote the standard as a medium for interoperability on the the theory that it creates a bigger pie for everyone to allow consumers to be sure that things will work together. As the Wi-Fi person said, “Wi-Fi is a set of tests”. It was a promising if relatively quiet start for something that would become, literally, the fabric that delivers the Internet.

Over the years, Wi-Fi standards multiplied and the trend has always been faster—faster data rates, and also faster oscillations. To get more bandwidth the constant striving to increase the operating frequency of Wi-Fi meant each new standard also used a new and faster chunk of spectrum.

Back in 1999, I was using a product from NCR called WaveLAN. This was a 2 Mbps wireless network operating in the license-free 900 MHz ISM (Industrial, Scientific, Medical) band, using the foundational technology of what would become 802.11, and eventually Wi-Fi. But Wi-Fi certified products started out at more than twice that frequency in the 2.4GHz ISM band.

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higher and higher—until it wasn’t

802.11n (Wi-Fi 4), 802.11ac (Wi-Fi 5), 802.11ax (Wi-Fi 6/6E), 802.11be (Wi-Fi 7), and the future 802.11bn (Wi-Fi 8) which will use frequencies as high as 71GHz and offer data rates up to 1Gbps—always higher always faster. Enter 802.11ah (HaLow) and a sudden drop to the sub-GHz frequencies, in fact, the same band as the 1997 WaveLAN used but with quite a difference in technology and result.

Quietly, 802.11ah devices have become available at the consumer level, like this HaLow point-to-point set.

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point-to-point ethernet connectivity up to 1km

But what is it?
802.11ah, called Wi-Fi Certified HaLow—pronounced “halo”(read the whitepaper), is a standard that’s been around a while but is now getting traction thanks to the appearance of SoC’s implementing the standard. It is the familiar Wi-Fi, with changes and extension to operate in sub-GHz ISM bands¹.

It is intended to compete with various other low power and long range standards, and offers several advantages:

  1. Low power consumption operation, competing with Bluetooth, Zigbee, and LoRa while offering much longer range than the first two and much higher data rates than the last. The Wi-Fi alliance claims a HaLow device can be powered for months or years on a coin cell.
  2. HaLow operates peer-to-peer and so requires no hubs or gateways. It can operate on a one-to-one or one-to-many basis, and can be operated as a mesh network.
  3. It uses OFDM for very narrow band operation, one of the factors limiting power consumption.
  4. It uses Wi-Fi security, allowing for secure connections as a native part of the standard.
  5. Unlike Bluetooth, Zigbee, and LoRa, it has native support for IP—a big implementation advantage.
  6. Even with its relatively high data rate, it can provide up to 1km of reach (depending on several factors including chosen data rate and environmental conditions, but even limited by these, it is much longer range than other options).
  7. The lower frequency operation means much better penetration through difficult materials, such as concrete.

License Free
Like its competition, HaLow operates in the ISM bands and so the actual operating frequency varies from region to region. In the US, it operates in the 902-928MHz band, while in Europe there is 7MHz of bandwidth combined in the 800MHz and 900MHz bands. In the US, the maximum width, 16MHz channels are supported.

High Speed (or Low Power)
Data rates vary depending on channel size, and go from 150kbps to 80Mbps! The higher data rate is unattainable by any competing technology². This means that you can use one standard for communications from simple sensors that need only very low data rates and require very low power consumption to devices that require high bandwidth and can tolerate the demand for power to make it happen (e.g.: security cameras).

One Protocol for Everything
This single standard operation is a big advantage as it creates a homogenous environment all using IP to communicate. Data communications protocol translations via gateways or hubs is not necessary simplifying architecture.

Use It Today (for Some Things)
The security camera industry has embraced HaLow and is the first heavy user of the protocol. You can now buy cheap modules for transmitting video over HaLow and I expect there will soon be integrated HaLow on MCU development boards as the availability of low cost SoCs for the protocol increases.

You can use HaLow today to bridge a Wi-Fi gap as a point-to-point link over a distance outdoors, or to improve connections in problematic buildings, and this is great stuff, but keep an eye on this because it is poised to displace a lot of things in the near future.
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1. Another standard, 802.11af, also operates in the sub-GHz range but uses cognitive radio technology to operate in unused portions of the VHF and UHF television allocations and requires licensing.

2. Of course there is always a cost to the higher data rates in terms of power consumption, and operating distance will be reduced—but if you need it, you need it.

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