Edgewater Wireless Systems Inc (KPIFF)

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WiFi Evolves For The IoT

Extending the usefulness of a ubiquitous wireless technology.

AUGUST 6TH, 2020 - BY: BRYON MOYER
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WiFi is everywhere, and it’s the most prevalent of the communication protocols that use unlicensed spectrum. But as a common protocol for the Internet of Things (IoT), it faces challenges both because of congestion and the amount of energy it consumes.

Two new approaches aim to address those concerns. One is to use multiple channels at once. The second involves the new 802.11 ah HaLow standard. Both will go a long way toward extending a wireless communications technology that is virtually ubiquitous.

“There are 8 billion WiFi devices,” said Andrew Skafel, CEO of Edgewater Wireless. “No one ever envisioned WiFi would be that successful. That success has created a challenge as more devices try to connect through WiFi. If your performance declines, most of that decline is due to interference and contention.”

WiFi will play an important role as part of the new 5G ecosystem. “5G is too expensive for short distances,” said Rita Horner, senior staff product manager at Synopsys. “So you have Bluetooth from your computer or phone to your headset, WiFi beyond that, and then 5G beyond that.”

While WiFi can augment 5G, the opposite is also true if WiFi coverage or capacity lags. “5G millimeter wave in the United States uses the higher S-band, while in other parts of the world they use a lower frequency band for millimeter wave, where that can be used to replace or augment what you have on a cell phone and WiFi,” said Kurt Shuler, vice president of marketing at Arteris IP.

More efficient usage of available WiFi bandwidth can make for less congested WiFi traffic. Meanwhile, the introduction of devices using the new WiFi HaLow (IEEE 802.11ah) standard can transmit farther with less power. Together, they have the potential to serve the IoT market more effectively.

Exploding WiFi
When WiFi first became available, the IoT was not a consideration. “WiFi was the poor cousin to cellular,” said Skafel. The expectation was, “You’re going to connect your big clunky laptop to your modem in the basement.”

Since then, the number of devices looking to jump onto WiFi for communication has ballooned. “All of a sudden, WiFi has just increased and increased, and now it’s in every laptop and smartphone, and it’s the primary mechanism for the Internet of Things,” he said. The existence of other protocols using the same unlicensed industrial, scientific, and medical (ISM) bands may not compete with WiFi outright, but those protocols make reception less clean.

This results in two major challenges — interference and contention. Interference is simply the fact that multiple transmitters are using the same frequency range and degrading the signals, regardless of the nature of the signal. Within WiFi, interference is avoided by checking first to see if anyone is talking before transmitting. If someone is talking, there is contention, and the new transmitter must back off and try again later. The more devices that use the same frequency, the harder it becomes for them to gain access to the channel.

As the number of devices being connected has grown, WiFi has become increasingly crowded. Some of the connections use very little bandwidth, such as the IoT and smart-home devices. Others, like those streaming high-definition video, use a lot of bandwidth — and they’re very sensitive to latency. With too many devices competing for the same frequencies, performance degrades.

The structure of WiFi
Mainstream WiFi — which today would be 802.11n or 802.11ac — uses two main frequency bands. One is clustered around 2.4 GHz, and the other is clustered around 5 GHz. The expectation is that the 5 GHz range provides higher bandwidth, but the tradeoff is range and the ability to penetrate walls.

“The 5-GHz frequency goes half as far as 2.4,” said Skafel. “So propagation stinks. It doesn’t go through walls very well, so your performance falls off a cliff every time. You could put your hand in front of the access point, and you’d see a decline in performance.” Within those bands are channels, and actual transmission occurs on one of those channels for a given connection.

The availability of multiple channels means that multiple devices should be able to use WiFi without necessarily competing with each other. But, in fact, a given WiFi access point (AP) will use one channel. “In the 2.4 gigahertz band, you have 11 channels, maybe up to 13, depending on where you are,” he said. “And traditional WiFi has been able to use only one of those channels at a time.”

Which channel an access point will use is often set at the factory, and it never changes. Most access points just turn on and they go to a channel, although some will sniff to see which one is interference-free at that moment in time and then select that channel. But If an entire neighborhood happened to have fixed-channel access points from the same manufacturer, they would all be contending for the same channel, while all of the other channels would go unused.

“About the worst thing that can happen is that someone fires up another access point in that band,” he said. “And then what happens is both of those radios interfere with one another, and the performance degrades.”

One instinct might be to time-slice access to allow everyone on. But that’s not allowed, according to Skafel. “If you were to time slice, you actually break the WiFi protocol,” he said.

The next obvious answer would be for an access point to use more than one channel — even load-balancing traffic as conditions changed. While such dynamic adaptation may be a thing of the future, for now, just the ability to use more than one channel would be a major step in relieving congestion. But most of the channels overlap, limiting the number of channels that could be simultaneously active. In the 2.4-GHz band, only channels 0, 6, and 11 are non-overlapping.

Full article here

https://semiengineering.com/wifi-evolves-for-the-iot/