Nuts and Volts - July/August 2018

peak in activity, it may not be able to deliver high speed streaming to a customer. So, the cellular operator offloads the data streaming to their Wi-Fi network. That works, but eats up spectrum that could otherwise be used by other services.

What’s Next?

The real question is where does Wi-Fi go from here? Up to now, the IEEE 802.11 standard group has focused mainly on incremental boosts in data rate and capacity. At this point, more speed may not be necessary.

For example, an upgrade of the 11ad 60 GHz standard designated 11ay is in the works. It offers a channel bandwidth of 8 GHz and a 4x4 MIMO configuration that can generate a max speed of up to 20 Gb/s. Do we need it?

Also consider that Wi-Fi has multiple offshoots that have not been based on the speed/capacity upgrade path. For example, a modified version of 802.11a called 802.11p has been proposed for vehicle-to-vehicle (V2V) communications systems that are planned to enhance the advanced driver assistance systems (ADAS) that are now being installed in most new cars. V2V allows cars to talk to one another so as to share location, speed, direction, stopped, or turning condition, and other data that can help avoid collisions.

Then, there are the 802.11af and 802.11ah standards. Both use a version of the Wi-Fi protocols but in different frequency bands. Both target Io T applications. For example, the 11af version uses the available “white space.” White space is the empty 6 MHz wide VHF and UHF TV channels commonly available in most areas. These lower frequencies in the 54 to 698 MHz range permit longer range communications of many kilometers. Traditional Wi-Fi range is typically only up to about 100 meters.

As mentioned, the 11ah standard also targets Io T uses. It’s designed to use the 902-928 MHz ISM band in the US.

Using 1, 2, 4, 8, or 16 MHz channels, it can achieve data rates up to about 100 kb/s. Speed is not usually needed in most Io T uses, so it’s not a problem. The propagation capability in the 902-928 MHz band is excellent and under good conditions like high antennas, range can be a kilometer or more.

Neither 11af or 11ah have been widely adopted. Most Io T applications today are the slower Wi-Fi standards, Bluetooth, ZigBee, Z-Wave, or some variation of the

802.15.4 standard like Thread. All of these with the exception of the Z-Wave operate in the already crowded

2. 4 GHz band.

Another emerging wireless technology is Li-Fi or Light Fidelity. It uses visible light as the data carrier. White LEDs illuminate spaces and are modulated by the data. High data rate downloads are easily accommodated. The range is limited because of the direct line of sight (LOS) path light takes, but it could be useful in some office or industrial settings as it is very secure. Li-Fi is not officially part of the Wi-Fi family, but who knows what will happen?

Finally, the big question is how does the new fifth generation (5G) wireless network impact Wi-Fi? 5G will deliver Wi-Fi like speeds to homes and businesses.