There are two new standards for WiFi that will be hitting the market in the next few years. The standards are 802.11ac and 802.11ad. The two new standards use different spectrum with 802.11ac at 5 GHz and 802.11ad at 60 GHz. Both new Wifi standards will be able to deliver up to 7 gigabits per second, compared to today’s WiFi that tops out at 600 megabits per second.
Looking at basic spectrum characteristics there are four major differences in the way these two standards will use the spectrum: bandwidth available, propagation characteristics, antenna size and interference.
The maximum data speed that can be delivered by any radio spectrum is limited by the amount of spectrum used and the signal-to-noise ratio. This limit is defined by the Shannon-Hartley Theorem. The 802.11ac at 5 GHz can use about 0.55 GHz of spectrum. The 802.11ad at 60 GHz can use up to 7 GHz. 802.11ac has channels that are 160 MHz wide while 802.11 will have channels that are 2,160 MHz wide. But the channels in 802.11ac can be bonded which will allow it to deliver almost as much bandwidth as 802.11ad.
802.11ac will use the same 5 GHz spectrum that is used by today’s Wifi and will have similar propagation characteristics. But the 802.11ad spectrum at 60 GHz will not travel through bricks, wood or paint and thus this technology will be most useful as an in-room technology.
For these spectrums to achieve full potential they need to be able to transmit multiple signals, meaning that they need multiple antennas. Antenna size is proportional to the wavelength being transmitted. A 5 GHz antenna has to be about an inch long and spaced at least an inch apart to be effective. But 60 GHz antennae only need to be 1/10 inch long and apart. This is going to make it easier to put 802.11ad into handsets or into any small device.
Finally is the issue of interference. There is already a lot of usage in the 5 GHz band today. In addition to being used for WiFi the spectrum is used for weather Doppler radar. There are also a few other channels in the band that have been allowed for other uses. And so 802.11ac will have to work around the other uses in the spectrum. The 60 GHz spectrum range is mostly bare today, and since this will go such short distances there should be very few cases of interference. However, multiple 801.11d devices in the same room will interfere with each other to some extent.
The 80211.ac standard is pretty much set but won’t be fully certified until 2014. However, there are already devices being shipped that include some of the features of the standard. For example, it’s included in the Samsung Galaxy S4 and MacBooks. But today’s version uses beamforming to send the signal to one device at a time. Beamforming means that the signal is sent to one device from each separate antenna in an array, but at slightly different times.
Still to come is the best feature of 80211.ac, which is to support separate sessions with different devices, different priorities and different power needs. This feature is called multi-user MIMO and it will revolutionize the way that WiFi is used. For example, you will be able to make a WiFi voice call while simultaneously downloading a video from another device. Your WiFi chip will determine the location of each device you will be talking to and will initiate a prioritized session with each. In this example it can give priority to the voice call.
The fully deployed 80211.ac will be the first generation wireless that is getting ready for the Internet of Things. It will be able to communicate with multiple devices in the environment at the same time. It will turn smartphones and tablets into workhorses able to gather data from sensors in the environment.
802.11ad is going to be far more limited due to its inability to pass through barriers. The most likely use for the spectrum will be to create very high-speed wireless data paths between devices, such as connecting a PC or laptop to a wireless network. It should be able to achieve speeds approaching 7 Gbps with only one device and one path in play.
One would expect by 2016 or 2017 for devices using these two technologies will become widespread. Certain in the telecom industry an upgrade to 802.11ac will allow carriers to deliver more bandwidth around a home or office and be able to handle multiple sessions with wireless devices. This new technology is a fork-lift upgrade and is not backwards compatible with earlier WiFi devices. This means it will take some time to break into the environment since all of the local wireless devices will need to be upgraded to the new standard. One would expect first generation 802.11ac routers to still include 802.11n capabilities.