WiFi Preps for 5G, IoT Roles
Next-gen 60 GHz effort begins
Rick Merritt
12/29/2014 09:10 AM EST
SAN JOSE, Calif. — WiFi standards in the works are preparing the hotspot technology for roles that range from 5G cellular backhaul to networking the Internet of Things, say two researchers working in the area. The efforts promise enhanced versions of WiFi running from 900 MHz to 60 GHz.
The so-called NG60 study group has had just two meetings so far and may require as much as two years to complete its first draft standard. It is working on an upgraded version of the 60 GHz version of WiFi, 802.11ad, capable of delivering 20 Gbit/s over a very short range.
Ultimately, NG60 also may include hardware support for mesh networks that could deliver a Gbit/s over 200 to 400 meters for backhaul links on small-cell base stations. Researchers at InterDigital Inc. are building a prototype of a 60 GHz directional mesh architecture using electronically steered phased array antennas that could support up to five hops.
“We’re now working on a software layer above the media access controller, but if the mesh can move to lower levels it becomes more efficient,” says Monisha Ghosh, a principal engineer at InterDigital who was recently named an IEEE fellow for her work in wireless.
A handful of 60 GHz chip vendors already are pursuing cellular backhaul as one application for chips based on the current 802.11ad standard. The NG60 work could enable a new version of chips supporting longer distances, higher data rates, and other new features.
Researchers at InterDigital and elsewhere are also developing simulations of channel models at millimeter wave frequencies such as 60 GHz. The efforts help pave the way for licensed and unlicensed 5G cellular services, which are expected to use still undetermined bands between 28 and 300 GHz.
“The spectrum today below 6 GHz lacks the bandwidth needed for the thousand-fold improvements people want,” says Ghosh.
The US Federal Communications Commission has put out notices of inquiry about how it may handle millimeter wave bands. An NOI on opening up the 64 to 71 GHz band for unlicensed uses for technologies such as WiFi has sparked particular interest.
“That would be a huge boon for WiFi… expanding by another 7 GHz, essentially doubling upper band use of WiFi,” notes Ghosh
Separately, engineers are working on an 802.11ax, essentially a suite of features bundled together under the concept of carrier-grade WiFi. The work would enable faster uplinks as well as faster connections in dense areas such as airports and train stations.
“When WiFi started, uplink wasn’t a big deal," says Ghosh, "but now everybody has Facebook and takes video so uplinks could use frequency or spatial multiplexing” to support more and faster uplinks.
The spec will embrace work in .11ai on fast initialization so access points (APs) don’t get swamped when groups of users try to connect at the same time. Other new features add to the sense of a more robust and reliable WiFi service.
“Today you can’t roam from AP to AP, and WiFi can get flooded faster than cellular… At a high level I see [carrier-grade service] as the big hope for .11ax,” says Robert DiFazio, chief engineer at InterDigital’s labs.
The .11ax spec aims to provide services for both 2.4 and 5 GHz bands. The task group started work earlier this year and could deliver a draft specification by the end of 2015, enabling certified devices in a couple years.
Separately, a first draft is already available for a narrowband version of WiFi at 900 MHz to link IoT nodes. The 802.11ah standard targets 100 kbits/s at a kilometer range using a 1 MHz mode.
Supporters hope to leverage the considerable WiFi ecosystem to make up for the fact they are late to IoT applications at 900 MHz, which have been served by many years by chips using the 802.15.4 radio standards. To speed time to market, the .11ah standard uses the existing .11ac media access controller with improvements to its power efficiency.
The .11ah work represents one of many 900 MHz efforts seen as promising for IoT. The band is on the rise at a time when engineers are starting to give up hope for global regulations opening the way for 700 MHz services sometimes known as TV white spaces (TVWS).
“From my perspective, it’s been a long haul,” says Ghosh, who has been working on 700 MHz efforts since 2004.
“We see some commercial [700 MHz] products out there, but most of them tend to be in niches pursued by small companies, many of them proprietary approaches,” says DiFazio. “We still look at it as promising technology, but one where companies are still not that excited about the market uptake.”
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