Gigabit Wi-Fi = bonus hetnet spectrum

28 Jun 2013

ITEM: The Wi-Fi Alliance began certifying 802.11ac gear for interoperability with other Wi-Fi products this week, and that could spell great news for the mobile sector in terms of spectrum availability, according to experts.

That’s because 802.11ac – which promises theoretical peak data speeds of 1.3 Gbps – operates on the 5-GHz band as well as the 2.4 GHz band.

Existing Wi-Fi standards 802.11a and 802.11n already support the 5 GHz band, of course. But most Wi-Fi-enabled devices typically don’t, because 2.4 GHz is commonly available, and it costs more money to stuff another frequency inside a device that’s already expected to support Wi-Fi, Bluetooth, GPS and up to half a dozen cellular bands.

That said, new devices like the iPhone 5 and Samsung Galaxy S4 – which have prestandard 11ac chips inside them – can make use of 5 GHz, but they won’t unless the AP also supports it.

However, between the Wi-Fi Alliance’s certification of 11ac devices, the promised data boost and the fact that the 2.4-GHz band is way overused, the argument for using 5 GHz becomes very compelling, reports NetworkWorld Asia:

Capacity is key for mobile operators, especially in crowded locations with many heavy users of mobile data. Carriers are picking up some additional frequencies through expensive auctions of private spectrum, but Wi-Fi networks running on free, unlicensed spectrum are a key element of their strategies. In busy places with heavy mobile users, such as airport lounges, the 2.4GHz band is starting to fall short, according to Yankee Group analyst Ken Rehbehn.

"The older Wi-Fi bands are just hideously overcrowded right now," Rehbehn said.

The 5GHz band, by contrast, has 25 distinct channels totalling about 500MHz of spectrum. It hasn't been used as heavily for Wi-Fi and isn't as crowded with other technologies, such as Bluetooth.

That does lead to a potential chicken/egg scenario: will carriers deploy/upgrade to 11ac before devices are ready to support it? And do device makers want to integrate 11ac chips before the 11ac-compatible APs are deployed?

Well, we’ve been here before with 11n, so that will sort itself out. And, as it happens, PCCW-HKT is already on the case. Earlier this week the Hong Kong incumbent announced plans to deploy a network of 802.11ac access points from Cisco Systems connected with gigabit fiber backhaul.

Meanwhile, carrier interest in small cells and hetnets could drive 11ac adoption, if only because spectrum availability is already expected to be tight in such scenarios – the ability to tap into more spectrum to offload traffic is always an attractive proposition.

On the other hand, as ZDnet points out, 5 GHz has a shorter range than 2.4 GHz. It does have beamforming capabilities to make up for that, but how well that works is going to depend on things like how many other APs or devices you’re competing with in that band.

ZDNet has a nice list of some other things operators will need to think about when integrating 802.11ac into their hotspot plans. At the top of the list: good luck getting an actual gigabit connection with it.

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