CES: Gigabit Wi-Fi takes center stage

John Cox, Network Worl, 1/9/2012

Goodbye Wi-Fi … at least as we’ve known Wi-Fi.

At this week’s Consumer Electronics Show, next-generation radio chips will finally make real what most people have only imagined for the past three years: Wi-Fi connections that measure their data rates in gigabits per second.

And if you’re in Las Vegas at CES 2012, vendors will show next-generation Wi-Fi in two different frequencies: 5GHz, for what will eventually be the IEEE 802.11ac standard, and 60GHz, for what will eventually be 802.11ad. The former can reach data rates of 1.3 gigabits per second, the latter, up to 7Gbps.

Usable throughput for the new Wi-Fi will be less, and the actual rate, and resulting throughput, depends on a range of factors including the width of the channels and the number of data streams and antennas. And initial products, due as early as mid-2012, likely won’t achieve the maximum data rates. But by contrast, 802.11n typically has a data rate of 150 megabits per second.

Initial products, likely a blend of infrastructure devices such as residential routers, access points and the like on the one hand, and client plug-in dongles for PCs and flat panel TVs, are expected as early as mid-2012. Both new specifications are backward compatible with the existing Wi-Fi standards, so your 11n tablet or smartphone will connect to an 11ac wireless router, even though you won’t get the benefit of an end-to-end 11ac boost. Likewise, your new 11ac dongle for your laptop will still connect at 11n or 11g rates to an existing access point.

Both of the formal IEEE standards are still in process, and won’t be final until probably 2013. But, as with previous wireless standards, vendors and the Wi-Fi Alliance are forging ahead with products that track the current standards closely. At this point, most observers expect any IEEE changes to be minimal, and that software updates will bring the products up-to-date.

The huge data rate increase will enable wireless in these unlicensed bands to speedily transfer vastly larger video, photos and data files, or to transfer the same amount of data in a fraction of the time compared to 11n and the still older 11g connections. And “advances in technology inherent in 802.11ac should result in improved range, reliability, coverage, and battery life over .11n,” according to Network World wireless blogger Craig Mathias.

“I’m expecting very rapid uptake of 802.11ac once products are available,” Mathias writes. “I don’t expect much of a price increase over 802.11n …”

First products are just months away

Chipmaker Broadcom last week announced that samples of its new family of 11ac chips are in the hands of a range of customers, including carriers. The company offers chips that support one, two and three data streams, with data rates respectively of 433Mbps, 867Mbps and 1.3Gbps. The press release quotes executives from nearly a dozen equipment manufacturers and other vendors, from Asus to ZTE.

Several vendors, such as Buffalo Technology, will be running 11ac “technology demonstrations” using the Broadcom chips at CES, and some of them will be announcing products for release later in 2012, perhaps as early as mid-year. The Wi-Fi Alliance is expected to make an 11ac announcement, likely dealing with the organization’s planned certification of products implementing the new very high-throughput Wi-Fi standards.

Buffalo Technology has said it will show a technology demonstration of a 5GHz product late Monday night, Jan. 9, Las Vegas time, but declined to go into details beforehand. The product uses Broadcom’s new family of 802.11ac chips.

(Taiwanese chip designer MediaTek revealed details of a powerful new system-on-a-chip that’s designed to handle processing and other chores for new gigabit Wi-Fi access points and routers using 802.11ac radio chips, including MediaTek’s own.)

Another group of vendors will demonstrate a complementary Wi-Fi standard running in the 60GHz band. The higher frequency means 802.11ad has less “penetrating power” than its lower frequency cousin. But 11ad has much more available spectrum, and still wider channels, and hence a much larger “wireless pipe” through which energy, and data, is being pushed. By relying on this spectrum, 11ad avoids the need for some of the innovative, but necessarily more complex, features in 11ac to maximize performance. Radios based on 11ad will forge short-range, very high-throughput connections between clients and access points and among client devices themselves. An example is in-room video distribution, between a set top box and various displays, or between a tablet and a large flat panel TV.

How do the specifications get their big data rate boosts?

The 11ac spec does it by improving a variety of technologies introduced with 802.11n. It uses the multiple data streams and multiple transmit and receive antennas (a technology called MIMO), but it uses more of them compared to 11n, up to eight data streams versus four for 11n, for example.

With 11ac, the wireless connection will make use of an even wider channel, or “pipe,” for data. In a conventional 20MHz channel, 802.11n with one spatial stream supports 72Mbps. Doubling the channel size to 40MHz boosts that data rate to about 150Mbps. By contrast, 11ac channels will be 80MHz, with an option to go to 160MHz: each stream has a data rate of 430Mbps, with three data streams reaching 1.3Gbps.

The wider channels will eventually pose a challenge for WLAN administrators. “At 80MHz, channel layout once again becomes a challenge, even in the relatively expansive 5GHz spectrum,” according to Matthew Gast, director of product management, Aerohive Networks. “Manufacturers will need to adapt automatic radio tuning capabilities to offer higher-bandwidth channels only where necessary to conserve spectrum.”

As did 11n, 11ac boosts the efficiency of the data transmission by using a much denser way of physically encoding the data on a carrier signal, in this case a radio wave. The encoding is done by changing (“modulating”) features of the signal, in this case using a scheme called quadrature amplitude modulation, usually called just QAM. 11n uses what’s called 64 QAM, but 11ac quadruples the density to 256 QAM.

11ac Wi-Fi will operate only in the 5GHz band, where for now there are many fewer devices and much less interference than in the 2.4GHz band.

A related change, noted by tech blogger Anand Lal Shimpi, writing at AnandTech, is one that will remove an on-device bottleneck created by the SDIO I/O interface, used in the Secure Digital specification, and its drivers. Currently, he notes, smartphones or tablets with 11n typically operate at 2.4GHz with a single spatial stream, for a maximum data rate of 72Mbps, and about half that for actual throughput. Though SDIO has a maximum bandwidth of 100Mbps, its software stack can limit that to the 30-40Mbps range, according to Lal Shimpi.

11ac will support an additional, more modern USB interface, High-Speed Inter-Chip or HSIC, with a maximum throughput of 480Mbps (it also uses half the power and takes up 75 percent less board area than conventional USB, according to the Wikipedia entry).

“Given that smartphones and tablets are expected to use single stream 802.11ac at 433Mbps, HSIC looks to be the appropriate SoC interface,” says Lal Shimpi.

11ac will draw more power, yet it could actually improve average power consumption in some cases, according to Lal Shimpi, in a separate introductory post on 11ac. The reason? “The specification is simply more complex and supporting things like wider channels requires more power,” he writes. “Although 802.11ac chipsets built on the same process as their [11]n counterparts will draw more active power, their higher performance should allow the WiFi stack to go to sleep sooner. Idle power in a well designed 802.11ac solution should be comparable to 802.11n, and a race to sleep generally results in improved average power.”

The 60GHz Wi-Fi products will be, relatively speaking, simpler than 11ac. More spectrum and still wider channels create a larger wireless pipe, supporting eventually the near-7Gbps data rate, though the first group of products, also expected around mid-2012, will likely be 1-2Gbps.

Blogger Mathias argues that this virgin spectrum, coupled with the new channel allocation challenges 11ac will create in the 5GHz band, mean that 11ad could have a role as an infrastructure connection in the enterprise. That could mean future Wi-Fi products that can switch, or be forced to switch, between 11ac and 11ad as needed, depending on what the client wants to do, the type and volume of data, other contending client devices, and the surrounding RF environment.

But if you’re in Las Vegas this week, you’ll have a chance to see a not-so-distant future with the first demonstrations of next-generation Wi-Fi.

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Posted on January 9, 2012 at 4:22 pm by lesliemanzara · Permalink
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