By contrast, 11ac can support as many as eight spatial streams. Yet no one expects to see that many, at least not soon and possibly ever. "Handheld clients in 11ac will probably continue to be single stream, because of size and power constraints," says Greg Ennis, technical director for the Wi-Fi Alliance, the industry group that's creating an 11ac interoperability testing and certification program.
Broadcom's Bekis says that most of the chip vendor's customers see three streams as offering the best cost-benefit trade-off. But he emphasizes those will be three 11ac streams, for a total capacity of 1Gbps compared to 300Mbps to 400Mbps for a three-stream 11n implementation.
One effect of 11ac that's not been widely noted is that 11ac radios can save battery power. Apart from efficiencies derived from advances in silicon processes and power management, 11ac's power boost is due to one simple fact: Because it can move the same amount of data so much faster, the radio shifts back into low-power mode much faster as a result. Broadcom, for example, claims its 11ac combo chip is six times more power efficient "than equivalent 802.11 solutions."
That doesn't mean your battery will last six times longer, but depending on your data behavior, it can extend battery life and give mobile device designers a bigger "power budget" to work with.
The IEEE draft specification has already gone through several rounds of balloting, says Greg Ennis of the Wi-Fi Alliance. Final IEEE approval isn't expected until early 2014. But products based on the draft are already shipping: Both Netgear and Buffalo Technology released routers in May.
The WFA plans to launch its 11ac certification program in early 2013, and products are expected to be announced if not shipping within weeks after that.
John Cox covers wireless networking and mobile computing for Network World. Twitter: http://twitter.com/johnwcoxnww Email: firstname.lastname@example.org
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