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In the off-the-wall Ruckus Room, in which the company speaks in something approaching a real voice, they maintain that 802.11n buys you bandwidth not QoS: And they’re right, of course. They have a real nice business in providing hardware and algorithms that make IPTV (that’s video over IP) work reliably using multiple antennas and beamforming. 802.11n adds a standardized method of having multiple radios split data into simultaneous but unique streams that follow different reflective paths at the same time, which is called spatial multiplexing. It’s a way of reusing the same spectrum by sorting out signals passing through the same physical space.
Ruckus notes that this might improve bandwidth but it doesn’t do anything for ensuring that streaming video works without a hiccup. They don’t mention 802.11e, which offers prioritization of streaming video packets, in this context, but 802.11e won’t necessarily work as expected within 802.11n. Why? Because 802.11e provides a way of tagging packets to ensure that some get more precedence over others, but it doesn’t ensure that the optimal methods are used to move data so that it arrives with the least amount of lost packets or least retransmission (depending on protocol).
With video, it’s not just important that packets arrive with priority over others, but that there are no gaps in arrival longer than the buffered interval stored on the receiving device if you want to have clean streaming and avoid artifacts. Ruckus claims their technology can overlay 802.11n to provide this. It’s definitely the next big wave, with many companies talking about 802.11n as having the bandwidth for multiple simultaneous high-definition video streams.
Of course, there’s still the other IP (intellectual property) part of this equation. While specific paired devices, such as those used in Windows Media Edition systems, can move video content around a network, there’s no generic accepted approach for taking high-def off the air or off future high-def DVDs (BluRay or HD-DVD) and streaming them to other devices. That’s an application-layer problem that involves lawyers, but it’s got to be solved if the vision of HD zooming around a home is to be achieved beyond specialized home electronics.
Posted by Glennf at April 20, 2006 1:13 PM
Wouldn't the underlying layers take care of the re-ordering of the packets.
[Editor's Note: It's not the re-ordering. That's a basic part of any packet-based system. It's the timing, synchronization, and priority. --gf]
Posted by: d at April 20, 2006 5:27 PM