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Network World - This vendor-written tech primer has been edited by Network World to eliminate product promotion, but readers should note it will likely favor the submitter’s approach.
With 802.11n ratification a distant memory, news reports regarding this giant leap in WLAN capability have also waned. But while 11n has quietly receded into the background, WLANs have crept out of our data-only world and taken flight as full-fledged network platforms.
Platforms, after all, enable the development of compelling applications, right? So, what's more compelling than being able to stream video between your home office server and your 56" LED TV without wires? Or walking into your company headquarters while on your mobile phone and having your call automatically transition from the cellular network to the WLAN to take advantage of significantly better signal strength? It's all thanks to 802.11n -- complex technology that enables conveniences we will soon come to depend on.
Though ratified, 802.11n is still evolving -- not the specification itself, but the equipment capable of taking advantage of it. For the most part, technology is just now beginning to catch up to the capabilities outlined in 802.11n, with still years before there's parity between available equipment and the maximum capabilities 802.11n can offer. Let's take a look at a few of the key technological advances in 802.11n and see how current technology stacks up.
MIMO, or multiple-input, multiple output, is probably the first thing that comes to mind when people think about what's new in 11n. It is the most visible and the most talked-about of the advanced technologies. MIMO uses complex radio frequency (RF) technology that allows multiple data streams to be transmitted over the same channel using the same bandwidth that is used for only a single data stream in 802.11a/b/g.
Two streams deliver twice the data. Three streams deliver three times the data. This is also why 11n access points (APs) have more antennas than the older a/b/g models. At least one antenna is required per data stream, but keep in mind that not every antenna must be used for data, so the maximum number of data streams is limited by, but not necessarily equal to, the number of antennas on the AP.
This is one area where technology is just catching up with theory. The 802.11n specification allows for up to four data streams. Most currently available equipment takes advantage of only two data streams, but equipment is finally coming to market that uses up to three data streams. APs using four streams are still rare.
To take full advantage of the increased throughput the wireless clients must also be capable of operating at the same number of data streams as the APs, and wireless client adapters are a bit further behind the APs, making three-stream capable wireless adapters still somewhat hard to come by from commercial channels.
Channel bonding does exactly that, it takes two existing 802.11 channels and groups them together to form a single channel, with twice the bandwidth. Two times the bandwidth is essentially equal to two times the throughput, so this is another significant feature in 11n.