The Power of 802.11 Draft-N 3x3

posted by David Angell on July 30, 2008

802.11 Draft-N is hot – up to 300 Mbps of bandwidth today with up to 450 Mbps of bandwidth tomorrow. But did you know that not all 802.11 Draft-N products are the same? To be a connoisseur of these differences, a little background is required.

The dramatic performance and range improvements of 802.11 Draft-N didn’t just come out of thin air. Well, actually they did thanks in large part to MIMO (pronounced my moh). Multiple Input, Multiple Output (MIMO) is a wireless breakthrough that takes on the physics of wireless signals by exploiting a radio-wave phenomenon called multipath. When a radio sends a signal, that signal will start to weaken as the distance from the transmitter increases. In addition, that signal can also get reflected and/or absorbed by walls, doors, or other obstacles resulting in weaker copies of the original radio signal.

802.11a/b/g networks with their simple Single Input, Single Output (SISO) technology can only receive and decode a single copy of these radio signals (usually the strongest signal received). 802.11 Draft-N networks with MIMO allow multiple antennas to receive multiple copies of the same signal in order to reconstruct the original signal. The more signals processed, the higher the likelihood of reconstructing the original signal. As a result, MIMO enables at least a 2x increase in range compared to SISO technology.

MIMO also uses multiple antennas to transmit multiple data streams (called spatial streams). By transmitting data over multiple antennas, performance or bandwidth increases by up to 5x with 300 Mbps Access Points and 8x with 450 Mbps Access points compared to SISO’s 54 Mbps single data stream. To use a highway metaphor, SISO systems are single lane roads and MIMO systems are multi-lane highways. More lanes mean more vehicles (i.e. data) at any given time.

Another point of interest is that MIMO supports different antenna configurations. A 1x2 configuration refers to a wireless device with 1Tx (transmit) and 2Rx (receive) antennas resulting in a receive data rate of up to 300 Mbps. Similarly, a 3x3 configuration typically refers to 3Tx and 3Rx antennas for a data rate of up to 450 Mbps when connected to tomorrow’s 450 Mbps Access Points; that’s 50% more than today’s 300 Mbps data rate.

Of course, these are raw data rate numbers and as with any wired or wireless network, are impacted by all kinds of factors, including Laptop configuration, network overhead, user congestion, distance, obstacles, and other types of interference.

The Intel® WiFi Link 5300 adapter for the new Intel® Centrino® 2 platform taps the raw power of 3x3 on the client side. And while no 3x3 APs are currently available, with performance numbers like these it’s only a matter of time. In the meantime, you can connect to today’s 802.11 networks including Draft-N APs. The bottom line is that for my next laptop purchase, I want the Intel® WiFi Link 5300 adapter for future-proofing. This performance will definitely come in handy for today’s and tomorrow’s apps like streaming HD video, mega-pixel photos, extreme gaming, gigabyte music collections, backups, etc.

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tagged: 3x3, 802.11, draft-n, intelcentrino2, intelwifilink5300, mimo, multipath, siso, wifi