As with other members of the 802.11 family of standards, 802.11n supports fallback rates when a connection cannot be made at the maximum data rate. Using the shorter 400 ns guard interval would increase this to up to 216.7 Mb/s. However, in the real world the shorter guard interval doesn’t normally cause problems, so it is enabled by the default configuration in most devices.Ĭombining the use of three data streams using standard 20 MHz channels and the standard 800 ns guard interval, the maximum throughput of a Wireless-N connection would be 195 Mb/s. Just as with channel bonding (40 MHz channel width), this can cause problems if there is excessive interference or low signal strength, resulting in decreased overall throughput due to signal errors and retries. By decreasing the guard interval from the standard 800 ns to an optional 400 ns, the maximum bandwidth increases by about 10%. In the real world I’ve seen throughput decrease dramatically with 40 MHz channels, such that the use of 40 MHz channels is disabled by default on most devices.Īnother optional feature is using a shorter guard interval (GI), which is the amount of time (in nanoseconds) the system waits between transmitting OFDM (orthagonal frequency division multiplexing) symbols in a data stream.
In addition, the wider channel takes up more of the band, causing more interference with other wireless networks in range. I say “in theory” because using the wider channels works well under very strong signal conditions, but can degrade rapidly under normal circumstances. By using channel bonding to increase the channel width to 40 MHz, more than double the bandwidth can be achieved in theory. The base configuration uses 20 MHz wide channels with an 800 ns guard interval between transmitted signals. The highest performance Wireless-N devices generally available on the market today use a 3 x 3:3 radio configuration, which supports three data streams for up to 450 Mb/s in bandwidth.Ĩ02.11n is significantly faster than 802.11g, but by how much? That depends mainly on how many data streams are supported, as well as whether a couple of other optional features are enabled or not. Those using more antennas than data streams allow for increased signal diversity and range.
Other common configurations include 2 x 2:2, 2 x 3:2, and 3 x 3:2, which include radios with 2 or 3 antennas supporting up to two data streams for up to 300 Mb/s in bandwidth. Common configurations that are used in Wireless-N devices include 1 x 1:1, 1 x 2:1, and 2 x 2:1, which include radios with 1 or 2 antennas supporting only a single data stream for up to 150 Mb/s in bandwidth. The maximum performance configuration supported by the standard is 4 x 4:4, (4 transmit/receive antennas and 4 data streams), which would support bandwidths of up to 600 Mb/s, however no devices are currently on the market using that configuration.
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