IEEE 802.11n, also known as 802.11n, is a wireless network standard using multiple antenna for increased data transfer rates. This standard was introduced to increase the network bandwidth compared to the existing standards (802.11a and 802.11g). The maximum bit rate has also been increased from 54 Mb/s to 600 Mb/s (megabits per second). 802.11n can operate at two frequency bands: 2.4 GHz or 5 GHz.
MIMO is a technology using multiple antennas to send a larger volume of data compared to a single antenna. The technology uses SDM (Spatial Division Multiplexing), in which multiple individual spatial data streams are transferred simultaneously in a single spectral channel. MIMO SDM technology allows to increase the bandwidth as a number of individual spatial data streams, however, each spatial stream requires an antenna, both in the transmitter and in the receiver. MIMO technology requires a converter and an analogue-digital converter for each antenna, which is a costly solution compared to non-MIMO systems.
The number of parallel data streams is limited by the minimum number of antennas used on both ends. The individual radio connections also limit the number of spatial streams that can include unique data.
With identical operating parameters compared to 802.11g network (54 Mb/s in a single 20 MHz channel with a single antenna), 802.11n network offers 72 Mb/s (in a single 20 MHz channel with a single antenna). 802.11n bit rates may be increased up to 150 Mb/s using two 20 MHz channels in 40 MHz mode without interferences, e.g. Bluetooth devices, microwave ovens or Wi-Fi devices. With a large number of antennas, 802.11n bit rate can reach up to 288 Mb/s at 20 MHz for four antennas or 600 Mb/s at 40 MHz for four antennas.
Data transfer at 600 Mb/s can be achieved for four spatial streams in a single 40 MHz spectral channel. Different types of modulation and coding are defined by the standards and stored in the modulation and coding scheme (MCS – Modulation and Coding Scheme). To achieve the maximum 802.11n efficiency, a 5 GHz network is recommended. 5 GHz band has a great potential due to the availability of multiple non-overlapping radio channels and reduced interference compared to 2.4 GHz band.
2.4 GHz band is relatively overcrowded. With 802.11n, the bandwidth for a single 40 MHz channel can be doubled, also doubling the bit rate.
General 802.11n certification includes 20 MHz and 40 MHz channels. For up two spatial data streams, the bandwidth is 144.4 Mb/s at 20 MHz and 300 Mb/s at 40 MHz (with a short interval).