Wireless N Networking refers to computers networks that follow specifications in IEEE 802.11n standard. 802.11n is a significant improvement over the previously used specification 802.11g regarding throughput, security with additional features such as error correction.

History of Wireless N

Development of 802.11n began in 2002. Multiple drafts of the standard were created before it was finalized and published in 2009.

However, many network equipment manufacturers started developing hardware using 802.11n specifications in 2006 itself and thus could not comply with 802.11n standard since the final version released 3 years after they started working on their hardware devices.

Alternate names such as “Wireless N” and “Draft N” were coined to distinguish these early products. Later on, the name ‘Wireless N’ stuck and was used in place of 802.11g even for fully compliant products.

Features

802.11n comes with the significant improvement in net data rates from 54 Mbps (maximum data transfer limit in 802.11g) to 600Mbps. Several features incorporated into IEEE 802.11n for achieving higher performance levels. Some of those features are as follows.

Introduction of MIMO

802.11n uses multiple antennas to increase data rates. Known as MIMO (multiple-input and multiple-output), it is an amendment to 802.11-2007 Wi-Fi standard.

In radio technology, MIMO is a method of multiplying the capacity of a radio link using multiple transmit and receive antennas from exploiting multipath propagation.

Multipath propagation refers to the phenomenon in which the radio signals reach the receiving antenna via two or more paths. 802.11n uses four spatial streams for data propagation at a channel width of 40MHz.

Number of antennas

MIMO simultaneously uses multiple streams to ensure a fast data transfer rate. However, the number of data streams that can be used is limited by the number of antennas on each side of the link. 802.11n specifications allow up to four antennas on each side restricting the maximum number of data streams to 4.

Channel bandwidth

802.11n uses two channel bandwidths for data transmission – 20 MHz and 40 MHz. By using four antennas, the speed of 802.11n can go up to 288 Mbps when operating in 20 MHz modes.

With 40 MHz channel bandwidth, the specifications support data transfer rate of 600 Mbps. Usage of 40 MHz channel requires a relative free radio spectrum which is not available in urban areas (2.4 GHz band is widely in use in metropolitan regions).

So, usage of 20 MHz is preferable in urban areas while channel bandwidth can be extended to 40 MHz in rural areas for satisfactory performance.

Frame aggregation

Maximum data rates provided by the wireless specification do not match the user level throughput because of protocol overheads. To improve performance on a user level, 802.11n employs frame aggregation where it packs multiple service or protocol frames together to reduce overheads. This method was first introduced in 802.11e and optimized in 802.11n.

Dual band frequency

802.11n specifications allow devices to communicate at both 2.4 GHz and 5 GHz frequency bands. This allows the backward compatibility with older specifications.

Backward compatibility switching

Backward compatibility with earlier versions of Wi-FI adds a significant overhead while data transfer. This reduces the data transfer capacity slowing down the network.

However, if all the devices in the network are 802.11n compatible, the overhead is removed. This speeds up the network. If any of the earlier devices re-enter the network, the backward compatibility overhead is also re-introduced, which eventually slows down the whole network. To ensure fast service, use all devices with 802.11n specifications.