IEEE 802.11n

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IEEE 802.11n ( n-WLAN , also called Draft-N in the preliminary version ) is a standard for wireless networks ( WLAN ). The standard defines a technique for setting up wireless local networks . The theoretically achievable gross data rate is 600 Mbit / s. Standard-compliant end devices that came onto the market before the standard was published in October 2009 were designated as Draft-n-compatible. IEEE 802.11n is also known as Wi-Fi 4 .

technology

802.11n uses Multiple Input Multiple Output (MIMO) technology for data transmission . Compared to older WLAN technologies, the standard either achieves the same data rates over greater distances or a higher data rate over the same distance. The broadening of the transmission channels from 20 MHz to 40 MHz and the use of up to four antennas increases the gross data rate to 600 Mbit / s.

802.11n can work in both the 2.4 GHz frequency range and the 5 GHz frequency range.

802.11n achieves a maximum of 150 Mbit / s (gross) per parallel content stream ; for higher data rates two to max. four streams are bundled. At least one transmitting and one receiving antenna is required for each stream in order to be able to separate the streams again. To improve the transmission properties, more antennas than currents are used, e.g. B. one often comes across three antennas for two streams (300 Mbit / s).

In technical terms, the number of transmitter and receiver currents present in a device is represented as a short form with the letters T for transmitter and R for receiver. Then describes z. B. the abbreviation 3T3R three transmit and receive streams .

The MIMO modulation in 802.11n uses an orthogonal frequency division multiplex modulation as the basic modulation. The individual carriers of this OFDM modulation can be modulated using 2-PSK , 4-PSK , 16- QAM or 64-QAM , depending on the quality of the connection .

compatibility

802.11n WLANs are compatible with 802.11b and 802.11g networks. The compatibility mode enables 802.11n and existing 802.11a networks to coexist. The compatibility mode can also be deactivated in some implementations (so-called “ greenfield mode ”) in order to increase the performance of the 11n network. However, this lowers the performance of other 802.11a networks active at the same location, since in this case they interpret the 802.11n network as emissions from radar devices and change their channel due to the prescribed DFS , which ultimately leads to a total failure due to DoS with the 802.11a Network can lead. Since the draft of 802.11n still mandated the use of WPA2, WPA2 (AES) must be explicitly selected as encryption for the Draft-N devices in order to be able to use the full bandwidth.

State of the development of the standard

The first draft (english draft ) of the standard was adopted on 20 January 2006, the final version was approved by the 12 September 2009 IEEE ratified. The WLAN standard 802.11n was originally supposed to be adopted by the IEEE in mid-2007. In May 2006, however, a final draft was not adopted.

In November 2008 the draft version 7.0 was adopted and in March 2009 version 8.0. The final version was officially adopted in September 2009 and published on October 29, 2009.

Comparison of the IEEE standards

Surname released Frequency
[GHz]
Modulation /
multiplex method
Range [m]
in the house (approx.)
depending on the walls
outdoors (approx.)
including a wall
802.11 1997 2.4 FHSS - GFSK , DSSS - DBPSK / DQPSK 20th 0100
802.11a 1999 5 OFDM - BPSK / QPSK / QAM 35 0120
802.11b 1999 2.4 DSSS - CCK 38 0140
802.11g 2003 2.4 OFDM - BPSK / QPSK / QAM 38 0140
802.11y 2008 2 3.6 like 802.11a 50 5000
802.11n 2009 1 2.4 / 5 MIMO - OFDM - BPSK / QPSK / QAM 70 0250
802.11ac 2013 5
swell
2 IEEE 802.11 Official Timelines ( English ) In: ieee.org . January 28, 2009.

Web links

Individual evidence

  1. Method And Apparatus For Adaptive Reduced Overhead Transmit Beamforming For Wireless Communication Systems . In: Patentdocs . Retrieved February 3, 2011.
  2. mentor.ieee.org
  3. ip-insider.de
  4. Jens Ihlenfeld: 802.11n: WLAN standard fails if voted . In: Golem.de , May 4, 2006. Accessed February 3, 2011. 
  5. a b Status of Project IEEE 802.11n (en) . March 2009. Retrieved February 3, 2011. 
  6. Alexandra Kleijn: IEEE ratifies WLAN standard 802.11n . In: heise online , September 12, 2009. Accessed February 3, 2011. 
  7. 802.11n-2009 IEEE Standard for Information technology - Telecommunications and information exchange between systems - Local and metropolitan area networks . 2009, ISBN 978-0-7381-6047-4 , doi : 10.1109 / IEEESTD.2009.5307322 (English, online [accessed August 25, 2010]).