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    Understanding the IEEE 802.11 Standard for Wireless Networks

    The IEEE 802.11 standard consists of a series of technological advances that have been developed over many years. Each new advancement is defined by an amendment to the standard that is identified by a one or two letter suffix to "802.11." The original 802.11 standard allowed up to 2 Mbps on only the 2.4-GHz band. 802.11b added new coding schemes to increase throughput to 6 Mbps. 802.11a added support on the 5-GHz band and Orthogonal Frequency Division Multiplexing (OFDM) coding schemes that increase throughput to 54 Mbps. 802.11g brought OFDM from 802.11a to the 2.4-GHz band. 802.11n added an assortment of high throughput advances to increase throughput roughly 10 times, such that high-end enterprise access points achieve signaling throughputs of 450 Mbps. The emerging 802.11ac standard promises to exceed 1 Gbps of throughput. The individual standards in use now are 802.11a, 802.11b, 802.11g, and 802.11n (which uses a more advanced technology than the others). The newest standard, 802.11ac, is the newest and fastest standard.

    The segment of the radio frequency spectrum used by 802.11 varies between countries.

    This topic describes:

    Differences Between 802.11 Standards

    The newer the 802.11 standard, the faster it is and the greater its capacity. The new 802.11ac specification will eventually enable multi-station WLAN throughput of 1 gigabit per second. Table 1 lists the differences between current 802.11 standards. The draft 802.11ac estimates are given in the last row of the table for comparison.

    Table 1: Differences Between 802.11 Protocols

    802.11 Protocol

    Frequency Band Used

    Bandwidth

    Data Rate per Stream

    n

    Up to 4 streams of data

    2.4-GHz
    5-GHz









    20 MHz

    7.2 mbps
    14.4 mbps, 21.7 mbps
    28.9 mbps, 43.3 mbps
    57.8 mbps, 65 mbps,
    72.2 mbps









    40 MHz

    15 mbps, 30 mbps,
    45 mbps, 60 mbps,
    90 mbps, 120 mbps,
    135 mbps, 150 mbps

    g

    1 stream of data

    2.4-GHz

    20 MHz

    6, 9, 12, 18, 24, 36, 48, 54

    b

    1 stream of data

    2.4-GHz

    20 MHz

    1 mbps, 2 mbps, 5.5 mbps, 11 mbps

    a

    1 stream of data

    5-GHz
    3.7-GHz

    20 MHz

    6 mbps, 9 mbps, 12 mbps, 18 mbps, 24 mbps, 36 mbps, 48 mbps, 54 mbps

    ac (draft)

    Up to 8 streams of data

    5- GHz

    20 MHz

    40 MHz

    60 MHz

    80 MHz

    up to 87.6 mbps

    up to 200 mbps

    up to 433.3 mbps

    up to 866.7 mbps

    Note: 802.11ng and 802.11na are Juniper Networks terminology and not part of the 802.11 standard. It is simply Juniper Networks notation for indicating 802.11n use on the 2.4-GHz band (11ng) or 802.11n use on the 5-GHz band (11na).

    802.11 Divides Each Frequency Band into Channels

    802.11 divides each of the frequency bands listed in Table 1 into channels.

    802.11 divides each frequency band into channels in a different way. For example the 2.4000-2.4835-GHz band is divided into 13 channels spaced 5 MHz apart. Channels 1, 6, and 11 were originally the only non-overlapping channels, but with the newer 802.11g standard there are now four non-overlapping channels—1, 5, 9 and 13. (There are now four because the orthogonal frequency-division multiplexing (OFDM) modulated 802.11g channels are 20 MHz wide.)

    Note: Many countries, including US allow use of channels 1 - 11 only.

    The amount of available spectrum for unlicensed use, which varies by country, in the 5-GHz band is much greater, and typical supports many more channels than in the 2.4-GHz band.

    Availability of channels is regulated by country and can change. Japan permits the use of 14 channels in the 2.4-GHz band, while other countries such as Spain initially allowed the use of only channels 10 and 11. Europe and Asia now allow channels 1 through 13. North America and some Central and South American countries allow only channels 1 through 11.

    What Is 802.11i Security?

    Wi-Fi Protected Access (WPA) and Wi-Fi Protected Access II (WPA2) are two security standards and security certification programs developed by the Wi-Fi Alliance to address security issues found in Wired Equivalent Privacy (WEP). Where WPA encryption was specifically designed to work with some wireless devices that support WEP, while WPA2 encryption does not work on any device that supports only WEP. For more information about encryption, see Understanding Wireless Encryption and Ciphers .

    What Is 802.1X?

    802.1X is an authentication protocol supported by the 802.11 standards that enables mobile devices to be authenticated by username and password or by various types of credentials such as an X.509 certificate, or SIM in cellular phones. 802.1X authentication works in conjunction with an AAA server (typically RADIUS) that provides centralized authentication and user management.

    Modified: 2018-01-23