802.11, also known as wireless LAN (WLAN) technology, goes by a variety of names, depending on who is talking about it. Some people call it 802.11 wireless Ethernet, to emphasize its shared lineage with the traditional wired Ethernet (802.3). The Wireless Ethernet Compatibility Alliance (WECA) has been pushing its Wi-Fi (wireless fidelity) certification programme. There are three principal wireless LAN technologies standards, namely 802.11b, 802.11a and 802.11g.
Wi-Fi certification programme
Any 802.11 vendor can have its products tested for interoperability. Equipment that passes the test suite can use the Wi-Fi mark. So, today we often use the term 'Wi-Fi' interchangeably with the term 'wireless LAN.'
802.11b
The IEEE 802.11b standard is the dominant standard for WLANs. It reuses many of the Ethernet Logical Link Control (LLC) components, and is designed to easily connect into Ethernet LANs. For these reasons, IEEE 802.11b is usually called ‘wireless Ethernet’, but its official name is wireless LAN. Some vendors selling 802.11b equipment have trademarked the name Wi-Fi to refer to 802.11b. There are two versions of 802.11b: frequency-hopping spread-spectrum (FHSS) systems run at 1 Mbps and 2 Mbps; and direct-sequence spread-spectrum (DSSS) systems run at 1 Mbps, 2 Mbps, 5.5 Mbps and 11 Mbps. DSSS systems dominate the marketplace because they are faster.
802.11a
The IEEE 802.11a standard for WLAN is newer than 802.11b. It operates in a 5-GHz frequency range. The total bandwidth is 300 MHz, substantially more than the 22 MHz of 802.11b. This means that it can transmit data faster than 802.11b. The possible data rates would be 6 Mbps to 54 Mbps. However, as it operates in 5-GHz range, it requires more power for transmission.
802.11g
The IEEE 802.11g comes after 802.11b and 802.11a. 802.11g is designed to combine many of the advantages of 802.11b and 802.11a. It can attain a transmission rate of 54Mbps, while it operates in the 2.4-GHz range and thus has more moderate power consumption than 802.11b. Currently, 802.11g is the most widely-used WLAN protocol.
802.11n is a recent amendment to previous 802.11 standards, and there is an 802.11i standard for securing wireless networks.
802.11n
802.11n is a recent amendment which improves upon the previous 802.11 standards by adding multiple-input multiple-output (MIMO) and many other newer features. Enterprises have begun migrating to 802.11n networks based on the Wi-Fi Alliance’s certification of products conforming to a 2007 draft of the 802.11n proposal. An 802.11n network operates at either 5GHz or 2.4GHz frequency bands, achieving a sustainable throughput of 144Mbps and a peak transmission rate of 600Mbps. The maximum indoor and outdoor ranges go up to 300 feet and 500 feet, respectively.
The current state of the art supports a maximum transmission rate of 450 Mbps, with the use of three spatial streams at a channel width of 40 MHz. Depending on the environment, this may translate into a sustainable throughput for TCP/IP of 110 Mbps.
The IEEE 802.11n task group has completed their work, and the amendment was approved by IEEE in September 2009. It will be followed by publication in mid October 2009. In other words, the IEEE 802.11n standard will finally be released after six years’ deliberation, which is an exceptionally long process of standardization in the telecommunications industry.
Major networking manufacturers have been releasing 'pre-N', 'draft n' or 'MIMO-based' products based on early specs. These vendors anticipated that the final version would not be significantly different from the draft, and in a bid to get the early mover advantage they pushed ahead with many of the new technologies. Depending on the manufacturer, a firmware update should make current 'Draft-N' hardware compatible with the final version. More importantly, the incompatibility issues among products from different manufacturers that have hindered the wide adoption of 802.11n will vanish gradually, and the era of 802.11n, representing high speed wireless LAN connectivity, will come soon.
802.11i
802.11i is a security protocol designed to protect the wireless network. It uses Extensible Authentication Protocol (EAP) with strong encryption scheme, and dynamically assigns every transmission its own key to heighten the protection of the data in transmit against taping or tampering. With 802.11i enabled, logging on to a wireless network is more complex than with WEP (Wired Equivalent Privacy) and, in return, a higher level of security protection can be achieved.
We will cover this protocol further, together with the subject of wireless security, in a later part of this module.
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