Do you know your Wireless LAN ABC?

This industry is predisposed to a multitude of abbreviations and seemingly incomprehensible names such as IEEE802.11 or TD-SCDMA. The following examples are used in connection with the Wireless LAN IEEE 802.11 standard.

IEEE

IEEE stands for the Institute of Electrical and Electronics Engineers, Inc. This is a nonprofit

association of more than 377,000 technical professionals in 150 countries. IEEE standards are formulated by working groups, and each version of the standard they are working on is allocated a letter to describe it - thus 802.11a or 802.11b, etc.

What is 802.11?

802.11 is a revised standard that dates from 1997. Originally, this standard specified operations at 1 and 2 Mb/s in the infrared band, and in the licence-exempt 2.4GHz Industrial, Scientific, and Medical (ISM) frequency band. In the early days, an 802.11 network was envisioned as consisting of a few PCs with wireless capability connected to an Ethernet (IEEE 802.3) LAN via a single network access point. Since 1997, 802.11 has acquired many new attributes. It still fulfils its original function, but can now also operate at higher speeds and in additional bands. As it grew, new issues arose including questions of security, roaming among multiple access points, and quality of service.

802.11

a) This is the fastest 802.11 standard, and it defines requirements for a physical layer (which determines, among other parameters, the frequency of the signal and the modulation scheme to be used) operating in the Unlicensed National Information Infrastructure (UNII) band at 5GHz, and at data rates ranging from 6 Mb/s to 54 Mb/s.

802.15.x

The 802.15 WPAN effort focuses on the development of consensus standards for Personal Area Networks or short distance wireless networks. These WPANs address wireless networking of portable and mobile computing devices such as PCs, Personal Digital Assistants (PDAs), peripherals, cell phones, pagers, and consumer electronics, allowing these devices to communicate and interoperate with one another. The goal is to publish standards, recommended practices, and guides that apply to a wide market and deal effectively with the issues of coexistence and interoperability with other wired and wireless networking solutions. (802.15 also includes Bluetooth).

The physical layer uses a scheme called Orthogonal Frequency Division Multiplexing (OFDM), which transmits data on multiple subcarriers within the communications channel. In many ways, it is similar to the physical layer specification for HiperLAN II, the European wireless standard.

b) This defines operation in the 2.4GHz ISM band at 5.5 Mb/s and 11 Mb/s (as well as the fallback rates of 1 Mb/s and 2 Mb/s). This physical layer uses Complementary Code Keying (CCK) modulation schemes and Packet Binary Convolutional Coding (PBCC). The standard is also known byits more popular name - Wi-Fi.

e) 802.11e is intended for real-time applications such as voice and video. To ensure that these time-sensitive applications have the necessary network resources when required, IEEE is working on adding mechanisms for ensuring quality of service to the second layer of the reference model, the medium-access layer or MAC. This layer controls which one of several competing devices in a shared system gets to use the medium of communication at each instant of time. The current draft contains both statistical and deterministic mechanisms for

differentiating traffic.

f) 802.11f implementations are evolving from small extensions of wired LANs into larger networks with multiple access points. These access points must communicate with one another to allow users to roam among them. The goal is to enable communication between access

points from different vendors.

g) The goal for 802.11g is a higher data rate than 802.11b. The current 802.11g draft adopts OFDM from 802.11a as well as two additional modulation schemes - PBCC and CCK-OFDM.

It also enables data rates as high as those in 802.11a (54 Mb/s). Although final ratification is not expected until 2003, some manufacturers have already announced 802.11g products.

h) The h in 802.11h stands for Europe. The goal is to modify the 802.11a physical layer to ensure that 802.11a can be used in Europe. The task group is adding dynamic frequency selection and transmit power control, which are required to meet European regulations. The major competitor within Europe is the HiperLAN II wireless standard, which is being officially endorsed by the European Telecommunications Standards Institute.

i) The original version of 802.11 incorprated a MAC-level privacy mechanism called Wired Equivalent Privacy (WEP), which has proved to be inadequate in many situations. The goal is

to improve security mechanisms. The current draft contains an improvement to WEP called Temporal Key Integrity Protocol (TKIP) and a new mode that incorporates the Advanced Encryption Standard (AES), which is widely used in the banking industry.