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Wireless Networking Handbook
(Publisher: Macmillan Computer Publishing)
Author(s): Jim Geier
ISBN: 156205631x
Publication Date: 09/01/96

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Who is IEEE? The IEEE is a non-profit professional organization founded by a group of engineers over a hundred years ago (1884) so they could consolidate ideas dealing with electrotechnology. Since then, the membership of IEEE has grown to over 320,000 members in 150 countries. IEEE consists of many individual societies, 35 in total, such as the Computer Society, Communications Society, and Antennas and Propagation Society. The IEEE publishes a great deal of technical proceedings, sponsors conferences, and develops standards. One of IEEE’s most notable standards is the IEEE 802 family, which includes 802.2 Logical Link Control, 802.3 Ethernet, and 802.5 Token Ring.

In May 1991 a group of people interested in the development of wireless LAN standards submitted a Project Authorization Request (PAR) to IEEE to initiate the 802.11 Working Group. This PAR states, “...the scope of the proposed [wireless LAN] standard is to develop a specification for wireless connectivity for fixed, portable and moving stations within a local area.” The PAR further says, “...the purpose of the standard is to provide wireless connectivity to automatic machinery and equipment or stations that require rapid deployment, which may be portable, handheld, or mounted on moving vehicles within a local area.”

As with other 802 standards such as ethernet and token ring, the primary service of the 802.11 standard is to deliver MSDUs (MAC Service Data Units) between LLC (Logical Link Control) connections to the network. In other words, the 802.11 standard will define a method of transferring data frames between network adapters without wires.

In addition, the 802.11 standard will include:

  Support of asynchronous and time-bounded delivery service
  Continuity of service within extended areas
  Accommodation of transmission rates between 1 and 20 Mbps
  Support of most market applications
  Multicast (including broadcast) services
  Network management services
  Registration and authentication services

According to the PAR, the 802.11 standard will provide Medium Access Control (MAC) and Physical Layer (PHY) specifications for 1 Mbps wireless connectivity between fixed, portable, and moving stations within a local area. In addition, a single MAC specification will support multiple PHYs using radio signals or infrared light for the transmission of data.

IEEE 802.11 meetings are open to anyone. The only requirement to attend is to pay dues which offset meeting expenses. Most of the active participants are representatives from companies developing wireless LAN components. The IEEE bylaws explain, though, that in order to vote on standards activities, you must participate in at least two out of four consecutive plenary meetings. Then, you must continue to attend meetings to maintain voting status. The 802.11 standards Working Group meets three times a year during the plenary sessions of the IEEE 802 and three times a year between plenary sessions.

The IEEE 802.11 consists of about 200 members, and membership falls into the following categories:

  Voting Members, who have maintained voting status.
  Nearly Members, who have participated in two sessions of meetings, one of which being a plenary session. Nearly members become voting members in the first session they attend following their qualification for nearly membership.
  Aspirant Members, who have participated in one plenary or interim session meeting.
  Sleeping Voting Members, those who were once voting members but have chosen to discontinue.

Companies, such as Proxim, Xircom, Windata, and many others, have been extremely active in forming standards within the 802.11 group. The final version of the 802.11 standard will make it an official standard, enabling the cross-vendor interoperability of wireless LAN components. As a result, most companies developing wireless LAN products today will certainly migrate their products to comply with 802.11.

Two subgroups comprise the 802.11 Working Group—the PHY Sub-Group and the MAC Sub-Group. The PHY Sub-Group of 802.11 is developing the physical layer of the standard. The PHY group has the following objectives: define the physical layer, develop a channel model, and develop conformance tests. The Working Group decided in July of 1992 to concentrate its radio frequency studies on the 2.4 GHz spread spectrum ISM band. This band is available license-free in most parts of the world. The 802.11 PHY Sub-Group established two ad-hoc groups, one for direct sequence and one for frequency hopping spread spectrum.

The PHY Sub-Group’s efforts will result in a standard specifying three physical media: 2.4 GHz direct sequence spread spectrum, 2.4 GHz frequency-hopping spread spectrum, and diffused infrared. This will allow you to purchase 802.11 wireless LAN adapters from different vendors for a particular media type and be assured they will interoperate. Products that use one of these media types, such as direct sequence, however, will not interoperate with products using a different media, such as frequency hopping. In addition, the standard will not address roaming because it falls outside the scope of the architectural layers that the 802.11 standard addresses. You cannot expect one vendor’s wireless access point to work with a different vendor’s access point. This means you will need to standardize on one particular type of access point.

The MAC Sub-Group is concentrating on the MAC (Medium Access Control) layer of a network’s architecture. The MAC layer defines the protocol that allows multiple stations to share the bandwidth of a common medium. The 802.11 group is developing a MAC layer that supports both asynchronous and Time Bounded Services (TBS).


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