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The Evolution of Wireless Standards

Standards define by law what certain values are, such as the pound or kilogram, gallon or liter, dollar or euro. Standards also define the specifics of a product or technology and enable suppliers of such to claim, use, and adhere to well-defined standards.

hub and it working would not be possible. In the communications industry, standards reduce the number of challenges with information exchange and product interoperability.

The more broadly adopted a standard is, the wider the market for providers of that technology. And providers using the most preferred standard, meaning one that has been ratified on a global basis, tend to capture more of the market share. This also tends to assist in driving costs down and improving quality. International standards are far more difficult in practice than in theory, however, and with wireless standards this is probably even more true.

The wireless world has many standards. They have been in place since the beginning of wireless. Without these standards, everyday things that are used in every facet of our life would not be possible. Think for a minute how often you use some form of wireless in your life today. Did you watch the news this morning? Remember the TV is receiving a signal that is wireless somewhere in the system (satellite to the cable company, or perhaps wireless all the way to your set). What about that remote control you used to turn the TV on or change the channel? Of course, that signal is likely infrared, but it is still considered wireless. Then there is the garage-door opener that you used to close your door as you backed out of the drive. And did you listen to the radio on the way to work? Was that an AM or FM radio? Or perhaps a satellite radio? You may have also used the technology with the biggest growth of wireless in history: your cell phone.

Without standards, mainstream adoption of these well-known wireless technologies would have occurred more slowly, if at all. This book restricts its discussion to mainly WLAN standards and focuses on the key 802.11 technologies.

The First Proprietary WLANs

To get a good understanding of 802.11, let's take a look at the evolution of WLAN technologies. The earliest WLAN systems were proprietary systems used mainly for bar code systems. These systems typically used what is called narrowband radio and were based in the UHF spectrum. A popular frequency band was 450 MHz, and the radios that were used were originally designed for voice communication. Just as a phone line was designed for voice and migrated to data with modem, so did voice-type radios. Whereas the radios followed a standard for communication at the radio frequency (RF) level, the data that was sent over them was proprietary to each and every vendor. One drawback to using these "voice-grade" radios was bandwidth. It was limited to about 9600 bps per system, and would only support up to perhaps 30 users for the entire system. A secondary problem was that these radio systems had to be licensed. In large cities such as Chicago or New York, most of the available frequencies were already spoken for.

Federal Communications Commission (FCC) had opened up several new unlicensed frequency bands for use with this new technology, and it promised to improve WLAN capabilities tenfold. The three new bands were defined as the ISM bands, indicating they were intended for industrial, scientific, and medical uses.

The first such band to be used was 900 MHz. It provided for data rates in the 1-Mbps range. But one issue with the early 900-MHz WLAN was the limited number of countries that allowed for the use of this type of equipment. The 900-MHz band could not be used in Europe and most Asia Pacific and South American countries.

Companies such as Ford Motor Company and IBM wanted a system that could be used in all their corporate locations, and because 900-MHz was limited to a handful of countries, there was a push from customers for a more widely acceptable solution.

In part because of these reasons (speed and global usage), the 2.4-GHz ISM band became the choice for innovative WLAN vendors. By the early 1990s, 2.4-GHz systems started to appear in the WLAN market, and the speed increased to an average of 2 Mbps. (One wireless LAN vendor, Breezecom, even pushed this limit to 3 Mbps.) The 2.4-GHz technology was permitted in more than 60 countries at that time; because of the higher speed and global availability, WLANs started moving into more mainstream networking.

Standards-Based WLAN Systems

There was still one drawback to investing in WLAN systems. There was no standard, and therefore WLANs were all proprietary and single-source products. A single-vendor implementation was, and still is, something most large users have a strong desire to avoid because, in part, they want to ensure equipment availability, service, and support in the event the vendor that sold them the equipment became unavailable or indifferent. Indeed some who chose to implement early WLANs ended up with a proprietary system that worked only with a single vendor's product line. Another risk in this approach was one of scaling, or in other words, expansion. If the vendor dropped the product line (which happened on more than one occasion) or worse, went out of business, you were left with a system that you could not expand or update, or in some cases, you could not even continue to get support for. This meant only one thingR&Rrip and replace! The industry and the Institute of Electrical and Electronics Engineers (IEEE) saw a need to compile standards for WLANs to follow that would allow interoperation across vendor platforms. The result was the formation of 802.11 Working Group within the IEEE. This new IEEE group started working on the WLAN standard in 1991. Even though it was six long years before the IEEE completed the standard, the standard has affected tremendously the adoption of 802.11 equipment by customers both large and small.

In lieu of any completed industry standard, one company, Proxim, tried to develop an industry de facto standard known as the Wireless LAN Interoperability Forum (WLIF). The WLIF specification was completed and in place while the IEEE was working on the 802.11 frequency hopping (FH) and direct sequence (DS). Some users again did not know which implementation to install. A philosophical war broke out between FH and DS vendors and customers, much like the debates that occurred between the VHS and Beta technology in the videotape arena. This confusion also prompted many potential WLAN customers to wait to install because they did not know which path to follow, FH or DS.

The new 802.11 systems had defined data rates only up to 2 Mbps, so the data rate advantage over the WLIF format was minimal, and therefore products based on the 802.11 took a little while to catch on. The main advantage of 802.11 was that it was an industry standard. Unlike WLIF, which was a standard clustered around a single company, 802.11 was intended to provide interoperability (and in many cases it did). However, there were still many issues with getting Vendor A to work with Vendor B, and users had to take the word of their potential vendors as to the level of interoperability. This again stalled the event of widespread WLAN adoption.

By the time the 802.11 products started to take hold in the industry, users were screaming for more and more bandwidth. Just two years after the first 802.11 standard was completed, the industry made a huge jump to 11 Mbps with the completion of the 802.11b standard and the introduction of 11-Mbps products based on the standard. As 802.11b devices started coming to fruition, there was still some skepticism about interoperability among vendors. This was the main reason that Wi-Fi certification was started. Known at that time as Wireless Ethernet Compatibility Alliance (WECA), the organization developed a program to assure users that Vendor A products would now have a minimum degree of interoperability with Vendor B products. The certification from this group was known as the Wi-Fi certification. The certification program was such a success that the term Wi-Fi was the unofficial wireless standard; in 2003, WECA even changed their name to the Wi-Fi Alliance (WFA).