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Additional Wireless Standards

Many other standards apply to the WLAN arena, most notably Bluetooth, HiperLAN, and Home RF. Each of these is unique. Some are designed for WLANs, whereas others are better suited for wireless personal-area networks (WPANs).

Other products also utilize 802.11 standards or proprietary standards for usage as a MAN or WAN.

Table 1-2 shows many of the network types that wireless products are included in, as well as typical usages for these various networks.

This book deals mainly with WLAN systems, with some attention to MAN/WAN systems that can be implemented using products modeled after the 802.11 specifications.

Bluetooth

Bluetooth in its initial conception was intended as a design that could be completed in a single US$5 silicon chip providing 10 kbps, for 10 feet, sufficient as a cable replacement. This was thought to be the wireless interface for all the desktop devices, including your laptop, phone, PDA, printer, and so on. Bluetooth meant no more cables. And 10 kbps was fast enough for most of these devices at the time of conception.

During development, data rates increased to 1 Mbps, and ranges increased to average around 30 feet. Although not true WLAN capabilities, some users have tried to use Bluetooth as an 802.11b replacement. However, Bluetooth has been limited to a cable replacement and is most common in technologies such as cell phone headsets and portable printer connections.

Bluetooth radios use a spread-spectrum, frequency-hopping, full-duplex signal at up to 1600 hops/sec. The signal hops among 79 frequencies at 1-MHz intervals to give a high degree of interference immunity. Up to seven simultaneous connections can be established and maintained.

HiperLAN

HiperLAN standards provide features and capabilities similar to those of the 802.11a WLAN standards. HiperLAN/1 provides communications at up to 20 Mbps on the 5-GHz band while HiperLAN/2 operates at speeds up to 54 Mbps in the same RF band. HiperLAN/2 is compatible with third-generation (3G) WLAN systems for sending and receiving data, images, and voice communications.

With the adoption rate of 802.11a and the advancements in that technology, the HiperLAN/2 technology has been slow to gain a foothold.

Home RF

A group called the Home RF Working Group developed a single specification, the Shared Wireless Access Protocol (SWAP), for a broad range of interoperable consumer devices. SWAP was an open industry specification that allowed PCs, peripherals, cordless telephones, and other consumer devices to share and communicate voice and data in and around the home without the complication and expense of running new wires. The technology behind the specification was frequency hopping and was limited to 2 Mbps.

The membership of the group exceeded 100 companies, but because of the limited acceptance of FH products (after the introduction of 802.11a, b, and now g products), and the user requirement of higher data rates, the group was officially disbanded in January 2003.

Ultra Wideband

Of all the technologies and standards, ultra wideband seems to have some very good potential, although its usage as a WLAN product hasn't been widely exploited. Much like spread spectrum in the 1980s, the technology for ultra wideband is one that for decades was the province of military labs. In the past few years, startups, information technology companies, and consumer electronics giants have begun pushing ultra wideband beyond the radarlike systems the military pioneered and into applications that could transform the home. Two companies are both pursuing the possibility of using ultra wideband transmission to wirelessly link DVD players, stereos, and TVs in home-entertainment systems. In the future, ultra wideband links could distribute extremely information-rich content, endowing a home or office with high-resolution 3D virtual-reality simulation.

The technology uses a very low-power transmitter and spreads the signal out over a very wide (much wider than DS) spectrum. As a result of these two features, the overall energy level is very hard to detect by a normal receiver and looks like noise to most receivers. However, its capability to transmit over long distances is also hampered by these requirements. Hence, its usage is limited to more of WPAN-type applications.