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sequence products. Aironet Wireless Communications and Nortel Networks are unique: They offer both frequency-hopping and direct-sequence products. For a quick look at the future of spread-spectrum product speeds, see "Where's 802.11 Heading?" (at www.networkcomputing.com/1004/1004buyers.html).

The Standards Watch The wireless LAN market is a mix of proprietary and standards-based products. Media attention has been focused primarily on the 802.11 standard, and most vendors are gradually gearing up support for that specification. Unlike more well-established standards, 802.11 is less mature, and interoperability between products cannot be assumed without testing. Some valuable work is being done at the University of New Hampshire's Interoperability Lab (www. iol.unh.edu/), where interoperability testing was conducted on a number of products during 1998. Vendors admit that some tweaking is needed to get products from one vendor to coexist with products from another, but from a practical standpoint, it's likely that a site will standardize on a single vendor for this kind of technology.

A number of products on the market are proprietary. In some cases, they simply represent legacy offerings by vendors committed to supporting an installed base while gradually migrating to a standards-compliant product line. In other cases, vendors are working outside the 802.11 committee for competitive reasons. For example, Proxim offers 802.11-based products, but actively promotes its proprietary OpenAir protocol as a simpler and more cost-effective alternative to 802.11; a number of vendors, including AMP, Intermec Technologies Corp. and Motorola, offer OpenAir-compatible products.

Aironet has jumped the gun somewhat on the 802.11 committee's efforts to develop a 10-Mbps standard by offering its own proprietary direct-sequence system, the Turbo DS 4800 series. It runs at up to 11 Mbps and offers compatibility with 802.11 devices when running at 1 Mbps or 2 Mbps. Aironet says it expects its product to be field-upgradable to the 802.11 high-speed standard. For more on Turbo DS, read our Sneak Preview at www.networkcomputing.com/1004/1004sp2.html.

And when will the high-speed standard arrive? Proposals for new PHY standards at both 2.4 GHz and 5 GHz have been approved, the former based on a joint design from Lucent and Harris Semiconductor, the latter on a joint design by Lucent and Nippon Telephone and Telegraph. Approval of the 2.4-GHz standard is expected as early as the end of 1999. The 2.4-GHz PHY will include modes for data transmission at 1, 2, 5.5 and 11 Mbps. The backward-compatible 1-Mbps and 2-Mbps standards will use DBPSK (Differential Binary Phase Shift Keying) and QPSK (Quadrature Phase Shift Keying) modulation schemes. The higher speeds will be based on CCK (Complementary Code Keying) modulation. Work on the 5-GHz standard will require additional effort and is not expected to be complete until well after 2000.

Outside of the IEEE, groups are working on other wireless specifications. The European Telecommunications Standards Institute's BRAN (Broadband Radio Access Network) Project has developed the HiperLAN system, which supports transmission rates of 24 Mbps at 5 GHz. At the lower end of the market is the Home RF Working Group. Founded by vendors including Compaq Computer Corp., Ericsson, Hewlett-Packard Co. and IBM Corp., the group has announced its intention to publish the SWAP (Shared Wireless Access Protocol) standard. SWAP is designed to provide low-cost wireless capabilities for homes and small offices. Similarly, the Bluetooth SIG, which counts IBM, Intel Corp. and Nokia as members, announced plans for a low-cost 1-Mbps wireless technology capable of providing a connection between mobile phones and notebook computers.

Wireless LAN Implementation While prices are still relatively high, the establishment of IEEE standards for wireless communications should make network managers more willing to take a look at new initiatives in untethered communication. Wireless LANs are more difficult to install and maintain than wired LANs, but both processes have gotten easier over the past few years as vendors have improved the quality of hardware and software implementations.

It is unusual for sites to deploy a strictly wireless LAN, but it could become a more popular option as the technology goes mainstream. The common case involves the installation of a wireless LAN as part of an internetwork that includes wired and wireless components. The typical combination of hardware is a set of PC Card wireless LAN adapters and a wireless AP (access point), generally a MAC-layer bridge that interconnects a wired LAN segment to a wireless environment.

Wireless PC Card implementations have improved significantly. Unlike the old days, when a fairly large antenna was plugged into the PC Card and then attached to the notebook via Velcro, the newer designs include integrated antennas. BreezeCOM's new BreezeNET PC Card includes two tiny retractable antennae that slide into the card when not in use, and Aironet's PC4500 has a clip-on antenna that extends less than half an inch from your notebook. Lucent's design uses a small nonremovable antenna that extends an inch or so, but Lucent also includes a jack that allows a higher-gain antenna to be attached to the PC Card--handy when distance is a priority.

Given the desire for mobility, it's not surprising that PC Cards are the most popular NIC form factor. However, some vendors offer ISA and PCI cards too. Others offer mini-bridges that let you attach any Ethernet device to a wireless network. While using these devices will cost you a bit on the performance end, they compensate by allowing you to stick with Ethernet cards with stable drivers.

Access points also have grown more sophisticated in recent years. Devices are now smaller, management capabilities have been improved and designs offer more flexibility. It's becoming more common for vendors to build access points that include a PC Card slot that lets you use alternative radio systems on a single access point. Lucent has taken this approach with its WavePoint II AP. It also includes two PC Card slots, letting you interconnect older proprietary systems with 802.11-compliant systems. This will simplify the migration process for sites that have a significant investment in older technologies.

Finally, vendors have improved their installation utilities, letting you measure signal levels and properly position access points to achieve the most efficient physical coverage within a building. But properly positioning access points to achieve optimum coverage in a large facility requires knowledge of channel spectrum allocations of each product, an understanding of the implications of overlapping cells, and lots of trial and error. Exercise a bit of skepticism when looking at vendor specs regarding transmission distance. And remember, every building is different.

Send your comments on this article to Dave Molta at dmolta@nwc.com.