802.11 Wireless Devices - 28 Jun 2001

Wireless networks are inherently flexible, providing convenience and reduced dependence on costly network cabling. Since 1997, when the IEEE published the 802.11 standard for wireless LANs, many businesses and individuals have shown interest in wireless networks. However, the 1Mbps-to-2Mbps bandwidth limit prompted many interested parties to wait for wireless technology to mature. In 1999, the IEEE amended the original 802.11 standard to include 5.5Mbps and 11Mbps speeds while maintaining backward compatibility with the original standard. This new standard, known as 802.11b, prompted wider adoption of wireless LAN solutions and created a large market for 802.11b-compliant hardware.

Our Buyer's Guide of wireless devices, originally published in Windows 2000 Magazine (July 2001) consists of products in two general categories: wireless NICs and wireless network infrastructure devices, which are generally known as access points (APs). The APs in this Buyer's Guide cover the spectrum of environments from the home office to the enterprise. WildPackets' AiroPeek packet analyzer for 802.11b wireless LANs is the only software-related product in this Buyer's Guide.

Before you choose an 802.11b solution, assess your performance requirements and expectations. Wall and ceiling composition and other potential obstructions can contribute to interference, which can degrade performance of wireless networks. You should look at relationships between speed and range and the environmental factors that can affect these relationships.

Theoretically, the 802.11b standard provides for a maximum speed of 11Mbps, but basic communication overhead guarantees that you'll never realize that speed at the application level. Furthermore, the 802.11b standard operates at 2.4GHz, so it might compete with cordless phones, microwaves, and other wireless networking architectures, such as Bluetooth. When your network devices encounter a certain level of interference, the devices cut back their transmission rates to 5.5Mbps or lower, if necessary. When interference is too great, wireless devices won't work at all.

The distance you are from an AP also directly affects the speed at which you can transmit. When a vendor advertises a device's maximum range, understand that such a distance is possible only at lower speeds and in the absence of physical obstructions. The range over which you can effectively transmit at 11Mbps might be only a fraction of the maximum range inside a building that has average interference. If you're considering a large implementation, start with a small pilot program to identify potential interference trouble spots.

Users who share an AP also share an Ethernet collision domain. The more wireless users that share the hub, the more performance suffers. The number of users an AP will support varies depending on the type of user. If a vendor claims its device can support 50 users, find out whether that number is practical or theoretical. You might need to invest in several APs to support your mobile user base.

Interoperability is another area you should investigate. Compliance with the 802.11b standard should ensure compatibility between different products, but the potential exists for incompatibilities between different hardware manufacturers' devices. The Wireless Ethernet Compatibility Alliance (WECA) sponsors a logo program known as Wi-Fi to promote adherence to the 802.11b standard. Products with the Wi-Fi logo have passed a series of lab tests that confirm adherence to 802.11b standards. I suggest that you purchase products with the Wi-Fi logo. As with any product purchase, be sure to do your homework ahead of time and choose the vendor that can satisfy your performance, reliability, and service requirements.

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