Today's most popular WLAN NIC option is the Type II PC Card interface, which comes in two variations. The older 16-bit PCMCIA PC Card has been compared to the ISA system bus found in older desktop systems, and the 32-bit CardBus PC card interface is analogous to the desktop PCI bus. The older interface was adequate for 11-Mbps 802.11b. However, newer WLAN standards, such as 802.11a and 802.11g, require CardBus interfaces, which are included in many notebook computers. But don't assume a product has a CardBus just because it's new--the PC Card expansion packs available for the popular iPAQ PDAs only provide 16-bit support.
Many newer notebook systems offer a 32-bit mini-PCI embedded interface. The mini-PCI slot often is accessible through a small covering on the bottom of a notebook. Today, most mini-PCI WLAN interfaces come preinstalled from the vendor, though you can sometimes buy the interfaces and install them after the initial purchase.
There are two primary approaches for connecting desktop computers to a WLAN. With the traditional solution, you install a PCI wireless NIC--a hassle for sure, and if your system sits on the floor, so will the antenna. It's usually more convenient to install a USB wireless interface. This lets you position the antenna for optimal reception and transmission. You still have to contend with installing a cable to get wireless access, and you may take a minor performance hit compared with using PCI.
Software Is Key
When shopping for WLAN NICs, look beyond the hardware specifications to ensure that the software will meet your needs. For shops running Windows XP, you may need only a compatible driver, because XP manages wireless configuration and access functions. Most organizations will have broader requirements, though, including support for a range of OSs and flexible client utilities.
WLAN NIC client utilities let you adjust all the virtual knobs and dials that come with wireless. Client utilities can be used for a number of functions, including storing WLAN network names, managing security parameters and tuning radio output power. A nice feature for users accessing multiple WLANs, perhaps at home and at the office, is the ability to maintain named configuration profiles that include optimal configurations for whichever network you are using at the time. Many client utilities also provide tools for conducting site surveys or troubleshooting problems.
Performance Considerations
Throughput should be between 50 percent and 60 percent of a product's data rate. For 11b NICs, look for a maximum single-station throughput of about 6 Mbps; for 11a and 11g products, expect around 27 Mbps. Of course, throughput is usually lower in the real world, where contention for network access exists.
Range is also a fundamental consideration, but there is no simple specification that will provide you with a clear predictor. A radio's output power, usually measured in milliwatts or dBm, is often associated with range, but so too is the radio's receiver sensitivity, the quality of its antenna design, and the system's ability to deal with multipath and other interference sources. For some applications, like a home wireless network or a low-density warehouse application, maximum range is clearly best. However, for many enterprise applications, where smaller cell size is needed to boost per-station performance, long range can be detrimental, causing interference with adjacent cells. The best products available provide features that support dynamic power output.
Looking Forward
There's plenty of room for innovation in the WLAN NIC market, and prices should continue to drop. The multiband/multimode trend will likely broaden in the coming year with NICs introduced that support 802.11 WLAN standards as well as wide area cellular standards like GPRS and 1xRTT, with transparent roaming between the two.
If there's a breakthrough that's needed, it's in the area of power efficiency. Today's products simply don't meet user expectations. For WLAN functionality to be extended beyond the notebook computer to smaller, battery-constrained devices, such as PDAs and cell phones, improvements in power management will be required.
Dave Molta is a senior technology editor of Network Computing. Write to him at dmolta@nwc.com.
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