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Take care when enhancing Wi-Fi beyond standard

Posted: 01 Feb 2006 ?? ?Print Version ?Bookmark and Share

Keywords:d'andre ladson? texas instruments? wi-fi? wlan connectivity? voip?

Sometimes, it seems as if the 802.11 Wi-Fi marketplace behaves like a vacuum, sucking in every enhancement with no end in sight. Technology vendors have taken to surpassing the performance levels specified in the pertinent standards as a way of continuing the growth of the marketplace.

Indeed, there are legitimate ways of enhancing 802.11 while conforming with the standard. Here are some tips on what to look for when you're putting together a WLAN and evaluating the enhanced features of various Wi-Fi products.

There are several categories as far as performance enhancements gorange (or reach) extensions, rate improvements and increased robustness. Extending the range of 802.11g WLANs to "whole-house" coverage can be done by exotic, expensive means, or it can be accomplished by doing two things in tandemincreasing the transmit power of the signal and improving signal sensitivity at the receiver end of the channel. Increase the energy content of transmit signals with caution because this can affect other factors, including transmit noise, the device's operating temperature and adjacent-channel interference rejection in receivers. These interrelated factors can mitigate the gains you are seeking by increasing the power in transmit signals. Careful network planning is required.

Two of the more common means of improving the rate or data throughput on 802.11g WLANs are packet aggregation and packet bursting. Packet aggregation techniques have generated rate improvements as high as 30 percent. Aggregation combines packets, reducing overhead on the WLAN by lengthening packets to sometimes as long as 4KB.

Some precautions must be taken to ensure that the network can react intelligently to current conditions. At WLAN throughput rates below 11Mbps, the increased transmission times for longer packets can detrimentally affect WLAN operation. Packet bursting, on the other hand, maximizes bandwidth use by lowering the media-access controller layer frame's transmission overhead. Bursting reduces the distributed interframe space and the back-off period. When applied to standard-length packets, bursting reduces the overhead portion of the packets and increases the payload. In this way, the technique delivers more data without increasing traffic on the network, avoiding the collision problems caused by increased traffic.

Security and its effect on the performance of a WLAN are also becoming important issues as real-time applications like VoIP become more prevalent. Make sure your WLAN security does not introduce delays or latencies that disrupt applications like VoIP.

Lastly, an important factor in WLAN planning is the impact of technology convergence. Clearly, convergence is continuing at a rapid pace. We should expect to see other types of devices with 802.11 capabilities in the near future. I suggest that WLAN designers carefully examine the product road maps of their technology suppliers to ensure the equipment deployed today is future-proof for as long as possible.

- D'Andre Ladson
Manager, WLAN subsystem residential-gateway and embedded systems
Texas Instruments Inc.

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