802.11a speeds wireless LANs

By Fred Anderson, Network World |  Networking

The COFDM technique would be technically difficult and very costly without concurrent advances in the CMOS semiconductor fabrication process. Current-generation deep submicron CMOS processes have allowed for a great increase in the complexity of the baseband processors to modulate/demodulate COFDM. The fundamental advances also lower power consumption, decrease chip size and cut development costs.

Wireless vendors now have a goal to boost wireless throughput beyond 100M bit/secc. While the 802.11a standard currently tops out at 54M bit/sec in 20-MHz channels, several firms are developing and proposing high-rate extensions to the 802.11a standard. These proposals generally envision at least doubling throughput to anywhere from 108M to 155M bit/sec.

Unfortunately, developers cannot further increase the index or complexity of the modulation on each subcarrier beyond the maximum symbol rate for wireless LAN transmissions because of the amount of noise allowed. Instead, they plan to increase the bandwidth of the COFDM channel, increasing and reallocating the individual carriers, and propose different coding rate schemes.

The broad application of wireless LAN technology has arrived. Thanks to the 802. 11a standard and its advances in wireless modulation techniques, users soon will be able to access broadband video, audio and data as easily as from their wired clients. They will have more freedom to use next-generation applications for increased efficiency, productivity and mobility.

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