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Subject: IP: fcvc rule mods 802.11
-----Original Message----- From: Charles Brownstein <cbrownst@cnri.reston.va.us> Date: Thu, 23 May 2002 12:01:34 To: farber@cis.upenn.edu Subject: fyi Back To Article May 23, 2002 05:22 AM FCC modifies rules governing 2.4GHz spectrum By Ephraim Schwartz IN RECOGNITION OF the growing significance of the unlicensed wireless band used by 802.11x and Bluetooth, among others, the FCC this week modified the rules that govern the 2.4GHz spectrum. The most significant result of the rule changes to FCC rule Part 15.247 will allow for the co-existence of wireless LAN devices with devices using Bluetooth. The changes will also mean that developers using the 2.4GHz band will not be limited to 11Mbps data rates and thus gives 802.11g, the recently adopted IEEE standard for these devices that perform at 54Mbps while being backward compatibility with the older 11MBps devices, the FCC seal of approval. The chairman of the Wireless Ethernet Compatibility Alliance (Wi-Fi), Dennis Eaton, praised the changes and said it will ultimately result in products with higher data rates and lower interference. The FCC has been extremely responsive to the industry and consumers. It recognizes how precious the spectrum is, said Eaton, in Mountain View, Calif. Under the previous rules, data rates were capped at 11Mbps in the 2400MHz-to-2483.5MHz (2.4GHz) band, while under the new rules there is no effective data rate limit. The ruling allows new digital transmission technologies such as OFDM (orthogonal division multiplexing), which have the higher data rates, to be used in the 2.4GHZ spectrum. Previous to the rules changes, OFDM could only be used in the 5.1GHz band. OFDM decreases what is called in the industry multipath fade. A phenomenon that is caused, especially indoors, as a single signal bounces off various barriers. By sending the same signal over multiple paths the signal power is less likely to fade or weaken. Meanwhile, the 2.4GHZ band has an inherently stronger signal with a longer range and can travel through walls better than the 5.1GHz band used by IEEE 802.11a. However, the 5GHz band allows more users to be on the same channel simultaneously. In the 2.4GHz band there is a maximum of three non-overlapping megahertz channels while in the 5GHz band there are 12 non-overlapping channels. This means more users can be co-located in the same spot not interfering with each other all using the same band, according to Eaton. Eaton also believes the FCC rulings will result in dual-band devices. The technology is headed toward dual-band chip sets in as soon as six months that support operation in both, like a dual-band chip set in a cell phone. By allowing the use of OFDM in both, it also allows for a lot of technology reuse, Eaton said. Reducing the number of hopping channels from a minimum of 75 to as little as 15 under the second rule change on adaptive hopping allows a Bluetooth radio signal to hop around when it is in the presence of Wi-Fi signal, Eaton said. The co-existence issue goes away, Eaton said. Laptop manufacturers can also be expected to more easily deploy notebooks with both Wi-Fi and Bluetooth built in. InfoWorld Editor at Large ABOUT INFOWORLD | CONTACT US | EMPLOYMENT | PRIVACY Copyright 2001 InfoWorld Media Group, Inc. -- Charles N. Brownstein Executive Director, XIWT Suite 100, 1895 Preston White Dr, Reston, VA 20191 email: brownstein@cnri.reston.va.us tel: 703 620 8990 desk: 703 262 5346 fax: 703 620 0913 web: <http://www.xiwt.org>Title: fyi
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