WASHINGTON — The Federal Communications Commission (FCC) approved on Thursday modifications in the rules governing spread spectrum technologies used by fixed wireless (Wi-Fi) operators. Three years in the making, the amended rules give wireless Internet service providers (WISPs) a much-needed boost in deploying effective high-speed Internet systems in their communities.
Perhaps most significantly, the new rule modifications will allow both Bluetooth and 802.11 technologies to be mounted on one device. While the FCC is setting the broad framework for this, the Commission plans for the various industry groups to set the actual standards.
Specifically, the FCC modified Part 15 of its rules to permit new digital transmission technologies to operate in the 902-928 MHz (915 MHz), 2400-2483.5 MHz (2.4 GHz) and 5725-5850 MHz (5.7 GHz) bands under the current rules for spread spectrum systems. The Commission also provided flexibility in the design and operation of frequency hopping spread spectrum (FHSS) systems in the 2.4 GHz band and eliminated the processing gain requirement for direct sequence spread spectrum (DSSS) systems.
Currently, the Part 15 rules permit the operation of DSSS and FHSS systems on a non-licensed basis. In both techniques, the power density of the transmission signal is reduced, which lowers the possibility that the transmitter will cause interference to other devices operating in the band. The FCC determined that because new digital modulation technologies have spectrum characteristics similar to DSSS systems, they can operate under the same rules as DSSS devices in the 915 MHz, 2.4 GHz and 5.7 GHz bands.
Thursday’s ruling removes the rule that limits systems in these bands to only DSSS and FHSS technology.
Because the spectrum is available for anyone to utilize, the FCC set up rules to ensure equipment running in the “free” bands don’t interfere with adjacent licensed bands. One of those rules was establishing the two spread spectrum technologies allowed to operate in the unlicensed band: DSSS and FHSS. By their very nature, the two technologies cause very little interference problems.
Part 15 rules determine what makes a spread spectrum technology truly spread spectrum. For example, the rules stipulate a minimum number of hops a FHSS signal must take on its 2.4 GHz route. The new FCC rules permit the use of as few as 15 hopping channels for FHSS in the 2.4 GHz band. These systems will be able to use channel bandwidth up to 5 MHz wide, but they must reduce their output power to 125 mW if fewer than 75 hopping channels are used.
The FCC said this action will allow new FHSS systems to better avoid interference than today’s systems by allowing them to avoid occupied channels. The Commission also eliminated the processing gain requirement for DSSS systems, concluding that manufacturers have market-driven incentives to design products that can withstand interference from other radio frequency devices.
Part 15 rules for spread spectrum systems have been in effect for more than 15 years, and have undergone several amendments to incorporate new technologies benefiting the wireless community. Recent advances with 802.11b and Bluetooth products show the unlicensed band will continue to thrive in tomorrow’s wireless world.
The FCC has been treading water in the unlicensed band debate, as more and more companies (with the millions and billions they’ve invested) go public on the airwaves. FCC Chairman Michael Powell told attendees at a recent convention 802.11 was heading for a meltdown as the playing field quickly filled up with competitors.
