View Messageham-80211 >I understand the argument that OFDM transmissions are not considered >spread spectrum. Yes ... a few years ago a company called WiLAN submitted an OFDM device to the FCC for certification under 15.247, arguing that, since it could pass the "CW jammer test" (intended to assure that devices exhibited the then- required 10 dB of process gain), it met the requirements of 15.247. The FCC labs rejected the request for certification, stating that OFDM did not meet the definition of DSSS and therefore the device did not comply with the rules. As of May 2002, the FCC allows non-spread spectrum systems on Part 15 bands at the higher power levels. The bandwidth has to be at least 500khz and the power density has to be less then 8dBm per 3khz sliver. This was done to allow the OFDM systems to be legal, and OFDM is not spread spectrum by anyone's definition. But the above can be applied to FSK as long as it mets the critiera above Here is the exact rule: 15.247(a)(2)(b)(3)(d) (2) Systems using digital modulation techniques may operate in the 902-928 MHz, 2400-2483.5 MHz, and 5725-5850 MHz bands. The minimum 6 dB bandwidth shall be at least 500 kHz. (b) The maximum peak output power of the intentional radiator shall not exceed the following: (3) For systems using digital modulation in the 902-928 MHz, 2400- 2483.5 MHz, and 5725-5850 MHz bands: 1 Watt. (d) For digitally modulated systems, the peak power spectral density conducted from the intentional radiator to the antenna shall not be greater than 8dBm in any 3 kHz band during any time interval of continuous transmission. FCC rejection of OFDM as Spread Spectrum: http://hraunfoss.fcc.gov/edocs_public/attachmatch/FCC-01-158A1.pdf