Hz channels 1 W, while in Europe the ETSI permits a maximum EIRP (equivalent isotropic radiated power) of just 100 mW EIRP or 10 mW/MHz of bandwidth, with variations in other countries. Table 4.4 shows a range of other regulatory differences that apply to the 2.4 GHz ISM band used for IEEE 802.b/g networks. The pace of regulatory change also differs from region to region. For example, the FCC developed regulations governing ultra wideband radio in 2002, while in Europe ETSI Task Group 31 was still working on similar regulations in 2006. Although the regulatory bodies impose conditions on the unlicensed use of parts of the RF spectrum, unlike their role in the licensed spectrum, these bodies take no responsibility for or interest in any interference between services that might result from that unlicensed use. In licensed parts of the RF spectrum, the FCC and similar bodies have a role to play in resolving interference problems, but this is not the case in unlicensed bands. Unlicensed means in effect that the band is free for all, and it is up to users to resolve any interference problems. This situation leads some observers to predict that the 2.4 GHz ISM band will eventually become an unusable junk band, overcrowded with cordless phone, Bluetooth, 802.11 and a cacophony of other transmissions. This impending "tragedy of the commons" may be prevented by the development of spectrum agile radios, described in Chapter 14. Further information on current spectrum regulation and future developments, including the further development of regulations on ultra Radio Communication Basics Table 4-5: Web Sites of Spectrum Regulators Regulator Country/Region www.fcc.gov Industry Canada Canada www.ic.gc.ca Europe www.etsi.org Japan www.arib.or.jp/english wideband radio outside the USA, can be found from the regulators web sites at the URLs shown in Table 4-5. Radio Transmission as a Network Medium Compared to traditional twisted-pair cabling, using RF transmission as a physical network medium poses a number of challenges, as out