ctor recently became interested as well, when the FCC published a report concluding that CR architectures can make effi- cient and intelligent use of the radio spectrum and encouraging the use and develop- ment of CR. The FCC is considering using unused television frequencies (between 54MHz and 862MHz) for CR. The FCC proposes to open up 300MHz of this UHF/ VHF spectrum as its first major test of CR. It would permit fixed-access systems transmitting up to 1 watt in power and portable devices up to 100 milliwatts. CR standards work is taking place as IEEE 802.22, the Working Group on WRANs (www.ieee802.org/22), which is working on the construction of wireless regional area networks (WRANs) using free TV bands. Its goal is to specify a cogni- tive air interface for fixed, point-to-multipoint WRANs that operate on the unused channels in the UHF/VHF TV bands that the FCC is opening up for experimenta- tion. There is ongoing contention between the WiMax community and the IEEE 802.22 group over who should have access to unused TV spectrum. (WiMax is dis- cussed in more detail in Chapter 15.) The IEEE 802.18 group, Radio Regulatory Technical Advisory Group, has a difficult task ahead in trying to coordinate the various international bodies and existing and emerging standards surrounding radio and radio regulation. Mobile IP Trains, planes, and automobiles were once simply ways to transport people between locations, but they now offer yet another opportunity to stay connected to the Internet. While this was not easily accomplished in the past, today we have Mobile IP, an open standard defined by the IETF in RFC 3344. With the advent of packet- based mobile data applications and the increase of wireless computing, there is corresponding need for seamless communication between mobile node devices and packet data networks, such as the Internet. Mobile IP allows a user with a mobile device whose IP address is associated with one network to stay connected when moving to a network that has a different IP address. In other word