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Service, Department of the Treasury, and other civilian agencies). The APCO Project-25 process has encouraged an unprecedented level of cooperation among municipal radio users.

7. These activities are carried out by the ITU Radiocommunication Sector (ITU-R) Working Party 8/13, later renamed ITU-R Task Group 8/1.

8. The implementation of standards based on IMT-2000 in Japan clearly would give Japanese companies early experience with the technology and perhaps position them to dominate future world markets for IMT-2000 products.

9. Although optical communications systems are not addressed in detail in this report, in large part because the commercial research focuses on indoor applications, the advantages of laser systems need to be mentioned. A laser produces optical radiation by stimulating emissions from an electronic or chemical material. Unlike light produced by incandescent or fluorescent sources, the resultant beam is coherent and exhibits extremely low angular divergence, properties that enable transmissions spanning great distances (i.e., thousands of miles). The data, voice, images, or other signals are modulated on a beam of light, which is detected by an optical receiver and decoded. The transmitter and receiver need to be in direct visual contact, and so the laser beam is steered in the appropriate direction using mirrors or other optical elements. Laser communications systems offer several advantages over RF systems. The main advantage is high capacity: Systems now under development will support transmissions in the range of hundreds of megabits per second, with systems under consideration attaining the gigabits-per-second range. Another advantage is the low power requirement for point-to-point communications (orders of magnitude lower than RF systems). All the energy is focused into a very narrow beam because the physical dispersion of a laser beam in space is minimal. Furthermore, laser communications systems offer security benefits because almost no energy is diffused outside the laser beam, which is therefore not easily detected by an adversary. This combination of features makes laser communications systems attractive for secure transmissions between hub points in mobile, dynamically changing environments (e.g., between base stations on vehicle-mounted switching facilities). However, laser systems are sensitive to interference from other light sources, such as the sun, and any obstructions of the visual link by dust, rain, or fog. There is also a risk of damage to the eyes of unprotected observers. Finally, components for laser-based systems are much more expensive than those for RF systems and therefore are unlikely to penetrate the commercial market for some time.

10. These activities are carried out by the ITU Telecommunications Sector, Study Group 11.

11. The ISM bands (at 902–928 MHz, 2400–2483 MHz, and 5700–5850 MHz) are available for any wireless device that uses less than 1 watt of transmit power.

12. The United States participates in the IMT-2000 process in Task Group 8/1 through a delegation led by the FCC.



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