The Radio Spectrum and RF Environment Radio is the penultimate medium for mobile communications, but it has also been used for many fixed-site applications such as AM/FM broadcast, satellite trunking, point-to-point microwave telephony, and digital TV. Although there are radio applications in very low frequencies (VLF) and extremely low frequencies (ELF), these bands require extensive fixed-site infrastructure whose size and cost is dominated by the mile-long antennas and megawatt-power handling requirements. SDR insertion opportunities in these bands are limited. . | Software Radio Architecture Object-Oriented Approaches to Wireless Systems Engineering Joseph Mitola III Copyright 2000 John Wiley Sons Inc. ISBNs 0-471-38492-5 Hardback 0-471-21664-X Electronic 3 The Radio Spectrum and RF Environment Radio is the penultimate medium for mobile communications but it has also been used for many fixed-site applications such as AM FM broadcast satellite trunking point-to-point microwave telephony and digital TV. Although there are radio applications in very low frequencies VLF and extremely low frequencies ELF these bands require extensive fixed-site infrastructure whose size and cost is dominated by the mile-long antennas and megawatt-power handling requirements. SDR insertion opportunities in these bands are limited. Therefore this text is concerned with the bands in which there are major economic opportunities for software-radio technology insertion HF through extremely high frequencies EHF . I. RF SIGNAL SPACE Figure 3-1 shows how terrestrial radio uses cluster in RF signal space. This figure shows the notional clusters of the significant band mode combinations addressed by software radio technology. This space is the two-dimensional cross product of radio frequency and duty Since coherent bandwidth is proportional to carrier frequency the figure is also labeled in terms of nominal instantaneous bandwidth. A QPSK encoded T- or E-carrier signal is on continuously for a duty cycle of . Low-duty-cycle modes such as burst communications and ultra-wideband UWB have high peak power as suggested by the additional label on the axis. This is not an exact correspondence but it shows a trend related to the thermal properties of power-handling devices. The PTT modes have the duty cycle of voice which is about 25 during speech epochs. Given conversational pauses a voice channel is typically occupied less than 10 of the time. The busiest military voice channels are occupied not more than 40 in a full duplex channel such as the .
