TABLE OF CONTENTS An ideal SDR offers a highly flexible and versatile platform that permits the instantiation of a variety of different waveforms [1] with widely varying specifications. More precisely, the radio must be capable of transmitting and receiving over a wide frequency range, at various power levels and bandwidths, using different modulation and multiple access schemes. The radio must also be capable of supporting various applications ranging, for example, from simple landing aid waveforms and secure voice communication to advanced data messaging or multimedia application over ad-hoc networks. This versatility imposes on the SDR multiple sets of requirements that must be met all in one platform. The aim of this chapter, then, is to discuss how high-level and link budget requirements can be derived and how they can be translated into low-level requirements and eventually into realizable system-design parameters.
This chapter is divided into three sections. In Section 4.1, high-level requirements and how they interrelate to one another is discussed in detail. The section starts off with a brief description of the Software Communications Architecture (SCA) and its role in future military and commercial software radios. This is followed by a discussion on usage scenarios and integrated platforms. The interdependence of high-level requirements on the environment, platform, and targeted application is highlighted.
In Section 4.2, the link budget analysis is discussed in detail. Path loss and the various degradations that impair the desired signal ranging from man-made to environmental are discussed. Finally, the sensitivity equation that determines the required...
