This article gives a tutorial about some critical milestones regarding the journey of tactical radios from legacy systems to cognitive radios. Although tactical radios have been in use for over 100 years, this tutorial focuses on the post-Vietnam War radios and uses examples from the U. S. Department of Defense major acquisition programs. The article considers legacy radios to be the generation of radios that was initiated by the U. S. Department of Defense in the 1970s that had spread-spectrum and frequency-hopping capabilities to resist jamming. The Link-16 system is covered in this article as a benchmark for legacy radios. Two major technological leaps came after these legacy radios. First was the software defined radios initiative, which brought about the ability to develop waveforms entirely in software in the absence of a defined hardware platform. As a result, different waveforms can be ported into the same hardware platform. This article presents the Wideband Networking Waveform, which is a complex waveform developed under a U. S. Department of Defense program, as a software-based waveform that can be downloaded into different hardware platforms. The next technological leap came with cognitive radios, which have the ability to sense their environments and adapt intelligently to the dynamics of the war theatre.
