Techniques to increase the spectrum efficiency of high capacity digital radios

This paper presents the research on digital radio communications designed to increase the transmission capacity, i.e., spectral efficiency (bits/s/Hz), as well as the necessary requirements and limitations imposed by these systems. An overview of this evolution, which led to an efficient high capacity transmission is presented and some countermeasures and transmission techniques, like frequency reuse, are also analyzed. Performance results, evaluated at Vimercate (Milan) and in some experimental links in Italy, demonstrating the improvements of these techniques are presented and discussed