to Radio Spectrum

Congested military spectrum means that next generation communication systems will have to achieve much greater spectral efficiency than their predecessors. In this paper, we consider various examples of approaches that increase the overall spectral efficiency of a communication system. Advanced signal processing techniques provide significant increases in throughput, replacing legacy VHF voice radios with networked systems supporting both voice and data. Multiple antenna technology exploits the spatial diversity in the multipath environments that are typically challenging for military radios, and provides much higher spectral efficiency with the same transmit power. The performance of this new technology can depend on frequency, antenna position and vehicle location, hence adaptivity of data rate and power is a key feature to provide robust communications for mobile platforms. For mobile systems, the properties of the radio channel can change quite rapidly. To achieve the desired quality of service while maintaining spectral and power efficiency, radios should adapt their operating characteristics, in particular, their transmit power and data rate, to make the most of the channel conditions. High spectral efficiency is not just achieved through the choice of modulation or spatial diversity; the overhead costs of feedback and retransmissions must also be taken into account.