A Technical Review of Software Defined Radios: Vision, Reality, and Current Status

Since the 1980s, the US military has been seeking a way to improve the ease and flexibility of communications within and between the Services. Forces deployed at that time used dozens of different radios, most of which could only communicate with other radios of the same type. Software Defined Radio (SDR) offered the promise of not only interoperating with all existing radios, but also allowing those legacy radios to communicate with each other. Just as important, SDR would enable future communications systems to be implemented on already-deployed hardware. This vision of interoperability and forward compatibility has not been realized, despite billions of dollars of investment in the Joint Tactical Radio System (JTRS). The authors reviewed JTRS program archives and studied the hardware and software architectures to determine whether there are fundamental technical reasons behind this failure. Our findings, which invoke the familiar trade off between performance and power consumption, are summarized in this paper. We identify three different architectural approaches used by the JTRS community over the years, and discuss why none has been able to realize the program´s goals.