Interoperability and regulatory issues around Software Defined Radio (SDR) implementation

In the case of personal computers (PCs), interoperability among PCs are sufficiently realized with the advent of Microsoft Windows to take the position of mainstream OS, and major software applications following the mainstream for standardization, for more and more user-friendly human machine interface. Considering the case for PCs as above, it is not surprising to us at all, if the same concept is pursued in a radio communications terminal, which can freely access to different radio systems just by replacing the embedded software. This means that the prospective end user will gain the benefit to be able to change his radio set to one of the desired systems in the field, by installing the software of his choice. Such radio equipment is called Software Defined Radio (SDR), and various kinds of applications are expected for development in many fields. However, for the SDR to be in widespread use, we have many outstanding issues to be solved, which are not limited only in the technical matters. One barrier is interoperability among manufacturers. Namely, even when a technical problem is solved, the appropriate technical solution should be shared for the interoperability among as many manufacturers as possible. If such interoperability is unachievable, that technical solution could only be for internal use within the specific manufacturer, failing to take advantage of the true value of the SDR. Another barrier might be the Radio Law of Japan. Unless overcoming this barrier, the commercial implementation of the SDR is unachievable, resulting in the failure to entertain the real benefit from the SDR implication. Under such a background, this paper first describes the concept of and definition for the SDR to make them clearer for the readers. Then, the interoperability issue, which would be the key to the widespread use of SDR, is taken up as next topic. The last topic is focused on the legal and regulatory issue, to discuss what would be the problem under the Radio Law of Japan.