How to determine reasonable royalty rates

Good evening

Thank you very much for your previous advice. I would like to ask about license royalty rates. In the course of our considerations of expanding into the EU market, we would like to discuss licensing options with our business partners there.

When going into licensing negotiations, how do we determine a reasonable royalty rate? Which approach would the prospective licensee employ? So far we have only been distributing our products directly to end-users.

We are a small company operating out of Tokyo. We develop software solutions that create top-speed, highly efficient software interfaces between smartphones and IoT Devices.