Small Cell Forum is not purely for SDR, but I wanted to introduce this since there are some documents that would help a lot for Software Architecture Design for LTE. The specific document that I wanted to introduce is nFAPI and FAPI specifications and this page will be mostly around this document. If you read this document along with analyzing the real source code from other LTE SDR project, you would have much better knowledge on overall architecture of those source code. I don't think the real source code from other LTE SDR project is written directly based on the SCF(Small Cell Forum) FAPI. So you would not see the one to one mapping between the source code and SCF document, but I am pretty sure that this document will help you understand the functionality of the source code.