Cognitive Radio as a technological breakthrough and enabler for concepts such as Opportunistic Spectrum Access and Dynamic Spectrum Access has so far received significant attention from the research community from a theoretical standpoint. In this work, we build upon the theoretical foundation and present an implementation of a Software Defined Radio/Cognitive Radio platform, with the feature under particular interest being the so-called Smart Transmission Layer. Smart Transmission Layer is a feature developed within the currently ongoing nSHIELD project, whose goal is establishing new paradigms for Security, Privacy and Dependability (SPD) of the future embedded systems. The role of the SPD-driven Smart Transmission Layer is providing reliable and efficient communications in critical channel conditions by using adaptive and flexible algorithms for dynamically configuring and adapting various transmission-related parameters. The implementation was done on the test bed consisting of two Secure Wideband Multi-role-Single-Channel Handheld Radios (SWAVE HH) coupled with the powerful proprietary multi-processor embedded platforms, and the corresponding auxiliaries. Several case studies were performed, namely: remote control of the radios, analysis of the installed waveforms, interference detection, and spectrum sensing using a quasi-real-time energy detector. A roadmap towards the future implementation aspects using the test bed was set.