New generation wireless communication systems should support the increasing demand for efficient utilization of the electromagnetic spectrum. The Cognitive Radio (CR) paradigm is envisioned as a new technique to realize this goal. Nowadays, Software Defined Radios (SDRs) are the foundations on which the CR will be achieved. In this thesis we implemented an SDR network testbed based on a GNU radio platform. The test network was used to evaluate the actual performance of two methods that attempt to contribute as constituents of a Radio Environment Map (REM). REMs are a new approach to provide situation awareness for CRs. The first technique under analysis was a colouring-based frequency allocation mechanism that optimizes the assignment of frequency channels in the 2.4 GHz band. Its effectiveness was demonstrated using several performance tests in different scenarios and conditions. This study also explores the viability of using our SDR testbed to execute real-time power measurements to estimate the dynamics of indoor radio propagation. This is a preliminary step to obtain complete radio environment awareness, and thus contribute towards realizing the REM and CR approaches.