The software approach to developing Digital Signal Processing (DSP) applications brings some great features such as flexibility, re-usability of resources and easy upgrading of applications. However, it requires long and tedious tests and verification phases because of the increasing complexity of the software applications. This implies the need of a software programming environment capable of putting together DSP modules and providing facilities to debug, verify and validate the code. The objective of the work is to provide such facilities as simulation and verification for developing DSP software applications. This led us to developing an extension toolkit, EPSPECTRA, built upon PSPECTRA, one of the first toolkits available to design basic software radio applications on standard PC workstations. In this paper, we first present EPSPECTRA, an ESTEREL-based extension of PSPECTRA that makes the design and implementation of portable DSP applications easier. It allows the drastic reduction of testing and verification time while requiring relatively little expertise in formal verification methods. Second, we demonstrate the use of EPSPECTRA, taking as an example the radio interface part of a GSM base station. We also present the verification procedures for the three safety properties of the implementation programs which have complex control-paths. These have to obey strict scheduling rules. In addition, EPSPECTRA achieves the verification of the targeted application since the same model is used for the executable code generation and for the formal verification.