The waterfall-based software development methodology usually requires significant efforts and lengthy intervals to develop, review, inspect, and test very large and complex real-time software systems. Although the methodology itself is stable and mature, the quality of software products still largely depends on development efforts expended in testing, which is usually very costly and time consuming. The author describes the implementation of an integrated approach of software development, review, inspection, and testing based on well-identified software requirements. Due to the huge size and the complex feature interactions of the 5ESS Switch software, the process of review, inspection, and testing has been very important to the project. To enhance the quality of the products, it is necessary to ensure the feature requirements requested by customers, external and internal, are developed correctly. The requirement traceability procedure described in the paper is a systematic method to assist 5ESS Switch scientists and engineers to achieve the goal. The results of the implementation of the requirement traceability procedure and its RADIX tool are significant