# A Model-Based Engineering Approach for Evaluating Software-Defined Radio Architecture
## 2 Descriptive Models
During the OOSEM model set-up phase, SysML was selected as the modeling language to build a descriptive model of a system. The OOSEM Specify and Design System process for the SDR-MM is organized using the SysML Package Diagram. The package organization includes stakeholder needs analysis, system requirements analysis, logical and physicalarchitecture definitions, and requirement traceability. Logical and physical architecture definitions were combined in one package, which includes functional analysis, structural analysis, and parametrics for each architecture alternative. This setup facilitated the functional decomposition analysis and evaluation process. Stylistic standards were defined for this project for the use of upper- and lower-case words and templates were established for diagram types. Information from various stakeholders, including primary user needs, government regulations related to the System of Interest (SOI), industry standards, and policies, can be collected and analyzed. For the SDR-MM, the stakeholder needs are characterized into six categories: (1) functional and performance needs, (2) interfaces, (3) design constraints, (4) electromagnetic environment effects, (5) environmental needs, and (6) lifecycle needs (reliability, safety, maintainability, testability, etc.). It is crucial to understand the needs and system-level requirements of the stakeholders before developing the SDR-MM, including the desired functionality, performance, and any constraints. In the example presented in this paper, the CONOP was derived based on the desired application of the SDR-MM: _which is to add a robust narrowband signal detection capability to an existing system. A fixed narrowband digital signal output is sent to a processor for detection processing. The data are requested based on the desired center frequency and bandwidth and passed over a low-speed data fabric._  
The system requirements are either derived or refined from stakeholder needs/CONOPs or are derived from decision analyses. It is important to keep in mind that system requirements are not set in stone and are subject to continuous updates as the architecture synthesis progresses. For the SDR-MM, 20 system requirements (Table 1) were developed, which are related to the six stakeholder needs categories previously mentioned. Traceability relations are used to ensure these system requirements are met during the architecture development process. The interactions between the SDR-MM and its external systems and environment were considered. The context structure is shown in the IBD in Figure 2 and depicts an operational configuration for the communication system during use. The SDR-MM is shown interacting with external systems that include a Low-Noise Amplifier (LNA), a Time-Frequency-Navigation Geodesy (TFNG) distribution card, an external host computer/processor, a power supply, the Communication Enclosure Air Environment (CEAE), and the Communication System Structure. Considering the SDR-MM as a black box, the IBD depicts how it interacts with other systems and defines the items (materials, energy, data, information, or signals) flowing between systems in the context. Figure 2: Interaction and interfaces between the system contexts. The SDR-MM's primary function is receiving and converting information from a radio source. A SysML activity diagram was created to depict the activities and behavior involved in the receive signal use case, as shown in Figure 3. This functional behavior definition