# Link and System-Level NOMA Simulator: The Reproducibility of Research
## 1 Introduction
Various simulator-related articles have been presented in the literature [9; 10; 11; 12] where, 4G-LTE-communication-network-lab presented an end-to-end 4G LTE and IMS Network Simulation-Test-Suite (STS) that includes all components such as NodeB, MME, Serving Gateway, and others to allow comprehensive LTE network testing [13]. Similarly, researchers in [12] presented a 4G Planning Tool that is a multi-agent-based mobile traffic simulator (MTS) built with Google Maps and JavaScript programming languages. However, the aforementioned works mainly focus the LTE or 4G standards and lacks the utilization of NOMA as multiple-access technique to support mass connection for 5G and beyond. As a result, to the best of our knowledge, our work is believed to be the first study provided as a software simulation suite related to NOMA. The main objective of this simulator is developing a platform for researchers to reproduce results related to NOMA. Although reproducibility is not an entirely new idea from the perspective of different studies such as mathematics and nature science, it is a relatively new proposal from the signal processing perspective. It deals with the reproduction of different results generally observed in numerous research articles [14; 15; 16; 17; 18]. Reproducing results from other papers is no doubt a challenging task because precise information is not shared in the articles for various reasons, such as lack of access to methodological details, suppressed information due to limitations in allowed pages, and under-reporting of undesirable experimental results. However, if a beginner or a cross-domain expat wants to further work on a published article, the omission of such minor details makes it difficult to generate the same results as published in the considered article. This situation becomes more tedious when the authors are unable to generate their expected simulation results [11; 19]. Reproducibility is especially important in areas where experimental research has been conducted [20]. The research community related to signal processing is even trying hard to work on the ideas that lead to negative results. Therefore, promoting the publication of negative results where one can discuss what hypothesis needs to be avoided in a particular domain is crucial; this will help freshers avoid repeating the mistakes carried out by others [21]. Therefore, this article presents a better software suite solution for the NOMA technique, where link-level and system-level environments for reproducible research are demonstrated. The main motivation behind the development of the NOMA simulator is to provide a simulation environment to the researchers, specifically for the generation of results that have already been published in the equivalent research article. This particular simulator follows the baseline of long-term evolution (LTE) as the Vienna LTE simulators presented in [20]. The link-level and system-level simulators for NOMA-based systems lead to the following contributions:  
* It can support both single carrier (SC) and the multi-carrier (MC) downlink NOMA system, which is based on orthogonal frequency division multiplexing (OFDM). * Different forms of SIC are considered for downlink scenarios such as perfect SIC, symbol level SIC, code-word level SIC and iterative SIC. * Generally, the trend followed by the research community is to focus on spectral efficiency as a performance metric to analyze the performance of any proposed techniques for SC and MC-NOMA based systems. However, the presented simulator provides an environment to evaluate the performance using different metrics in addition to the spectral efficiency, e.g., uncoded bit error rate (BER), coded BER and throughput. * For system-level analysis, 7-cell and 19-cell scenarios are considered together with the wrap-around concept. Normally, NOMA-related publications only analyze two users; however, we also examine the effects of more than two users in a cell. * Intercell interference is also considered for multicell scenarios.