# Link and System-Level NOMA Simulator: The Reproducibility of Research
## 1 Introduction  
Dependency on mobile wireless communication has increased at enormous rates over the past few decades. The rapid increase in the demand for subscribers has posed challenges in terms of improved data rate, low latency, large coverage, and enhanced reliability [1]. Therefore, to satisfy market demands, the research community is focusing on the proposal of new techniques and approaches for the development of 5G mobile networks. These networks are aimed at a three-fold expansion in the spectral efficiency of future systems as compared to existing networks [1]. Several potential candidates have gained the attention of researchers for future radio access (FRA), where new non-orthogonal multiple access (NOMA) schemes have been examined, such as multi-user shared access (MUSA), which uses a special spreading sequence to overlap and transmit the data through the channel [2, 3]. Pattern-division multiple access (PDMA) is another type of multiple access scheme that utilizes encoded patterns to multiplex data at the same time, frequency, and spatial resources [4]. Similarly, sparse code multiple access (SCMA) is a non-orthogonal multiple access scheme that is a code-book-based data mapping technique to enhance the sparsity and shaping gain of each layer, where the message passing algorithm is used for multi-user detection [5]. Furthermore, various state-of-the-art techniques related to NOMA have been presented by researchers to explore and analyze the quality of service andsuccessful SIC operation at the receiver side. The full-duplex NOMA system is presented in [6], where researchers have demonstrated improved throughput and energy efficiency by utilizing the cooperative NOMA technique. Multi-subchannel resource allocation was investigated in [7]; to maintain the low complex structure of NOMA and enhance energy efficiency. The purpose of these techniques is to improve the resource allocation, SIC, and interference management process that provide significant gains in terms of bit error rate (BER), energy efficiency and signal detection probability at the receiving end. The above-mentioned schemes manifest the basic principle of NOMA to multiplex users in the time, frequency, and spatial domains. This article mainly deals with the power domain NOMA (PD-NOMA), which comprises a superposition coding (SC) algorithm to combine the user's data at the transmitter side and successive interference cancellation (SIC) at the receiver side to recover the data. As the name indicates, NOMA works in a non-orthogonal fashion, where users are multiplexed in the power domain instead of the time or frequency domain. The significance of user multiplexing in the power domain is resource allocation, where users share the entire time/frequency-domain resource block simultaneously. This approach is different from the conventional orthogonal multiple access (OMA) system, where resources are exclusively allocated to one user, and triggers the scarcity of resources for the other users. Although, NOMA has not been standardized, it has been suggested in the 13 th release of 3 GPP-LTE (A) as multiuser superposition transmission. To meet the demands of future 5G networks, the NOMA technique confirms the improved performance of the system owing to its ability to work on top of other technologies such as multiple-input-multiple-output (MIMO) and distributed antenna systems [8]. Using NOMA on top of such technologies will provide extra frequency reuse gain to further boost performance. The employment of NOMA in combination with beamforming technologies in the small-cell environment is an intriguing application scenario as well. However, despite the cost of a complex detection procedure, the benefits provided by NOMA on top of these technologies, including optimal resource allocation, higher data rate, and reduced latency, are substantial. The research conducted herein is specifically related to the development of a simulator for NOMA-based systems.