# A Novel Multi-Cell Interference-Aware Cooperative QoS-Based NOMA Group D2D System
### Related Work  
Recently, a lot of research works have been performed on NOMA and D2D relaying separately. However, little attention has been paid to relaying in NOMA-based D2D communication. The authors in [13] proposed a two-phase cellular and D2D transmission scheme which is based on the principle of NOMA. The authors considered a single-cell network with two users (near and far), where the base station (BS) transmits data simultaneously to both the users. However, based on the decoding status, either the D2D transmitter or receiver send the BS data to the far user. In order to demonstrate the effectiveness of the proposed scheme, the authors conducted extensive simulations to analyze the overall throughput of the system. The results show that the proposed system outperforms the existing systems, which are based on the OMA technique. However, the system only considers two users and is limited to only a single-cell scenario. In [14], the authors proposed a joint subchannel and power allocation algorithm for a NOMA-associated D2D communication system. The authors proposed a novel many-to-one matching-theory-based subchannel allocation algorithm which was then used to solve the non-convex power-allocation problem. The simulation results show that the sum rate of the NOMA-associated D2D systems is better than the OMA-based D2D system. However, the authors only considered a single cell without corporation between the users. In [15], the authors considered an OMA-based full-duplex (FD) cooperative D2D (C-D2D) network. The D2D transmitter (DT) assumes the role of FD relay in order to realize bidirectional communication between the BS and cellular user. The authors employed NOMA in order to manage resources between cellular and D2D users. Further, the overall system performance was evaluated by deriving the analytical expressions for achievable rates (cellular and D2D users) and outage probability (FD and half-duplex (HD) systems). The numerical results demonstrate that the proposed system manages to achieve better outage performance for both the cellular and D2D user. However, the proposed system lacks analysis of its interference and is also limited to the single-cell scenario. The authors in [16] explored a NOMA-based cooperative cellular network. In the proposed network setting, only the center cell users can establish a direct communication link with the BS, whereas the edge cell users would require a relay in HD mode to facilitate its transmission. Further, a new two-stage relay selection strategy (TSRS) was proposed which aims to reduce the outage probability of center cell users while enhancing the probability of successful reception at the edge cell user. The authors derived the closed-form analytical expressions for outage probability at each user (center and edge) in order to evaluate the performance. The results show that the proposed D2D-aided cooperative NOMA system achieves better outage performance than the conventional partial-relay selection scheme. The authors in [17] introduced the idea of NOMA-based group D2D communication. The system uses a power allocation scheme to reduce the interference between different D2D groups using the same sub-channels. The authors only considered a single-cell scenario which lacks the effect of interference, and the spatial distribution of the D2D does not follow any specific distribution. A group D2D-enabled system model in a NOMA communication system was proposed in [18], and the authors calculated the outage performance of the system in a multi-cell scenario, but the cooperation between the nodes, which would further improve the system's performance, was not analyzed. In [19], the authors proposed a cooperative full-duplex (FD) D2D-based NOMA communication network. The strong and weak users in a single cell co-operate with each other to increase the outage performance of the system. The base station sends the signal to an FD-enabled strong user and forward it to its predefined weak user pair.