# A Novel Multi-Cell Interference-Aware Cooperative QoS-Based NOMA Group D2D System
### Related Work
The authors in [19] only consider a single-cell scenario,i.e., no interference characterization at the receiver and no spatial topology was considered for D2D users. The effect of the integration of D2D in a downlink NOMA system was investigated in [20]. The authors proposed power control techniques for a pair of D2D users underlaid with a pair of cellular users. The superiority of NOMA over OMA was shown in terms of sum rate. An uplink multi-carrier NOMA-based D2D system underlaid with a cellular network was considered in [21]. The authors proposed an iterative algorithm using the Karush-Kuhn-Tucker (KKT) condition to enhance the channel throughput of the system. The system achieves near optimal performance. However, device clustering of the D2D network was ignored. In [22], a D2D-aided cooperative relaying system employing NOMA to increase the spectral efficiency of the system was proposed. In the proposed model, the base station transmits a signal to the relay and receivers. To increase the spectral efficiency of the system, the receiver obtains another independent signal from the relay. The relay also transmits its signal to another receiver, thus further enhancing the spectral efficiency. A power allocation strategy was also proposed, to enhance the capacity and the signal-to-noise ratio (SNR). However, when considering a multi-cell scenario, their results cannot be generalized and no particular random distribution was followed to define the spatial distribution of D2D users. The authors in [23] developed a sector-based green NOMA D2D system. A novel multiple-interference cancellation scheme was proposed which minimizes the interference in the network with optimized resource allocation. The proposed system is inferior to the SIC-based NOMA system. However, some performance gains in terms of energy efficiency and fairness factor were achieved. A D2D-assisted NOMA relaying scheme was proposed by the authors of [24]. The authors improved the signal-to-interference-noise ratio (\(SINR\)) of a far user by employing maximal ratio combining (MRC) on a NOMA signal in the first phase of communication from a base station and in a D2D-assisted NOMA signal from relay in the second phase. The proposed system achieves a better average data rate than the traditional OMA system. However, the user location is assumed to be fixed and no interference is assumed at the receivers, which make the proposed system very simple and unrealistic. The authors in [25] investigated an under-laid NOMA-based D2D network. The sum rate of the overall system is maximized by employing a joint power allocation and user clustering. The proposed model achieves performance gain in terms of average sum rate and user connectivity as compared to a traditional NOMA and OMA system. The proposed model deploys the D2D users at fixed locations and follows PPP, which cannot fully comprehend a D2D network [18; 26]. A cooperative NOMA-associated D2D system employing decode and forward relaying was considered in [27]. The authors assumed a direct link between the base station and D2D user and an extra power-line link for weak users. The system was analyzed for the optimum and operational value of the power allocation coefficient for the strong user. The simulation results showed that the outage probability reduced sufficiently with the addition of a power-line link at low SNR values. However, a multi-cell corporation analysis was not included in the discussion. In [28], the proposed system's model employs the NOMA power domain to separate the user data in a large-scale D2D network using a cooperative hybrid automatic repeat request (HARQ). The system performance in terms of outage and throughput was studied and it was shown that the proposed system outperforms OMA and non-cooperative NOMA. A potential limitation in this system's model is that the authors only consider two user NOMA transmissions in D2D communication.