To improve the system throughput, this paper proposes a network non-orthogonal multiple access (N-NOMA) technique for the uplink coordinated multi-point transmission (CoMP). In the considered scenario, multiple base stations collaborate with each other to serve a single user, referred to as the CoMP user, which is the same as for conventional CoMP. However, unlike conventional CoMP, each base station in N-NOMA opportunistically serves an extra user, referred to as the NOMA user, while serving the CoMP user at the same bandwidth. The CoMP user is typically located far from the base stations, whereas users close to the base stations are scheduled as NOMA users. Hence, the channel conditions of the two kind of users are very distinctive, which facilitates the implementation of NOMA.Compared to the conventional orthogonal multiple access based CoMP scheme, where multiple base stations serve a single CoMP user only, the proposed N-NOMA scheme can support larger connectivity by serving the extra NOMA users, and improve the spectral efficiency by avoiding the CoMP user solely occupying the spectrum. A stochastic geometry approach is applied to model the considered N-NOMA scenario as a Poisson cluster process, based on which closed-form analytical expressions for outage probabilities and ergodic rates are obtained. Numerical results are presented to show the accuracy of the analytical results and also demonstrate the superior performance of the proposed N-NOMA scheme. Y. Sun and X. Dai are with the Key network NOMA (N-NOMA), coordinated multi-point (CoMP), stochastic geometry (SG), Poisson cluster process (PCP), multiple access.
I. INTRODUCTIONRecently, non-orthogonal multiple access (NOMA) has attracted significant research attentions in both academia and industry community, not only due to its superior spectral efficiency but also because of its compatibility with other advanced communication techniques [1]- [4]. The key idea of NOMA is to serve more than one user in each orthogonal channel resource block, e.g., a time slot, a frequency channel, a spreading code, or an orthogonal spatial degree of freedom. NOMA has been recognized as a key enabling multiple access technique for the fifth generation (5G) mobile networks. For example, downlink NOMA has been adopted by 3GPP-LTE systems as multiuser superposition transmission (MUST) [5]. Moreover, NOMA has been recently proposed for the forthcoming digital TV standard (ATSC 3.0), where it is referred to as layered division multiplexing (LDM) [6].
A. Related LiteratureThe concept of NOMA was initially proposed in [1] for future wireless netwroks. The performance of NOMA with randomly deployed users in a downlink scenario was investigated in [7], which shows that NOMA can outperform conventional orthogonal multiple access (OMA) in terms of outage performance and ergodic sum rates. To enhance the performance of users with weak channel conditions, cooperative NOMA was proposed in [8] by treating users with strong channel condition as relays. The user fairness of NOMA was studi...
