Virtual user pairing based non-orthogonal multiple access in downlink coordinated multipoint transmissions

In this study, joint transmission coordinated multi-point (JT-CoMP) is integrated with virtual user pairing based non-orthogonal multiple access (VP-NOMA), termed as JT-CoMP VP-NOMA. JT-CoMP is a multi-cell coordination scheme, where base stations of neighbouring cells coordinate with each other to improve the performance of their common cell edge users (CEUs). On the other hand, VP-NOMA is a one-to-many user pairing scheme in non-orthogonal multiple access (NOMA), where one cell centre user (CCU) within a cell can be paired/multiplexed with multiple CEUs for better spectrum utilisation. The proposed scheme combines both VP-NOMA for enhancing ergodic sum capacity (ESC) within a cell and JT-CoMP for mitigating inter-cell interference (ICI) between neighbouring cells. To demonstrate the achieved performance gains, ESC of a three-cell scenario is analysed as a key performance metric, where each cell contains two users; a CCU and a CEU. Closed-form expressions for ESC of the considered system are derived, and validated through simulations. Furthermore, the analytical and simulation results of JT-CoMP VP-NOMA are compared with orthogonal multiple access, NOMA, and VP-NOMA to show the achieved performance gains. It is shown that the proposed JT-CoMP VP-NOMA outperforms the other schemes in the viewpoint of ESC.