Device-to-device (D2D) communication is a promising technology in which the spectrum resources are reused efficiently with cellular mobile users (CMUs) in an underlay of the fifth generation network. Using it, network capacity and spectral efficiency increase but it introduces the cochannel interference. Moreover, massive connectivity has not been fully exploited for efficient spectral efficiency usage in the existing solutions. Therefore, to address the aforementioned challenges, we integrate power domain nonorthogonal multiple access (PD-NOMA) technique with the D2D mobile groups (DMGs) to maximize their sum rate and to maintain the signal-to-interference noise ratio provided by CMUs. We formulate the problem of spectrum reuse as mixed-integer nonlinear programming and then converted it into two subproblems. First, the DMGs are formed between the D2D transmitter and D2D mobile users to reduce the intrauser interference using successive interference cancellation technique. Second, the resource allocation scheme for both the CMUs and DMGs is designed to mitigate the cross and cochannel interference using many-to-many mapping scheme. Also, to fully exploit the potential benefits of DMGs, the group rate selection criterion based resource block reuse algorithm among DMGs is designed. Finally, for power optimization, we use the difference of two convex functions programming approach based on a successive convex approximation low complexity. To simulate the proposed scheme, the 3GPP urban path loss model based on release 15 and RAN1 is used. Numerical results demonstrated that the proposed scheme has superior sum rate as compared to the existing NOMA and orthogonal frequency-division multiple access schemes.
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