Power minimization in 5G Heterogeneous Cellular Networks

In this paper, the minimizing transmit power in 5th generation (5G) is investigated. To minimize transmit power, different appropriate schemes such as heterogeneous cellular network (HetNet) and non-orthogonal multiple access (NOMA) have been proposed in 5G. In NOMA scheme more than one user can be allocated in the same sub-carrier. Th is scheme uses superposition coding (SC) on transmitter side to multiplexing the multiple users, and successive interference cancellation (SIC) on the receiver side to separating user’s signal. Obtaining joint sub-carrier and power allocation in NOMA-based HetNet is the aim of this work. In this regard, the proposed objective function is to minimize the total transmitted power in all cells subject to the constraint related to NOMA scheme in addition to user’s minimum rate requirement constraint. An iterative algorithm is applied to solve our problem. Since the problem is nonconvex and incorporate both integer and continuous variables, it cannot be solved directly. Th erefore, we decompose it into two subproblems: sub-carrier and power allocation. In each iteration, the sub-carrier allocation is updated by applying integer linear programing (ILP) and, the power allocation is updated by applying successive convex approximation for low complexity (SCALE). Simulations results show that the proposed algorithm in NOMA-based system performs better than the OFDMA-based system.