Sum-Rate Improvement With Power Distribution Scheme for Low-Complexity Decoding Rate Splitting

The combination of Non-Orthogonal Multiple Access (NOMA) and Multiple Input Multiple Output (MIMO) technologies has been identified as a powerful strategy to achieve high spectral efficiency and improved wireless services. Imperfect Channel State Information at Transmitter (CSIT) can lead to multiuser interference issues that pose obstacles for wireless networks utilizing MIMO technology. Instead of maintaining the accurate CSIT, Rate Splitting (RS) directly addresses the issue of imperfect CSIT by dividing user messages into private and common messages. Generalized RS is designed to maximize the achievable rate and Quality of Service (QoS) at the cost of transceiver complexity. The increasing number of users served by the Generalized RS raises the number of Successive Interference Cancellation (SIC) processes; consequently, this can place a more significant burden on users in carrying out the SIC process. This paper aims to improve RS performance by employing power distribution adjustment without increasing the number of SICs, which would burden users in the overloaded network. We apply power distribution adjustment to 1-layer RS and 2-layer Hierarchical RS (HRS), called 1-layer RSPDA and 2-layer HRSPDA, which require one or two SICs per user. The simulation results demonstrate the capabilities of the proposed methods to enhance the total sum rate of the system for low-complexity decoding RS. 1-layer RSPDA and 2-layer HRSPDA achieve an increase of 13.68 % and 12.64% in sum rate compared to Generalized RS at Signal-to-Noise Ratio (SNR) of 30 dB, respectively.