Non-Orthogonal Multiple Access Scheme And Signal Design For 5G Mobile Communication Systems

With the worldwide spread of 4G wireless technology, mobile internet has been developed rapidly. Explosive growth of traffic volume, massive interconnected devices and new diverse services all challenge the future mobile communications technology. The fifth generation (5G) mobile communication has attracted significant focus and research.Facing with the higher requirements in all aspects, the main demand for 5G systems are still the higher capacity and higher quality of user experience. Non-orthogonal multiple access (NOMA) suggests one candidate technique for future radio access owing to its advantages in significantly increasing system spectrum efficiency.The traditional NOMA scheme and signal design have been investigated in many literatures. These schemes multiplex users in power-domain at the transmitter side and separate signals at the receiver side based on successive interference cancellation. From a theoretical perspective, the NOMA schemes implemented in power-domain can only achieve the vertices of the Gaussian multiple-access channel capacity region. In addition, once the power is allocated for each user, the transmit rate is correspondingly determined no matter whether it is appropriate.To overcome the shortcomings of the traditional NOMA schemes, we propose a rate-splitting non-orthogonal multiple access (RS-NOMA)scheme and signal design for practical scenarios in 5G mobile communication systems. The main idea of the RS-NOMA scheme is to split original data streams from users into virtual data streams, then split the original power and assign them to the virtual data streams to adjust the users' rates. Since the rate-splitting technique achieves every point of the boundary of the capacity region, the RS-NOMA scheme can flexibly adjust the users' rates according to practical demand while the sum rate remains maximum, no matter whether the power is allocated for each user or constrained.We emphasize on the practical design for the RS-NOMA scheme. We investigate the signal-to-noise ratio (SNR) region division for the proposed scheme and then a splitting factor optimizing algorithm to enable the system achieving the maximum throughput. Simulation results show that the RS-NOMA scheme significantly improves the user flexibility without loss to the system spectrum efficiency. The RS-NOMA scheme off ers an optimal splitting approach to solve the mismatch between service demand and channel conditions of users, which can efficiently improve the system performance.