TCM-assisted Non-orthogonal Multiple Access OFDM Systems

• Main Authors: Hsieh, Jung-Ching, 謝榮敬
• Other Authors: Wu, Wen-Rong
• Format: Others
• Language: en_US
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/69631208471884639286

碩士 === 國立交通大學 === 電信工程研究所 === 104 === It is known that non-orthogonal multiple access (NOMA) can provide higher capacity than orthogonal multiple access. In 3GPP, some NOMA schemes have been standardized, known as multiuser-superposition-transmission (MUST). In this thesis, we study MUST schemes and propose a trellis-coded-modulation (TCM) assisted NOMA system. The proposed system consists of a convolutional code operated in bit-level and a cascaded TCM code operated in symbol-level. To have an unequal-error-protection property for near and far users, four-dimensional TCM is used to construct square-shape QAM constellations, providing two transmission rates for the near user. Power allocation is reserved in the proposed scheme, effectively increasing the flexibility in real-word applications. At the receiver, an iterative decoding scheme is conducted with the BCJR algorithm. With the proposed scheme, dependence is not only introduced in the bit level but also in the symbol level in the subcarriers. This will enhance the resisting capability for frequency-selective fading. The proposed scheme requires minimum changes in current LTE specifications and its real-world application is highly feasible. Simulation shows that the proposed method performs much better than the existing NOMA scheme.