Transmitting with fewer constellation points

High spectral efficiency coded modulation schemes would induce complex quantifier and high peak to average ratio (PAPR) due to great number of constellation points. Based on the idea that a one-to-one mapping is only necessary from information bit sequences to channel symbol sequences, a novel scheme is proposed to reduce the constellation size. Key parameter of the system includes code rate, constellation size and labeling strategy. Optimization of these parameters and the system design criteria are discussed and analyzed. Iterative decoding and demodulation at the receiver side are also of great importance for the successful implementation of the system, thus its details are introduced. The new scheme achieves earlier Turbo cliff than coded modulation system with normal QAM constellation due to its increased distance between constellation points. Numerical results show the effectiveness of the novel scheme.