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传统理论认为,带限信道中传输码元的速率不能大于Nyquist速率,否则将会引起严重的码间串扰(ISI),降低通信系统的可靠性。然而在1975年Mazo提出,在加性白高斯噪声信道中,若码元速率超过Nyquist速率在25%以内,则仍可保证误码性能不下降。基于上述研究背景,文章结合基带传输系统无ISI传输的条件,给出了Nyquist速率的定义,介绍了利用部分响应系统实现Nyquist速率传输的思路和方法,并从进一步提高数据速率的角度,引出了FTN传输的概念,说明了部分响应与FTN的联系和区别,最后在介绍了信号空间、欧氏距离和均衡的基础上,结合波形阐述了FTN传输的基本思想和技术特点。
According to the traditional theory, the transmission rate of symbols in a band limited channel can not be greater than the Nyquist rate, otherwise it will cause serious inter-symbol interference (ISI) and reduce the reliability of the communication system. However, in 1975 Mazo proposed that in the additive white Gaussian noise channel, if the symbol rate is within 25% of the Nyquist rate, the error performance can still be guaranteed. Based on the above research background, this paper gives the definition of Nyquist rate based on the condition of no ISI transmission in baseband transmission system. The idea and method of using Nyquist rate transmission with partial response system are introduced. From the perspective of further increasing the data rate, The concept of FTN transmission shows the connection and difference between partial response and FTN. Finally, based on the introduction of signal space, Euclidean distance and equalization, the basic idea and technical characteristics of FTN transmission are described in combination with waveforms.