概述了OFDM物理层射频调制的CMMB(中国移动多媒体广播)发射机的系统结构.OFDM多载波调制存在峰均比过高的缺陷,会直接恶化功率放大器的效率.作为唯一和CMMB发射系统相匹配的峰均比抑制方案,削波结合星座图扩展的技术,以其结构简单,节约频谱资源的优势,是目前工程实现的热点.设计的CMMB发射机射频调制方案就是以成熟的削波和星座图扩展技术为基础的.大量的实验证明,这种方案在高斯信道条件下可以有效地提高峰均比抑制特性,并且不会削弱系统的误比特性能.%In this paper, an overview of China Mobile Multimedia Broadcasting (CMMB) transmitter system is given, which is based on Orthogonal Frequency Division Multiplexing (OFDM) structure as the modulation mode in physical layer. However, the high pcak-to-average power ratio (PAPR) in OFDM modulation systems can significantly reduce power efficiency and performance. As the only PAPR reduction method backward compatible with CMMB transmission scheme, the clipping based active constellation extension (ACE) technique is simple and attractive for practical implementation- Based on mature signal processing Clipping, ACE, an unabridged structure of CMMB transmitter modulation is designed Extensive simulations in additive white Gaussian noise (AWGN) channel show how this approach can improve the PAPR reduction without degrading the Bit Error Rate ( BER) performance.
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