On Companding Schemes for PAPR Reduction in OFDM Systems Employing Higher Order QAM
On Companding Schemes for PAPR Reduction in OFDM Systems Employing Higher Order QAM
复制标题
DOI：
10.1109/tbc.2015.2511627
复制
发表时间：
2016-01
影响因子：
4.5
通讯作者：
Sana Mazahir;S. A. Sheikh
中科院分区：
文献类型：
--
作者：
Sana Mazahir;S. A. Sheikh
高峰均功率比(PAPR)是正交频分复用(Ofdm)系统中一个亟待解决的问题，因为它阻碍了模拟前端的有效设计。压扩是一种众所周知的技术，它通过使用确定性幅度变换来降低PAPR，该变换是通过假设信号幅度的瑞利分布来设计的。但在采用高阶QAM的正交频分复用系统中，如16-QAM或-QAM，这种概率模型不足以对信号的真实特征进行建模。这是由于平均符号功率的随机性质，其改变了从一个ofdm符号到另一个符号的完整幅度分布。这导致压实器的PAPR降低性能下降。在本文中，我们提出了两种改进压扩运算以适应符号功率随机性的新方案。对符号的平均功率与其组成样本的幅度的关系进行了概率分析。这产生了在设计所建议的低复杂性解决方案时所采用的理论框架。所提出的方案本质上使压扩操作本身不确定/自适应，即它在应用运行时根据变化的符号幅度分布进行调整。
Large peak-to-average power ratio (PAPR) of the signal is an imperative problem in orthogonal frequency division multiplexing (OFDM) systems, as it impedes the efficient design of their analog front end. Companding is a well-known technique that reduces the PAPR by using a deterministic amplitude transform, which is designed by assuming Rayleigh distribution for the signal amplitude. But in OFDM systems employing higher order QAM, like 16- or 64-QAM, this probabilistic model is insufficient to model the true characteristics of the signal. This is due to the stochastic nature of average symbol power, which alters the complete amplitude distribution from one OFDM symbol to another. This leads to degradation in the companders' PAPR reduction performance. In this paper, we propose two novel schemes that modify the companding operation to accommodate the randomness of symbol power. Probabilistic analysis of symbol's average power, in relationship with the amplitude of its constituent samples, is carried out. This yields the theoretical framework employed in the design of the proposed low-complexity solutions. The proposed schemes essentially make the companding operation itself nondeterministic/adaptive, i.e., it adjusts to comply with the changing symbol amplitude distribution during application runtime.