【作者】 黄勋；

【导师】 刘卫忠；

【作者基本信息】 华中科技大学 ， 软件工程， 2011， 硕士

【摘要】 正交频分复用(OFDM)是一种高速并行多载波传输方案,具有很强的抗多径衰落和窄带干扰的能力,但它存在一个很大的缺点,即具有较高的峰值平均功率比(PAPR),导致发送端对高功率放大器的线性度要求很高且发送效率极低,而且增加了A/D和D/A转换器的复杂度,限制OFDM的实际应用。因此,消减PAPR则成为了OFDM系统应用过程要解决的关键技术问题。目前已经提出了很多种降低PAPR的方法。最常见的有:限幅法、编码法、概率法、障碍函数法(IPM)。限幅类方法会造成信号的畸变;概率类方法如选择映射法(SLM)和部分传输序列法PTS,虽然都是无失真算法,但需要进行多次额外的IFFT运算,无疑增加了计算量,因此出现了使用IPM法抑制PAPR。它主要是通过调用凸集优化算法求解函数的最小值,经过几次迭代后有效地抑制PAPR。本文首先研究IPM函数,并通过OFDM系统的星座误差向量级数EVM和超额功率条件构造障碍函数。然后,在研究IPM法降低PAPR的方法基础上,研究了BFGS算法求解系统PAPR全局最优点的问题。与一般IPM法中使用牛顿迭代法不同的是,该算法在求最小值过程中,不再直接计算二阶求导矩阵(Hessian式)及其逆,而是使用校正公式得到Hessian的近似,从而减少了计算量。通过Matlab软件仿真表明,该算法可以有效地抑制系统PAPR,同时也降低了系统的数据存储和计算量。更多还原

【Abstract】 OFDM(Orthogonal frequency Division Multiplexing) is an very attractive technique for wireless high-bit-rate transmission due to the minimizing effects of frequency-selective fading and its high bandwidth efficiency. Howerer, OFDM has the high PAPR(Peak-to-Average-Power Ratio) which is its inherent disadvantage. These large peaks cause saturation in high-powered amplifier,leading to the lower transmitted efficiency, and increasing the complexity of A/D and D/A convertor.Therefore,the high PAPR limits the practical applications of OFDM.So,the PAPR reduction is of viral importance for OFDM systems with power efficient transmitter.Now,there are some technologys to solve it,such as signal pre-distortion techniques, and probability techniques. And two typical methods of probability techniques are SLM(Selective Mapping) and PTS(Partial Transmit Sequence) , which is widely used.Although SLM and PTS has little distortion,the computation complexity is quite large for the extra IFFT calculations. Then, IPM(interior point methods)has been propo- sed.IPM ,also refered to as the barrier methods, are a class of algorithms to solve linear and non-linear convex optimization problems, and through several Iterative convex programming Algorithm, optimal solution could be achieved faster than PTS or SLM.In this thesis, firstly,I would do research on the IPM algorithm. And based on Constellation EVM(Error Vector Magnitude) and power overhead, barrier function would be built.Secondly,I would do research on the recent algorithms of lowering the PAPR of OFDM signals by IPM , and then present BFGS algorithm to solve the IPM and get the global optimization.Different from the general IPM algorithms ,which use Newton methods to achive the optimal value, BFGS builds up an approximation of the inverse Hessian,so the complexity is reduced. Through MATLAB simulation , the results verify BFGS algorithm reduces PAPR value effectively, but the complexity is lower then the traditional Newton methods.更多还原