bp

对语音信号进行加噪，求它的功率谱，降噪处理(Adding noise to speech signal and reducing noise)

its a matlab code for the orthoganal

说明：  在AM信号中，载波分量并不携带信息，仍占据大部分功率，如果抑制载波分量的发送，就能够提高功率效率，这就抑制载波双边带调制DSB-SC（Double Side Band with Suppressed Carrier），简称双边带调制（DSB）。(In AM signal, the carrier component does not carry information and still occupies most of the power. If the transmission of the carrier component is suppressed, the power efficiency can be improved. This is called double side band with suppressed carrier (DSB for short).)

OFDM通信系统的仿真代码，可用作数字通信的分析参考(The simulation code of OFDM communication system can be used as analysis reference of digital communication.)

A 2x2 multiple-input multiple-output (MIMO) architecture using dual-polarized antennas (DPAs) is considered with orthogonal frequency division multiplexing (OFDM). The performance of DPAs is evaluated for adaptive polarization (AP) transmission techniques in time-varying multipath channels impaired by polarization mode dispersion (PMD) and polarization-dependent loss (PDL). AP transmission techniques considered include power gain maximization, polarization dispersion minimization for interference avoidance, polarization multiplexing with waterfilling, and a suboptimal multiplexing strategy that enables direct recovery of the polarization multiplexed streams, thereby simplifying the design of the receiver. Measured time-varying dual-polarized channel realizations from mobile-to-mobile experiments are used to estimate the capacity, diversity, and interference avoidance performance of the adaptive approaches.

无线信道建模一直以来都很复杂，而且不同场景下的模型差异较大，这是一本专门讲解无线信道建模方法的书籍配套的matlab例程(Channel modeling has been very complex, and the model under different scenarios are quite different, which is the one devoted to channel modeling method books matching matlab routines)

a document wich explain spectral null codes

本程序分析了MIMO系统中发射天线数目对系统容量的影响(This program analyzes the MIMO system, the number of transmit antennas of the system capacity,)

1. 关于无线信道的多普勒谱，请回答以下问题： (1) 在某些无线信道中，多普勒频移会引起无线信道输出信号的混叠。请清楚的描述产生混叠的各种原因； (2) 无线信道中的多普勒谱有一种经典谱(classic spectrum)，请解释产生这种谱形状的机理； (3) 请用S-function产生一单径瑞利信道，其多普勒谱为经典谱，其中移动速率为120km/h。并请回答：证明自己用计算机产生的经典谱是正确的可能方法。 (Doppler spectrum of radio channel 1, please answer the following questions (1) In some wireless channel, radio channel Doppler shift will cause the output signal aliasing. Please clearly describe aliasing for various reasons )

说明：  载波同步是QPSK信号相干解调的一项关键技术。(Carrier synchronization signal coherent QPSK demodulation is a key technology.)