los信道 matlab,莱斯信道 - 木头弯弯的小窝 - 与非博客 - 与非网

我要产生一个赖斯信道,用一个这样的matlab语句:channel=racianchan(ts,fd,k,tau,pdg),tau和pdg向量,其长度是由k确定的吧?可是这两个向量的元素数值怎么设置啊?请大侠指教

Rician信道参数k才是实质重要的参数，tau和pdb是根据信道的profile delay可得的

rice分布是一个两参数分布，s^2和sigma^2，s^2表示接收信号中的非衰落信号分量(又称为镜像分量)，s^2/sigma^2就是函数里面的K，具体推导翻翻随机过程的书就能找到了

瑞利分布是赖斯分布的特例

当发送端到接收端没有一条直射路径的信道是瑞利信道，有一条的是莱斯信道

信道中存在LOS的信道，就是基站和MS之间视距可见是莱斯信道

莱斯信道通常用来模拟同时接收某个基站的主播以及多路反射波信道的情况

无线信道是大量统计的结果，如果信道的统计特性满足莱斯分布，就是莱斯信道。莱斯信道的特征是有一个直射路径。

首先无线移动信道一般都是多径信道，当我们传输的信号带宽小于信道相干带宽，这种信道称为平坦衰落信道，也可以称为频率非选择性衰落信道，在这个前提下，发送信号在传输的过程中发生多径传输，导致在接收端接收信号的幅度因多经信号叠加会发生衰落，这个接受信号幅度的分布可以是瑞利分布或是莱斯分布，当多条散射路径没有一个散射路径占主导地位时，就称为瑞利衰落信道；如果多径中有一条路径占主导地位，称为视距(LOS)分量，此时莱斯衰落信道

信宿接收到信源发射的视距直射信号(LOS)和其他反射信号/绕射信号的叠加(根据概率大数定理，n路独立同分布随机信号叠加近似为高斯分布)，所形成的信号(高斯分布+线性接收LOS信号=赖斯分布)服从莱斯分布(也称广义瑞利分布，在其零阶贝赛尔函数自变量为零的条件下，得到锐利分布)，具有赖斯分布特性的信道就成为赖斯分布。

Quote the explaination from Matlab help as follow:

chan =ricianchan(ts,fd,k,tau,pdb) constructs a frequency-selective ("multiple path" fading channel object that models the first discrete path as a Rician fading process and each of the remaining discrete paths as an independent Rayleigh fading process. tau is a vector of path delays, each specified in seconds. pdb is a vector of average path gains, each specified in dB.

函数channel = ricianchan(ts,fd,k,tau,pdg)生成一个多径衰落信道，信道的第一径服从rician分布，其余径服从rayleigh分布。其中ts为采样间隔，单位是s；fd为最大多普勒频移，单位是Hz；k是表示rician衰落中固定分量和发散分量的线性比值；tau是个数组，每个元素对应多径的时延；pdg与tau对应，表示每条径的功率，单位是dB。将发送的数据x经过滤波函数y= filter(channel，x)即可得到经过信道后的数据

chan = ricianchan(ts,fd,k)constructs a frequency-flat (single path) Rician fading-channel object. ts is the sample time of the input signal, in seconds. fd is the maximum Doppler shift, in hertz. k is the Rician K-factor in linear scale. You can model the effect of the channel chan on a signal x by using the syntax y = filter(chan,x). See filter (channel) for more information.单径莱斯，平坦

chan = ricianchan(ts,fd,k,tau,pdb)constructs a frequency-selective(multiple paths) fading-channel object. If k is a scalar, then the first discrete path is a Rician fading process (it contains a line-of-sight component) with a K-factor of k, while the remaining discrete paths are independent Rayleigh fading processes (no line-of-sight component). If k is a vector of the same size as tau, then each discrete path is a Rician fading process with a K-factor given by the corresponding element of the vector k. tau is a vector of path delays, each specified in seconds. pdb is a vector of average path gains, each specified in dB.多径，频率选择，可以有多条莱斯径

chan = ricianchan(ts,fd,k,tau,pdb,fdLOS) specifies fdlos as the Doppler shift(s) of the line-of-sight component(s) of the discrete path(s), in hertz. fdlos must be the same size as k. If k and fdlos are scalars, the line-of-sight component of the first discrete path has a Doppler shift of fdlos, while the remaining discrete paths are independent Rayleigh fading processes. If fdlos is a vector of the same size as k, the line-of-sight component of each discrete path has a Doppler shift given by the corresponding element of the vector fdlos. By default, fdlos is 0. The initial phase(s) of the line-of-sight component(s) can be set through the property DirectPathInitPhase.每条莱斯径都能有fd

chan = ricianchan sets the maximumDoppler shiftto 0, the Rician K-factor to 1, and the Doppler shift and initial phase of the line-of-sight component to 0. This syntax models a

If Doppler shift =0 thenit’s called Static channel, else dynamic channel

If Path number=1 then it’s called frequency-flat else ,frequency-selective : path number

The toolbox implements a baseband channel model for multipath propagation scenarios that include:

N discrete fading paths, each with its own delay and average power gain. A channel for which N = 1 is called a frequency-flat fading channel. A channel for which N > 1 is experienced as a frequency-selective fading channelby a signal of sufficiently wide bandwidth.

A Rayleigh or Rician model for each path.

By default, each path of the channel is modeled with a Jakes Doppler spectrum, with a maximum Doppler shift that can be specified. Other types of Doppler spectra are allowed (identical or different for all paths): flat, restricted Jakes, asymmetrical Jakes, Gaussian, bi-Gaussian, and rounded.

If the maximum Doppler shift is set to 0or omitted during the construction of a channel object, then the channel is modeled as static (i.e., the fading does not evolve with time), and the Doppler spectrum specified has no effect on the fading process.

主径一般定义为功率最强的径，第一径为第一条到达的径，line-of-sight视线可见路径

一般情况下，有line-of-sight时，line-of-sight功率最强，是主径，第一径

Echo时，由于发射功率的不同，可能先到达的未必是最强的。

PI PO TU6等信道是指定了多少条径以及每条径的分布特性以及tau, pdb等各种参数的信道，其中某些径可能服从让rayleigh或rician分布

Matlab的rayleighchan,ricianchan函数并没有显式指定sigma，应该用的是1,如果需要其他sigma，可以自己修改

每条径都可以有Doppler，虽然大部分情况只设置1个Doppler

径的分辨率由采样频率决定，1M采样，则sample周期1us，则多径分辨率1us,小于1us的无法看到

To model a channel that involves both fading and additive white Gaussian noise, use a fading channel block connected in series with the AWGN Channel block, where the fading channel block comes first.先加fading后加AWGN

Communication channels introduce noise, fading, interference, and other distortions into the signals that they transmit。噪声，衰落，干扰

Some useful topics in Matlab：

doppler.ajakes, doppler.bigaussian, doppler.jakes, doppler.rjakes, doppler.flat, doppler.gaussian, and doppler.rounded.

reset(chan)

plot(chan)

copy(chan)

Multipath Rician Fading Channel

Multipath Rayleigh Fading Channel

Rayleigh Noise Generator

Rayleigh Distribution

Channels

Gaussian Noise Generator

AWGN Channel

channel visualization tool

raylpdf

raylfit

randseed