Unraveling the Relation between QCN9274 QCN6274|Wallys WiFi7

文章介绍了WiFi7技术及其对无线连接速度和性能的提升。QCN9274和QCN6274这两款芯片是WiFi7的核心,它们协同工作,提供超高速度、低延迟和出色的可靠性。这种组合在提高网络速度、覆盖范围和稳定性方面具有革命性影响,尤其适用于数据密集型应用和物联网设备。WallysCommunications(Suzhou)Co.,LTD提供了支持WiFi7的解决方案,强调了其对产品质量和客户满意度的承诺。

Welcome to the future of wireless connectivity! As technology continues to evolve, we are witnessing the emergence of WiFi 7, promising unimaginable speeds and enhanced performance. In this post, we'll explore the exciting relation between two cutting-edge wireless chips that are at the forefront of this revolution: the QCN9274 and the QCN6274.

Understanding WiFi 7:

WiFi 7, also known as 802.11be, represents the latest iteration of the IEEE 802.11 standard. It is designed to take wireless connectivity to a whole new level, promising even higher data transfer rates and greater capacity than its predecessor, WiFi 6 (802.11ax).

Meet the QCN9274:

The QCN9274 is a powerful and advanced wireless chip developed by a leading tech company. It is a key component that enables devices to support the blazing-fast speeds of WiFi 7. This chip is engineered to deliver ultra-high data rates, lower latency, and exceptional reliability.

The Role of QCN6274:

On the other hand, the QCN6274 is another high-performance wireless chip that complements the QCN9274. While the QCN9274 focuses on handling the critical aspects of WiFi 7, the QCN6274 works in harmony to boost overall performance and ensure seamless connectivity.

Synergy for Unmatched Performance:

The combination of the QCN9274 and QCN6274 is truly a game-changer. Together, they form a powerful duo that enhances not only the speed but also the coverage and reliability of WiFi 7 networks. This synergy allows users to experience lag-free streaming, faster downloads, and unparalleled performance in congested environments.

A Leap in Wireless Technology:

With the QCN9274 and QCN6274 duo, the world of wireless technology is taking a giant leap forward. As more devices integrate these chips, users will enjoy a future-proof network that can handle the ever-increasing demands of data-intensive applications, smart homes, and Internet of Things (IoT) devices.

Embracing the Future:

As WiFi 7 continues to gain traction, we can expect to see a wider range of devices leveraging the capabilities of QCN9274 and QCN6274. From smartphones and laptops to smart TVs and smart appliances, the possibilities are endless.

In conclusion, the relation between QCN9274 and QCN6274 is pivotal in enabling Blazing-Fast Speeds WiFi 7. Their combined power ensures a wireless revolution that sets the stage for a connected future with unparalleled speed and performance.

These days, Wi-Fi 7 solutions are offered by Wallys !

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More DATE AND INFORMATION

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Looking ahead, Wallys Communications (Suzhou) Co., LTD is committed to continuing its tradition of innovation and excellence. The company will continue to invest in research and development to create new and improved communication solutions that meet the evolving needs of its customers.

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BY:Wallys Communications (Suzhou ) Co., LTD

EMAIL:​sales4@wallystech.com

``` function [T21, err90, err95, err99] = causality_est(xx1, xx2, np) % % function [T21, err90, err95, err99] = causality_est(x1, x2, np) % % Estimate T21, the information transfer from series X2 to series X1 % dt is taken to be 1. % % On input: % X1, X2: the series (n by 1 colum vectors) % np: integer >=1, time advance in performing Euler forward % differencing, e.g., 1, 2. Unless the series are generated % with a highly chaotic deterministic system, np=1 should be % used. % % On output: % T21: info flow from X2 to X1 (Note: Not X1 -> X2!) % err90: standard error at 90% significance level % err95: standard error at 95% significance level % err99: standard error at 99% significance level % % Citations: % X. San Liang, 2014: Unraveling the cause-effect relation between time series. Phys. Rev. E 90, 052150. % X. San Liang, 2015: Normalizing the causality between time series. Phys. Rev. E 92, 022126. dt = 1; [nm, one] = size(xx1); dx1(:,1) = (xx1(1+np:nm, 1) - xx1(1:nm-np, 1)) / (np*dt); x1(:,1) = xx1(1:nm-np, 1); dx2(:,1) = (xx2(1+np:nm, 1) - xx2(1:nm-np, 1)) / (np*dt); x2(:,1) = xx2(1:nm-np, 1); clear xx1 xx2; N = nm-np; C = cov(x1, x2); dC(1,1) = sum((x1 - mean(x1)) .* (dx1 - mean(dx1))); dC(1,2) = sum((x1 - mean(x1)) .* (dx2 - mean(dx2))); dC(2,1) = sum((x2 - mean(x2)) .* (dx1 - mean(dx1))); dC(2,2) = sum((x2 - mean(x2)) .* (dx2 - mean(dx2))); dC = dC / (N-1); % C_infty = cov(x1, x2); C_infty = C; detc = det(C); a11 = C(2,2) * dC(1,1) - C(1,2) * dC(2,1); a12 = -C(1,2) * dC(1,1) + C(1,1) * dC(2,1); % a21 = -C(1,2) * dC(1,2) + C(1,1) * dC(2,2); % a22 = C(2,2) * dC(1,2) - C(1,2) * dC(2,2); a11 = a11 / detc; a12 = a12 / detc; % a21 = a21 / detc; % a22 = a22 / detc; f1 = mean(dx1) - a11 * mean(x1) - a12 * mean(x2); % f2 = mean(dx2) - a21 * mean(x1) - a22 * mean(x2); R1 = dx1 - (f1 + a11*x1 + a12*x2); % R2 = dx2 - (f2 + a21*x1 + a22*x2); Q1 = sum(R1 .* R1); % Q2 = sum(R2 .* R2); b1 = sqrt(Q1 * dt / N); % b2 = sqrt(Q2 * dt / N); % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % covariance matrix of the estimation of (f1, a11, a12, b1) %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % NI(1,1) = N * dt / b1/b1; NI(2,2) = dt/b1/b1 * sum(x1 .* x1); NI(3,3) = dt/b1/b1 * sum(x2 .* x2); NI(4,4) = 3*dt/b1^4 * sum(R1 .* R1) - N/b1/b1; NI(1,2) = dt/b1/b1 * sum(x1); NI(1,3) = dt/b1/b1 * sum(x2); NI(1,4) = 2*dt/b1^3 * sum(R1); NI(2,3) = dt/b1/b1 * sum(x1 .* x2); NI(2,4) = 2*dt/b1^3 * sum(R1 .* x1); NI(3,4) = 2*dt/b1^3 * sum(R1 .* x2); NI(2,1) = NI(1,2); NI(3,1) = NI(1,3); NI(3,2) = NI(2,3); NI(4,1) = NI(1,4); NI(4,2) = NI(2,4); NI(4,3) = NI(3,4); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% invNI = inv(NI); var_a12 = invNI(3,3); % % approx. variance of a12, corr. to variance of T21 % % % Information transfer: T21 = C12/C11 * a12 % T12 = C21/C22 * a21 % T21 = C_infty(1,2)/C_infty(1,1) * (-C(2,1)*dC(1,1) + C(1,1)*dC(2,1)) / detc; % T12 = C_infty(2,1)/C_infty(2,2) * (-C(1,2)*dC(2,2) + C(2,2)*dC(1,2)) / detc; % var_T21 = (C_infty(1,2)/C_infty(1,1))^2 * var_a12; % % From the standard normal distribution table, % significance level alpha=95%, z=1.96 % 99%, z=2.56 % 90%, z=1.65 % z99 = 2.56; z95 = 1.96; z90 = 1.65; err90 = sqrt(var_T21) * z90; err95 = sqrt(var_T21) * z95; err99 = sqrt(var_T21) * z99;```解释这段代码
03-27
<think>好的,我现在需要解释用户提供的MATLAB代码。首先,我需要理解这段代码的功能和结构。代码名为causality_est,估计两个时间序列X2到X1的信息传递,并输出T21以及不同显著性水平下的标准误差。 首先,我会通读代码,了解整体流程。函数输入是xx1、xx2和np,输出是T21和三个误差项。根据注释,该方法是基于Liang在2014和2015年的论文,涉及信息流(因果)的估计。 接下来,我会逐步分析代码的各个部分: 1. **输入处理**:检查输入参数,xx1和xx2是列向量,np是用于前向差分的时间步长。dt设为1,说明时间间隔为1单位。 2. **数据预处理**:计算dx1和dx2,即使用np步长的前向差分来近似导数。例如,dx1是xx1的未来np步减去当前值,除以np*dt。同时,x1和x2被截断为原始数据的前nm-np个点,以便与导数对齐。 3. **协方差矩阵计算**:计算x1和x2的协方差矩阵C,然后计算dC,即协方差的变化率。这里通过元素相乘求和后除以N-1得到。 4. **参数估计**:根据协方差矩阵和其变化率,计算系数a11和a12,这些可能对应于动态系统中的参数。然后计算残差R1,以及其平方和Q1,进而得到b1,即噪声项的标准差估计。 5. **信息矩阵和方差估计**:构建NI矩阵(可能是Fisher信息矩阵的负矩阵),然后求逆得到参数估计的协方差矩阵。这里关注的是a12的方差var_a12,进而计算T21的方差var_T21。 6. **信息传递计算**:根据公式,T21由C_infty的元素和a12等计算得出。这里的公式可能基于Liang的论文中的推导,将信息流表示为协方差与参数的乘积。 7. **标准误差计算**:使用正态分布的分位数(z值)乘以标准差,得到不同置信水平下的误差范围。 在理解过程中,我需要验证每一步的数学背景。例如,协方差矩阵C和其变化率dC的作用,参数a11和a12的推导,以及信息流T21的具体公式来源。同时,需要确认NI矩阵的构造是否符合最大似然估计或最小二乘法的信息矩阵计算方式。 可能存在的疑问点包括:为什么使用前向差分而不是其他数值微分方法?协方差变化率dC的计算是否有特定理论依据?信息流T21的公式如何从论文中的理论转化为代码中的表达式?此外,NI矩阵的具体形式是否与参数估计的协方差有关? 还需注意,代码中的注释提到C_infty被赋值为C,但原注释中C_infty = cov(x1, x2),而实际代码中是C_infty = C,可能因为前面已经计算过C,这里直接使用。需要确认是否正确。 最后,总结各部分如何组合起来实现信息流的估计,并解释输出结果的含义,即T21的大小及其在不同置信水平下的误差范围,用于判断因果关系的显著性。</think>以下是对该MATLAB代码的逐步解释: ### 1. **函数功能** 该函数用于估计两个时间序列$X_2 \to X_1$的因果信息流$T_{21}$,并计算不同显著性水平下的标准误差。基于Liang提出的信息流理论(参考文献见代码注释)。 --- ### 2. **输入参数** - `xx1`, `xx2`: 时间序列数据(列向量) - `np`: 前向差分的时间步长(用于数值微分) --- ### 3. **输出参数** - `T21`: $X_2$对$X_1$的因果信息流强度 - `err90`, `err95`, `err99`: 90%/95%/99%显著性水平下的标准误差阈值 --- ### 4. **关键步骤解析** #### 4.1 **数据预处理** - 计算导数近似: ```matlab dx1 = (xx1(np+1:end) - xx1(1:end-np)) / (np*dt) % X1的导数 x1 = xx1(1:end-np) % 截断后的X1 ``` 同理处理`dx2`和`x2`,通过前向差分近似导数。 #### 4.2 **协方差计算** - 协方差矩阵: ```matlab C = cov(x1, x2) % x1和x2的协方差矩阵 ``` - 协方差变化率`dC`: ```matlab dC(1,1) = sum((x1 - mean(x1)) .* (dx1 - mean(dx1))) / (N-1) % dC11/dt ``` 其他元素类似,反映协方差随时间的变化。 #### 4.3 **参数估计** - 动态系统参数: ```matlab a11 = [C(2,2)*dC(1,1) - C(1,2)*dC(2,1)] / det(C) a12 = [-C(1,2)*dC(1,1) + C(1,1)*dC(2,1)] / det(C) ``` 这些参数描述$X_1$和$X_2$对$X_1$变化的贡献。 #### 4.4 **残差与噪声估计** - 残差计算: ```matlab R1 = dx1 - (f1 + a11*x1 + a12*x2) % 实际导数与模型预测的差 ``` - 噪声标准差: ```matlab b1 = sqrt(sum(R1.^2) * dt / N) % 白噪声强度估计 ``` #### 4.5 **信息矩阵与方差** - 构建Fisher信息矩阵`NI`: ```matlab NI(2,2) = dt/(b1^2) * sum(x1.^2) % 参数a11的Fisher信息 NI(3,3) = dt/(b1^2) * sum(x2.^2) % 参数a12的Fisher信息 ``` - 求逆得协方差矩阵`invNI`,提取`a12`的方差`var_a12`。 #### 4.6 **信息流计算** - 最终信息流: ```matlab T21 = (C_infty(1,2)/C_infty(1,1)) * (-C(2,1)*dC(1,1) + C(1,1)*dC(2,1)) / det(C) ``` 该公式源于Liang理论,量化$X_2$对$X_1$的因果影响。 #### 4.7 **标准误差** - 通过正态分布分位数计算显著性阈值: ```matlab err95 = sqrt(var_T21) * 1.96 % 95%置信水平的误差阈值 ``` --- ### 5. **使用建议** - **数据要求**:输入序列需平稳,避免剧烈波动 - **参数`np`选择**:通常设为1,除非系统高度混沌 - **结果解读**:若`T21 > err95`,则认为$X_2 \to X_1$因果关系在95%水平显著 --- ### 6. **参考文献** - Liang, X. S. (2014). *Phys. Rev. E* 90, 052150 - Liang, X. S. (2015). *Phys. Rev. E* 92, 022126 该代码实现了一个基于协方差分析的因果推断方法,适用于气候、经济等复杂系统的因果分析。
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