### 电子工程代写|计算机及网络安全代写Computer and Network Security代考|ICCWS2022

statistics-lab™ 为您的留学生涯保驾护航 在代写计算机及网络安全Computer and Network Security方面已经树立了自己的口碑, 保证靠谱, 高质且原创的统计Statistics代写服务。我们的专家在代写计算机及网络安全Computer and Network Security方面经验极为丰富，各种代写计算机及网络安全Computer and Network Security相关的作业也就用不着说。

• Statistical Inference 统计推断
• Statistical Computing 统计计算
• Advanced Probability Theory 高等楖率论
• Advanced Mathematical Statistics 高等数理统计学
• (Generalized) Linear Models 广义线性模型
• Statistical Machine Learning 统计机器学习
• Longitudinal Data Analysis 纵向数据分析
• Foundations of Data Science 数据科学基础

## 电子工程代写|计算机及网络安全代写Computer and Network Security代考|Analog Encoding of Digital Data

Recall that digital information is in the form of $1 \mathrm{~s}$ and $0 \mathrm{~s}$. To send this information over some analog medium such as the telephone line, for example, which has limited bandwidth, digital data needs to be encoded using modulation and demodulation to produce analog signals. The encoding uses a continuous oscillating wave, usually a sine wave, with a constant frequency signal called a carrier signal.

The carrier has three modulation characteristics: amplitude, frequency, and phase shift. The scheme then uses a modem, a modulation-demodulation pair, to modulate and demodulate the data signal based on any one of the three carrier characteristics or a combination. The resulting wave is between a range of frequencies on both sides of the carrier, as shown below [1]:

• Amplitude modulation represents each binary value by a different amplitude of the carrier frequency. The absence of or low carrier frequency may represent a 0 , and any other frequency then represents a 1 . However, this is a rather inefficient modulation technique and is therefore used only at low frequencies up to 1200 bps in voice grade lines.
• Frequency modulation also represents the two binary values by two different frequencies close to the frequency of the underlying carrier. Higher frequencies represent a 1 , and low frequencies represent a 0 . The scheme is less susceptible to errors.
• Phase shift modulation changes the timing of the carrier wave, shifting the carrier phase to encode the data. A 1 is encoded as a change in phase by $180^{\circ}$, and a 0 may be encoded as a 0 change in phase of a carrier signal. This is the most efficient scheme of the three, and it can reach a transmission rate of up to 9600 bps.

## 电子工程代写|计算机及网络安全代写Computer and Network Security代考|Digital Encoding of Digital Data

In this encoding scheme, which offers the most common and easiest way to transmit digital signals, two binary digits are used to represent two different voltages. Within a computer, these voltages are commonly 0 and 5 volts. Another procedure uses two representation codes: nonreturn to zero level $(N R Z-L)$, in which negative voltage represents binary one and positive voltage represents binary zero, and nonreturn to zero, invert on ones (NRZ-I). See Figs. $1.6$ and $1.7$ for an example of these two codes. In NRZ-L, whenever a 1 occurs, a transition from one voltage level to another is used to signal the information. One problem with NRZ signaling techniques is the requirement of a perfect synchronization between the receiver and transmitter clocks. This is, however, reduced by sending a separate clock signal. There are yet other representations such as the Manchester and differential Manchester, which encode clock information along with the data.

One may wonder, why go through the hassle of digital encoding and transmission? There are several advantages over its cousin, analog encoding. These include the following:

• Plummeting costs of digital circuitry
• More efficient integration of voice, video, text, and images
• Reduction of noise and other signal impairment because of the use of repeaters
• The capacity of channels is utilized best with digital techniques
• Better encryption and hence better security than in analog transmission

## 电子工程代写|计算机及网络安全代写Computer and Network Security代考|Analog Encoding of Digital Data

• 幅度调制通过载波频率的不同幅度来表示每个二进制值。载波频率的缺失或低可以表示 0 ，而任何其他频率则表示 1 。然而，这是一种相当低效的调制技术，因此仅用于语音等级线路中高达 1200 bps 的低频。
• 频率调制还通过接近底层载波频率的两个不同频率来表示两个二进制值。高频代表 1 ，低频代表 0 。该方案不易出错。
• 相移调制改变载波的时序，移动载波相位以对数据进行编码。A 1 被编码为相位变化180∘，并且0可以被编码为载波信号的相位变化0。这是三者中效率最高的方案，它可以达到高达 9600 bps 的传输速率。

## 电子工程代写|计算机及网络安全代写Computer and Network Security代考|Digital Encoding of Digital Data

• 数字电路成本直线下降
• 更高效的语音、视频、文本和图像的集成
• 由于使用中继器，减少了噪音和其他信号损伤
• 数字技术最好地利用信道容量
• 比模拟传输更好的加密，因此更好的安全性

## 广义线性模型代考

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## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。