### 电子工程代写|计算机网络概论代写Introduction to Computer Networking代考|CS6250

statistics-lab™ 为您的留学生涯保驾护航 在代写计算机网络概论Introduction to Computer Networking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网络概论Introduction to Computer Networking方面经验极为丰富，各种代写计算机网络概论Introduction to Computer Networking相关的作业也就用不着说。

• Statistical Inference 统计推断
• Statistical Computing 统计计算
• (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|计算机网络概论代写Introduction to Computer Networking代考|Asynchronous Transmission

Asynchronous transmission is used in low-speed applications where communication is only sporadic. An example of this kind of situation is the connection of a console (terminal) to a router. In an asynchronous transmission, a special bit called the ‘start’ bit is sent before the bits that make up the character and one ‘stop’ bit (or possibly two stop bits) is sent at the end. For this reason, an alternative term for asynchronous transmission is start-stop transmission. The start bit alerts the receiving device to the fact that a character is about to be transmitted. The stop bit tells the receiver that no more bits will be sent for a while.

Figure $2.4$ illustrates asynchronous transmission. In the diagram, the transmission of the capital letter ‘ $\mathrm{J}$ ‘ is shown. A 7-bit ASCII code is being used (1001010). The diagram should be read from right to left. The communications line is initially in the idle condition-nothing is happening. Then, out of the blue, a start bit arrives. This warns the receiver that the next bit will be the least significant bit of a character. The remaining bits of the character follow. The $0 \mathrm{~s}$ and $1 \mathrm{~s}$ are represented by different voltages on the communications line, for example, $+5$ and $0 \mathrm{~V}$.
After the most significant bit of the character, there is a parity bit-a check for errors. In Fig. 2.4, even parity is being used. This means that over the whole of the character and the parity bit there is an even number of ‘ 1 ‘ bits. If the received bit pattern does not accord with this, then it is assumed that there has been a transmission error. Alternatively, odd parity could have heen employed, in which case with no errors there would be an odd number of ‘ 1 ‘ bits over the whole of the character and the parity bit. An 8-bit code could have been used instead with no parity check. There is further coverage of error control methods later in this chapter (see Section 2.6). After the parity bit, there is a stop bit to tell the receiver that transmission has ceased for the time being. EIA/TIA-232 (RS232-C), mentioned in Section 3.2.1, is an example of an asynchronous protocol.

## 电子工程代写|计算机网络概论代写Introduction to Computer Networking代考|Simplex, Half-Duplex and Full-Duplex Communications

Simplex transmission is transmission that can take place only ever in one direction. Añ example of simplex communications is a househoold radio set, which can reeceeive data from radio stations but cannot transmit. In half-duplex transmission, data can be transmitted in either direction across a communications link, but in only one direction at a time. A walkie-talkie radio is an example of a half-duplex device because only one person can talk at a time. In full-duplex transmission, data is transmitted in two directions at the same time. A telephone is an example of a full-duplex device because the people at both ends of the line can talk at the same time.

In computer communications, simplex is less common than either half- or fullduplex working. Many fibre optic systems are simplex, with a different strand of fibre having to be used for each direction. Many satellite services are also simplex. In such systems, a satellite is used for downloads and some other system-a dialup modem, for example (see Chapter 5) – is used for communication in the other direction. Satellite and optical fibre are covered in more detail later in this chapter. Simplex transmission is illustrated in Fig. 2.6. In computer communications, halfduplex and full-duplex working are more commonly found, however.

Half-duplex working is fine for transferring files between computers when most data is flowing in one direction at a time. However, when used for other applications, it may cause delays. When low-speed versions of the popular LAN protocol Ethernet are used with a hub instead of a layer-2 switch (see Chapter 4), they can use half-duplex transmission only. Two computers connected to a half-duplex Ethernet LAN must take turns to send information to each other. A computer has to wait for the transmission that it is sending to end before it can receive data. Fullduplex working removes this restriction. Half-duplex transmission is illustrated in Fig. 2.7.

Full-duplex transmission is illustrated in Fig. 2.8. Full-duplex working is ideal for interactive applications because it eliminates the waiting time referred to in the previous paragraph. Ethernet used with a layer- 2 switch is an example of fullduplex transmission. The switch can automatically sense whether the device at the other end of the wire, for example, the NIC of a PC, has a full-duplex capability. If full-duplex transmission can be used, this has the effect of speeding up the operation of the LAN.

## 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。