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• 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|计算机及网络安全代写Computer and Network Security代考|Wireless Communication

Wireless communication and wireless networks have evolved as a result of rapid development in communication technologies, computing, and people’s need for mobility. Wireless networks fall in one of the following three categories depending on distance as follows:

• Restricted Proximity Network: This network involves local area networks (LANs) with a mixture of fixed and wireless devices.
• Intermediate/Extended Network: This wireless network is actually made up of two fixed LAN components joined together by a wireless component. The bridge may be connecting LANs in two nearby buildings or even further.
• Mobile Network: This is a fully wireless network connecting two network elements. One of these elements is usually a mobile unit that connects to the home network (fixed) using cellular or satellite technology.

These three types of wireless networks are connected using basic media such as infrared, laser beam, narrow-band and spread-spectrum radio, microwave, and satellite communication [2].

Infrared During an infrared transmission, one network element remotely emits and transmits pulses of infrared light that carry coded instructions to the receiving network element. As long as there is no object to stop the transmitted light, the receiver gets the instruction. Infrared is best used effectively in a small confined area, within 100 feet, for example, a television remote communicating with the television set. In a confined area such as this, infrared is relatively fast and can support high bandwidths of up to $10 \mathrm{Mbps}$.

电子工程代写|计算机及网络安全代写Computer and Network Security代考|Open System Interconnection (OSI) Protocol Suite

The development of the OSI model was based on the secure premise that a communication task over a network can be broken into seven layers, where each layer represents a different portion of the task. Different layers of the protocol provide different services and ensure that each layer can communicate only with its own neighboring layers. That is, the protocols in each layer are based on the protocols of the previous layers.

Starting from the top of the protocol stack, tasks and information move down from the top layers until they reach the bottom layer where they are sent out over the network media from the source system to the destination. At the destination, the task or information rises back up through the layers until it reaches the top. Each layer is designed to accept work from the layer above it and to pass work down to the layer below it, and vice versa. To ease interlayer communication, the interfaces between the layers are standardized. However, each layer remains independent and can be designed independently, and each layer’s functionality should not affect the functionalities of other layers above and below it.

Table $1.1$ shows an OSI model consisting of seven layers and the descriptions of the services provided in each layer.

In peer-to-peer communication, the two communicating computers can initiate and receive tasks and data. The task and data initiated from each computer start from the top in the application layer of the protocol stack on each computer. The tasks and data then move down from the top layers until they reach the bottom layer, where they are sent out over the network media from the source system to the destination. At the destination, the task and data rise back up through the layers until the top. Each layer is designed to accept work from the layer above it and pass work down to the layer below it. As data passes from layer to layer of the sender machine, layer headers are appended to the data, causing the datagram to grow larger. Each layer header contains information for that layer’s peer on the remote system. That information may indicate how to route the packet through the network or what should be done to the packet as it is handed back up the layers on the recipient computer.

计算机及网络安全代考

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

• Restricted Proximity Network：此网络涉及局域网 (LAN)，其中混合了固定和无线设备。
• 中间/扩展网络：这个无线网络实际上是由两个固定的 LAN 组件组成，它们通过一个无线组件连接在一起。该网桥可能正在连接附近两座建筑物甚至更远的 LAN。
• 移动网络：这是一个连接两个网络元素的完全无线网络。这些元素之一通常是使用蜂窝或卫星技术连接到家庭网络（固定）的移动单元。

电子工程代写|计算机及网络安全代写Computer and Network Security代考|Open System Interconnection (OSI) Protocol Suite

OSI 模型的开发基于安全前提，即网络上的通信任务可以分为七层，其中每一层代表任务的不同部分。协议的不同层提供不同的服务，并确保每一层只能与自己的相邻层通信。也就是说，每一层的协议都是基于前一层的协议。

有限元方法代写

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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。

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