# 计算机代写|密码学与网络安全代写cryptography and network security代考|CS587

## 计算机代写|密码学与网络安全代写cryptography and network security代考|Relative Redundancy and Efficiency

The absolute redundancy is the difference between the actual information transmission rate and $I(X ; Y)$ and the maximum possible value,
Absolute redundancy for a noisy channel $=C-I(X ; Y)$
$$=\log N-H(X) \text {. (5.55) }$$
The ratio between the absolute redundancy and the channel capacity is defined as the system relative redundancy,

Relative redundancy for a noiseless channel, $D=\frac{\log N-H(X)}{\log N}$
$$=1-\frac{H(X)}{\log N} \text {. }$$
The system efficiency is defined as the complement of the relative redundancy,
Efficiency of the noiseless channel, $E=\frac{I(X ; Y)}{\log N}=\frac{H(X)}{\log N}$
$$=1-D \text {. }$$
When the transmitted symbols do not occupy the same time interval, it is still possible to define the average information transmission rate for the noiseless channel as
$$R_T=\frac{-\sum_{i=1}^N p\left(x_i\right) \log p\left(x_i\right)}{\sum_{i=1}^N p\left(x_i\right) T_i}$$
in which $T_i$ represents the symbol intervals.

## 计算机代写|密码学与网络安全代写cryptography and network security代考|Computer Networks

Computer networks have become ubiquitous and permeate the society. They are the main means of social communication, which includes voice, data, and video communication, and services, including electronic commerce, information search, distance learning, academic consultation, events, business, and malicious activities. A typical computer network, with the servers of network and users’ machines, is illustrated in Figure 6.1.
Computer networks differ from telephone networks, which dominated the second half of the twentieth century, in the switching technique used and in the transmission rates. They use packet switching, transmission rates, and variable topology. Information routing is performed at each node in the system.

The telephone networks, in turn, use exchanges with circuit switching, and they have a transmission rate limited to $64 \mathrm{khits} / \mathrm{s}$, for fixed telephony, and use a star topology, with the switches located in the center of the star (Hammond and O’Reilly, 1986).

The purpose of this chapter is to introduce the concepts of data flow, qucuc models, structurc and topology, performance mcasurcs, traffic, channel capacity, latency, protocols, and more representative architectures of computer networks.

These concepts are quickly incorporated into the communication systems, in a way that its intrinsic data traffic characteristics need to be taken into account in the design of the systems. In particular, the information is essential to understand how common activities take place, such as sending files, searching for information, and telephony via the computer network, known as IP telephony.

# 密码学与网络安全代考

## 计算机代写|密码学与网络安全代写cryptography and network security代考|相对冗余和效率

$$=\log N-H(X) \text {. (5.55) }$$

$$=1-\frac{H(X)}{\log N} \text {. }$$

$$=1-D \text {. }$$

$$R_T=\frac{-\sum_{i=1}^N p\left(x_i\right) \log p\left(x_i\right)}{\sum_{i=1}^N p\left(x_i\right) T_i}$$
，其中$T_i$表示符号间隔

## 计算机代写|密码学与网络安全代写cryptography and network security代考|Computer Networks

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