---
# System prepended metadata

title: '通訊系統 W15,W16'
tags: [通訊系統]

---

# 通訊系統 W15,W16
###### tags: `通訊系統`

# Chap 9: Using Telephone and Cable Networks for Data Transmission

## Chap 9-1 Telephone Network

![](https://hackmd.io/_uploads/H1YZ3JiSh.png)

### Point of oresences(POPs)

![](https://hackmd.io/_uploads/rkey1xsHh.png)

![](https://hackmd.io/_uploads/S10z1xorh.png)

### Note: The tasks of data transfer and signaling are seperated in modrn telephone networks: data transfer is done by one network,signaling is by another.

## Chap 9-2 Dial-Up Models

*　Ｍodem stands for modulator/demodulator

![](https://hackmd.io/_uploads/SJMoQxjB3.png)


## Chap 9-3 Digital Subscribe Line

### Note: ADSL is an asymmetric communication technology designed for residential users; it is not suitable for business.

### NOte: ADSL is an adaptive tecknology. The system uses a data rate based on the condition of the local loop line.

![](https://hackmd.io/_uploads/SkwoLeoHn.png)

![](https://hackmd.io/_uploads/HkO38ljS3.png)



| ADSL Bandwidth | 對照頻段功能 |
| -------- | -------- |
| ![](https://hackmd.io/_uploads/SJJGOlsB3.png)     | ![](https://hackmd.io/_uploads/Sykm_loB2.png)  |
| ADSL modem | DSLAM |
|![](https://hackmd.io/_uploads/BkvEYeoHn.png)     | ![](https://hackmd.io/_uploads/B1FBFesBh.png)  |


## Chap 9-4 Cable TV Networks

### Note: Communication in the "traditional cable" TV network can be budirectional.

![](https://hackmd.io/_uploads/SyCpcgjHh.png)


### Note: Communication in an "HFC cable" TV network can be budirectional.

![](https://hackmd.io/_uploads/ryTCqgsrh.png)

## Chap 9-5 Cable TV for Data Transfer 


![](https://hackmd.io/_uploads/S1G9jxoS3.png)


![](https://hackmd.io/_uploads/ByncoxiHh.png)

# Chap 10: Error Detection and Correction

### Note: Data can be corrupted durong transmission. Some applications require that errors be detected and corrected.

## Chap 10-1 Introduction

### Error
1. Single bit error(整個訊息錯一個以上)
2. Burst error(整個訊息錯兩個以上)
### Note: In a single-bit error, only 1 bit in the data unit has changed.

### Note: A burst error means that 2 or more bits int the data unit have changed.

### Redundancy
用於作為檢查碼(detect and correct errors)

### To detect or correct eooros, we need to send extra(redundant) bits with data.

### Detection
Only給予有錯或沒錯的回覆

### Crrection
要給出錯在哪裡，並且更正錯誤

1. Forward error corrction => 繼續傳送，並且檢查錯哪裡
2. Retransmission => 直接重傳，花頻寬


* The structure of encoder and decoder
### Note: In this book, we concentrate on(專注於) "block codes"; we leave convolution codes to advanced texts. 

![](https://hackmd.io/_uploads/rJIqgboSn.png)

### In modulo-N arithmetic, we use only the intergers in  the range 0 to (N-1), inclusive.

![](https://hackmd.io/_uploads/SJOUdZjS3.png)

## Chap 10-2 Block Coding
先把資料切為blocks，並放入一些bits為datawords，放入k bits，並再放入r bits for redundant bits，最為codewords



![](https://hackmd.io/_uploads/B1XsubiB3.png)


### Note: An error-detecting code can detect only the types of errors for which it is designed; other types of errors may remain undetected.

### Note: The Hamming destance between two words is the number of differences between corresponding bits.

### The minimum Hamming distance is the smallest Hamming distance between all poossible pairs in a set of words.

### Note: To guarantee the detection of up to s errors in all cases, the minimum Hamming distance in a block code must be d_min = s + 1

![](https://hackmd.io/_uploads/HJGYBQNUn.png)

### The guarantee correction of up to t errors in all cases, the minimum Hamming distance in a block code must be d_min = 2t + 1

![](https://hackmd.io/_uploads/SJzjr7EUn.png)

## Chap 10-3 Linear Block Codes

### note: In a  linear block code, the exclusive OR(XOR) of any two valid codewords creaes another valid codeword.

### Note: A simple parity-check code is a single-bit error-detecting code in which n = k+1 with d_min = 2


![](https://hackmd.io/_uploads/B1n9D7VIh.png)



## 2 dimensional parity-check code

![](https://hackmd.io/_uploads/B1hOr4VUh.png)

![](https://hackmd.io/_uploads/S1YYHVV83.png)


### Note: All Hamming codes discussed in this book have d_min = 3. The relationship between m data and n in these codes is n = 2m -1.

![](https://hackmd.io/_uploads/HJARBNVU2.png)

![](https://hackmd.io/_uploads/Syq18NE83.png)

## Chap 10-4 Cyclic Codes

![](https://hackmd.io/_uploads/r1WXdV4In.png)

![](https://hackmd.io/_uploads/BykVd4NUh.png)

## Hardwared design

![](https://hackmd.io/_uploads/SyhnJS4U2.png)

![](https://hackmd.io/_uploads/rkpR1r4Un.png)


## Chap 10-5 Checksum