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# System prepended metadata

title: Fundamental Knowledge for Wireless Communications

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# Fundamental Knowledge for Wireless Communications
[TOC]
## Communication Layer
In wireless communication technology, it’s defined in OSI layer that means Open System Interconnection from international standard initiation. When we’re going to implement the wireless system, we have to implement seven layers starting from physical layer, data link layer, network layer, transport layer, session layer, presentation layer, and application layer.
## Shannon Channel Coding Theorem
Shannon coding is lossless data compression technique for constructing a prefix code based on a set of symbols and probabilities. The original 1948 Shannon Theory contains measurement of information, source coding theory, channel coding theory. Shannon showed that there is a way to measure information in terms of number of bits called entropy function.
![](https://i.imgur.com/3GlAHCH.jpg)
The application of source coding has applied to JPEG for image compression, data compression, MPEG for audio/video compression, and MP3 for audio compression. Meanwhile, the application for channel coding theorem has applied to VCD/DVD, wireless communication, optical communication, and computer network. 
## Huffman Coding
Huffman coding is lossless data compression algorithm that assign variable-length codes to input characters, lengths of the assigned codes are based on the frequencies of corresponding characters. Huffman coding has two steps of algorithm: iterate and assign bits. In iterate, we merge the least probable symbols and then sort. After that assign and then get code. The advantages using Huffman Coding are fast implementations and error resilient resynchronizes in ~l2 steps. The weaknesses using Huffman Coding are the code tree grows exponentially when the source is extended and the symbol probabilities are built-in in the code. 
Huffman coding is hard to use for extended sources/large alphabets or when the symbol probabilities are varying by time.
 

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# Comment
Huffman coding and Shannon coding are two data encoding algorithms but they have difference. The Huffman coding uses prefix code while Shannon coding uses cumulative distribution function but also produces prefix codes.

# Personal Studying Report
- Review the topic that has been learned today.
- Learn more about shannon coding and huffman coding and their differences.
- Create summary

# Discussion with Team
- Partition our job for final presentation.
- Study and discuss the sub-topic together.
