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Transmission Efficiency

Lesson Objectives. By the end of this lesson, you will be able to:Define transmission efficiencyDefine compression Apply run length encoding compressionConstruct a Huffman codeDescribe some common data and video compression schemesDefine multiplexingDescribe frequency division multiplexingDe

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Transmission Efficiency

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    1. Transmission Efficiency Revised May 11, 2005 Updated April 22, 2006Revised May 11, 2005 Updated April 22, 2006

    2. Lesson Objectives By the end of this lesson, you will be able to: Define transmission efficiency Define compression Apply run length encoding compression Construct a Huffman code Describe some common data and video compression schemes Define multiplexing Describe frequency division multiplexing Describe synchronous TDM Derive the speed and configuration of a T-1 frame Describe statistical TDM

    3. Transmission Efficiency Goal Goal to get the biggest bang for the communications buck: maximize communications for any given system capacity Send as much information as possible over the network, and minimize the capacity of the system Airplane analogy why use a Boeing 747 when a Learjet provides enough capacity?Airplane analogy why use a Boeing 747 when a Learjet provides enough capacity?

    4. Compression Overview Virtually all data forms have redundant elements Compression is effective if: Redundancy is eliminated before transmission Receiving end can reconstruct data to original format Net effect is fewer data transmitted AND data manipulation is transparent to receiving party Numerous compression schemes are in use today

    5. Compression Schemes Lossless Compression Reversible Receiving end completely reverses compression that was applied at transmitting end Result is a reinsertion of all eliminated bits Resultant bit stream is identical to original stream Lossy compression Bits are eliminated in the transmitting process Not all bits are reinserted at receiving end Resultant bit stream is not identical to original stream Resultant stream is close enough so it does not detract from functionality of the information = perceptually equivalent BMP, GIF, PNG lossless compression schemes BMP native to Windows. 24 bits/pixel. For unsophisticated line drawings GIF 8 bits/pixel. Line art, logos PNG 48 bits/pixel. Good compression JPEG lossy compression. 24 bits/pixelBMP, GIF, PNG lossless compression schemes BMP native to Windows. 24 bits/pixel. For unsophisticated line drawings GIF 8 bits/pixel. Line art, logos PNG 48 bits/pixel. Good compression JPEG lossy compression. 24 bits/pixel

    6. Run Length Encoding Possibly the simplest Lossless compression technique Utilizes spatial redundancy Transmitting end searches for sequences of repeating characters in data stream Sequences are replaced with 3-character code Sc = First character indicator that compression follows X = Second character character being repeated Cc = Third character number of characters being compressed Note that character must repeat four or more times before compression can take place efficientlyNote that character must repeat four or more times before compression can take place efficiently

    7. Run Length Encoding Application

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