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Unformatted text preview: ECEN 455 Lab 4: Source Coding Overview: Bits are the universal unit of information in todays digital world. Any information source can be represented using bits and bits can be transmitted reliably over an unreliable physical channels. In this lab, we study how to use bits to efficiently represent a source consisting of English text. Standard English texts are composed of English letters, numbers, and special symbols. For example, many texts contain only the 26 English letters (ignoring capital letters), 10 numerical digits, and 9 special symbols including (space), , (comma), . (period), ? (question mark), ! (exclamation point), (apostrophe), (quotation mark), - (hyphen), and : (colon). This gives a total of 45 different symbols. A simple way to represent these 45 different symbols using bits is to assign a unique binary string of length 6 to each symbol. Text-to-bit and bit-to-text conversions can be performed using a lookup table, which records the predetermined one-to-one correspondence between the text symbols and their binary representation. This simple approach uses the same number of bits to represent each of the text symbols. This may not be very smart considering that some text symbols appear a lot more often than the others. Assigning variable-length bit strings allows one to reduce thea lot more often than the others....
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This note was uploaded on 11/13/2011 for the course ECEN 455 taught by Professor Staff during the Spring '08 term at Texas A&M.
- Spring '08