Turbo_Code_Presentation.v3.0 - Kyu Seob Kim (kk524) Daniel...

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Kyu Seob Kim (kk524) Daniel Rivera (djr257)
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Agenda Background Information o Channel Coding o Base Codes o Shannon Capacity o History of Turbo Code Structure of Turbo Code o Encoder o Interleaver o Decoder Turbo Code Performance Current/Future Application o CDMA2000 o UMTS o Deep Space Communication o In Rayleigh Fading Channels
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Channel Coding Backward Error Correction (BEC) o It requires only error detection. o When an error is detected, the sender retransmits the message. o It requires duplex communication and causes delays. Forward Error Correction (FEC) o the decoder is capable of correcting a certain number of errors. o FEC codes are attractive in wireless communication. o Turbo Code is one example of FEC code.
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Base Codes Block Code o It breaks the message stream into fixed-size blocks. o The encoder processes each block into a larger block called a code bit block. o The additional bits added are called redundancy bits. Convolutional Code o The encoder keeps M previous input bits in memory. o Each output bit depends on the current input bit as well as the M stored bits. Code Rate o the input size divided by the output size Hamming Weight o The number of non-zero symbols in the code word.
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Shannon Capacity Claude Shannon developed theories on Channel Capacity o Emphasis came during WWII Shannon Capacity sets a limit to the energy efficiency of a code. Even in the beginning of the 1990s, the gap between the theoretical bound and practical implementation was 3dB.
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History of Turbo Codes Class of Codes to approach rates of channel capacity. o 1963 LDPC Codes More theoretically than practical o 1993 Turbo Codes Helped bring back relevancy to LDPC Limits proposed by Shannon, but nothing was practically realized. Main emphasis at time was not increasing rate Reliability
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History (cont.) Developed in ‘93 o Introduced by Claude Berrou, Alain Glavieux, Punya Thitimajshima o " Near Shannon Limit Error-correcting Coding and Decoding: Turbo-codes In a following paper, Berrou referenced the creators of LDPC
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The Generic Turbo Encoder
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Data is written row-wise and read column-wise. While very simple, it also provides little randomness.
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Turbo_Code_Presentation.v3.0 - Kyu Seob Kim (kk524) Daniel...

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