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Wireless CommunicationChapter: Analog and Digital
Transmission
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In a wireless communication link, coding can essentially reduce the number of bit errors. Because of fading the BER without coding remains relatively large even with good signal to noise ratios. See examples of BER for the cellular channel. Typically the BER only vansihes inversely proportically to the SNR.
With error correction coding, one can achieve that error only coding if t or more errors occur simultaneously, where t is a parameter of the coding method in use. Now if one can achieve, for instance through interleaving, that bit errors are independent, the BER can be reduced to the extent that
BER = SNR-t
Note that in the uncoded case t = 1, and with coding t > 1. this explains how coding can improve the performance in a manner that is similar to diversity.
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Coding
Theory: |
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Jim Massey discusses the history of coding theory. Experts used to declare
coding theory as dead, just to experience a new revival of the field. |
1 2 3 4 5 6 Part I. The early days. 1 2 3 4 Part II. Hamming codes, BCH codes. 1 2 Part III. Reed Solomon Codes. 1 2 Part IV. Convolutional codes. 1 2 3 4 Part V. The first death of coding theory around 1960. 1 2 3 4 Part VI. Concatenated Codes. How to overcome the bandwidth expansion problem? 1 2 3 4 Part VII. 1969 A big triumph: NASA's use of codes for communication with 'deep space' from the Pioneer probe. 1 2 3 4 5 6 Part VIII. The Viterbi decoder. 1 2 3 4 Part IX. What came after the convolutional codes? The Third Death. Trellis Coded Modulation. 1 2 1 2 3 4 5 6 7 8 Part XI. Turbo Codes. Performance close to Shannon's theoretical limits. It really works, but why? 1 2 Part XII. Jim's conclusion. Coding theory will die again soon, when we intuitively understand Turbo codes. Will it rise again?. |
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massey.m3u playlist of MP3 audio files |
(Books by Massey) |
