Lecture notes on turbo codes.
Lecture notes on turbo codes.
Lecture notes on turbo codes.
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Thus for recursive CC’s the interleaving gain (or BER reducti<strong>on</strong>) goes as1/N. On the other hand all n<strong>on</strong>recursive CC and block <strong>codes</strong> have w min = 1,so such <strong>codes</strong> are not useful in Parallel C<strong>on</strong>catenated Codes.The next most important c<strong>on</strong>stituent code parameter is z min , the minimumparity-check weight in the code sequences with w=2. For a large range ofSNR, the behaviour of PCCC is determined by the “effective free distance”d free,eff = 2 + 2 z min .It is possible to achieve z min = (n-1)(2 v-1 + 2) with a rate 1/n recursive CCwith memory v.PCCC’s exhibit error floor effect (defined as the change of slope of BERcurve for Turbo <strong>codes</strong>) at lower BER. Initially the coding gain increaseswith the number of iterati<strong>on</strong>s. However, after a number of iterati<strong>on</strong>s (10-12in AWGN) the performance improvement is marginal.Extensi<strong>on</strong>s to c<strong>on</strong>sider:1. Turbo <strong>codes</strong> with multilevel modulati<strong>on</strong>2. Turbo TCM3. Iterative Equalizati<strong>on</strong> and Decoding – Turbo Equalizati<strong>on</strong>.20
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