Communications Blockset

Manipulating Delays

Some models require you not only to compute delays but to manipulate them. For example, if a model incurs a delay between a block encoder and its corresponding decoder, the decoder might misinterpret the boundaries between the code words that it receives and, consequently, return meaningless results. More generally, such a situation can arise when the path between paired components of a block-oriented operation (such as interleaving, block coding, or bit-to-integer conversions) includes a delay-causing operation (such as those listed in Sources of Delays). To avoid this problem, you can insert an additional delay of an appropriate amount between the encoder and decoder. If the model also computes an error rate, then the additional delay affects that process as described in Computing Delays. This section uses examples to illustrate the purpose, methods, and implications of manipulating delays in a variety of circumstances. The subsections are:

• Delays and Alignment Problems
• Aligning Words of a Block Code
• Aligning Words for Interleaving
• Aligning Words of a Concatenated Code

Punctured Coding Model

Delays and Alignment Problems