Communications Blockset

Signal Terminology

This section defines important terms related to matrix and frame-based signals.

Matrices, Vectors, and Scalars

This document uses the unqualified words scalar and vector in ways that emphasize a signal's number of elements, not its strict dimension properties:

• A scalar signal is one that contains a single element. The signal could be a one-dimensional array with one element, or a matrix of size 1-by-1.
• A vector signal is one that contains one or more elements, arranged in a series. The signal could be a one-dimensional array, a matrix that has exactly one column, or a matrix that has exactly one row. The number of elements in a vector is called its length or, sometimes, its width.

In cases when it is important for a description or schematic to distinguish among different types of scalar signals or different types of vector signals, this document mentions the distinctions explicitly. For example, the terms one-dimensional array, column vector, and row vector distinguish among three types of vector signals.

The size of a matrix is the pair of numbers that indicate how many rows and columns the matrix has. The orientation of a two-dimensional vector is its status as either a row vector or column vector. A one-dimensional array has no orientation.

A matrix signal that has more than one row and more than one column is called a full matrix signal.

Frame-Based and Sample-Based Signals

In Simulink, each matrix signal has a frame attribute that declares the signal to be either frame-based or sample-based, but not both. (A one-dimensional array signal is always sample-based, by definition.) Simulink indicates the frame attribute visually by using a double connector line in the model window instead of a single connector line. In general, Simulink interprets frame-based and sample-based signals as follows:

• A frame-based signal in the shape of an M-by-1 (column) matrix represents M successive samples from a single time series.
• A frame-based signal in the shape of a 1-by-N (row) matrix represents a sample of N independent channels, taken at a single instant in time.
• A sample-based matrix signal might represent a set of bits that collectively represent an integer, or a set of symbols that collectively represent a code word, or something else other than a fragment of a single time series.

Signal Support

Processing Matrices, Vectors, and Scalars