The OSTBC Encoder block encodes an input symbol sequence using orthogonal space-time block code (OSTBC). The block maps the input symbols block-wise and concatenates the output codeword matrices in the time domain. For more information, see the OSTBC Encoding Algorithms section of this help page.
The block supports time and spatial domains for OSTBC transmission. It also supports an optional dimension, over which the encoding calculation is independent. This dimension can be thought of as the frequency domain. The following illustration indicates the supported dimensions for the inputs and output of the OSTBC Encoder block.
The following table describes the variables.
|F||The additional dimension; typically the frequency domain. The encoding does not depend on this dimension.|
|T||Input symbol sequence length for the time domain.|
|R||Symbol rate of the code.|
|N||Number of transmit antennas.|
F can be any positive integer. N can be 2, 3 or 4, indicated by Number of transmit antennas. For N = 2, R must be 1. For N = 3 or 4, R can be 3/4 or 1/2, indicated by Rate. The time domain length T must be a multiple of the number of symbols in each codeword matrix. Specifically, for N = 2 or R = 1/2, T must be a multiple of 2 and when R = 3/4, T must be a multiple of 3.
To understand the block's dimension propagation, refer to the following table.
|F = 1||Column vector||2-D|
|F > 1||2-D||3-D|
For information about the data types each block port supports, see the Supported Data Type table on this page. The output signal inherits the data type from the input signal. For fixed-point signals, the complex conjugation may cause overflows which the fixed-point parameter Overflow mode must handle.
The output signal inherits frame type from the input signal. A column vector input requires either frame-based or sample-based input; otherwise, the input must be sample-based.
The OSTBC Encoder block supports five different OSTBC encoding algorithms. Depending on the selection for Rate and Number of transmit antennas, the block implements one of the algorithms in the following table:
|Transmit Antenna||Rate||OSTBC Codeword Matrix|
In each matrix, its (l, i)
entry indicates the symbol transmitted from the ith
antenna in the lth time slot of the block. The
value of i can range from 1 to N (the
number of transmit antennas). The value of l can
range from 1 to the codeword block length.
Sets the number of antennas at the transmitter side. The block supports 2, 3, or 4 transmit antennas. The value defaults to 2.
Sets the symbol rate of the code. You can specify either 3/4 or 1/2. This field only appears when using more than 2 transmit antennas. This field defaults to for more than 2 transmit antennas. For 2 transmit antennas, there is no rate option and the rate defaults to 1.
Sets the overflow mode for fixed-point calculations. Use this parameter to specify the method to be used if the magnitude of a fixed-point calculation result does not fit into the range of the data type and scaling that stores the result. For more information refer to Precision and Range in DSP System Toolbox™.
|Port||Supported Data Types|
For an example of this block in use, see OSTBC Over 3x2 Rayleigh Fading Channel in the Communications System Toolbox™ documentation. The model shows the use of a rate ¾ OSTBC for 3 transmit and 2 receive antennas with BPSK modulation using independent fading links and AWGN
You can also see the block in the Concatenated OSTBC with TCM example by typing commtcmostbccommtcmostbc. View the IEEE 802.16–2004 OFDM PHY Link, Including Space-Time Block Coding example by typing commwman80216dstbccommwman80216dstbc at the MATLAB® command line.