qammod — Map integer or bit symbols to QAM constellation points in MATLAB and RunMat.

qammod(X, M) maps integer symbols or bit groups X to complex QAM constellation points for modulation order M. Gray, binary, and custom symbol-ordering behavior follow MATLAB semantics.

Syntax

qammod(X, M)

How qammod works

• X must contain finite integer values in the inclusive range [0, M-1].
• InputType='bit' groups rows of X in log2(M) chunks per column/channel and maps each bit group to one symbol.
• M must be a power-of-two integer greater than one.
• Square QAM orders such as 4, 16, 64, and 256 use symmetric odd integer amplitudes with minimum distance two.
• Non-square power-of-two orders use a rectangular grid with the larger dimension on the in-phase axis.
• The default 'gray' order applies Gray coding independently to the in-phase and quadrature grid indexes.
• 'UnitAveragePower', true scales the complete constellation so its average power is one.
• 'OutputDataType', 'single' rounds the real and imaginary samples through single precision before returning the complex tensor or resident complex gpuArray output.
• 'PlotConstellation', true is not implemented yet.

Does RunMat run qammod on the GPU?

RunMat represents complex GPU tensors as interleaved real/imaginary buffers with complex storage metadata, so downstream GPU-aware FFT and signal paths can consume the modulation output without a host result.

The provider hooks receive a validated constellation table and write the complex output on device. They read back only a compact validation state for MATLAB-compatible symbol or bit errors.

GPU memory and residency

The builtin declares NewHandle residency for gpuArray inputs. Integer-symbol and bit-input gpuArrays stay resident through provider-side constellation modulation when provider support is available.

Examples

Default 16-QAM Gray mapping

y = qammod(0:15, 16)

Expected output:

y = [-3+3i -3+1i -3-3i -3-1i -1+3i -1+1i -1-3i -1-1i 3+3i 3+1i 3-3i 3-1i 1+3i 1+1i 1-3i 1-1i]

Binary symbol ordering

y = qammod(0:4, 16, 'bin')

Expected output:

y = [-3+3i -3+1i -3-1i -3-3i -1+3i]

Unit-average-power 16-QAM

y = qammod(0:15, 16, 'UnitAveragePower', true);
mean(abs(y).^2)

Expected output:

ans = 1

Bit input for 16-QAM

bits = [0 1; 0 1; 0 1; 0 1];
y = qammod(bits, 16, 'InputType', 'bit')

Expected output:

y = [-3+3i 1-1i]

Using qammod with coding agents

Open a RunMat example with live inputs, then ask the agent to explain how qammod changes the result.

FAQ

Related Comms functions

Open-source implementation

Unlike proprietary runtimes, every RunMat function is open-source. Read exactly how qammod is executed, line by line, in Rust.

• View the source for qammod in Rust on GitHub
• Learn how the RunMat runtime works
• Found a bug? Open an issue with a minimal reproduction.

About RunMat

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