OFDM Waveform#

class OFDMWaveform(subcarrier_spacing=1000.0, num_subcarriers=1024, dc_suppression=True, resources=None, structure=None, **kwargs)[source]#

Bases: ConfigurablePilotWaveform, Serializable

Generic Orthogonal-Frequency-Division-Multiplexing with a flexible frame configuration.

The internally applied FFT size is OFDMWaveform.num_subcarriers() times CommunicationWaveform.oversampling_factor().

The following features are supported:

The modem can transmit or receive custom-defined frames. Frames may contain UL/DL data symbols, null carriers, pilot subcarriers, reference signals and guard intervals.
SC-FDMA can also be implemented with a precoder.
Subcarriers can be modulated with BPSK/QPSK/16-/64-/256-QAM.
Cyclic prefixes for interference-free channel estimation and equalization are supported.

This implementation has currently the following limitations:

All subcarriers use the same modulation scheme

Parameters:

subcarrier_spacing (float, optional) – Spacing between individual subcarriers in Hz. \(1~\mathrm{kHz}\) by default.
num_subcarriers (int, optional) – Maximum number of assignable subcarriers. Unassigned subcarriers will be assumed to be zero. \(1024\) by default.
dc_suppression (bool, optional) – Suppress the direct current component during waveform generation. Enabled by default.
resources (List[FrameResource], optional) – Frequency-domain resource section configurations.
structure (List[FrameSection], optional) – Time-domain frame configuration.
**kwargs (Any) – Waveform generator base class initialization parameters. Refer to CommunicationWaveform for details.

add_resource(resource)[source]#

Add a OFDM frequency resource to the waveform.

Parameters:: resource (FrameResource) – The resource description to be added.
Return type:: None

add_section(section)[source]#

Add a frame section to the OFDM structure.

Parameters:: section (FrameSection) – The section to be added.
Return type:: None

demodulate(signal)[source]#

Demodulate a base-band signal stream to data symbols.

Parameters:: signal (np.ndarray) – Vector of complex-valued base-band samples of a single communication frame.
Return type:: Symbols
Returns:: The demodulated communication symbols

map(data_bits)[source]#

Map a stream of bits to data symbols.

Parameters:: data_bits (np.ndarray) – Vector containing a sequence of L hard data bits to be mapped onto data symbols.
Returns:: Mapped data symbols.
Return type:: Symbols

modulate(symbols)[source]#

Modulate a stream of data symbols to a base-band signal containing a single data frame.

Parameters:: data_symbols (Symbols) – Singular stream of data symbols to be modulated by this waveform.
Return type:: ndarray

Returns: Samples of the modulated base-band signal.

pick(placed_symbols)[source]#

Pick the mapped symbols from the communicaton frame.

Additionally removes interleaved pilot symbols.

Parameters:: placed_symbols (StatedSymbols) – The placed symbols.
Return type:: StatedSymbols

Returns: The symbols with the mapped symbols picked from the frame.

place(placed_symbols)[source]#

Place the mapped symbols within the communicaton frame.

Additionally interleaves pilot symbols.

Parameters:: symbols (Symbols) – The mapped symbols.
Return type:: Symbols

Returns: The symbols with the mapped symbols placed within the frame.

unmap(symbols)[source]#

Map a stream of data symbols to data bits.

Parameters:: symbols (Symbols) – Sequence of K data symbols to be mapped onto bit sequences.
Returns:: Vector containing the resulting sequence of L data bits In general, L is greater or equal to K.
Return type:: np.ndarray

property bandwidth: float#

Bandwidth of the frame generated by this generator.

Used to estimate the minimal sampling frequency required to adequately simulate the scenario.

Returns:: Bandwidth in Hz.
Return type:: float

property bit_energy: float#

Returns the theoretical average (discrete-time) bit energy of the modulated baseband_signal.

Energy of baseband_signal \(x[k]\) is defined as \(\sum{|x[k]}^2\) Only data bits are considered, i.e., reference, guard intervals are ignored.

dc_suppression: bool#

property modulation_order: int#

Access the modulation order.

Returns:: The modulation order.
Return type:: int

property num_data_symbols: int#: Number of bit-mapped symbols contained within each communication frame.

property num_subcarriers: int#

Maximum number of subcarriers.

Sometimes also referred to as FFT-size.

Returns:: Number of subcarriers.
Return type:: int

property pilot_section: PilotSection | None#

Static pilot section transmitted at the beginning of each OFDM frame.

Required for time-domain synchronization and equalization of carrier frequency offsets.

Returns:: FrameSection of the pilot symbols, None if no pilot is configured.

property pilot_signal: Signal#

Model of the pilot sequence within this communication waveform.

Returns:: The pilot sequence.
Return type:: Signal

property power: float#

Returns the theoretical average symbol (unitless) power,

Power of baseband_signal \(x[k]\) is defined as \(\sum_{k=1}^N{|x[k]|}^2 / N\) Power is the average power of the data part of the transmitted frame, i.e., bit energy x raw bit rate

property references_per_frame: int#: Number of reference symbols per OFDM frame.

property resources: List[FrameResource]#

OFDM grid resources.

Returns: List of resources.

property samples_per_frame: int#: Number of time-domain samples per processed communication frame.

property sampling_rate: float#

Rate at which the waveform generator signal is internally sampled.

Returns:: Sampling rate in Hz.
Return type:: float

property structure: List[FrameSection]#

OFDM frame configuration in time domain.

Returns: List of frame elements.

property subcarrier_spacing: float#

Subcarrier spacing between frames.

Returns:: Spacing in Hz.
Return type:: float

property symbol_duration: float#: Duration of a single symbol block.

property symbol_energy: float#

The theoretical average symbol (discrete-time) energy of the modulated baseband_signal.

Energy of baseband_signal \(x[k]\) is defined as \(\sum{|x[k]}^2\) Only data bits are considered, i.e., reference, guard intervals are ignored.

Returns:: The average symbol energy in UNIT.

property symbols_per_frame: int#: Number of symbols per OFDM frame.

property words_per_frame: int#: Number of words per OFDM frame.