lteFrequencyCorrect

Frequency offset correction

Syntax

out = lteFrequencyCorrect(cfg,in,foffset)

Description

out = lteFrequencyCorrect(cfg,in,foffset) corrects for a specified frequency offset, foffset, in the time-domain waveform, in, by performing simple frequency modulation (FM). The parameters of the waveform, in, are specified in a settings structure, cfg, which must contain either the field NDLRB or NULRB to control whether a downlink or uplink signal is expected in in.

The input, foffset is the frequency offset, in hertz, present on the waveform, in. Therefore, the correction applied is FM modulation by –foffset.

Examples

Correct for Specified Frequency Offset

Perform frequency offset estimation and correction on an uplink signal, to which a frequency offset has been applied.

Generate uplink RMC A3-2.

[txWaveform,rgrid,cfg] = lteRMCULTool('A3-2',[1;0;0;1],'Fdd',2);

Apply an arbitrary frequency offset of 51.2 Hz.

t = (0:length(txWaveform)-1).'/cfg.SamplingRate;
txWaveform = txWaveform .* exp(1i*2*pi*51.2*t);

Estimate and display the frequency offset.

offset = lteFrequencyOffset(cfg,txWaveform);
disp(['Frequency offset: ' num2str(offset) ' Hz'])

Frequency offset: 51.2 Hz

Correct for the frequency offset.

rxWaveform = lteFrequencyCorrect(cfg,txWaveform,offset);

Finally, perform SC-FDMA demodulation.

rxGrid = lteSCFDMADemodulate(cfg,rxWaveform);

Input Arguments

cfg — Waveform parameter settings

structure

Waveform parameter settings, specified as a structure. cfg must contain either the field NDLRB, to specify a downlink configuration, or the field NULRB, to specify an uplink configuration.

Parameter Field	Required or Optional	Values	Description
NDLRB	Required	Positive scalar integer	Number of downlink resource blocks ($$N_{\text{RB}}^{\text{DL}}$$) Set this parameter field to specify a downlink configuration.
CyclicPrefix	Required	'Normal' (default), 'Extended'	Cyclic prefix length in the downlink Only set this parameter field if you are specifying a downlink configuration.
NULRB	Required	Scalar integer from 6 to 110	Number of uplink resource blocks. ($$N_{\text{RB}}^{\text{UL}}$$) Set this parameter field to specify an uplink configuration.
CyclicPrefixUL	Required	'Normal' (default), 'Extended'	Uplink cyclic prefix length. Only set this parameter field if you are specifying an uplink configuration.

Data Types: struct

in — Time-domain waveform

numeric column vector

Time-domain waveform, specified as a numeric column vector.

Data Types: double | single
Complex Number Support: Yes

foffset — Waveform frequency offset

scalar value

Waveform frequency offset, specified as a scalar value expressed in Hertz. The correction applied to in is FM modulation by –foffset.

Data Types: double

Output Arguments

out — Offset-corrected waveform

numeric column vector

Offset-corrected waveform, returned as a numeric column vector.

Data Types: double | single
Complex Number Support: Yes

Version History

Introduced in R2014a