lteOFDMInfo

R2026b

OFDM modulation related information

Syntax

info = lteOFDMInfo(enb)

info = lteOFDMInfo(enb,Nfft)

Description

info = lteOFDMInfo(enb) provides information related to the OFDM modulation performed by lteOFDMModulate, given the cell-wide settings structure, enb.

info = lteOFDMInfo(enb,Nfft) specifies the number of IFFT points to use in the modulation.

Examples

Get Information Related to OFDM Modulation

Find the sampling rate of a 50 resource block configuration, corresponding to a 10 MHz waveform after OFDM modulation.

enb = struct('NDLRB',50,'CyclicPrefix','Normal');
lteOFDMInfo(enb)

ans = struct with fields:
           SamplingRate: 15360000
                   Nfft: 1024
              Windowing: 6
    CyclicPrefixLengths: [80 72 72 72 72 72 72 80 72 72 72 72 72 72]
                 NSCPRB: 12

Input Arguments

enb — Cell-wide settings

structure

Cell-wide settings, specified as a structure. enb contains the following fields.

Parameter Field	Required or Optional	Values	Description
NDLRB	Required	Scalar integer from 6 to 110	Number of downlink resource blocks ($$N_{\text{RB}}^{\text{DL}}$$)
CyclicPrefix	Optional	'Normal' (default), 'Extended'	Cyclic prefix length
SubcarrierSpacing	Optional	15 (default), 7.5, 2.5, 1.25, 0.37	Subcarrier spacing in kHz for MBSFN subframes or slots. Applies only when CyclicPrefix is set to 'Extended'.
Windowing	Optional	Nonnegative integer	Number of time-domain samples over which the function applies windowing and overlapping of OFDM symbols

Data Types: struct

Nfft — Number of IFFT points

positive integer

The number of IFFT points to use in the OFDM modulation, specified as a positive integer.

Output Arguments

info — OFDM information

structure

OFDM information, returned as a structure. info contains the following fields.

SamplingRate — Sampling rate of the OFDM modulator

integer

Sampling rate of the OFDM modulator, returned as an integer.

Data Types: double

Nfft — Number of FFT points

scalar power of 2

Number of FFT points used in the OFDM modulator, returned as a scalar power of 2.

Data Types: uint32

Windowing — OFDM sample span

nonnegative integer

Number of time-domain samples over which the function applies windowing and overlapping of OFDM symbols, returned as a nonnegative integer.

If enb.Windowing is absent, info.Windowing returns a default value chosen as a function of enb.NDLRB to compromise between the effective duration of cyclic prefix (and therefore the channel delay spread tolerance) and the spectral characteristics of the transmitted signal (not considering any additional FIR filtering). See lteOFDMModulate for details.

Data Types: int32

CyclicPrefixLengths — Cyclic prefix length

even integer

Cyclic prefix length (in samples) of each OFDM symbol in a subframe.

info.Nfft	CyclicPrefixLengths
	for CyclicPrefix = 'Normal'	for CyclicPrefix = 'Extended'
2048	[160 144 144 144 144 144 144 160 144 144 144 144 144 144]	[512 512 512 512 512 512 512 512 512 512 512 512]
1024	[80 72 72 72 72 72 72 80 72 72 72 72 72 72]	[256 256 256 256 256 256 256 256 256 256 256 256]
512	[40 36 36 36 36 36 36 40 36 36 36 36 36 36]	[128 128 128 128 128 128 128 128 128 128 128 128]
256	[20 18 18 18 18 18 18 20 18 18 18 18 18 18]	[64 64 64 64 64 64 64 64 64 64 64 64]
128	[10 9 9 9 9 9 9 10 9 9 9 9 9 9]	[32 32 32 32 32 32 32 32 32 32 32 32]

Note

For 15 kHz subcarrier spacing with info.Nfft < 2048, info.CyclicPrefixLengths are the CyclicPrefixLengths for info.Nfft = 2048 scaled by info.Nfft / 2048.

When CyclicPrefix is set to 'Extended' and SubcarrierSpacing is less than 15 kHz, the OFDM symbol duration increases and the number of symbols per subframe or slot decreases. The following table shows CyclicPrefixLengths for each subcarrier spacing at 10 MHz bandwidth. For other bandwidths, each element of CyclicPrefixLengths equals info.Nfft/4 for subcarrier spacings of 7.5, 2.5, and 1.25 kHz, and info.Nfft/9 for 0.37 kHz.

SubcarrierSpacing (kHz)	info.Nfft (10 MHz)	Symbols	CyclicPrefixLengths
7.5	2048	6	[512 512 512 512 512 512]
2.5	6144	2	[1536 1536]
1.25	12288	1	[3072]
0.37	41472	1	[4608]

Data Types: uint32

NSCPRB — Number of subcarriers per PRB

positive integer

Number of subcarriers per physical resource block (PRB), returned as a positive integer. The possible values are 12, 24, 72, 144, and 486. They respectively correspond to SubcarrierSpacing values of 15, 7.5, 2.5, 1.25, and 0.37 kHz.

Data Types: double

Data Types: struct

Version History

Introduced in R2014a

R2022b: Specify IFFT size

You can specify the IFFT size by using the Nfft input.