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lteSLSCFDMAInfo

Sidelink SC-FDMA modulation information

Syntax

info = lteSLSCFDMAInfo(ue)

Description

example

info = lteSLSCFDMAInfo(ue) returns a structure containing information related to the sidelink SC-FDMA modulation performed by lteSLSCFDMAModulate, using the specified UE settings structure.

For details, see Sidelink SC-FDMA Modulation.

Examples

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Calculate the sampling rate of a 5 MHz sidelink waveform after sidelink SC-FDMA modulation.

Create a UE settings structure. Specify 25 resource blocks, which corresponds to 5 MHz channel bandwidth.

ue = struct('NSLRB',25);

For the specified channel bandwidth, find the sidelink SC-FDMA modulation sampling rate.

slscfdmaInfo = lteSLSCFDMAInfo(ue);
samplingRate = slscfdmaInfo.SamplingRate
samplingRate =

     7680000

Input Arguments

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User equipment settings, specified as a parameter structure containing these fields:

Number of sidelink resource blocks, specified as an integer scalar from 6 to 110. (NRBSL)

Example: 6, which corresponds to a channel bandwidth of 1.4 MHz.

Data Types: double

Cyclic prefix length, specified as 'Normal' or 'Extended'.

Data Types: char

Number of time-domain samples over which windowing and overlapping of sidelink SC-FDMA symbols is applied, specified as a positive integer scalar.

ue.Windowing must be even. For the ue.Windowing field, the default depends on NSLRB and CyclicPrefixSL.

Data Types: double

Data Types: struct

Output Arguments

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Sidelink SC-FDMA modulated waveform information, returned as a parameter structure containing these fields:

Sampling rate of the time-domain sidelink waveform, in Hz, returned as a positive numeric scalar. SamplingRate = Nfft × (30.72e6 / 2048).

The number of FFT points, returned as a positive integer scalar. Nfft is a function of the number of resource blocks (NRBSL)

NSLRB (NRBSL)Nfft

6

128

15

256

25

512

50

1024

75

2048

100

2048

In general, Nfft is the smallest power of 2 greater than or equal to (12 × ) / 0.85. Specifically, Nfft is the smallest FFT that spans all subcarriers and results in no more than 85% of bandwidth occupancy (12 ×  / Nfft).

Number of time-domain samples over which windowing and overlapping of sidelink SC-FDMA symbols is applied, returned as a positive integer scalar.

Cyclic prefix length in symbols for each sidelink SC-FDMA symbol in a subframe, returned as an NSYM-by-1 integer vector. NSYM is 14 for normal cyclic prefix and 12 for extended cyclic prefix.

The vector returned for info.CyclicPrefixLengths depends on the FFT size.

  • When info.Nfft = 2048, then CyclicPrefixLengths is:

    • [160 144 144 144 144 144 144 160 144 144 144 144 144 144] for normal cyclic prefix

    • [512 512 512 512 512 512 512 512 512 512 512 512] for extended cyclic prefix

  • For other values of info.Nfft, these element values in CyclicPrefixLengths are scaled by info.Nfft / 2048.

More About

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Sidelink SC-FDMA Modulation

The sidelink SC-FDMA modulation processing in lteSLSCFDMAModulate performs IFFT calculation, half-subcarrier shifting, cyclic prefix insertions, and optional raised-cosine windowing and overlapping of adjacent sidelink SC-FDMA symbols. TS 36.211 specifies that for PSSCH (Section 9.3.6), PSCCH (9.4.6), PSDCH (9.5.6) and PSBCH (9.6.6), resource elements in the last SC-FDMA symbol within a subframe should be counted in the mapping process but not transmitted. Therefore, before performing the IFFT, the last SC-FDMA symbol of each subframe in the input resource grid is set to zero.

For sidelink SC-FDMA modulation, calling lteSLSCFDMAModulate on a multi-subframe array of resource grids is recommended.

  • When the resource element grid input to lteSLSCFDMAModulate spans multiple subframes, the windowing and overlapping is applied between all adjacent SC-FDMA symbols, including the last symbol of the previous subframe and the first symbol of the next subframe. Multi-subframe modulation processing results in a waveform that does not have discontinuities between subframes.

  • A time-domain waveform that concatenates individually modulated subframes has discontinuities at the start and end of each subframe. To avoid these discontinuities, the resulting multi-subframe time-domain waveform must be created by manually overlapping symbols at the subframe boundaries.

  • If the value for windowing is zero, issues concerning concatenation of subframes before sidelink SC-FDMA modulation do not apply.

If ue.Windowing is absent, info.Windowing returns a default value chosen as a function of NRB. The chosen value is a compromise between:

  • The effective duration of cyclic prefix, and therefore the channel delay spread tolerance

  • The spectral characteristics of the transmitted signal, not considering any additional FIR filtering

Introduced in R2016b

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