lteDLFrameOffset

Syntax

``offset=lteDLFrameOffset(enb,waveform)``
``[offset,corr]=lteDLFrameOffset(enb,waveform)``
``[offset,corr]=lteDLFrameOffset(enb,waveform,corrcfg)``
``[offset,corr]=lteDLFrameOffset(enb,waveform,'TestEVM')``

Description

example

````offset=lteDLFrameOffset(enb,waveform)` returns the timing offset, in samples, between the start of the input `waveform` and the start of the first frame. `offset` is measured using the reference signals defined in the LTE standard.`lteDLFrameOffset` performs synchronization using the PSS and SSS for the time-domain waveform, given cell-wide settings structure, `enb`. Note that this function does not perform PSS/SSS cell identity search. The cell identity must be provided in `enb`. The function `lteCellSearch` can be used to perform cell identity search.```
````[offset,corr]=lteDLFrameOffset(enb,waveform)` also returns a complex matrix, `corr`, of the same dimensions as the input `waveform`. ```
````[offset,corr]=lteDLFrameOffset(enb,waveform,corrcfg)` provides control over which reference signals are used for timing estimation, as specified in the input structure, `corrcfg`. ```
````[offset,corr]=lteDLFrameOffset(enb,waveform,'TestEVM')`, provides the input `'TestEVM'` to stipulate alignment of the correlation configuration with TS 36.104, Annex E [1].```

Examples

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Synchronization and demodulation of Test Model output which has been delayed by five samples.

Initialize cell-wide parameters structure. Generate waveform for test model 1.1 with 5MHz bandwidth. A five sample delay is achieved by inserting five zeros at the beginning of the waveform. Compute and display the offset. Perform demodulation of the waveform accounting for the offset delay by adjusting waveform start index.

```enb = lteTestModel('1.1','5MHz'); tx = [0; 0; 0; 0; 0; lteTestModelTool(enb)]; offset = lteDLFrameOffset(enb,tx)```
```offset = 5 ```
`rxGrid = lteOFDMDemodulate(enb,tx(1+offset:end));`

Input Arguments

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Cell-wide settings, specified as a structure. `enb` can contain these fields.

Parameter FieldRequired or OptionalValuesDescription
`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

`NCellID`Required

Integer from 0 to 503

Physical layer cell identity

`DuplexMode`Optional

`'FDD'` (default), `'TDD'`

Duplexing mode, specified as either:

• `'FDD'` for Frequency Division Duplex

• `'TDD'` for Time Division Duplex

The following parameters are only required for `CellRS = 'On'` or `'OmitEdgeRBs'`. See `corrcfg`.

`CellRefP`Required

1, 2, 4

Number of cell-specific reference signal (CRS) antenna ports

The following parameters are only required when `DuplexMode = 'TDD'` and ```CellRS = 'On'``` or `'OmitEdgeRBs'`. See `corrcfg`.

`TDDConfig`Optional

0, 1 (default), 2, 3, 4, 5, 6

`SSC`Optional

0 (default), 1, 2, 3, 4, 5, 6, 7, 8, 9

Special subframe configuration (SSC)

Data Types: `struct`

Time-domain waveform, specified as a T-by-P numeric matrix, where T is the number of time-domain samples and P is the number of receive antennas. `waveform` should be at least one subframe long and contain the PSS and SSS signals. Use `lteOFDMModulate` or one of the channel model functions (`lteFadingChannel`, `lteHSTChannel`, or `lteMovingChannel`) to generate this matrix.

Data Types: `double` | `single`

Control reference signals used for timing estimation, specified as a structure containing any or all of these fields.

Parameter FieldRequired or OptionalValuesDescription
`PSS`Optional

`'On'` (default), `'Off'`

Primary synchronization signal (PSS) correlation mode

`SSS`Optional

`'On'` (default), `'Off'`

Secondary synchronization signal (SSS) correlation mode

`CellRS`Optional

`'Off'` (default), `'OmitEdgeRBs'`, `'On'`

Cell-specific reference signal (CRS) correlation mode

For the `corrcfg` fields, `lteDLFrameOffset` uses the reference signals, (`PSS`, `SSS`, or `CellRS`) as configured by initializing particular reference signal correlation mode(s) to `'On'`. For `CellRS`, using the mode setting, `'OmitEdgeRBs'`, instead of `'On'`, removes the uppermost and lowermost resource block of reference signals from the correlation. The `'OmitEdgeRBs'` method is specified for EVM testing in TS 36.104, Annex E [1]. Omitting band edge RBs removes potential transmit filtering nonlinear phase response and the resulting influence on group delay response for the overall band.

Data Types: `struct`

Test EVM setting, specified as `'TestEVM'`. As defined in TS 36.104 [1], Annex E, sets correlation with:

• `PSS` to `'On'`,

• `SSS` to `'Off'`, and

• `CellRS` to `'OmitEdgeRBs'`.

Data Types: `char` | `string`

Output Arguments

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Timing offset from the start of the input waveform to the start of the first frame, returned as a numeric scalar. It indicates the number of samples from the start of `waveform`, to the position in `waveform` where the first frame begins. `offset` is computed by extracting the timing of the peak of the correlation between `waveform` and the internally generated time-domain reference waveforms containing PSS and SSS signals. The correlation is performed separately for each antenna. `lteDLFrameOffset` uses the antenna with the earliest correlation peak and a correlation peak magnitude at least 50% of the maximum across the antennas to compute `offset`.

Data Types: `double`

Signal used to extract the timing offset, returned as a complex numeric matrix of the same size as `waveform`. Each column of `corr` is the correlation for each column (antenna) of `waveform`.

Data Types: `double`
Complex Number Support: Yes

References

[1] 3GPP TS 36.104. “Base Station (BS) radio transmission and reception.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA).

Version History

Introduced in R2014a