# lteEPDCCHDMRSIndices

EPDCCH DM-RS resource element indices

## Syntax

``ind = lteEPDCCHDMRSIndices(enb,chs)``
``ind = lteEPDCCHDMRSIndices(enb,chs,opts)``

## Description

example

````ind = lteEPDCCHDMRSIndices(enb,chs)` returns indices of the Enhanced Physical Downlink Control Channel Demodulation Reference Signal (EPDCCH DM-RS) resource elements (RE) associated with an EPDCCH transmission candidate in a subframe. By default, `ind` is a column vector of indices in one-based linear indexing form. Use this form to directly index the EPDCCH DM-RS REs of an N-by-M-by-4 array that represents the subframe resource grid across the four possible EPDCCH antenna ports (p = 107...110). You can also generate alternative index representations. The order of the indices is the same as required for the complex EPDCCH DM-RS symbols mapping. `lteEPDCCHDMRS` generates these symbols.The indices are parameterized in terms of a configured PRB pair set which defines:the overall set of possible EPDCCH candidates and the aggregation of one or more consecutive enhanced control channel elements (ECCE). This aggregation identifies the specific EPDCCH instance that the DM-RS are associated with.The DM-RS indices are created only for the specific PRB pairs and antenna ports that the corresponding EPDCCH is mapped to. They do not account for any external precoding operations.For a localized EPDCCH transmission, the EPDCCH is associated with a single antenna port from p = 107...110, dependent on the `RNTI` and ECCEs selected. Thus, the DM-RS antenna port indices (1...4 respectively, if one-based) are output for that single port.For a distributed transmission, the EPDCCH is mapped to two antenna ports in an alternating fashion. Therefore, the DM-RS indices are generated for the PRBs in both ports: p = 107,109 for normal cyclic prefix and p = 107,108 for extended cyclic prefix. The output is ordered so that the symbols for the lowest antenna index plane come first. These indices are suitable for indexing an N-by-M-by-4 array representing the subframe resource grid across the four possible EPDCCH antenna ports (p = 107...110).This syntax returns an NRE length column vector of one-based linear indices for the DM-RS resource elements associated with a particular EPDCCH candidate. The function is initialized according to the cell-wide settings, `enb`, and the EPDCCH transmission configuration, `chs`.```
````ind = lteEPDCCHDMRSIndices(enb,chs,opts)` formats the returned indices using options specified by `opts`.```

## Examples

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Specify the cell-wide settings and channel transmission configuration in parameter structures `enb` and `chs`.

```enb = struct('CyclicPrefix','Normal','DuplexMode','FDD'); enb.NDLRB = 6; enb.NSubframe = 0; chs.EPDCCHECCE = [0 7]; chs.EPDCCHType = 'Localized'; chs.EPDCCHPRBSet = 2:3; chs.RNTI = 1;```

Create the EPDCCH DM-RS indices for an EPDCCH having eight ECCEs.

`ind = lteEPDCCHDMRSIndices(enb,chs)`
```ind = 12x1 uint32 column vector 1898 1903 1908 1910 1915 1920 1970 1975 1980 1982 ⋮ ```

## Input Arguments

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eNodeB cell-wide settings, specified as a structure containing these parameter 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

`NSubframe`Required

0 (default), nonnegative scalar integer

Subframe number

`DuplexMode`Optional

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

Duplexing mode, specified as one of the following:

• `'FDD'` — Frequency division duplex (default)

• `'TDD'` — Time division duplex

The following parameters apply when `DuplexMode` is set to `'TDD'`.

`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)

Channel-specific transmission configuration, specified as a structure that can contain the following parameter fields.

Parameter FieldRequired or OptionalValuesDescription
`EPDCCHECCE`Required

1-element or 2-element vector specifying the 0-based ECCE index or inclusive [`begin`, `end`] ECCE index range according to the aggregation level `L` (```L = end – begin + 1```). The number of ECCEs in the candidate must be a power of 2.

If no transmission is required, leave this parameter empty.

The set of one or several consecutive ECCEs defining the EPDCCH transmission candidate in the overall EPDCCH set.

`EPDCCHType`Required

`'Localized'`, `'Distributed'`

EPDCCH transmission type

`EPDCCHPRBSet`Required

Vector of zero-based indices for the PRB pairs corresponding to the EPDCCH PRB set. The number of PRB pair indices must be a power of 2.

If no transmission is required, leave this parameter empty.

EPDCCH PRB pair indices

The following parameters apply when `EPDCCHType` is set to `'Localized'`.

`RNTI`Required

0 (default), scalar integer

Radio network temporary identifier (RNTI) value (16 bits)

Index generation options, specified as a character vector, cell array of character vectors, or string array. For convenience, you can specify several options as a single character vector or string scalar by a space-separated list of values placed inside the quotes. Values for `opts` when specified as a character vector include (use double quotes for string):

OptionValuesDescription
Indexing style

`'ind'` (default), `'mat'`, `'sub'`

Style for the returned indices, specified as one of the following:

• `'ind'` — returns the indices in linear index form as a column vector (default)

• `'mat'` — returns the indices in linear index form as a matrix, where each column contains indices for an individual port.

• `'sub'` — returns the indices in `[subcarrier, symbol, antenna]` subscript row style. The number of rows in the output, `ind`, is the number of resource elements (NRE). Thus, `ind` is an NRE-by-3 matrix.

Index base

`'1based'` (default), `'0based'`

Base value of the returned indices. Specify `'1based'` to generate indices where the first value is 1. Specify `'0based'` to generate indices where the first value is 0.

Indexing format

`'rsonly'` (default), `'rs+unused'`

RE locations mode of the returned indices.

• `'rsonly'` — returns only active DM-RS locations (default)

• `'rs+unused'` — also includes all RE locations, which should be unused because of DM-RS transmission on other EPDCCH antenna ports p = 107...110 that are not used by this EPDCCH transmission

Example: `'ind rsonly'`, `"ind rsonly"`, `{'ind','rsonly'}`, or `["ind","rsonly"]` specify the same formatting options.

Data Types: `char` | `string` | `cell`

## Output Arguments

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EPDCCH DM-RS resource element indices, returned by default as a numeric vector of length NRE-by-1. Optionally, for subscript-specific indexing style [`subcarrier`, `symbol`, `antenna`], `ind` is returned as an NRE-by-3 numeric matrix. NRE is the number of subframe resource elements. You can also return the indices in a linear indexing matrix, where each column contains indices for an individual antenna port. By default, the indices are returned in one-based linear indexing form, which you can use to directly index the EPDCCH DM-RS resource elements.

Data Types: `double`

## Version History

Introduced in R2014b