# Documentation

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# ltePDCCH

## Syntax

``````[sym,info] = ltePDCCH(enb,cw)``````
``````[sym,info] = ltePDCCH(enb,cw,NREG)``````
``````[sym,info] = ltePDCCH(enb,cw,NREG,CCEGAINS)``````

## Description

example

``````[sym,info] = ltePDCCH(enb,cw)``` returns an `NRE`-by-`CellRefP` complex matrix, `sym`, of modulation symbols given the input bit vector `cw`. The function returns a matrix (`sym`) of complex modulation symbols generated by the set of Physical Downlink Control Channels (PDCCH) in a subframe. The channel processing includes the stages of scrambling, QPSK modulation, layer mapping and precoding, followed by REG interleaving and cyclic shifting. For a given input bit vector (typically the PDCCH multiplex), the output matrix `sym` contains the QPSK symbols in column-wise antenna form. Any input bits with value < 0 are turned into `<NIL> ('0')` symbols. The optional structure `info` returns control resourcing information about the output symbols (see `ltePDCCHInfo` for details). ```
``````[sym,info] = ltePDCCH(enb,cw,NREG)``` returns matrix `sym`. sets the number of output QPSK symbols, `NRE`, based on the `NREG` input value (`NRE` = 4 × `NREG`) instead of calculating it from the parameters of the `enb` structure. ```
``````[sym,info] = ltePDCCH(enb,cw,NREG,CCEGAINS)``` returns matrix `sym`. `CCEGAINS` allows control of the QPSK symbol gains on a per control channel element (CCE) basis.```

## Examples

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Generate complex modulated symbols for the PDCCH. The PDCCH symbols are QPSK modulated. Each QPSK symbol represents two bits.

Create a cell-wide configuration structure, iniitialized for RMC R.0. Retrieve the PDCCH information.

```enb = lteRMCDL('R.0'); pdcchInfo = ltePDCCHInfo(enb) ```
```pdcchInfo = struct with fields: NREG: 113 NRE: 452 NCCE: 12 NREGUsed: 108 NREUsed: 432 MTot: 904 NSymbols: 3 ```

The field `pdcch.MTot` indicates the maximum number of input bits that can be transmitted on the PDCCH.

Generate a codeword that is `MTot` bits long. Using the codeword, generate PDCCH symbols.

```cw = randi([0,1],pdcchInfo.MTot,1); [pdcchSym,info] = ltePDCCH(enb,cw); numCodewordBits = length(cw) numPDCCHSymbols = length(pdcchSym) ```
```numCodewordBits = 904 numPDCCHSymbols = 452 ```

Since there are two bits per symbol, the number of output PDCCH symbols is half length of the codeword bit stream.

## Input Arguments

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

Parameter FieldRequired or OptionalValuesDescription
`CellRefP`Required

1, 2, 4

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

`NCellID`Required

Integer from 0 to 503

Physical layer cell identity

`NSubframe`Required

Integer greater than 0

Subframe number

`NDLRB`Required

Nonnegative scalar integer (6,...,110)

Number of downlink resource blocks. (${N}_{\text{RB}}^{\text{DL}}$)

`CyclicPrefix`Optional

`'Normal'` (default), `'Extended'`

Cyclic prefix length

`CFI`Required

1, 2, or 3

Control format indicator value

`Ng`Required

`'Sixth'`, `'Half'`, `'One'`, `'Two'`

PHICH group multiplier

`DuplexMode`Optional

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

Duplexing mode, specified as:

• `'FDD'` for Frequency Division Duplex or

• `'TDD'` for Time Division Duplex

The following field is required when `DuplexMode` is set to `'TDD'`.
`TDDConfig`Optional

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

Data Types: `struct`

Input bit vector that is 32 elements in length, specified as a vector. If `length(cw) < 32`, `cw` is padded with zeros before channel processing. If ```length(cw) > 32```, only the first 32 elements are used.

Example: `cw = lteCFI(struct('CFI',1));`

Data Types: `int8`

Resource element groups (REGs) assigned to PDCCH.

Vector that controls the QPSK symbol gains on a per CCE basis. Each CCE (Control Channel Element) is a group of 36 QPSK symbols (72 bits) and is the minimum unit that a single coded DCI can be mapped to. The number of complete CCE, NCCE = floor(NREG/9), is available via the `NCCE` field in `info`. Each element of `CCEGAINS` acts as a linear multiplier to all 36 symbols generated from the associated block of 72 input bits. If `CCEGAINS` does not cover all the `NREG` symbols, specifically length(`CCEGAINS`) < `NCCE`, then the uncovered CCE receives zero power. All symbols are interleaved before they are output.

Data Types: `double`
Complex Number Support: Yes

## Output Arguments

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PDCCH modulation symbols, given the input bit vector `cw`, returned as a `NRE`-by-`CellRefP` complex matrix. `NRE` is the number of QPSK symbols per antenna and `CellRefP` is the number of TX antenna ports. `NRE` corresponds to the number of control region resource elements assigned to the PDCCH given the structure `enb`.

Data Types: `double`
Complex Number Support: Yes

Information for various PDCCH resourcing quantities, returned as a structure. It contains fields including `NRE`, `NREG`, and `MTot`.

`MTot` is the maximum number of input bits that can be transmitted on the `NRE` symbols (`MTot` = 2×`NRE` = 8×`NREG`). If `length(cw)<MTot`, the input is padded with (`MTot`-length(`cw`)) `<NIL>` elements which translate to zero valued symbols. Any elements of input vector `cw` valued < 0 are also treated as `<NIL>` elements. If length(`cw`) > `MTot` then only the first `MTot` bits are used.

Data Types: `struct`