lteNPDSCHDecode

NB-IoT physical downlink shared channel decoding

Syntax

[cw,stateout,symbols] = lteNPDSCHDecode(enb,chs,sym)

[cw,stateout,symbols] = lteNPDSCHDecode(enb,chs,sym,statein)

[cw,stateout,symbols] = lteNPDSCHDecode(enb,chs,sym,hest,noiseest)

[cw,stateout,symbols] = lteNPDSCHDecode(enb,chs,hest,noiseest,statein)

Description

[cw,stateout,symbols] = lteNPDSCHDecode(enb,chs,sym) performs the inverse of NB-IoT physical downlink shared channel (NPDSCH) processing on the matrix of complex modulated NPDSCH symbols, sym, using cell-wide settings structure, enb, and channel-specific configuration structure, chs. The channel inverse processing includes the deprecoding, layer demapping, soft demodulation, descrambling, and codeword recovery. The deprecoding is performed using matrix pseudo-inversion of the precoding matrices. lteNPDSCHDecode returns a column vector, cw, of soft bit vectors, a structure, stateout, of the decoding state, and a vector, symbols, of received constellation symbol vectors. For more information, see TS 36.211 10.2.3 [1], and lteNPDSCH. cw is optionally scaled by channel state information (CSI) calculated during the equalization process.

[cw,stateout,symbols] = lteNPDSCHDecode(enb,chs,sym,statein) specifies the initial decoder state in the statein structure.

[cw,stateout,symbols] = lteNPDSCHDecode(enb,chs,sym,hest,noiseest) performs the inverse of NPDSCH processing using the channel estimate, hest, and the noise estimate, noiseest.

The behavior varies based on the enb.NBRefP setting. For the TxDiversity transmission scheme (NBRefP = 2), the deprecoding is performed using an orthogonal space frequency block code decoder. For the Port0 transmission scheme (NBRefP = 1), the reception is performed using MMSE equalization. hest is assumed in terms of transmission layers, using the NRS reference signals. Therefore, the MMSE equalization produces MMSE-equalized layers.

[cw,stateout,symbols] = lteNPDSCHDecode(enb,chs,hest,noiseest,statein) performs the inverse of NPDSCH processing using the channel estimate, hest, the noise estimate, noiseest, and the initial decoder state, statein.

Examples

Generate and Receive NPDSCH Symbols

Generate and receive the NPDSCH symbols subframe by subframe for a bundle of 12 subframes.

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

enb.NNCellID = 0;
enb.NBRefP = 1;
enb.NFrame = 1;
chs.NSF = 3;
chs.NRep = 4;
chs.RNTI = 0;
chs.NPDSCHDataType = 'NotBCCH';

Set the output codeword length to 960 and generate the codeword bits. Do not provide the encoder or decoder states at the start of the bundle.

cwLen = 960;
estate = [];
dstate = [];
cw = ones(cwLen,1);

Generate the NPDSCH symbols for each of the 12 subframes and then decode them.

for subframeIdx = 0:(chs.NSF*chs.NRep-1)
    enb.NSubframe = subframeIdx;
    [sym,estate] = lteNPDSCH(enb,chs,cw,estate);
    [rxcw,dstate] = lteNPDSCHDecode(enb,chs,sym,dstate);
end

The value of the field CWSFCount in structure dstate indicates that all three subframes in the codeword have been received four times.

dstate.EndOfTx

ans = logical
   1

dstate.CWSFCount

ans = 3×1

     4
     4
     4

Input Arguments

enb — eNodeB cell-wide settings

structure

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

Parameter Field	Required or Optional	Values	Description
NNCellID	Required	Nonnegative integer	NB-IoT physical layer cell identity
NSubframe	Required	Nonnegative integer	Subframe number
NFrame	Optional	0 (default), nonnegative integer	Frame number
NBRefP	Required	1, 2	Number of narrowband reference signal antenna ports

chs — Channel-specific transmission configuration

structure

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

Parameter Field	Required or Optional	Values	Description
NPDSCHDataType	Optional	'NotBCCH' (default), 'SIB1NB', 'BCCHNotSIB1NB'	Type of the data carried by NPDSCH
NSF	Required (See note)	Integer	Number of subframes that a codeword is mapped to (not including repetitions)
NRep	Required	Integer	Number of repetitions
RNTI	Required (See note)	Integer	Radio network temporary identifier (16-bit)
CSI	Optional	'On' (default) or 'Off'	Determines if soft bits are weighted by CSI
Note NSF and RNTI are required only when NPDSCHDataType is not equal to 'SIB1NB'. If NPDSCHDataType = 'SIB1NB', then NSF is set to 8 and RNTI is set to 65535 (SI-RNTI).

sym — Complex modulated NPDSCH symbols

N_RE-by-N_RxAnts numeric matrix

Complex modulated NPDSCH symbols, specified as a N_RE-by-N_RxAnts numeric matrix. N_RE is the number of QPSK symbols per antenna assigned to the NPDSCH. N_RxAnts is the number of receive antennas.

Data Types: double
Complex Number Support: Yes

statein — Initial decoder state

structure

Input decoder state for the transmission of a bundle, specified as a structure. statein can be empty only when no information is provided, such as, at the first subframe of a bundle. The statein structure is normally generated and recycled from the stateout of previous calls to lteNPDSCHDecode, as part of a sequence of bundle transmission.

Data Types: struct

hest — Channel estimate

N_RE-by-N_RxAnts-by-NBRefP numeric array

Channel estimate, specified as a N_RE-by-N_RxAnts-by-NBRefP numeric array. N_RE is the number of QPSK symbols per antenna assigned to the NPDSCH per subframe. N_RxAnts is the number of receive antennas. NBRefP is the number of NRS antenna ports, given by enb.NBRefP.

Data Types: double

noiseest — Noise estimate

numeric array

Noise estimate of the noise power spectral density per RE on the received subframe, specified as a numeric array.

Data Types: double

Output Arguments

cw — Codeword

vector of bit values

Codeword, returned as a vector of bit values required to modulate one codeword.

Data Types: double

stateout — Output decoder state

structure

Output decoder state for the next subframe, returned as a structure. stateout contains the internal state of each transport block in the following fields:

Parameter Field	Values	Description
SubframeIdx	0, 1, 2, …, chs.NSF×chs.NRep–1	0-based index of a subframe in a bundle.
InitNSubframe	Integer	Subframe number at the initialization point of the scrambling sequence.
InitNFrame	Integer	Frame number at the initialization point of the scrambling sequence.
CWBuffer	Numeric column vector	Buffer used to store the soft-combined LLR bits after codeword descrambling. The length of the buffer is the same as the length of the codeword.
CWSFCount	Numeric column vector	Counters for the number of repetitions received in the CWBuffer for all the chs.NSF subframes of a codeword. The counters vector is of size chs.NSF-by-1.
EndOfCW	false, true	Indicator of whether all subframes in a codeword have been received at least once, that is, all the elements in CWSFCount are greater than or equal to 1.
EndOfTx	false, true	Indicator of whether the transmission of all subframes in a bundle is complete.

The output SubframeIdx in stateout is equal to its input in statein increased by 1. When SubframeIdx reaches the maximum value, it wraps around to 0. If inputs do not exist in statein, the default input is 0. An output value 0 indicates that all subframes in a bundle have been received and stored in CWBuffer, so the output EndOfTx is true.

When the subframe under processing is at the initialization point of the scrambling sequence, InitNSubframe is equal to enb.NSubframe, and InitNFrame is equal to enb.NFrame. If the subframe is not at the initialization point, InitNSubframe and InitNFrame are equal to their respective inputs in statein, if the inputs exist. If the inputs do not exist, InitNSubframe is equal to enb.NSubframe and InitNFrame is 0.

At the beginning of a bundle, the function resets CWBuffer, CWSFCount, EndOfCW, and EndOfTx.

Data Types: struct

symbols — Received constellation symbols

complex column vector

Received constellation symbols, returned as a complex column vector, resulting from performing the inverse of NPDSCH processing.

Data Types: double

References

[1] 3GPP TS 36.211. “Physical Channels and Modulation.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA). URL: http://www.3gpp.org.