Documentation

lteDLPerfectChannelEstimate

Downlink perfect channel estimation

Syntax

  • h = lteDLPerfectChannelEstimate(enb,chs)
    example
  • h = lteDLPerfectChannelEstimate(enb,chs,toffset)

Description

example

h = lteDLPerfectChannelEstimate(enb,chs) performs perfect channel estimation for a system configuration given by cell-wide settings, enb, and channel configuration structure, chs. It produces a perfect channel estimate, h. The perfect channel estimates are only produced for the fading channel model created using the lteFadingChannel function. The lteDLPerfectChannelEstimate function provides a perfect MIMO channel estimate after OFDM modulation. Perfect channel estimation is achieved by setting the channel with the desired configuration and sending a set of known symbols through it for each transmit antenna in turn.

chs is the fading channel configuration structure. It must include all the fields required to parameterize lteFadingChannel, except for the SamplingRate field. lteDLPerfectChannelEstimate sets SamplingRate internally to the sampling rate of the time domain waveform passed to lteFadingChannel for channel filtering.

h = lteDLPerfectChannelEstimate(enb,chs,toffset) takes the additional parameter, toffset. This parameter allows h to be the precise channel resulting when the receiver is precisely synchronized. Use lteDLFrameOffset to derive toffset.

Examples

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Perform Perfect DL Channel Estimation

Perform perfect channel estimation for a given propagation channel configuration in the downlink

Initialize eNodeB & propagation channel configuration structures, then compute channel estimate

enb.NDLRB = 6;
enb.CyclicPrefix = 'Normal';
enb.CellRefP = 4;
enb.TotSubframes = 1;
chs.Seed = 1;
chs.DelayProfile = 'EPA';
chs.NRxAnts = 2;
chs.DopplerFreq = 5.0;
chs.MIMOCorrelation = 'Low';
chs.InitPhase = 'Random';
chs.InitTime = 0.0;
chs.ModelType = 'GMEDS';
chs.NTerms = 16;
chs.NormalizeTxAnts = 'On';
chs.NormalizePathGains = 'On';
H = lteDLPerfectChannelEstimate(enb,chs);
sizeH = size(H)
sizeH =

    72    14     2     4

Input Arguments

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enb — Cell-wide settingsscalar structure

Cell-wide settings, specified as a structure with the following fields.

Parameter FieldRequired or OptionalValuesDescription
NDLRBRequired

Scalar integer (6, ..., 110). Standard bandwidth values are 6, 15, 25, 50, 75, and 100. NDLRB will also accept the standardized bandwidths in string format from the set {'1.4MHz', '3MHz', ‘5MHz', '10MHz', ‘15MHz', ‘20MHz'}.

Number of downlink (DL) resource blocks (RBs)

CyclicPrefixOptional

'Normal' (default), 'Extended'

Cyclic prefix length

CellRefPRequired

1, 2, 4

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

TotSubframesRequired

Nonnegative scalar integer

Total number of subframes to generate

Data Types: struct

chs — Channel configurationstructure

Channel configuration, specified as a structure having the following fields.

Parameter FieldRequired or OptionalValuesDescription
NRxAntsRequired

Positive scalar integer

Number of receive antennas

MIMOCorrelationRequired

'Low', 'Medium', 'UplinkMedium', 'High', 'Custom'

Correlation between UE and eNodeB antennas

  • 'Low' correlation is equivalent to no correlation between antennas.

  • 'Medium' correlation level is applicable to tests defined in TS 36.101 [1].

  • 'UplinkMedium' correlation level is applicable to tests defined in TS 36.104 [2].

NormalizeTxAntsOptional

'On' (default), 'Off'

Transmit antenna number normalization, specified as a string.

  • 'On', lteDLPerfectChannelEstimate normalizes the model output by 1/sqrt(P), where P is the number of transmit antennas. Normalization by the number of transmit antennas ensures that the output power per receive antenna is unaffected by the number of transmit antennas.

  • 'Off', normalization is not performed.

DelayProfileRequired

'EPA', 'EVA', 'ETU', 'Custom', 'Off'

Delay profile model.

Setting DelayProfile to 'Off' switches off fading completely and implements a static MIMO channel model. In this case, the antenna geometry corresponds to chs.MIMOCorrelation, chs.NRxAnts, and the number of transmit antennas. The temporal part of the model for each link between transmit and receive antennas consists of a single path with zero delay and constant unit gain.

The following fields are required or optional (as indicated) when DelayProfile is set to a value other than 'Off'.
  DopplerFreqRequiredScalar value

Maximum Doppler frequency, in Hertz.

  InitTimeRequiredNumeric scalar

Fading process time offset, in seconds.

  NTermsOptional

16 (default)

scalar power of 2

Number of oscillators used in fading path modeling.

  ModelTypeOptional

'GMEDS' (default), 'Dent'

Rayleigh fading model type.

  • 'GMEDS', the Rayleigh fading is modeled using the Generalized Method of Exact Doppler Spread (GMEDS), as described in [4].

  • 'Dent', the Rayleigh fading is modeled using the modified Jakes fading model described in [3].

    Note:   ModelType = 'Dent' is not recommended. Use ModelType = 'GMEDS' instead.

  NormalizePathGainsOptional

'On' (default), 'Off'

Model output normalization.

  • 'On', the model output is normalized such that the average power is unity.

  • 'Off', the average output power is the sum of the powers of the taps of the delay profile.

  InitPhaseOptional'Random' (default), scalar value (in Radians), or N-by-L-by-P-by-NRxAnts array

Phase initialization for the sinusoidal components of the model, may be set as follows:

  • the string 'Random', the phases are randomly initialized according to Seed.

  • a scalar value, assumed to be in radians, is used to initialize the phases of all components.

  • an N-by-L-by-P-by-NRxAnts array which is used to explicitly initialize the phase in radians of each component. In this case, N is the number of phase initialization values per path, L is the number of paths, P is the number of transmit antennas, and NRxAnts is the number of receive antennas.

    Note:  

    • When ModelType is set to 'GMEDS', N = 2 × NTerms.

    • When ModelType is set to 'Dent', N = NTerms.

The following field is required when DelayProfile is set to a value other than 'Off' and InitPhase is set to 'Random'.
  SeedRequiredScalar value

Random number generator seed. To use a random seed, set Seed to zero.

    Note:   MathWorks® recommends using Seed values in the range 0...231 – 1 – (K(K – 1)/2), where K = P × model.NRxAnts, the product of the number of transmit and receive antennas. Seed values outside of this range are not guaranteed to give distinct results.

The following fields are required when DelayProfile is set to 'Custom'.
  AveragePathGaindBRequiredVector

Average gains of the discrete paths, expressed in dB.

  PathDelaysRequiredVector

Delays of the discrete paths, expressed in seconds. This vector must have the same size as AveragePathGaindB.

The following fields are required when MIMOCorrelation is set to 'Custom'.
  TxCorrelationMatrixRequiredMatrix

Correlation between each of the transmit antennas, specified as a P-by-P complex matrix.

  RxCorrelationMatrixRequiredMatrix

Correlation between each of the receive antennas, specified as a complex matrix of size NRxAnts-by-NRxAnts.

Data Types: struct

toffset — Timing offsetnonnegative numeric scalar

Timing offset from the start of the output of the channel to the OFDM demodulation starting point, specified as a nonnegative numeric scalar.

Data Types: double

Output Arguments

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h — Perfect channel estimatenumeric matrix

Perfect channel estimate, returned as a numeric matrix of size M-by-N-by-NRxAnts-by-CellRefP. Where M is the number of subcarriers, N is the number of OFDM symbols, NRxAnts is the number of receive antennas, and CellRefP is the number of cell-specific reference signal antenna ports.

Data Types: double

References

[1] 3GPP TS 36.101. "User Equipment (UE) Radio Transmission and Reception." 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA). URL: http://www.3gpp.org.

[2] 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). URL: http://www.3gpp.org.

[3] Dent, P., G. E. Bottomley, and T. Croft. "Jakes Fading Model Revisited." Electronics Letters. Vol. 29, 1993, Number 13, pp. 1162–1163.

[4] Pätzold, Matthias, Cheng-Xiang Wang, and Bjørn Olav Hogstad. "Two New Sum-of-Sinusoids-Based Methods for the Efficient Generation of Multiple Uncorrelated Rayleigh Fading Waveforms." IEEE Transactions on Wireless Communications. Vol. 8, 2009, Number 6, pp. 3122–3131.

Introduced in R2013b

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