lteRISelect
PDSCH rank indication calculation
Description
Examples
Rank Indication example
This example shows how to populate an empty resource grid for RMC R.13 with cell-specific reference signal symbols. The signal is passed through a channel and OFDM demodulated. Estimates of the channel and noise power spectral density are used for RI and PMI calculation. A CodebookSubset bitmap of all ones means that no codebook subset restriction is applied, allowing any PMI/RI combination applicable for the configured transmission scheme to be selected during RI selection.
Create empty resource grid and populate with cell specific reference symbols. Set enb.PDSCH.CodebookSubset
to all ones so the PMI selection is unconstrained
enb = lteRMCDL('R.13'); enb.PDSCH.CodebookSubset = '1111111111111111'; reGrid = lteResourceGrid(enb); reGrid(lteCellRSIndices(enb)) = lteCellRS(enb); [txWaveform,txInfo] = lteOFDMModulate(enb,reGrid);
Initialize the channel configuration structure (chcfg
), filter the signal through a channel and demodulate the signal.
chcfg.DelayProfile = 'EPA'; chcfg.NRxAnts = 4; chcfg.DopplerFreq = 5; chcfg.MIMOCorrelation = 'Low'; chcfg.SamplingRate = txInfo.SamplingRate; chcfg.Seed = 1; chcfg.InitPhase = 'Random'; chcfg.ModelType = 'GMEDS'; chcfg.NTerms = 16; chcfg.NormalizeTxAnts = 'On'; chcfg.NormalizePathGains = 'On'; chcfg.InitTime = 0; rxWaveform = lteFadingChannel(chcfg,txWaveform); rxSubframe = lteOFDMDemodulate(enb,rxWaveform);
Estimate corresponding channel, including noise spectral density and reference signal subcarriers. Use lteRISelect
to calculate RI & PMI
cec.FreqWindow = 1; cec.TimeWindow = 15; cec.InterpType = 'cubic'; cec.PilotAverage = 'UserDefined'; cec.InterpWinSize = 1; cec.InterpWindow = 'Centered'; [hest,noiseEst] = lteDLChannelEstimate(enb,cec,rxSubframe); [ri,pmi] = lteRISelect(enb,enb.PDSCH,hest,noiseEst)
ri = 3
pmi = 13
Input Arguments
enb
— eNodeB cell-wide settings
structure
eNodeB cell-wide settings, specified as a structure containing the following parameter fields:
Parameter Field | Required or Optional | Values | Description |
---|---|---|---|
NDLRB | Required | Scalar integer from 6 to 110 | Number of downlink resource blocks () |
NCellID | Required | Integer from 0 to 503 | Physical layer cell identity |
CellRefP | Required | 1, 2, 4 | Number of cell-specific reference signal (CRS) antenna ports |
CyclicPrefix | Optional |
| Cyclic prefix length |
DuplexMode | Optional |
| Duplexing mode, specified as either:
|
The following parameters
apply when | |||
TDDConfig | Optional | 0, 1 (default), 2, 3, 4, 5, 6 | Uplink–downlink configuration |
SSC | Optional | 0 (default), 1, 2, 3, 4, 5, 6, 7, 8, 9 | Special subframe configuration (SSC) |
The
following parameters apply when
| |||
NSubframe | Required | 0 (default), nonnegative scalar integer | Subframe number |
The following parameters apply when
| |||
CSIRefP | Required | 1 (default), 2, 4, 8 | Array of number of CSI-RS antenna ports |
CSIRSConfig | Required | Scalar integer | Array CSI-RS configuration indices. See TS 36.211, Table 6.10.5.2-1. |
CSIRSPeriod | Optional |
| CSI-RS subframe configurations for one or more CSI-RS resources. Multiple CSI-RS resources can be configured from a single common subframe configuration or from a cell array of configurations for each resource. |
NFrame | Optional | 0 (default), nonnegative scalar integer | Frame number |
chs
— Channel-specific transmission configuration
structure | structure array
Channel specific transmission configuration, specified as scalar structure, or structure array containing the following parameter fields:
Parameter Field | Required or Optional | Values | Description | ||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
PMIMode | Optional |
| PMI reporting mode. | ||||||||||||||||||||
TxScheme | Optional |
| PDSCH transmission scheme, specified as one of the following options.
| ||||||||||||||||||||
CodebookSubset | Optional | Character vector, string scalar, or integer vector, all ones (default) | Codebook subset restriction, specified as a character vector or
string scalar bitmap. The default values are all ones, permitting all PMI values. This parameter
is configured by higher layers and indicates the values of PMI that can be reported. The bitmap,
defined in TS 36.213, Section 7.2, is arranged a_A-1,a_A-2,...a_0. For example, the element
CodebookSubset(1) corresponds to a_A-1 and the element CodebookSubset(end) corresponds to a_0.
The length of the bitmap is given by the | ||||||||||||||||||||
The following parameter applies for
| |||||||||||||||||||||||
AltCodebook4Tx | Optional |
| If set to |
hest
— Channel estimate
multidimensional array
Channel estimate, specified as a K-by-L-by-NRxAnts-by-P array where:
K is the number of subcarriers.
L is the number of OFDM symbols.
NRxAnts is the number of receive antennas.
P is the number of transmit antennas.
Data Types: double
Complex Number Support: Yes
noiseest
— Receiver noise variance
numeric scalar
Receiver noise variance, specified as numeric scalar. It is an estimate of the received noise power spectral density.
Data Types: double
Output Arguments
ri
— Rank indication
scalar
Rank indication, returned as a scalar, indicates the optimal number of layers to use for transmission to maximize SINR.
pmiset
— Precoder matrix indications
scalar | column vector
Precoder matrix indications, returned as a scalar, or a column vector.
For wideband reporting (
NSubbands
=1),pmiset
is a scalar specifying the selected wideband codebook index,i2.For the
'Port7-14'
transmission scheme with eight CSI-RS ports, or for CSI reporting with the alternative codebook for four antennas,pmiset
hasNSubbands+1
rows. The first row indicates wideband codebook index, i1, and the subsequentNSubbands
rows indicate the subband codebook indices, i2.For other numbers of CSI-RS ports in the
'Port7-14'
transmission scheme, and for other transmission schemes,pmiset
hasNSubbands
rows, each row returns the subband codebook index for that subband.
The number of subbands, NSubbands
,
is a field in the info
structure output by ltePMIInfo
and ltePMISelect
.
More About
RI Selection
The PDSCH rank indication (RI) selection process determines the optimal number of layers (NLayers) to use for transmission to maximize SINR. The range of NLayers to consider is calculated based on the transmission scheme and the configured reference signal ports.
For ν = 1,...,NLayers,
Use
ltePMISelect
, withchs.NLayers
= ν, to perform PMI selection.Record the selected PMI and total SINR across all layers, excluding layers with SINR below the threshold of 0 dB.
Select the number of transmission layers, ν, that maximizes the SINR of the transmission and return as the rank indication,
ri
and corresponding PMI set,pmiset
.
RI selection corresponds to:
Report Type 3 (for reporting Mode 1-0 or Mode 1-1) on the PUCCH.
Reporting Mode 1-2 or Mode 3-1 on the PUSCH.
For more information on RI selection, see TS 36.213 Section 7.2.
PMI Selection
PDSCH precoder matrix indication (PMI) selection
calculates a PMI set, pmiset
. Functions, such
as lteRMCDLTool
or ltePDSCH
, can use the returned pmiset
to
configure the PMI for downlink transmissions they generate. PMI selection
is performed using the PMI definitions specified in TS 36.213, Section
7.2.4.
The CSI reporting codebook is used for:
'Port7-14'
transmission scheme with eight CSI-RS portsCSI reporting with the alternative codebook for four antennas (alternativeCodeBookEnabledFor4TX -r12 = true).
The codebook for closed-loop spatial multiplexing, defined in TS 36.211 Tables 6.3.4.2.3-1 and 6.3.4.2.3-2, is used for other cases.
The PMI feedback type associated with the PMI selection process can be wideband or subband:
PMIMode = 'Wideband'
corresponds to PUSCH reporting Mode 1-2 or PUCCH reporting Mode 1-1 (PUCCH Report Type 2).PMIMode = 'Subband'
corresponds to PUSCH reporting Mode 3-1.
PMI selection is based on the rank indicated by
chs.NLayers
, except for 'TxDiversity'
transmission
scheme, where the rank is 1. In PUCCH reporting Mode 1-1, you can achieve codebook
subsampling for submode 2, as specified in TS 36.213, Table 7.2.2-1D, with an appropriate
chs
.CodebookSubset
.
References
[1] 3GPP TS 36.213. “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network. URL: https://www.3gpp.org.
[2] 3GPP TS 36.211. “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network. URL: https://www.3gpp.org.
Version History
Introduced in R2014b
See Also
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