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1205 lines
51 KiB
Matlab
1205 lines
51 KiB
Matlab
10 years ago
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%lteDLChannelEstimate Downlink channel estimation
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% [HEST NOISEEST] = lteDLChannelEstimate(...) returns HEST, the estimated
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% channel between each transmit and receive antenna and NOISEEST, an
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% estimate of the noise power spectral density on the reference signal
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% subcarriers.
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%
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% HEST is an M-by-N-by-NRxAnts-by-CellRefP (optionally
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% M-by-N-by-NRxAnts-by-NLayers for UE-specific beamforming transmission
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% schemes) array where M is the number of subcarriers, N is the number of
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% OFDM symbols, NRxAnts is the number of receive antennas, CellRefP is
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% the number of cell-specific reference signal antenna ports and NLayers
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% is the number of transmission layers. Using the reference signals, an
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% estimate of the power spectral density of the noise present on the
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% estimated channel response coefficients is returned.
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%
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% [HEST NOISEEST] = lteDLChannelEstimate(ENB, RXGRID) returns the
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% estimated channel coefficients using the method described in
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% TS36.104/TS36.141 Annex E/F for the purposes of transmitter EVM
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% testing.
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%
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% ENB is a structure and must contain the following fields:
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% NDLRB - Number of downlink resource blocks
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% CellRefP - Number of cell-specific reference signal antenna ports
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% (1,2,4)
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% NCellID - Physical layer cell identity
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% NSubframe - Subframe number
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% CyclicPrefix - Optional. Cyclic prefix length
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% ('Normal'(default),'Extended')
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% DuplexMode - Optional. Duplex mode ('FDD'(default),'TDD')
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% Only required for 'TDD' duplex mode:
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% TDDConfig - Optional. Uplink/Downlink Configuration (0...6)
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% (default 0)
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% SSC - Optional. Special Subframe Configuration (0...9)
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% (default 0)
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% Only required for CEC.Reference='CSIRS' below:
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% CSIRefP - Number of CSI-RS antenna ports (1,2,4,8)
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% CSIRSConfig - CSI-RS configuration index (TS 36.211 Table
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% 6.10.5.2-1)
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% CSIRSPeriod - Optional. CSI-RS subframe configuration:
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% ('On'(default),'Off',Icsi-rs,[Tcsi-rs Dcsi-rs])
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%
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% RXGRID is a 3-dimensional M-by-N-by-NRxAnts array of resource elements.
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% The second dimension of RXGRID can contain any whole number of
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% subframes worth of OFDM symbols i.e. for normal cyclic prefix each
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% subframe contains 14 OFDM symbols, therefore N is a multiple of 14.
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% Note: to adhere to the estimation method defined in TS36.104/TS36.141,
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% RXGRID must contain 10 subframes.
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%
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% [HEST NOISEEST] = lteDLChannelEstimate(ENB, CEC, RXGRID) returns the
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% estimated channel using the method and parameters defined by the
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% configuration structure CEC.
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%
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% CEC is a structure which defines the type of channel estimation
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% performed. CEC must contain a set of the following fields:
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% PilotAverage - Type of pilot averaging ('TestEVM', 'UserDefined')
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% FreqWindow - Size of window in resource elements used to average
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% over frequency.
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% TimeWindow - Size of window in resource elements used to average
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% over time
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% InterpType - Type of 2D interpolation used(see <a href="matlab:
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% doc('griddata')">griddata</a> for types)
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% InterpWindow - Interpolation window type: ('Causal','Non-causal',
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% 'Centred','Centered'). Note: 'Centred' and 'Centered'
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% are equivalent
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% InterpWinSize - Interpolation window size:
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% 'Causal','Non-causal' - any number >=1
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% 'Centred','Centered' - odd numbers >=1
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%
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% The 'TestEVM' pilot averaging will ignore other structure fields in
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% CEC, and the method follows that described in TS36.104/TS36.141 Annex
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% E/F for the purposes of transmitter EVM testing.
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%
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% The 'UserDefined' pilot averaging uses a rectangular kernel of size
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% CEC.FreqWindow-by-CEC.TimeWindow and performs a 2D filtering operation
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% upon the pilots. Note that pilots near the edge of the resource grid
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% will be averaged less as they have no neighbors outside of the grid,
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% or a limited number of neighbors outside of the grid obtained by the
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% creation of virtual pilots.
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%
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% [HEST NOISEEST] = lteDLChannelEstimate(ENB, CHS, CEC, RXGRID) returns
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% the estimated channel given cell-wide settings structure ENB, PDSCH
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% transmission configuration CHS and channel estimator configuration CEC.
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% CHS must include the following fields:
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% TxScheme - Transmission scheme, one of:
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% 'Port0' - Single-antenna port, Port 0
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% 'TxDiversity' - Transmit diversity scheme
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% 'CDD' - Large delay CDD scheme
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% 'SpatialMux' - Closed-loop spatial multiplexing scheme
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% 'MultiUser' - Multi-user MIMO scheme
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% 'Port5' - Single-antenna port, Port 5
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% 'Port7-8' - Single-antenna port, port 7 (when
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% NLayers=1); Dual layer transmission, port 7
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% and 8 (when NLayers=2)
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% 'Port8' - Single-antenna port, Port 8
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% 'Port7-14' - Up to 8 layer transmission, ports 7-14
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% PRBSet - A 1- or 2-column matrix, containing the 0-based Physical
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% Resource Block indices (PRBs) corresponding to the resource
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% allocations for this PDSCH.
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% RNTI - Radio Network Temporary Identifier (16-bit)
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%
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% For the 'Port5', 'Port7-8', 'Port8' and 'Port7-14' transmission
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% schemes, the channel estimator configuration structure CEC contains the
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% following additional field:
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% Reference - Optional. Specifies point of reference (signals to
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% internally generate) for channel estimation.
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% ('DMRS'(default), 'CSIRS')
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%
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% For the 'Port5', 'Port7-8', 'Port8' and 'Port7-14' transmission
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% schemes, with Reference='DMRS', the channel estimation is performed
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% using UE-specific reference signals and the returned channel estimate
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% will be of size M-by-N-by-NRxAnts-by-NLayers. Alternatively, with
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% Reference='CSIRS' the channel estimation is performed using the CSI
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% reference signals (CSI) and the returned channel estimate will be of
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% size M-by-N-by-NRxAnts-by-CSIRefP. For other transmission schemes the
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% channel estimation is performed using cell-specific reference signals
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% and the channel estimate will be of size M-by-N-by-NRxAnts-by-CellRefP.
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% Note that CSI-RS based channel estimation and hence Reference='CSIRS'
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% is strictly only valid within the standard for the 'Port7-14'
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% transmission scheme. The optional CSIRSPeriod parameter controls the
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% downlink subframes in which CSI-RS will be present, either always 'On'
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% or 'Off', or defined by the scalar subframe configuration index Icsi-rs
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% (0...154) or the explicit subframe periodicity and offset pair [Tcsi-rs
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% Dcsi-rs] (TS 36.211 Section 6.10.5.3).
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%
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% For the 'Port7-8' and 'Port7-14' transmission schemes with
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% 'UserDefined' pilot averaging, if CEC.TimeWindow = 2 or 4 and
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% CEC.FreqWindow=1 the estimator will enter a special case where an
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% averaging window of 2 or 4 pilots in time will be used to average the
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% pilot estimates; the averaging is always applied across 2 or 4 pilots,
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% regardless of their separation in OFDM symbols. This operation ensures
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% that averaging is always done on 2 or 4 pilots. This provides the
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% appropriate "despreading" operation required for the case of UE RS
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% ports / CSI-RS ports which occupy the same time/frequency locations but
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% use different orthogonal covers to allow them to be differentiated at
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% the receiver. For the CSI-RS and any number of configured CSI-RS ports
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% (given by ENB.CSIRefP), the pilot REs occur in pairs, one pair per
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% subframe, that require averaging with CEC.TimeWindow=2 and will result
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% in a single estimate per subframe. For the UE RS with between 1 and 4
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% layers (given by CHS.NLayers), the pilot REs occur in pairs, repeated
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% in each slot, that require averaging with CEC.TimeWindow=2 and will
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% result in two estimates per subframe, one for each slot; for between 5
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% and 8 layers, the pairs are distinct between the slots of the subframe
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% and the required averaging is CEC.TimeWindow=4, resulting in one
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% estimate per subframe.
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%
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% Example:
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% Transmit RMC R.12 (4-antenna transmit diversity), model the propagation
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% channel by combining all transmit antennas onto one receive antenna,
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% OFDM demodulate and finally channel estimate.
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%
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% enb = lteRMCDL('R.12');
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% cec = struct('FreqWindow',1,'TimeWindow',1,'InterpType','cubic',...
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% 'PilotAverage','UserDefined','InterpWinSize',3,...
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% 'InterpWindow','Causal');
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% txWaveform = lteRMCDLTool(enb,[1;0;0;1]);
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% rxWaveform = sum(txWaveform,2);
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% rxGrid = lteOFDMDemodulate(enb,rxWaveform);
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% hest = lteDLChannelEstimate(enb,cec,rxGrid);
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%
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% See also lteOFDMDemodulate, lteEqualizeMMSE, lteEqualizeZF,
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% lteDLPerfectChannelEstimate, griddata.
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% Copyright 2009-2013 The MathWorks, Inc.
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function [H_EST, NoisePowerEst, AvgEstimates, Estimates] = lteDLChannelEstimate2(varargin)
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if(isstruct(varargin{2}))
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if(isstruct(varargin{3}))
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PDSCH = varargin{2};
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CEC = varargin{3};
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RXGRID = varargin{4};
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else
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PDSCH = [];
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CEC = varargin{2};
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RXGRID = varargin{3};
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avgrefs = varargin{4};
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end
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else
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% If no configuration structure then use the TestEVM method
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PDSCH = [];
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CEC.PilotAverage = 'TestEVM';
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RXGRID = varargin{2};
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end
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ENB = varargin{1};
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% Get dimensions of resource grid
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Dims = lteDLResourceGridSize(ENB);
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K = Dims(1);
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Lsf = Dims(2);
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% Determine number of subframes
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nsfs = size(RXGRID,2)/Dims(2);
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% Determine number of Tx- and RxAntennas
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NRxAnts = size(RXGRID,3);
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if (~isempty(PDSCH) && any(strcmpi(PDSCH.TxScheme,{'Port5' 'Port7-8' 'Port8' 'Port7-14'})))
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if (~isfield(CEC,'Reference'))
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CEC.Reference='DMRS';
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end
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if (strcmpi(CEC.Reference,'DMRS')==1)
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NTx = PDSCH.NLayers;
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elseif (strcmpi(CEC.Reference,'CSIRS')==1)
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NTx = ENB.CSIRefP;
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else
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error('lte:error','Reference must be "DMRS" or "CSIRS", see help for details.');
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end
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else
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if (~isfield(CEC,'Reference'))
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CEC.Reference='CellRS';
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end
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NTx = ENB.CellRefP;
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end
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% Initialize size of estimated channel grid
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H_EST = zeros([size(RXGRID,1) size(RXGRID,2) size(RXGRID,3) NTx]);
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% Preallocate noise power estimate vector for speed
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noiseVec = zeros(size(NRxAnts,NTx));
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if (NTx == 4)
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nn=3;
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else
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nn=NTx;
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end
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RefEstimates=zeros(nn,2*2*2*ENB.NDLRB*10);
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for rxANT = 1:NRxAnts
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for nTxAntLayer = 1:NTx
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% Extract pilot symbols from received grid and calculate least
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% squares estimate
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[ls_estimates,specialvec,DwPTS]= GetPilotEstimates(ENB,nTxAntLayer-1,RXGRID(:,:,rxANT),PDSCH,CEC);
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Estimates(nTxAntLayer,1:length(ls_estimates(3,:))) = ls_estimates(3,:);
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% Average the pilots as defined by CEC.PilotAverage, this can
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% be 'UserDefined' or 'TestEVM'.
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% Note: Setting the window size to 1x1 is equivalent to no
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% averaging. It is recommended that no averaging should be
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% carried out when a high SNR is present, as this would have an
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% adverse effect on the least squares estimates
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if strcmpi(CEC.PilotAverage,'UserDefined')&&(CEC.FreqWindow==1)&&(CEC.TimeWindow==1)
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P_EST = ls_estimates;
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ScalingVec = 0;
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else
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[P_EST, ScalingVec]= PilotAverage(PDSCH,CEC,H_EST,ls_estimates);
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end
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%AvgEstimates(nTxAntLayer,1:length(P_EST(3,:))) = P_EST(3,:);
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P_EST(3,:)=avgrefs;
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if strcmpi(CEC.PilotAverage,'TestEVM')
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% Channel estimation as defined in TS36.141 Annex F.3.4 is
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% performed, the pilots are averaged in time and frequency
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% and the resulting vector is linearly interpolated.
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%----------------------
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% Interpolate eq coefficients extrapolating to account for
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% missing pilots at the edges
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interpEqCoeff = interp1(find(P_EST~=0),P_EST(P_EST~=0),(1:length(P_EST)).','linear','extrap');
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% ---------------------
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% The DC carrier needs to be accounted for during
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% interpolation
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% Get pilot symbol index values
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ind = lteCellRSIndices(ENB,0);
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% Using initial index value calculate position of pilot
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% symbols within interpolated coefficients
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if ind(1)-3>0
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vec = (ind(1)-3):3:K;
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else
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vec = ind(1):3:K;
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end
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% Determine the index values of the pilots either side of
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% the DC carrier
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preDC = vec(length(vec)/2);
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postDC = vec(1+length(vec)/2);
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% Interpolate the section using the DC carrier and insert
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% this into the interpolated vector containing the
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% coefficients
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interpEqCoeffTemp = interp1(1:4:5,[interpEqCoeff(preDC) interpEqCoeff(postDC)],1:5,'linear');
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interpEqCoeff(preDC:K/2) = interpEqCoeffTemp(1:length(interpEqCoeff(preDC:K/2)));
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interpEqCoeff(1+K/2:postDC) = interpEqCoeffTemp(2+length(interpEqCoeff(preDC:K/2)):end);
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%----------------------
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% Generate grid by replicating estimated equalizer channel
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% coefficients
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H_EST(:,:,rxANT,nTxAntLayer) = repmat(interpEqCoeff,1,Lsf*nsfs);
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% The value of the noise averaged pilot symbols are placed
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% into P_EST(3,:) matrix and these are used to determine
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% the noise power present on the pilot symbol estimates of
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% the channel.
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P_EST = ls_estimates;
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tempGrid = squeeze(H_EST(:,:,rxANT,nTxAntLayer));
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P_EST(3,:) = tempGrid(sub2ind(size(H_EST),P_EST(1,:),P_EST(2,:)));
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else
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% Channel estimation is performed by analyzing up to
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% 'CEC.InterpWinSize' subframes together and estimating
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% virtual pilots outwith the bounds of the subframe.
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% Averaging window can be set to Causal, Non-causal or
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% Centred, Centered.
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% Using the desired subframeAveraging type the initial
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% position of the window is determined
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if(CEC.InterpWinSize>=1)
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if strcmpi(CEC.InterpWindow,'Centred')||strcmpi(CEC.InterpWindow,'Centered')
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% For Centered averaging the window size must be odd
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if ~mod(CEC.InterpWinSize,2)
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error('lte:error','Window size must be odd for centered window type');
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end
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||
|
|
% For Centered windowing both current,future and past
|
||
|
|
% data are used to estimate current channel coefficients
|
||
|
|
x = floor(CEC.InterpWinSize/2);
|
||
|
|
y = floor(CEC.InterpWinSize/2);
|
||
|
|
elseif strcmpi(CEC.InterpWindow,'Causal')
|
||
|
|
% For causal windowing current and past data are used
|
||
|
|
% to estimate current subframe channel coefficients
|
||
|
|
x = 0;
|
||
|
|
y = CEC.InterpWinSize-1;
|
||
|
|
elseif strcmpi(CEC.InterpWindow,'Non-causal')
|
||
|
|
% For non-causal windowing current and future data are
|
||
|
|
% used to estimate current subframe channel
|
||
|
|
% coefficients
|
||
|
|
x = CEC.InterpWinSize-1;
|
||
|
|
y = 0;
|
||
|
|
else
|
||
|
|
error('lte:error','Channel estimation structure field InterpWindow must be one of the following: Causal,Non-causal,Centred,Centered');
|
||
|
|
end
|
||
|
|
else
|
||
|
|
error('lte:error','InterpWinSize cannot be less than 1');
|
||
|
|
end
|
||
|
|
|
||
|
|
% Interpolate using averaged pilot estimates and defined
|
||
|
|
% interpolation settings
|
||
|
|
for sf = 0:nsfs-1
|
||
|
|
if specialvec(sf+1)=='U'
|
||
|
|
H_EST(:,sf*Lsf+1:(sf+1)*Lsf,rxANT,nTxAntLayer) = NaN;
|
||
|
|
else
|
||
|
|
% Extract the pilots from required subframes
|
||
|
|
p_use = P_EST;
|
||
|
|
p_use(:,p_use(4,:)>(sf+1)+x)=[];
|
||
|
|
p_use(:,p_use(4,:)<(sf+1)-y)=[];
|
||
|
|
|
||
|
|
% Account for DC offset
|
||
|
|
p_use(1,(p_use(1,:)>K/2)) = p_use(1,(p_use(1,:)>K/2))+1;
|
||
|
|
|
||
|
|
if strcmpi(CEC.InterpType,'Cubic')||strcmpi(CEC.InterpType,'Linear')
|
||
|
|
% VPVEC is used to determine if virtual pilots are
|
||
|
|
% needed at the beginning or end of the
|
||
|
|
% interpolation window, if the current subframe,sf,
|
||
|
|
% is located at beginning or end of the window then
|
||
|
|
% virtual pilots are created accordingly
|
||
|
|
vpvec = unique(p_use(4,:));
|
||
|
|
|
||
|
|
if (strcmp(CEC.Reference,'CellRS')==1)
|
||
|
|
% Create virtual pilots and append to vector
|
||
|
|
% containing pilots using cell-specific RS
|
||
|
|
% methodology.
|
||
|
|
vps = createVirtualPilots(ENB,p_use(1:3,:),1,1,(sf+1==min(vpvec)),(sf+1==max(vpvec)));
|
||
|
|
p_use = [p_use(1:3,:) vps];
|
||
|
|
else
|
||
|
|
% Create edge virtual pilots suitable for
|
||
|
|
% UE RS which can have partial bandwidth,
|
||
|
|
% or CSI-RS.
|
||
|
|
if (~isempty(p_use))
|
||
|
|
vps = createEdgeVirtualPilots(ENB,p_use(1:3,:));
|
||
|
|
p_use = [p_use(1:3,:) vps];
|
||
|
|
end
|
||
|
|
end
|
||
|
|
end
|
||
|
|
% Perform 2D interpolation
|
||
|
|
% Interpolation is carried out on a (K+1)-by-L
|
||
|
|
% matrix to account for DC offset being added in
|
||
|
|
if (~isempty(p_use))
|
||
|
|
Htemp = griddata(p_use(2,:)-Lsf*sf,p_use(1,:),p_use(3,:),1:Lsf,(1:K+1)',CEC.InterpType); %#ok<GRIDD>
|
||
|
|
% Remove DC offset
|
||
|
|
Htemp(1+(K/2),:) = [];
|
||
|
|
|
||
|
|
if specialvec(sf+1)=='S'
|
||
|
|
Htemp(:,DwPTS+1:Lsf) = NaN;
|
||
|
|
end
|
||
|
|
H_EST(:,sf*Lsf+1:(sf+1)*Lsf,rxANT,nTxAntLayer) = Htemp;
|
||
|
|
|
||
|
|
if isnan(H_EST)
|
||
|
|
error('lte:error','H_EST NaN');
|
||
|
|
end
|
||
|
|
end
|
||
|
|
end
|
||
|
|
end
|
||
|
|
end
|
||
|
|
if nTxAntLayer<3 || (~isempty(PDSCH) && any(strcmpi(PDSCH.TxScheme,{'Port7-8' 'Port7-14'})))
|
||
|
|
% The noise level present can be determined using the noisy
|
||
|
|
% least squares estimates of the channel at pilot symbol
|
||
|
|
% locations and the noise averaged pilot symbol estimates of the
|
||
|
|
% channel
|
||
|
|
noise = ls_estimates(3,~isnan(ls_estimates(3,:))) - P_EST(3,~isnan(P_EST(3,:)));
|
||
|
|
if strcmpi(CEC.PilotAverage,'UserDefined')
|
||
|
|
noise = sqrt(ScalingVec./(ScalingVec+1)).*noise;
|
||
|
|
end
|
||
|
|
|
||
|
|
% Additional averaging for noise estimation in LTE-A case,
|
||
|
|
% to suppress interference from orthogonal sequences on
|
||
|
|
% other antennas in same time-frequency locations.
|
||
|
|
if (~isempty(PDSCH) && any(strcmpi(PDSCH.TxScheme,{'Port7-8' 'Port7-14'})) &&...
|
||
|
|
(CEC.TimeWindow==2 || CEC.TimeWindow==4) && CEC.FreqWindow==1)
|
||
|
|
if (~isempty(ls_estimates))
|
||
|
|
if (strcmpi(CEC.Reference,'DMRS')==1)
|
||
|
|
temp=[];
|
||
|
|
pilotSC = unique(ls_estimates(1,:));
|
||
|
|
for i = pilotSC
|
||
|
|
x=find(ls_estimates(1,:)==i);
|
||
|
|
x=[x(1) x(end)];
|
||
|
|
temp=[temp mean(noise(x))*2]; %#ok<AGROW>
|
||
|
|
end
|
||
|
|
noise=temp;
|
||
|
|
end
|
||
|
|
end
|
||
|
|
end
|
||
|
|
|
||
|
|
% Taking the variance of the noise present on the pilot symbols
|
||
|
|
% results in a value of the noise power for each transmit and
|
||
|
|
% receive antenna pair
|
||
|
|
if (isempty(noise))
|
||
|
|
noiseVec(rxANT,nTxAntLayer)=NaN;
|
||
|
|
else
|
||
|
|
noiseVec(rxANT,nTxAntLayer) = mean(noise.*conj(noise));
|
||
|
|
end
|
||
|
|
end
|
||
|
|
end
|
||
|
|
end
|
||
|
|
|
||
|
|
% The mean of the noise power across all the transmit/receive antenna
|
||
|
|
% pairs is used as the estimate of the noise power
|
||
|
|
NoisePowerEst = mean(mean(noiseVec));
|
||
|
|
|
||
|
|
end
|
||
|
|
|
||
|
|
% GetPilotEstimates Obtain the least squares estimates of the reference
|
||
|
|
% signals
|
||
|
|
% [ls_estimates] = GetPilotEstimates(ENB,nTxAntLayer,RXGRID) Extracts the
|
||
|
|
% reference signals for a specific transmit/receive antenna pair and
|
||
|
|
% calculates their least squares estimate. The results are placed in a
|
||
|
|
% 3xNp matrix containing the subcarrier and OFDM symbol location, row and
|
||
|
|
% column subscripts, and value. Np is the number of cell specific
|
||
|
|
% reference (pilot) symbols per resource grid
|
||
|
|
%
|
||
|
|
% RXGRID is an MxN array where M is the number of subcarriers,
|
||
|
|
% N is the number of OFDM symbols. Dimension M must be
|
||
|
|
% 12*NDLRB where NDLRB must be {6,15,25,50,75,100}.
|
||
|
|
% Dimension N must be a multiple of number of symbols in a subframe L,
|
||
|
|
% where L=14 for normal cyclic prefix and L=12 for extended cyclic
|
||
|
|
% prefix.
|
||
|
|
%
|
||
|
|
% nTxAntLayer defines which transmit antennas' or layers' pilot symbols to extract
|
||
|
|
%
|
||
|
|
% ENB is a structure and must contain the following fields:
|
||
|
|
% NDLRB - Number of downlink resource blocks
|
||
|
|
% NCellID - Physical layer cell identity
|
||
|
|
% CellRefP - Number of transmit antenna ports {1,2,4}
|
||
|
|
% CyclicPrefix - Optional. Cyclic prefix length{'Normal'(default),'Extended'}
|
||
|
|
%
|
||
|
|
%
|
||
|
|
% Example
|
||
|
|
% Return the least squares estimate of the pilots symbols in a 3xNp array
|
||
|
|
% where the first row is the subcarrier index,k the second row is the OFDM
|
||
|
|
% symbol,l and the third row defines the least squares estimate of the
|
||
|
|
% pilot located at that position.
|
||
|
|
%
|
||
|
|
% enb=struct('NDLRB',6,'CellRefP',1,'NCellID',0,'CyclicPrefix','Normal');
|
||
|
|
% rxGrid=ones(lteDLResourceGridSize(enb));
|
||
|
|
% nTxAntLayer=0;
|
||
|
|
% ls_estimates = GetPilotEstimates(enb,nTxAntLayer,rxGrid).'
|
||
|
|
% ans =
|
||
|
|
% 1.0000 1.0000 -0.7071 - 0.7071i
|
||
|
|
% 7.0000 1.0000 -0.7071 - 0.7071i
|
||
|
|
% 13.0000 1.0000 -0.7071 - 0.7071i
|
||
|
|
% . . .
|
||
|
|
% . . .
|
||
|
|
% . . .
|
||
|
|
% 58.0000 12.0000 -0.7071 + 0.7071i
|
||
|
|
% 64.0000 12.0000 0.7071 - 0.7071i
|
||
|
|
% 70.0000 12.0000 0.7071 - 0.7071i
|
||
|
|
|
||
|
|
% Copyright 2009-2010 The MathWorks, Inc.
|
||
|
|
function [ls_estimates,specialvec,DwPTS] = GetPilotEstimates(ENB,nTxAntLayer,RXGRID,PDSCH,CEC)
|
||
|
|
|
||
|
|
% Get dimensions of resource grid
|
||
|
|
Dims = lteDLResourceGridSize(ENB);
|
||
|
|
nsfs = size(RXGRID,2)/Dims(2);
|
||
|
|
K = Dims(1);
|
||
|
|
L = Dims(2);
|
||
|
|
|
||
|
|
if (rem(nsfs,1)~=0)
|
||
|
|
error('lte:error','The received grid input must contain a whole number of subframes.');
|
||
|
|
end
|
||
|
|
|
||
|
|
if (~isempty(PDSCH) && any(strcmpi(PDSCH.TxScheme,{'Port5' 'Port7-8' 'Port8' 'Port7-14'})))
|
||
|
|
if (strcmp(CEC.Reference,'DMRS')==1)
|
||
|
|
% create UE RS indices
|
||
|
|
PDSCH.NTxAnts=0;
|
||
|
|
PDSCH.W=[];
|
||
|
|
linearIndSF = lteDMRSIndices(ENB,PDSCH,'mat');
|
||
|
|
else
|
||
|
|
% create CSI-RS indices and symbols and deal with zero removal
|
||
|
|
linearIndSF = lteCSIRSIndices(ENB,'mat');
|
||
|
|
CsiRS = lteCSIRS(ENB,'mat');
|
||
|
|
CsiRS = CsiRS(:,nTxAntLayer+1);
|
||
|
|
linearIndSF(CsiRS==0,:)=[];
|
||
|
|
CsiRS(CsiRS==0)=[];
|
||
|
|
end
|
||
|
|
% If more than one TxAntenna is used we need to adjust indices values so that
|
||
|
|
% they start in first antenna plane
|
||
|
|
linearIndSF = linearIndSF(:,nTxAntLayer+1) - (K*L*nTxAntLayer);
|
||
|
|
else
|
||
|
|
% Extract linear indices of reference signals for particular TxAntenna
|
||
|
|
dumENB = ENB;
|
||
|
|
dumENB.NSubframe = 0;
|
||
|
|
linearIndSF = lteCellRSIndices(dumENB,nTxAntLayer);
|
||
|
|
% If more than one TxAntenna is used we need to adjust indices values so that
|
||
|
|
% they start in first antenna plane
|
||
|
|
linearIndSF = linearIndSF - (K*L*nTxAntLayer);
|
||
|
|
end
|
||
|
|
|
||
|
|
% Create grid for pilot symbols
|
||
|
|
linearIndGrid = zeros(size(linearIndSF,1),nsfs);
|
||
|
|
idealPilotGrid = zeros(size(linearIndSF,1),nsfs);
|
||
|
|
offset = double(ENB.NSubframe);
|
||
|
|
specialvec = char(zeros(1,0));
|
||
|
|
DwPTS = 0;
|
||
|
|
for sf = ENB.NSubframe:ENB.NSubframe+nsfs-1
|
||
|
|
ENB.NSubframe = mod(sf,10);
|
||
|
|
linearIndGrid(:,sf-offset+1) = (linearIndSF+(sf*K*L));
|
||
|
|
if (~isempty(PDSCH) && any(strcmpi(PDSCH.TxScheme,{'Port5' 'Port7-8' 'Port8' 'Port7-14'})))
|
||
|
|
if (strcmp(CEC.Reference,'DMRS')==1)
|
||
|
|
% create UE RS symbols
|
||
|
|
DMRS = lteDMRS(ENB,PDSCH,'mat');
|
||
|
|
idealPilotGrid(1:length(DMRS),sf-offset+1) = DMRS(:,nTxAntLayer+1);
|
||
|
|
else
|
||
|
|
% use CSI-RS symbols created earlier
|
||
|
|
idealPilotGrid(1:length(CsiRS),sf-offset+1) = CsiRS;
|
||
|
|
end
|
||
|
|
else
|
||
|
|
CellRS = lteCellRS(ENB, nTxAntLayer);
|
||
|
|
idealPilotGrid(1:length(CellRS),sf-offset+1) = CellRS;
|
||
|
|
end
|
||
|
|
dupinfo = lteDuplexingInfo(ENB);
|
||
|
|
if strcmpi(dupinfo.SubframeType,'Special')
|
||
|
|
specialvec = [specialvec 'S']; %#ok<AGROW>
|
||
|
|
DwPTS = dupinfo.NSymbolsDL;
|
||
|
|
elseif strcmpi(dupinfo.SubframeType,'Uplink')
|
||
|
|
specialvec = [specialvec 'U']; %#ok<AGROW>
|
||
|
|
elseif strcmpi(dupinfo.SubframeType,'Downlink')
|
||
|
|
specialvec = [specialvec 'D']; %#ok<AGROW>
|
||
|
|
else
|
||
|
|
error('lte:error','Invalid SubframeType, in structure dupinfo');
|
||
|
|
end
|
||
|
|
end
|
||
|
|
|
||
|
|
if (~isempty(idealPilotGrid))
|
||
|
|
ulvec = find(idealPilotGrid(size(idealPilotGrid,1),:)==0);
|
||
|
|
linearIndGrid(:,ulvec) = [];
|
||
|
|
idealPilotGrid(:,ulvec) = [];
|
||
|
|
else
|
||
|
|
ulvec = [];
|
||
|
|
end
|
||
|
|
|
||
|
|
linearIndGrid = linearIndGrid - (offset*K*L);
|
||
|
|
% Extract the row and column subscripts of the pilot symbols for entire
|
||
|
|
% grid
|
||
|
|
[p_estSC, p_estSym] = ind2sub(size(RXGRID),linearIndGrid);
|
||
|
|
|
||
|
|
% Calculate least squares channel estimates at pilot locations
|
||
|
|
p_est = RXGRID(linearIndGrid)./idealPilotGrid;
|
||
|
|
|
||
|
|
% Create a vector - [k;l;p_est]
|
||
|
|
sfref = repmat((1:nsfs),length(linearIndSF),1);
|
||
|
|
sfref(:,ulvec) = [];
|
||
|
|
ls_estimates = [double(p_estSC(:).') ; double(p_estSym(:).') ; p_est(:).';double(sfref(:)).'];
|
||
|
|
|
||
|
|
end
|
||
|
|
|
||
|
|
%PilotAverage Average reference signals
|
||
|
|
% [P_EST] = PilotAverage(PDSCH,CEC,H_EST,LS_EST) performs a moving average of pilot
|
||
|
|
% symbols
|
||
|
|
%
|
||
|
|
% LS_EST is a 3xNp matrix containing the least square estimates of the
|
||
|
|
% pilots symbols and their column and row indices within the received
|
||
|
|
% grid.
|
||
|
|
% LS_EST = [k;l;p_est]
|
||
|
|
% H_EST is an MxN matrix and defines the size of the grid that the
|
||
|
|
% averaging will be performed on
|
||
|
|
%
|
||
|
|
% CEC is a structure which defines the type of channel estimation
|
||
|
|
% performed. CEC must contain a set of the following fields:
|
||
|
|
% PilotAverage - Type of pilot averaging {'TestEVM', 'UserDefined'}
|
||
|
|
% FreqWindow - Size of window used to average in frequency in
|
||
|
|
% resource elements.
|
||
|
|
% TimeWindow - Size of window used to average in time in resource
|
||
|
|
% elements
|
||
|
|
% InterpType - Type of 2D interpolation used(see griddata for types)
|
||
|
|
%
|
||
|
|
% The dimensions of the averaging window are defined in structure CEC.
|
||
|
|
% The window is defined in terms of Resource Elements, and depending on
|
||
|
|
% the size of the averaging window, averaging will be performed in either
|
||
|
|
% the time or frequency direction only, or a combination of both creating
|
||
|
|
% a square/rectangular window. The pilot to be averaged will always be
|
||
|
|
% placed at the center of the window, therefore the window size must be
|
||
|
|
% an odd number.
|
||
|
|
%
|
||
|
|
% Frequency Direction: 9x1 Time Direction: 1x9
|
||
|
|
%
|
||
|
|
% x
|
||
|
|
% x
|
||
|
|
% x
|
||
|
|
% x
|
||
|
|
% P x x x x P x x x x
|
||
|
|
% x
|
||
|
|
% x
|
||
|
|
% x
|
||
|
|
% x
|
||
|
|
%
|
||
|
|
%
|
||
|
|
% Square window: 9x9
|
||
|
|
% x x x x x x x x x
|
||
|
|
% P x x x x x x P x
|
||
|
|
% x x x x x x x x x
|
||
|
|
% x x x x x x x x x
|
||
|
|
% x x x x P x x x x
|
||
|
|
% x x x x x x x x x
|
||
|
|
% x x x x x x x x x
|
||
|
|
% P x x x x x x P x
|
||
|
|
% x x x x x x x x x
|
||
|
|
%
|
||
|
|
% Performing EVM compliance testing as per TS36.141 AnnexF.3.4, requires
|
||
|
|
% time averaging be done over 10 subframes(i.e. 1 Frame) across each
|
||
|
|
% pilot symbol carrying subcarrier creating a TotalNumberPilotsx1 vector.
|
||
|
|
% This is then frequency averaged using a moving window average with a window
|
||
|
|
% size of 19. This type of averaging can be performed by setting the
|
||
|
|
% PilotAverage type in structure CEC to 'TestEVM'.
|
||
|
|
|
||
|
|
% Copyright 2009-2013 The MathWorks, Inc.
|
||
|
|
|
||
|
|
function [P_EST, scalingVec] = PilotAverage(PDSCH,CEC,H_EST,P_EST)
|
||
|
|
|
||
|
|
switch lower(CEC.PilotAverage)
|
||
|
|
|
||
|
|
case 'userdefined'
|
||
|
|
if(CEC.FreqWindow<1)||(CEC.TimeWindow<1)
|
||
|
|
error('lte:error','Frequency and time averaging window size cannot be less than 1');
|
||
|
|
end
|
||
|
|
|
||
|
|
if (~isempty(PDSCH) && any(strcmpi(PDSCH.TxScheme,{'Port7-8' 'Port7-14'})) &&...
|
||
|
|
(CEC.TimeWindow==2 || CEC.TimeWindow==4) && CEC.FreqWindow==1)
|
||
|
|
|
||
|
|
% Perform averaging in time direction using a moving window
|
||
|
|
% of size N = CEC.TimeWindow
|
||
|
|
N = CEC.TimeWindow;
|
||
|
|
|
||
|
|
if (~isempty(P_EST))
|
||
|
|
% Average only subcarriers which contain RS symbols. Extract RS
|
||
|
|
% symbols on a per subcarrier basis and use window to average.
|
||
|
|
for subcarrier = unique(P_EST(1,:))
|
||
|
|
|
||
|
|
% Store DRS symbols from relevant slot in vector for easy access
|
||
|
|
symbVec = (P_EST(3,P_EST(1,:)==subcarrier)).';
|
||
|
|
|
||
|
|
% Define temporary vector to store the averaged values
|
||
|
|
avgVec = zeros(size(symbVec));
|
||
|
|
|
||
|
|
% Check length of input at least equal to size of window;
|
||
|
|
% if not, reduce window size. Despreading will be incomplete
|
||
|
|
% here
|
||
|
|
if (length(symbVec) < N)
|
||
|
|
N = length(symbVec);
|
||
|
|
end
|
||
|
|
|
||
|
|
% Determines position of window w.r.t element being averaged,
|
||
|
|
% and performs the averaging
|
||
|
|
for symbNo = 1:length(symbVec)
|
||
|
|
if (symbNo-(N/2+1)<=0)
|
||
|
|
avgVec(symbNo)= sum(symbVec(1:N))/N;
|
||
|
|
else
|
||
|
|
avgVec(symbNo) = sum(symbVec(end-(N-1):end))/N;
|
||
|
|
end
|
||
|
|
end
|
||
|
|
|
||
|
|
% Update P_EST with averaged values
|
||
|
|
P_EST(3,P_EST(1,:)==subcarrier)= avgVec;
|
||
|
|
end
|
||
|
|
|
||
|
|
end
|
||
|
|
|
||
|
|
% This vector is used to scale the noise by the number of averaging
|
||
|
|
% elements in the window
|
||
|
|
scalingVec = ones(size(P_EST(3,:)))*N;
|
||
|
|
|
||
|
|
else
|
||
|
|
|
||
|
|
if (strcmpi(CEC.InterpWindow,'Centred')||strcmpi(CEC.InterpWindow,'Centered'))
|
||
|
|
if (~mod(CEC.FreqWindow,2)||~mod(CEC.TimeWindow,2))
|
||
|
|
error('lte:error','Window size must be odd in time and frequency for centred/centered window type');
|
||
|
|
end
|
||
|
|
end
|
||
|
|
|
||
|
|
% Define number of subcarriers
|
||
|
|
K = size(H_EST,1);
|
||
|
|
|
||
|
|
% Define an empty resource grid with the DC offset subcarrier
|
||
|
|
% inserted
|
||
|
|
grid = zeros(size(H_EST,1)+1,size(H_EST,2));
|
||
|
|
|
||
|
|
% Account for DC offset
|
||
|
|
P_EST(1,(P_EST(1,:)>K/2)) = P_EST(1,(P_EST(1,:)>K/2))+1;
|
||
|
|
|
||
|
|
% Place the pilot symbols back into the received grid with the
|
||
|
|
% DC offset subcarrier in place
|
||
|
|
grid(sub2ind(size(grid),P_EST(1,:),P_EST(2,:))) = P_EST(3,:);
|
||
|
|
|
||
|
|
% Define convolution window
|
||
|
|
kernel = ones(CEC.FreqWindow,CEC.TimeWindow);
|
||
|
|
|
||
|
|
% Perform convolution
|
||
|
|
grid = conv2(grid,kernel,'same');
|
||
|
|
|
||
|
|
% Extract only pilot symbol location values and set the rest of
|
||
|
|
% the grid to zero
|
||
|
|
tempGrid = zeros(size(grid));
|
||
|
|
tempGrid(sub2ind(size(grid),P_EST(1,:),P_EST(2,:))) = grid(sub2ind(size(grid),P_EST(1,:),P_EST(2,:)));
|
||
|
|
grid = tempGrid;
|
||
|
|
|
||
|
|
% Normalize pilot symbol values after convolution
|
||
|
|
[grid, scalingVec] = normalisePilotAverage(CEC,P_EST,grid);
|
||
|
|
|
||
|
|
% Place averaged values back into pilot symbol matrix
|
||
|
|
P_EST(3,:) = grid(sub2ind(size(tempGrid),P_EST(1,:),P_EST(2,:)));
|
||
|
|
|
||
|
|
% Remove DC offset
|
||
|
|
P_EST(1,(P_EST(1,:)>K/2)) = P_EST(1,(P_EST(1,:)>K/2))-1;
|
||
|
|
|
||
|
|
end
|
||
|
|
|
||
|
|
|
||
|
|
case 'testevm'
|
||
|
|
% As defined in TS36.141 Annex F.3.4 pilots are averaged in
|
||
|
|
% time across all pilot carrying subcarriers. The resulting
|
||
|
|
% vector is averaged in frequency direction with a moving
|
||
|
|
% averaging window of 19.
|
||
|
|
|
||
|
|
% Get phase (theta) and magnitude(radius) of complex estimates
|
||
|
|
[theta,radius] = cart2pol(real(P_EST(3,:)),imag(P_EST(3,:)));
|
||
|
|
|
||
|
|
% Declare vector to temporarily store averaged phase and
|
||
|
|
% magnitude
|
||
|
|
phasemagVec = zeros(size(H_EST,1),2);
|
||
|
|
|
||
|
|
% Perform averaging in time and frequency for phase and
|
||
|
|
% magnitude separately and recombine at end
|
||
|
|
for phaseOrMag = 1:2
|
||
|
|
% Define temporary P_EST vector and set estimates row to
|
||
|
|
% phase then magnitude
|
||
|
|
P_EST_temp = P_EST;
|
||
|
|
if phaseOrMag==1
|
||
|
|
P_EST_temp(3,:) = theta;
|
||
|
|
elseif phaseOrMag==2
|
||
|
|
P_EST_temp (3,:) = radius;
|
||
|
|
end
|
||
|
|
|
||
|
|
% Declare averaging vector
|
||
|
|
avgVec = zeros(size(H_EST,1),1);
|
||
|
|
vec = [];
|
||
|
|
|
||
|
|
% Average across pilot symbol carrying subcarriers in time,
|
||
|
|
% unwrapping performed on a subcarrier basis
|
||
|
|
for i = 1:size(H_EST,1)
|
||
|
|
if ~isempty(P_EST(3,(P_EST(1,:)==i)))
|
||
|
|
if phaseOrMag==1
|
||
|
|
avgVec(i) = mean(unwrap(P_EST_temp(3,(P_EST(1,:)==i))));
|
||
|
|
|
||
|
|
elseif phaseOrMag==2
|
||
|
|
avgVec(i) = mean(P_EST_temp(3,(P_EST(1,:)==i)));
|
||
|
|
end
|
||
|
|
vec = [vec i]; %#ok<AGROW>
|
||
|
|
end
|
||
|
|
end
|
||
|
|
|
||
|
|
% Remove subcarriers which contained no pilot symbols, then
|
||
|
|
% perform frequency averaging
|
||
|
|
avgVec = avgVec(vec);
|
||
|
|
|
||
|
|
% Perform averaging in frequency direction using a moving
|
||
|
|
% window of size N, N = 19 in TS36.141 Annex F.3.4
|
||
|
|
% Performs a moving average of window size N. At the edges, where less than
|
||
|
|
% N samples are span the window size is reduce to span 1, 3, 5, 7 ...
|
||
|
|
% samples.
|
||
|
|
N = 19;
|
||
|
|
|
||
|
|
% avgVec must be a column vector
|
||
|
|
if (size(avgVec,2) > 1)
|
||
|
|
error('lte:error','Input to moving average function must be a column vector.')
|
||
|
|
end
|
||
|
|
|
||
|
|
% N max window size 19 as defined in Annex F.3.4
|
||
|
|
if ~mod(N,2)
|
||
|
|
error('lte:error','Window size N must be odd');
|
||
|
|
end
|
||
|
|
|
||
|
|
if (length(avgVec) < N)
|
||
|
|
% sprintf ('Input signal must have at least %d elements',N);
|
||
|
|
error('lte:error','Input signal must have at least %d elements',N);
|
||
|
|
end
|
||
|
|
|
||
|
|
% Use filter to perform part of the averaging (not normalized)
|
||
|
|
zeroPad = zeros(N-1,1);
|
||
|
|
data = [avgVec; zeroPad];
|
||
|
|
weights = ones(N,1);
|
||
|
|
freqAvg = filter(weights,1,data);
|
||
|
|
|
||
|
|
% Remove unwanted elements
|
||
|
|
removeIdx = [ 2:2:N ( length(data)-(2:2:N)+1 )];
|
||
|
|
freqAvg(removeIdx) = [];
|
||
|
|
|
||
|
|
% Normalization factor
|
||
|
|
normFactor = [1:2:N-2 N*ones(1,length(freqAvg)-(N-1)) N-2:-2:1]';
|
||
|
|
freqAvg = freqAvg./normFactor;
|
||
|
|
|
||
|
|
% Place frequency averaged pilots into temporary storage
|
||
|
|
% vector
|
||
|
|
phasemagVec(vec,phaseOrMag) = freqAvg;
|
||
|
|
|
||
|
|
end
|
||
|
|
% Convert averaged symbols back to Cartesian coordinates
|
||
|
|
[X,Y] = pol2cart(phasemagVec(:,1),phasemagVec(:,2));
|
||
|
|
P_EST = complex(X,Y);
|
||
|
|
scalingVec = [];
|
||
|
|
|
||
|
|
otherwise
|
||
|
|
error('lte:error','Channel estimation structure field PilotAverage must be one of the following: "UserDefined" or "TestEVM"');
|
||
|
|
|
||
|
|
end
|
||
|
|
end
|
||
|
|
|
||
|
|
function [avgGrid, scalingVec] = normalisePilotAverage(CEC,p_est,grid)
|
||
|
|
|
||
|
|
% Determine total number of pilots within half a subframe
|
||
|
|
nPilots = length(p_est);
|
||
|
|
|
||
|
|
avgGrid = zeros(size(grid));
|
||
|
|
scalingVec = zeros(1,size(p_est,2));
|
||
|
|
|
||
|
|
for n = 1:nPilots
|
||
|
|
% Determine in which subcarrier and OFDM symbol pilot is located
|
||
|
|
sc = p_est(1,n);
|
||
|
|
sym = p_est(2,n);
|
||
|
|
% Determine number of REs to look at either side of pilot
|
||
|
|
% symbol in time and frequency
|
||
|
|
half_freq_window = floor(CEC.FreqWindow/2);
|
||
|
|
half_time_window = floor(CEC.TimeWindow/2);
|
||
|
|
% Set the location of the window at the back of the pilot
|
||
|
|
% to be averaged in frequency direction
|
||
|
|
upperSC = sc-half_freq_window;
|
||
|
|
% If this location is outwith the grid dimensions set it to
|
||
|
|
% lowest subcarrier value
|
||
|
|
if upperSC<1
|
||
|
|
upperSC = 1;
|
||
|
|
end
|
||
|
|
% Set the location of the window in front of the pilot to
|
||
|
|
% be averaged in frequency direction
|
||
|
|
lowerSC = sc+half_freq_window;
|
||
|
|
% If this location is outwith the grid dimensions set it to
|
||
|
|
% highest subcarrier value
|
||
|
|
if lowerSC>size(grid,1)
|
||
|
|
lowerSC = size(grid,1);
|
||
|
|
end
|
||
|
|
% Set the location of the window in front of the pilot to
|
||
|
|
% be averaged in time direction
|
||
|
|
leftSYM = sym-half_time_window;
|
||
|
|
% If this location is outwith the grid dimensions set it to
|
||
|
|
% lowest OFDM symbol value
|
||
|
|
if leftSYM<1
|
||
|
|
leftSYM = 1;
|
||
|
|
end
|
||
|
|
% Set the location of the window at the back of the pilot
|
||
|
|
% to be averaged in time direction
|
||
|
|
rightSYM = sym+half_time_window;
|
||
|
|
% If this location is outwith the grid dimensions set it to
|
||
|
|
% highest OFDM symbol value
|
||
|
|
if rightSYM>size(grid,2)
|
||
|
|
rightSYM = size(grid,2);
|
||
|
|
end
|
||
|
|
|
||
|
|
% Define the window to average using the determined
|
||
|
|
% subcarrier and OFDM symbol values
|
||
|
|
avgVec = grid(upperSC:lowerSC,leftSYM:rightSYM);
|
||
|
|
|
||
|
|
% Remove the zero values from the window so that the average is
|
||
|
|
% calculated using only valid pilots
|
||
|
|
avgVec = avgVec(avgVec~=0);
|
||
|
|
% Average the desired pilot using all pilots within
|
||
|
|
% averaging window
|
||
|
|
if isempty(avgVec)
|
||
|
|
avgVec = 0;
|
||
|
|
end
|
||
|
|
|
||
|
|
avgGrid(sc,sym) = grid(sc,sym)/numel(avgVec);
|
||
|
|
scalingVec(n) = numel(avgVec);
|
||
|
|
end
|
||
|
|
end
|
||
|
|
|
||
|
|
%createVirtualPilots Create virtual pilots.
|
||
|
|
% [VP] = createVirtualPilots(..) returns a 3xNvp matrix which contains
|
||
|
|
% the time/frequency and least squares estimate of virtual pilots.
|
||
|
|
% Nvp is the number of virtual pilots.
|
||
|
|
%
|
||
|
|
% The inputs are:
|
||
|
|
%
|
||
|
|
% ENB structure which must contain the following fields:
|
||
|
|
% NDLRB - Number of downlink resource blocks
|
||
|
|
% CyclicPrefix - Optional. Cyclic prefix length {'Normal'(default),'Extended'}
|
||
|
|
%
|
||
|
|
% P_EST - A matrix containing the pilots within the grid. The matrix must
|
||
|
|
% have three rows. Each column contains the information for each pilot:
|
||
|
|
% [subcarrier_indices symbol_indices pilot_channel_estimate]
|
||
|
|
%
|
||
|
|
% ANTENNA - The current antenna port
|
||
|
|
% CREATE_TOP,CREATE_BOTTOM,CREATE_FRONT,CREATE_END - a value {0 or 1}
|
||
|
|
% indicating whether to return virtual pilots in each position. A 1
|
||
|
|
% indicates virtual pilots should be returned, a 0 indicates they should
|
||
|
|
% not be returned.
|
||
|
|
%
|
||
|
|
% Example:
|
||
|
|
%
|
||
|
|
% Create virtual pilots on the top of a grid of pilots (estimates)
|
||
|
|
% VP_TOP = createVirtualPilots(ENB,estimates,0,1,0,0,0);
|
||
|
|
%
|
||
|
|
% Add virtual pilots to current pilot estimates for interpolation
|
||
|
|
% estimates = [estimates VP_TOP];
|
||
|
|
|
||
|
|
% Copyright 2009-2010 The MathWorks, Inc.
|
||
|
|
function VP = createVirtualPilots(ENB,P_EST,CREATE_TOP,CREATE_BOTTOM,CREATE_FRONT,CREATE_END)
|
||
|
|
|
||
|
|
% Initialize outputs
|
||
|
|
VP = zeros(3,0);
|
||
|
|
|
||
|
|
% Get resource grid dimensions
|
||
|
|
dims = lteDLResourceGridSize(ENB);
|
||
|
|
K = dims(1);
|
||
|
|
|
||
|
|
% Virtual pilot cut-off values - indices in time or frequency at which
|
||
|
|
% the virtual pilot shall be discarded. As the symbol indices of the
|
||
|
|
% pilots passed in may be positive and negative the start and end of
|
||
|
|
% the effective grid varies therefore affecting the front and end pilot
|
||
|
|
% cut-off values
|
||
|
|
coTop = -6; %
|
||
|
|
coBottom = K+6; %
|
||
|
|
coFront = min(P_EST(2,:))-7; % floor(min(P_EST(2,:))/L)*L-5; %
|
||
|
|
coEnd = max(P_EST(2,:))+7; % ceil(max(P_EST(2,:))/L)*L+5;
|
||
|
|
|
||
|
|
% Number of pilots in a subcarrier is dependent upon antenna
|
||
|
|
% noPilotinSC = (2-floor(ANTENNA/2))*nSF;
|
||
|
|
noPilotinSC = numel(P_EST(P_EST(1,:)==P_EST(1,1)));
|
||
|
|
|
||
|
|
% Number of pilots in a symbol
|
||
|
|
noPilotinSym = K/6;
|
||
|
|
|
||
|
|
% Sort by subcarrier
|
||
|
|
[~, indices] = sortrows(P_EST(1,:).');
|
||
|
|
p_est_sorted_sc = P_EST(:,indices).';
|
||
|
|
|
||
|
|
if CREATE_TOP
|
||
|
|
% Repeat first and second SC containing pilots
|
||
|
|
p_est_rep_above = p_est_sorted_sc(1+noPilotinSC:noPilotinSC*2,:);
|
||
|
|
p_est_rep_above = [p_est_rep_above.' p_est_sorted_sc(1:noPilotinSC,:).'].';
|
||
|
|
|
||
|
|
% Subtract six to normalize subcarrier indices
|
||
|
|
p_est_rep_above(:,1) = p_est_rep_above(:,1) - 6;
|
||
|
|
|
||
|
|
% Remove virtual pilots which are too far
|
||
|
|
p_est_rep_above(p_est_rep_above(:,1) < coTop,:) = [];
|
||
|
|
|
||
|
|
% Initialize vp vector
|
||
|
|
VP_TOP = zeros(size(p_est_rep_above));
|
||
|
|
|
||
|
|
% Create virtual pilots on top
|
||
|
|
for p = 1:size(p_est_rep_above)
|
||
|
|
VP_TOP(p,:) = calculatePilot(p_est_rep_above(p,:), p_est_sorted_sc);
|
||
|
|
end
|
||
|
|
|
||
|
|
% Transpose to make suitable for output
|
||
|
|
VP = [VP VP_TOP.'];
|
||
|
|
end
|
||
|
|
|
||
|
|
if CREATE_BOTTOM
|
||
|
|
% Repeat last and second last SC containing pilots
|
||
|
|
p_est_rep_below = p_est_sorted_sc(end-noPilotinSC*2+1:end-noPilotinSC,:);
|
||
|
|
p_est_rep_below = [p_est_rep_below.' p_est_sorted_sc(end-noPilotinSC+1:end,:).'].';
|
||
|
|
|
||
|
|
% Add six to normalize subcarrier indices
|
||
|
|
p_est_rep_below(:,1) = p_est_rep_below(:,1) + 6;
|
||
|
|
|
||
|
|
% Remove virtual pilots which are too far
|
||
|
|
p_est_rep_below(p_est_rep_below(:,1) > coBottom,:) = [];
|
||
|
|
|
||
|
|
% Initialize vp vector
|
||
|
|
VP_BOTTOM = zeros(size(p_est_rep_below));
|
||
|
|
|
||
|
|
% Create virtual pilots on bottom
|
||
|
|
for p = 1:size(p_est_rep_below)
|
||
|
|
VP_BOTTOM(p,:) = calculatePilot(p_est_rep_below(p,:), p_est_sorted_sc);
|
||
|
|
end
|
||
|
|
|
||
|
|
% Transpose to make suitable for output
|
||
|
|
VP = [VP VP_BOTTOM.'];
|
||
|
|
end
|
||
|
|
|
||
|
|
% Sort by symbol
|
||
|
|
[~, indices] = sortrows(P_EST(2,:).');
|
||
|
|
p_est_sorted_sym = P_EST(:,indices).';
|
||
|
|
|
||
|
|
if CREATE_FRONT
|
||
|
|
% Repeat first symbol containing pilots
|
||
|
|
p_est_rep_front = p_est_sorted_sym(noPilotinSym+1:(noPilotinSym*2),:);
|
||
|
|
|
||
|
|
% Add subcarrier above and below
|
||
|
|
p_est_rep_front = addSCs(p_est_rep_front,noPilotinSym);
|
||
|
|
|
||
|
|
% Repeat second symbol containing pilots
|
||
|
|
p_est_rep_front_second = p_est_sorted_sym(1:noPilotinSym,:);
|
||
|
|
|
||
|
|
% Add subcarrier above and below
|
||
|
|
p_est_rep_front_second = addSCs(p_est_rep_front_second,noPilotinSym);
|
||
|
|
|
||
|
|
% Concatenate to create virtual pilots
|
||
|
|
p_est_rep_front = [p_est_rep_front.' p_est_rep_front_second.'].';
|
||
|
|
|
||
|
|
% Subtract seven to normalize symbol indices
|
||
|
|
p_est_rep_front(:,2) = p_est_rep_front(:,2) - 7;
|
||
|
|
|
||
|
|
% Remove virtual pilots which are too far
|
||
|
|
p_est_rep_front = removeTooFar(p_est_rep_front,p_est_sorted_sym,coTop,coBottom,coFront,coEnd);
|
||
|
|
|
||
|
|
% Initialize vp vector
|
||
|
|
VP_FRONT = zeros(size(p_est_rep_front));
|
||
|
|
|
||
|
|
% Create virtual pilots on front
|
||
|
|
for p = 1:length(p_est_rep_front)
|
||
|
|
VP_FRONT(p,:) = calculatePilot(p_est_rep_front(p,:), p_est_sorted_sc);
|
||
|
|
end
|
||
|
|
|
||
|
|
% Transpose for output
|
||
|
|
VP = [VP VP_FRONT.'];
|
||
|
|
end
|
||
|
|
|
||
|
|
if CREATE_END
|
||
|
|
% Repeat last symbol containing pilots
|
||
|
|
p_est_rep_end = p_est_sorted_sym(end-(noPilotinSym*2)+1:end-noPilotinSym,:);
|
||
|
|
|
||
|
|
% Add subcarrier above and below
|
||
|
|
p_est_rep_end = addSCs(p_est_rep_end,noPilotinSym);
|
||
|
|
|
||
|
|
% Repeat second symbol containing pilots
|
||
|
|
p_est_rep_end_second = p_est_sorted_sym(end-noPilotinSym+1:end,:);
|
||
|
|
|
||
|
|
% Add subcarrier above and below
|
||
|
|
p_est_rep_end_second = addSCs(p_est_rep_end_second,noPilotinSym);
|
||
|
|
|
||
|
|
% Concatenate to create virtual pilots
|
||
|
|
p_est_rep_end = [p_est_rep_end.' p_est_rep_end_second.'].';
|
||
|
|
|
||
|
|
% Add seven to normalize symbol indices, mod controls case when
|
||
|
|
% only 2 pilots per subcarrier
|
||
|
|
p_est_rep_end(:,2) = p_est_rep_end(:,2) + 7;
|
||
|
|
|
||
|
|
% Remove virtual pilots which are too far
|
||
|
|
p_est_rep_end = removeTooFar(p_est_rep_end,p_est_sorted_sym,coTop,coBottom,coFront,coEnd);
|
||
|
|
|
||
|
|
% Initialize vp vector
|
||
|
|
VP_END = zeros(size(p_est_rep_end));
|
||
|
|
|
||
|
|
% Create virtual pilots on front
|
||
|
|
for p = 1:length(p_est_rep_end)
|
||
|
|
VP_END(p,:) = calculatePilot(p_est_rep_end(p,:), p_est_sorted_sc);
|
||
|
|
end
|
||
|
|
|
||
|
|
% Transpose for output
|
||
|
|
VP = [VP VP_END.'];
|
||
|
|
end
|
||
|
|
end
|
||
|
|
|
||
|
|
function vp = calculatePilot(p_est_rep, p_est_sorted)
|
||
|
|
% Calculate Euclidean distance between virtual pilot and other
|
||
|
|
% pilots
|
||
|
|
ind = sqrt((p_est_rep(1)-p_est_sorted(:,1)).^2+ (p_est_rep(2)-p_est_sorted(:,2)).^2);
|
||
|
|
% ind = (abs(p_est_rep(1)-p_est_sorted(:,1))+ abs(p_est_rep(2)-p_est_sorted(:,2)));
|
||
|
|
|
||
|
|
% Sort from shortest to longest distance
|
||
|
|
[~, ind] = sortrows(ind);
|
||
|
|
|
||
|
|
% Take three closest pilots
|
||
|
|
ind = ind(1:10);
|
||
|
|
pilots_use = p_est_sorted(ind,:);
|
||
|
|
|
||
|
|
% If first 3 pilots used are in the same subcarrier or symbol then use 4th instead of 3rd
|
||
|
|
while ((pilots_use(3,1) == pilots_use(2,1)) && (pilots_use(2,1) == pilots_use(1,1)) || (pilots_use(3,2) == pilots_use(2,2)) && (pilots_use(2,2) == pilots_use(1,2)))
|
||
|
|
pilots_use(3,:) = [];
|
||
|
|
end
|
||
|
|
|
||
|
|
% Calculate virtual pilot value
|
||
|
|
vp = calculateVirtualValue(pilots_use(3,:),pilots_use(1,:),pilots_use(2,:),p_est_rep(1),p_est_rep(2));
|
||
|
|
end
|
||
|
|
|
||
|
|
function new = calculateVirtualValue(a,b,c,xnew,ynew)
|
||
|
|
% Calculate vectors
|
||
|
|
AB = b-a;
|
||
|
|
AC = c-a;
|
||
|
|
|
||
|
|
% Perform cross product
|
||
|
|
cro = cross(AB,AC);
|
||
|
|
|
||
|
|
% Break out X, Y and Z plane coeffs
|
||
|
|
x = cro(1);
|
||
|
|
y = cro(2);
|
||
|
|
z = cro(3);
|
||
|
|
|
||
|
|
% Calculate normal in equation
|
||
|
|
c = sum(cro.*a);
|
||
|
|
|
||
|
|
% Calculate new z value
|
||
|
|
znew = (c - xnew*x - ynew*y)/z;
|
||
|
|
|
||
|
|
% Return new point
|
||
|
|
new = [xnew ynew znew];
|
||
|
|
end
|
||
|
|
|
||
|
|
function pilots = addSCs(pilots, noPilotinSym)
|
||
|
|
% Add on extra subcarrier above
|
||
|
|
pilots(end+1,:) = pilots(1,:);
|
||
|
|
pilots(end,1) = pilots(end,1) - 6;
|
||
|
|
|
||
|
|
% Add on extra subcarrier below
|
||
|
|
pilots(end+1,:) = pilots(noPilotinSym,:);
|
||
|
|
pilots(end,1) = pilots(end,1) + 6;
|
||
|
|
end
|
||
|
|
|
||
|
|
function pilots = removeTooFar(pilots,p_est_sorted_sym,coTop,coBottom,coFront,coEnd)
|
||
|
|
pilots((pilots(:,2) < coFront) | (pilots(:,1) < coTop) | (pilots(:,2)> coEnd) | (pilots(:,1) > coBottom),:) = [];
|
||
|
|
|
||
|
|
% Remove virtual pilots which fall within resource grid
|
||
|
|
removeInd = [];
|
||
|
|
for i = 1:size(pilots)
|
||
|
|
if (find(p_est_sorted_sym(:,2) == pilots(i,2)))
|
||
|
|
removeInd = [removeInd i]; %#ok<AGROW>
|
||
|
|
end
|
||
|
|
end
|
||
|
|
pilots(removeInd,:) = [];
|
||
|
|
end
|
||
|
|
|
||
|
|
%CreateEdgeVirtualPilots
|
||
|
|
% Creates virtual pilots on the edges of the resource grid to improve
|
||
|
|
% interpolation results. Also adds virtual pilots around the current pilot
|
||
|
|
% estimates.
|
||
|
|
function vps = createEdgeVirtualPilots(enb,p_est)
|
||
|
|
|
||
|
|
% Determine dimensions of current subframe
|
||
|
|
dims=lteDLResourceGridSize(enb);
|
||
|
|
K=dims(1);
|
||
|
|
L=dims(2);
|
||
|
|
|
||
|
|
% Calculate virtual pilots beyond upper and lower bandwidth edge based
|
||
|
|
% on pilots present on subcarriers. Also create virtual pilots 1/2 RB
|
||
|
|
% above and below extent of current pilots.
|
||
|
|
vps=createDimensionVirtualPilots(p_est,2,unique([-6 min(p_est(1,:)-6) max(p_est(1,:)+6) K+6]));
|
||
|
|
|
||
|
|
% Combine these frequency-direction VPs with original pilots.
|
||
|
|
temp = [p_est vps];
|
||
|
|
|
||
|
|
% Calculate virtual pilots beyond start and end of subframe based on
|
||
|
|
% pilots and frequency-direction VPs present in symbols. Also create
|
||
|
|
% virtual 1 OFDM symbol before and after extent of current pilots.
|
||
|
|
vps = [vps createDimensionVirtualPilots(temp,1,unique([-1 min(p_est(2,:)-1) max(p_est(2,:)+1) L+1]))];
|
||
|
|
|
||
|
|
end
|
||
|
|
|
||
|
|
% dim=1 adds VPs in time
|
||
|
|
% dim=2 adds VPs in frequency
|
||
|
|
function vps = createDimensionVirtualPilots(p_est,dim,points)
|
||
|
|
|
||
|
|
vps=[];
|
||
|
|
|
||
|
|
pilots = unique(p_est(dim,:));
|
||
|
|
for i = pilots
|
||
|
|
x=find(p_est(dim,:)==i);
|
||
|
|
rep=1+double(length(x)==1);
|
||
|
|
adj=(1:rep)-rep;
|
||
|
|
pil = interp1(p_est(3-dim,x)+adj,repmat(p_est(3,x),1,rep),points,'linear','extrap');
|
||
|
|
for j=1:length(points)
|
||
|
|
vps = [ vps [i;points(j);pil(j)] ]; %#ok<AGROW>
|
||
|
|
end
|
||
|
|
end
|
||
|
|
|
||
|
|
if (dim==2)
|
||
|
|
vps = vps([2 1 3],:);
|
||
|
|
end
|
||
|
|
|
||
|
|
end
|
||
|
|
|