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LTE-Advanced Functionality

The LTE System Toolbox™ supports enhancements to the LTE Release 8 and 9 offerings. LTE-Advanced builds upon these earlier releases. A brief description of significant Release 9 updates is provided here prior to discussing the LTE-Advanced functionality. 3GPP defines LTE-Advanced functionality in Releases 10, 11, and 12 of the LTE Standard.

Release 9 Positioning Reference Signal

Release 9 defines several changes to the provision for positioning within the LTE standard. These changes, which enable the network to compute the position of the UE, include:

  • UE reception of a new downlink positioning reference signal (PRS) transmitted by the eNodeB.

  • Transmission of the time difference of arrival to the eNodeB as a measurement.

LTE System Toolbox supports the PRS with the ltePRS and ltePRSIndices functions.

To learn how to use the PRS to perform time-difference of arrival (TDOA) position estimation, see Time Difference Of Arrival Positioning Using PRS.

Release 9 Dual-Layer UE-Specific Beamforming

Release 9 provides a dual-layer UE-specific beamforming mode. It defines two UE-specific reference signals (antenna ports 7 and 8). Two independent streams of data can be sent, one on each layer. These streams of data can be to a single UE (one rank 2 transmission) or to two UEs (two rank 1 transmissions).

LTE System Toolbox supports the antenna port 5, 7, and 8 reference signals with the lteDMRS and lteDMRSIndices functions. These functions support the transmission of UE-specific reference signals for Release 8, 9 and 10. The particular UE-specific reference signals created are controlled by the transmission scheme parameter, TxScheme. For Release 9, you have the option to set TxScheme to these transmission schemes.

Parameter SettingDescription
'Port7-8'Release 9 single-antenna port, port 7 (if NLayers=1)

Release 9 dual layer transmission, ports 7 and 8 (if NLayers=2)

'Port8'Single-antenna port, port 8

PDSCH transmissions, associated with antenna ports 7 and 8 (or any transmission scheme), can be made using the ltePDSCH and ltePDSCHIndices functions. These functions accept settings for the TxScheme parameter as described in the preceding table.

The UE-specific beamforming of the reference signals and PDSCH transmission is specified by the parameter W provided to lteDMRS and ltePDSCH. The lteDMRSIndices and ltePDSCHIndices functions use the NTxAnts parameter to specify the number of transmission antennas. See the function reference pages for details.

At the receiver, ltePDSCHDecode decodes PDSCH transmissions made on ports 7 and 8, under the assumption that the input will be equalized back to the transmission layers. Hence, no deprecoding is required. This behavior is consistent with the operation of lteDLChannelEstimate, which cannot assume knowledge of the UE-specific beamforming used at the transmitter when it produces the channel matrices between transmission layers and receive antennas. Therefore, the MMSE equalization carried out within ltePDSCHDecode outputs the PDSCH layers, which are then layer demapped, demodulated, and descrambled to produce soft bit estimates.

Release 9 transmissions on antenna ports 7 and 8 are associated with DCI Format 2B, which is supported by the lteDCI, lteDCIDecode, lteDCIInfo, ltePDCCHSearch, and lteDCIResourceAllocation functions.

Release 10 Downlink Enhanced MIMO

Release 10 provides a further extension to downlink UE-specific beamforming with reference signals (antenna ports) for up to 8 layers. These reference signals are called demodulation reference signals (DM-RS) in the standard. To support channel estimation for up to 8 layers (noting the cell-specific reference signals support only 4 antenna ports) a new channel state information reference signal (CSI-RS) set has been added, with 8 antenna ports specifically designed for CSI estimation.

The DM-RS antenna ports are numbers 7 through 14, with ports 7 and 8 being compatible with the dual-layer UE-specific beamforming capability of Release 9. LTE System Toolbox supports these reference signals with the lteDMRS and lteDMRSIndices functions. These functions support the transmission of UE-specific reference signals for Release 8, 9 and 10. The particular UE-specific reference signals created are controlled by the transmission scheme parameter, TxScheme. For Release 10, you have the option to set TxScheme to this transmission scheme.

Parameter SettingDescription
'Port7-14'Release 10 up to 8-layer transmission, ports 7–14 (NLayers=1…8)

PDSCH transmissions, associated with antenna ports 7 through 14 (or any transmission scheme), can be made using the ltePDSCH and ltePDSCHIndices functions. These functions accept settings for the TxScheme parameter as described in the preceding table.

The UE-specific beamforming of the reference signals and PDSCH transmission is specified by the parameter W provided to lteDMRS and ltePDSCH. The lteDMRSIndices and ltePDSCHIndices functions use the NTxAnts parameter to specify the number of transmission antennas. See the function reference pages for details.

At the receiver, ltePDSCHDecode decodes PDSCH transmissions made on ports 7 through 14, under the assumption that the input will be equalized back to the transmission layers. Hence, no deprecoding is required. This behavior is consistent with the operation of lteDLChannelEstimate, which cannot assume knowledge of the UE-specific beamforming used at the transmitter when it produces the channel matrices between transmission layers and receive antennas. Therefore, the MMSE equalization carried out within ltePDSCHDecode outputs the PDSCH layers, which are then layer demapped, demodulated, and descrambled to produce soft bit estimates.

For PMI feedback, lteDLChannelEstimate can optionally perform channel estimation against the CSI-RS. To do so, set the Reference parameter to 'CSIRS'. Then, provide this channel estimate to ltePMISelect to perform PMI selection based on the codebook for CSI reporting, which is implemented using the lteCSICodebook function.

Release 10 transmissions on antenna ports 7 through 14 are associated with DCI Format 2C, which is supported by the lteDCI, lteDCIDecode, lteDCIInfo, ltePDCCHSearch, and lteDCIResourceAllocation functions.

Release 10 Uplink MIMO

Release 10 supports uplink MIMO, with 2 codewords transmitted on up to 4 layers on 4 antennas for the PUSCH. LTE System Toolbox supports uplink MIMO similar to how it supports downlink MIMO, using cell arrays to represent multiple codeword vectors, and using multiple column matrices to represent multiple layers and transmission antennas.

Uplink MIMO transmission is provided by the ltePUSCH and lteULSCH functions. In the receiver, the timing offset function, lteULFrameOffset, searches its input across all configured DM-RS signals. By default, lteULChannelEstimate provides channel estimates to the precoded DM-RS signals, or transmission antennas, and ltePUSCHDecode uses knowledge of the precoding matrices used to perform MIMO equalization. Alternatively, you can configure lteULChannelEstimate to provide channel estimates to the DRS layers. To do so, set the Reference parameter to 'Layers'. In this case, ltePUSCHDecode equalizes back to transmission layers.

The ltePUSCHPrecode and ltePUSCHDeprecode functions perform MIMO precoding and deprecoding for the PUSCH.

The lteLayerMap and lteLayerDemap functions provide support for the uplink and downlink.

The lteACKDecode, lteACKEncode, lteRIDecode, and lteRIEncode functions support the increased number of bits that can be coded in Release 10.

To learn how to create and simulate an uplink MIMO PUSCH performance test, see Release 10 PUSCH Multiple Codeword Transmit and Receive Modeling.

Release 10 Spatial Orthogonal Resource Transmit Diversity (SORTD)

Release 10 incorporates spatial orthogonal resource transmit diversity (SORTD) transmission on the PUCCH and SRS channels. SORTD transmits independent versions of an encoded and modulated signal on each transmission antenna by using a different orthogonal resource for each transmission antenna. For the PUCCH, the different orthogonal resources are different PUCCH resource indices, n1PUCCH, n2PUCCH, and n3PUCCH. For the SRS, the different orthogonal resources are different reference signal cyclic shifts, alpha.

SORTD transmission is supported by the ltePUCCH1, ltePUCCH1DRS, ltePUCCH1DRSIndices, ltePUCCH1Indices, ltePUCCH2, ltePUCCH2DRS, ltePUCCH2DRSIndices, ltePUCCH2Indices, lteSRS, and lteSRSIndices functions.

For PUCCH formats 1 and 2 and their DM-RS signals, specify SORTD using the ResourceIdx parameter, For Release 10 this parameter is a vector of indices, rather than a scalar index as for Release 8. For the SRS, specify SORTD using the NTxAnts parameter.

In the receiver, the timing offset functions, lteULFrameOffsetPUCCH1 and lteULFrameOffsetPUCCH2, search their input across all configured DM-RS signals. The channel estimators, lteULChannelEstimatePUCCH1 and lteULChannelEstimatePUCCH2, make a channel estimate against all DM-RS signals, or transmission antennas. If using a pilot averaging frequency window size, orthogonal despreading of different DM-RS signals is supported. The pilot averaging frequency window size is always a multiple of 12.

Release 10 PUCCH Format 3

Release 10 introduces a new PUCCH format, format 3, designed to transmit a large number of ACK indications in a single subframe. The LTE System Toolbox implements PUCCH format 3 with the ltePUCCH3, ltePUCCH3Decode, ltePUCCH3DRS, ltePUCCH3DRSIndices, ltePUCCH3Indices, ltePUCCH3PRBS, lteULChannelEstimatePUCCH3 and lteULFrameOffsetPUCCH3 functions.

Release 11 Enhanced Physical Downlink Control Channel (EPDCCH)

Release 11 introduces the Enhanced Physical Downlink Control Channel, EPDCCH, which is designed to achieve improved spectral reuse of control channel resources. It supports CoMP, downlink MIMO, beamforming and frequency domain inter-cell interference coordination (ICIC). LTE System Toolbox implements EPDCCH with the lteEPDCCH, lteEPDCCHIndices, lteEPDCCHDMRS, lteEPDCCHDMRSIndices, and lteEPDCCHPRBS functions.

Coordinated multipoint (CoMP) operation in LTE Release 11 takes advantage of low latency and high capacity backhaul between base stations within a cooperating set. For a demonstration of CoMP in a dynamic point selection (DPS) scheme, see CoMP Dynamic Point Selection with Multiple CSI Processes.

Release 12 Carrier Aggregation

Release 12 introduced intersite carrier aggregation to coordinate the capabilities and backhaul of adjacent cells. For a demonstration on how to create a signal covering multiple LTE carriers using carrier aggregation, see Release 12 Downlink Carrier Aggregation Waveform Generation, Demodulation and Analysis.

Release 12 Alternative Codebook

Release 12 introduced an alternative codebook for channel state information reporting. For more information, see lteCSICodebook.

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