About DL Decode Info (LTE)

Menu Path (downlink): Trace > Data > Demod > DL Decode Info

DL Decode Info contains the decoded information from PBCH Physical Broadcast Channel, PDCCH Physical Downlink Control Channel, PHICH Physical Hybrid ARQ Indicator Channel, and PCFICH Physical Control Format Indicator Channel.

The upper section shows the status of the PBCH, PDCCH, PCFICH, and PDSCH Physical Downlink Shared Channel decoders (On or Off).

The lower part of the table shows the decoded information for each frame.

The data is color coded to match the color of the corresponding channel in the Frame Summary trace. For example, any text that is colored green represents information about PBCH.

The screenshot below shows the decoded data for two frames.

PHICH information

The decoded PHICH Hybrid-ARQ Automatic Repeat Request 1) A distinct unit of data that is carried on an ARQ-enabled connection. Such a unit is assigned a sequence number, and is managed as a distinct entity by the ARQ state machines. Block size is a parameter negotiated during connection establishment. 2) automatic retransmission request - A signal used in digital communications systems used to signal the transmitting device to retransmit a block of data. (HARQ Hybrid Automatic Repeat Request) values are listed by PHICH Group for each subframe.

The values of the PHICHs in each PHICH group are listed in increasing order of PHICH Sequence index, starting with sequence 0 in the leftmost position and ending with N^PHICH_{SF 1) Spreading Factor, or 2) service flow: A unidirectional flow of medium access control (MAC) service data units (SDUs) on a connection that is provided a particular Quailty of Service (QoS).} - 1.

The values of the PHICHs are one of the following:

• A - ACK Acknowledgement
• N - NACK Negative Acknowledgement
• O - Off (inactive PHICH sequence index)

PBCH information

PBCH decoded information is available when PHICH Duration or Allocation(Ng) are set to Auto in the Downlink Control Channel Properties: Basic tab or when PBCH Bits is set to a value other than None.

The following is a list of all the information contained in the PBCH section of the DL Decode Info trace.

• FrameNum - system frame number for each frame in the Measurement Interval.

• Transmission Bandwidth - one of 1.4MHz(6RB), 3MHz(15RB), 5MHz(25RB), 10MHz(50RB), 15MHz(75RB), 20MHz(100RB).
• NumTxAnt - number of C-RS Cell-specific RS antenna ports
• PHICH - PHICH resource Allocation size (Ng) and Duration. These values always come from the decoded PBCH bits and are unaffected by the PHICH Duration or Allocation(Ng) parameters in the Downlink Control Channel Properties: Basic tab.

PCFICH information

Decoded PCFICH information is available when the Auto check box is selected in the PDCCH Allocations section of the Downlink Control Channel Properties: Basic tab dialog box or when PCFICH Bits is set to a value other than None.

# PDCCH SymPerSubframe shows a comma separated list of values, one for each subframe, that indicate the number of symbols at the beginning of a subframe which are allocated to PDCCH.

PDCCH information

PDCCH information is available when RB Auto Detect Mode is set to Decode PDCCH or when PDCCH Bits is set to a value other than None.

The following is a list of all the information contained in the PDCCH section of the DL Decode Info trace.

• RNTI - Radio Network Temporary Identifier. Identifies the intended recipient(s) of a DCI (downlink control information) transmission.

• PBoost (dB) - Autodetected Power Boost value for PDCCH. PBoost (dB) is reported in dB relative to the 0 dB level defined by C-RS Power Boost. See the Downlink Control Channel Properties: Basic tab topic for more information about how the 0 dB level is defined.

  The value reported for PBoost (dB) can be used to verify that the PDCCH Power Boost (dB) +/- Increments (dB) parameter has been set correctly.

• CCEOffst - Control Channel Element Offset Start Index for decoded PDCCH

• L - Aggregation level, which is one of {1, 2, 4, 8}.

• A - DCI payload bit length (message+CRC)

• DCIFmt - DCI format, which is one of {0, 1, 1A, 1B, 1C, 1D, 2, 2A, 3, 3A}

• RBAssign - Resource block assignment contained in a DCI message

• Nprb - Number of physical resource blocks assigned to PDSCH/PUSCH Physical Uplink Shared Channel allocation

• Hop - Indicates whether Frequency Hopping is On or Off when using DCI Format 0 to schedule a PUSCH transmission.

• Type - PDSCH Resource Allocation Type

  PDSCH Resource Allocation types

  Type	Resource Allocation Type	DCI Formats
  0	Bitmapped RBG allocations	1, 2, 2A
  1	Bitmapped RBG Subset allocations	1, 2, 2A
  2(L)	Localized allocations	1A, 1B, 1D
  2(D1)	Distributed Ngap1 allocations	1A, 1B, 1C, 1D
  2(D2)	Distributed Ngap2 allocations	1A, 1B, 1C, 1D

• lmcs(n) - Modulation and coding for transport block n

• NDI(n) - New Data Indicator for transport block n. The value toggles when new data is signalled to be sent on a particular HARQ process

• RV(n) - Redundancy Version for transport block n

• TBS(n) - Transport Block Size for transport block n

• CRC(n) - Cyclic Redundancy Check result (Pass/Fail) for PDSCH transport block n, whose allocation is indicated by the PDCCH.

  CRC Pass/Fail metric is only reported when RB Auto Detect Mode is set to Decode PDCCH and PDSCH Bits is set to a value other than None.

• EPRE - average Energy Per Resource Element, per transmit antenna.

• P_A(n) - PDSCH UE User Equipment (e.g. cell phone)-specific relative power level (P_A) for transport block n.

• TBSwap - Transport Block to Codeword Swap flag (present in DCI formats 2 and 2A)

• CShift - UL Up Link (reverse link: from cell phone to base station) PUSCH Cyclic Shift value (present in DCI format 0)

• TPC - Transmit Power Control value

  For DCI formats other than 3 and 3A, the TPC Transmit Power Control value is shown as a 2-bit decimal value (0-3).

  For formats 3 and 3A, the TPC value is shown as a 32-bit hex value, regardless of the payload size (A). The decoded TPC bits are located in the A least significant bits and the unused most significant bits are zero padded.

  The payload size (A) is the same as DCI Format 0 (whose payload size is L_format0 as defined in 3GPP TS Technical Specification 36.212, Sections 5.3.3.1.6 and 5.3.3.1.7).

  The LTE demodulator does not differentiate between DCI Formats 3 and 3A when showing the TPC bits and all L_format0 bits are shown.

  • Format 3
    • A = L_format0 is even: the least significant A bits contain N 2-bit TPC commands (least significant bit does not need to be zero padded in this case).
    • A = L_format0 is odd: the least significant A bits contain N 2-bit TPC commands followed by a single zero-padded bit in the LSB Least Significant Bit: In a binary coding scheme, the bit having the least numerical value. Analogous to the units position in a decimal number. position according to 3GPP TS 36.212, Section 5.3.3.1.6.
  • Format 3A: the least significant A bits contain M 1-bit TPC commands.

  Target uplink channel for TPC value

  DCI Format	Target uplink channel
  Format 0	PUSCH
  Formats 1, 1A, 1B, 1D, 2, 2A	PUCCH Physical Uplink Control Channel
  Formats 3, 3A	PUCCH and PUSCH

• HARQ - Hybrid Automatic Repeat Request process number (present in DCI formats 1, 1A, 1B, 1C, 1D, 2, and 2A). Explicitly signalled for asynchronous downlink HARQ operation.
• DAI - Downlink Assignment Index (present in TDD Time Division Duplex: A duplexing technique dividing a radio channel in time to allow downlink operation during part of the frame period and uplink operation in the remainder of the frame period. signals only and in DCI formats 0, 1, 1A, 1B, 1D, 2, 2A). TDD signals only (UL/DL Down Link (forward link: from base station to cell phone) Configurations 1-6). See Section 5.3.3.1.1 of TS 36.212.
• TPMI - Transmitted Precoding Matrix Indicator (present in DCI formats 1B, 1D, 2, 2A). TPMI information indicates which codebook index is used Table 6.3.4.2.3-1 or Table 6.3.4.2.3-2 of TS 36.211.
• PMI - confirmation of Precoding Matrix Indicator for precoding (present in DCI format 1B). See Section 5.3.3.1.3A of TS 36.212.
• PwrOffset - Downlink Power Offset (present in DCI format 1D)
• CQIReq - Uplink Channel Quality Indicator request (present in DCI format 0). See Section 5.3.3.1.1 of TS 36.212 and Section 7.2.1 of TS 36.213 for more information.

• ScID - Scrambling Identity (present in DCI format 2B). See Section 5.3.3.1.5B of TS 36.212.

  See the n_SCID  parameter in the LTE Allocation Editor.

Querying summary table data results programmatically

To programmatically query the Trace Summary Table data results using the Summary() and SummaryUnit() methods in the MeasurementData object.

See the How To Query Summary Table Data Results topic for more information.

Syntax: app.Display.Traces.SelectedItem.DataName = "Demod DL Decode Info1";

The indexes of the DL Decode Info data values change depending on which channels are enabled in the Profile tab of the LTE Demod Properties dialog box. Instead of using hardcoded indexes to retrieve the data values, you can use a data result name to query the data value.

Below is a table with the list of possible data result names.

DL Decode Info data results

Data Result Name	Description
PBCH Decoder PCFICH Decoder PDCCH Decoder PDSCH Decoder	Decoder status for channel: On or Off
PBCH_Fx_IE	Decoded information from PBCH for frame x
PCFICH_Fx_IE	Decoded information (number of PDCCH symbols allocated for each subframe) decoded from PCFICH for frame x
PHICH_Fx_SFnIE	Decoded HARQ Ack/Nack from PHICH for frame x and subframe n
PDCCH_Fx_SFnIE#t	Decoded DCI message from PDCCH for frame x, subframe n, and transport block t

See Also

About Frame Summary

About Symbol Table

Available Summary Tables