PDSCH Bits (LTE-Advanced)

Default: None

Range: None, Descrambled, Deratematched, Decoded CB, Decoded TB Transport Block

PDSCH Bits specifies how much coding to undo before showing the bits from PDSCH Physical Downlink Shared Channel on the CW0/1 Decoded Symbol Tables. See 3GPP TS Technical Specification 36.212, Section 5.3.2 for a diagram of the coding operations performed on PDSCH.

Only the bits from PDSCH allocations transmitted on C-RS Cell-specific RS antenna ports are shown on the CW0/1 Decoded Symbol Tables. This is because PDSCH allocations transmitted on UE-RS UE-specific Reference Signal antenna ports do not undergo any precoding (and their bits are shown on the Symbol Table).

The following is a list of the available PDSCH Bits selections and the resulting bits:

Mapped - no decoding is performed on PDSCH bits. Mapped bits for this channel will be shown on the Symbol Table.
Descrambled - descrambled (rate-matched) bits for each subframe are shown in the CW0/1 Decoded Symbol Tables.
Deratematched - S (16 + LEN_i) bits per subframe

Each set of bits for a PDSCH transmission consists of an 16-bit length field (LEN_i) followed by the deratematched (channel coded) bits.

LEN_i indicates the number of deratematched bits for the i^th PDSCH allocation in a subframe and can be used to determine where one set of deratematched bits ends and the next set begins in the CW0/1 Decoded Symbol Tables.

LEN_i = 3 * (Codeblock Length + CRC Cyclic Redundancy Check Length + Trellis Termination Bit Length) where Trellis Termination Bit Length = 4.
Decoded CB - S (16 + LEN_i) bits per subframe

Each set of bits for a PDSCH codeblock consists of a 16-bit length field (LEN_i), the decoded codeblock bits, and a 24-bit CRC. When codeblock segmentation is not performed (Transport Block Size (TBS(n)) is less than 6144), the codeblock + CRC bits shown are the same as the transport block + CRC bits .

LEN_i indicates the number of decoded bits (including CRC) for the i^th PDSCH codeblock in a subframe and can be used to determine where a set of codeblock bits ends and the next set begins in the CW0/1 Decoded Symbol Tables.

LEN_i = Codeblock Length + CRC Length
Decoded TB - S (Transport Block Sizes + 24) decoded transport block bits (including CRCs) per subframe

Each set of bits consists of the decoded transport block bits followed by a 24-bit CRC. There is no LEN field for decoded transport block bits since the Transport Block Size for each PDSCH allocation is shown on the DL Decode Info table in the TBS(n) data result.

To determine where one set of transport block bits ends and the next set begins in the CW 0/1 Decoded Symbol Table, use the DemodOFDMSubcarType key in the trace header. This key can be included when saving a trace to disk or can be accessed programmatically from the Trace.MeasurementData.State dictionary.

The PDSCH decoder is On when PDSCH Bits is not set to None.

PDSCH decoding is only available when RB Auto Detect Mode is set to Decode PDCCH.