LTE DL SCH basics | LTE DL SCH physical layer processing
This page describes LTE DL SCH basic function and mention DL SCH physical layer processing. The LTE physical layer used for DL SCH processing is also described.
DL-SCH is used to transmit SIBs, RRC signalling and application data. Transport blocks of DL-SCH will have variable size. DL-SCH can transmit either 1 or 2 TBs of application data per subframe per connection. 2 Transport blocks(TB) can be transmitted when UE is in good coverage area and it is configured with either 2x2 MIMO or 4x4 MIMO.
The figure below depicts LTE DL SCH physical layer processing.
• CRC allows error detection at the receiver.
• second module after CRC ensures that block of data has a size of atleast 40 bits segments blocks of data larger than 6144 bits, adds an additional 24 bits CRC to any segmented blocks.
• channel coding module provides redundancy to protect the data across the air interface
• Rate matching module interleaves and adjusts the quantity of data to match the capacity offered by PDSCH
• concatenation of individual code blocks if segmentation was completed earlier.
• Code block concatenation is completed if segmentation is needed prior to channel coding module. segments are concatenated to generate single codeword.
• DL-SCH codewords are modulated using QPSK, 16QAM or 64QAM. QPSK is used for SI transmission. This is because QPSK is most robust modulation scheme. 16QAM and 64QAM is used in good coverage conditions to benefit in higher data rate.
• Modulated codewords are mapped onto allocated PDSCH resource elements.
LTE Physical Layer
Refer 3GPP TS 36.212 for LTE DL-SCH Physical layer processing. Refer LTE Physical layer >> for detailed description on eNodeB and UE physical layer transmitter compliant to LTE standard.
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