OFDM Code Block Alignment for Faster ACK/NACK and SIC
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Solution Overview
Problem
The LTE type of code block segmentation does not align with orthogonal frequency division multiplexing (OFDM) symbols, leading to partial transmission of code blocks across two OFDM symbols, which delays acknowledgments (ACKs)/negative acknowledgments (NACKs) and hinders successive interference cancellation (SIC) by preventing interference subtraction until the entire code block is received.
Innovation Solution
Aligning code blocks with OFDM symbol borders, either through perfect alignment or grouping OFDM symbols to maintain suitable code block sizes, allowing for independent processing of OFDM symbols, earlier ACK/NACK transmission, and enhanced SIC within the current OFDM symbol.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If code blocks are segmented according to LTE standard without alignment to OFDM symbols, then the maximum code block size of 6144 bits can be maintained, but code blocks are partially transmitted across two OFDM symbols causing delayed ACK/NACK and preventing timely SIC
Solution Approach 1:
The patent segments the transmission timeline into groups of consecutive OFDM symbols, where each group is allocated to carry a complete code block. This segmentation ensures that code blocks are transmitted within single OFDM symbol groups rather than spanning across symbol boundaries, enabling timely reception and acknowledgment while maintaining code block integrity.
2Reliability
If code blocks span across two OFDM symbols, then the code block size can be maintained, but interference from partially received code blocks cannot be subtracted until the entire code block is received in the second symbol
Solution Approach 1:
The patent performs preliminary alignment of code blocks to OFDM symbol group boundaries before transmission. By ensuring that each code block is contained within a single OFDM symbol group, the receiver can immediately begin SIC processing as soon as the OFDM symbol group is received, without waiting for subsequent symbols to complete the code block reception.
3Loss of time
If perfect alignment of code blocks to OFDM symbols is enforced, then independent processing of OFDM symbols is enabled and ACK/NACK latency is reduced, but code block sizes become significantly shorter
Solution Approach 1:
The patent transitions from aligning code blocks to individual OFDM symbols to aligning code blocks to groups of consecutive OFDM symbols. This dimensional change allows code blocks to span multiple symbols within a group while still maintaining alignment boundaries, thus preserving adequate code block sizes while enabling independent processing of aligned symbol groups.
Data Source
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Figure 3A~3B
AI summary
According to some embodiments, a method in a wireless transmitter of aligning code blocks with modulation symbols comprises: receiving a block of information bits for wireless transmission in a plurality of modulation symbols; partitioning the plurality of modulation symbols into groups of one or more modulation symbols, wherein the modulation symbols in a group are contiguous in time; and assigning each of the information bits to one of the groups. Tor each of the groups the method further comprises: segmenting the assigned information bits in the group into one or more code blocks; encoding each code block into coded bits; and assigning the coded bits of the one or more code blocks to the group of modulation symbols the information bits are assigned to. The method further comprises transmitting the groups of modulation symbols to a wireless receiver