MAC Segmentation for HARQ Retransmission Limits in 5G Downlink
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
HARQ retransmissions in 5G networks may not improve the decoding probability of transport blocks (TBs) in degraded channel conditions, leading to resource wastage, increased latency, and packet loss, especially when incremental redundancy reaches its limit.
Innovation Solution
Implement MAC segmentation at the medium access control (MAC) layer to split TBs into segments, using lower modulation and coding schemes for transmission, and combine successfully decoded segments for reliable delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If HARQ retransmissions are used to improve TB decoding reliability, then decoding probability improves under normal conditions, but resource wastage increases and latency increases when channel conditions are highly degraded
Solution Approach 1:
The patent segments a transport block (TB) into multiple medium access control (MAC) segments when the New Data Indicator (NDI) is toggled and a MAC segmentation indicator is set. This segmentation allows the receiver to process and decode smaller segments independently rather than waiting for complete TB retransmissions, thereby reducing latency while maintaining reliability in degraded channel conditions
Solution Approach 2:
The patent dynamically switches between traditional HARQ retransmission mode and MAC segmentation mode based on channel conditions and NDI toggling. When NDI is toggled and segmentation is indicated, the system transitions to segment-based transmission; otherwise, it uses conventional HARQ processes, providing adaptive optimization between reliability and latency
2Reliability
If incremental redundancy is increased to improve decoding probability, then reliability improves, but resource usage increases and eventually reaches a limit where further retransmissions are wasteful
Solution Approach 1:
Instead of transmitting complete TB retransmissions with incremental redundancy, the patent transmits only partial MAC segments containing the necessary new data. This partial action approach provides sufficient redundancy for decoding while avoiding the excessive resource consumption of full TB retransmissions, especially when channel conditions are poor
Solution Approach 2:
The patent changes the transmission parameter from complete TB retransmissions to segmented MAC segment transmissions. By modifying the data unit size and structure (from TB to MAC segments), the system achieves better resource efficiency while maintaining decoding probability through selective retransmission of critical segments
3Reliability
If complete TB retransmissions are performed to ensure successful decoding, then reliability improves, but productivity decreases due to increased latency and resource consumption
Solution Approach 1:
The patent divides the TB into multiple MAC segments that can be transmitted and decoded independently. This segmentation enables parallel processing at the receiver, where successfully decoded segments can be delivered to higher layers while other segments are still being received, significantly improving throughput and productivity compared to waiting for complete TB decoding
Solution Approach 2:
The patent performs preliminary segmentation of the TB into MAC segments before transmission. This preliminary action allows the receiver to start decoding segments as they arrive rather than waiting for the complete TB, enabling earlier data delivery and improving overall system productivity
Data Source
AI summary
An apparatus configured to attempt to decode a first transport block (TB) scheduled for downlink (DL) reception by a first downlink control information (DCI), the first TB associated with a first hybrid automatic repeat request (HARQ) process and containing a first medium access control (MAC) protocol data unit (PDU), when the attempt to decode the first TB and receive the first MAC PDU is unsuccessful, generate, for transmission to a network, a first non-acknowledgment (NACK), detect, in a second DCI, an indication that the first MAC PDU is to be segmented into at least two MAC segments to be transmitted, attempt to decode at least two further TBs, each further TB containing a respective one of the at least two MAC segments and concatenate each successfully decoded MAC segment to receive the first MAC PDU.