Network Coding for 5G Grant-Free Access Reliability
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Solution Overview
Problem
In 5G NR communication systems, the two-step grant-free random access (GFRA) procedure is limited for long-length packet transmission due to increased random access attempts by devices, leading to higher collision probabilities and latency, especially when a large number of devices transmit data.
Innovation Solution
The method involves dividing a long-length packet into transport blocks, applying network coding to combine them redundantly, and transmitting these blocks with forward error correction (FEC) codes, allowing for increased reliability and reduced latency by adjusting the number of network coding blocks based on link quality and network state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the two-step grant-free random access (GFRA) procedure is used for long-length packet transmission, then device access speed is improved, but collision probability increases due to increased random access attempts
Solution Approach 1:
The long-length packet is divided into multiple transport blocks (TBs), which are then independently encoded and transmitted. This segmentation allows the system to manage long packets in smaller units, reducing the impact of collisions on the entire transmission while maintaining fast access through GFRA
Solution Approach 2:
Network coding blocks are generated in advance by combining multiple transport blocks using pre-configured linear combination coefficient matrices. This preliminary encoding prepares redundant information before transmission, enabling the receiver to recover original data even when some transmissions collide or fail
2Loss of time
If the two-step grant-free random access (GFRA) procedure is used for long-length packet transmission, then latency is reduced, but transmission reliability deteriorates
Solution Approach 1:
Multiple network coding blocks are generated in advance from the transport blocks using linear combination operations. These pre-generated redundant blocks are transmitted along with the original data blocks, ensuring that sufficient copies reach the receiver within the GFRA timing constraints, thus maintaining low latency while improving reliability
Solution Approach 2:
The system transmits more network coding blocks than the minimum required for reconstruction (M+KN blocks for M transport blocks). This excess transmission acts as a cushion against packet loss and collisions, guaranteeing reliable delivery even in high-interference environments without significantly increasing latency
3Reliability
If network coding is applied to combine transport blocks redundantly, then transmission reliability is improved, but system complexity increases
Solution Approach 1:
The base station pre-configures multiple linear combination coefficient matrices with different parameters (K values representing different numbers of redundant blocks). The terminal selects appropriate matrices based on channel conditions and packet importance, allowing dynamic adjustment of redundancy levels without requiring complex real-time encoding decisions at the terminal
Data Source
AI summary
An operation method of a terminal may include: receiving, from a base station, an addition value KN, information on linear combination coefficient matrices for respective numbers of transport blocks, and configuration information on each linear combination coefficient matrix; dividing a source block into M transport blocks; selecting one linear combination coefficient matrix among the linear combination coefficient matrices based on M; generating (M+KN) network coding blocks by performing network coding on the M transport blocks with the selected one linear combination coefficient matrix; and transmitting, to the base station, messages each including one network coding block among the network coding blocks, a control index of the one linear combination coefficient matrix, and a preamble.