NR Unlicensed Contention Window Adjustment via CBG HARQ Feedback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The increasing demand for network resources due to the rise in user equipment and data bandwidth necessitates enhanced bandwidth, latency, and data rate, which existing technologies struggle to meet, especially in licensed spectrum scarcity, prompting the exploration of unlicensed spectrum utilization in cellular networks.
Innovation Solution
The implementation of 5G NR systems in unlicensed spectrum using code block groups (CBGs) for HARQ feedback and adjustable contention window sizes based on listen-before-talk (LBT) procedures to ensure fair coexistence with incumbent technologies, allowing for efficient data transmission and spectral management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If unlicensed spectrum is utilized to increase bandwidth and meet growing network demand, then network capacity and data rate are improved, but coexistence with incumbent technologies and fair spectrum access become challenging
Solution Approach 1:
The system performs Listen-Before-Talk (LBT) procedure before transmitting data in unlicensed spectrum. The base station senses the channel for a predetermined time period and determines channel availability in advance of data transmission, preventing interference with incumbent technologies while ensuring fair spectrum access
Solution Approach 2:
The system implements Hybrid Automatic Repeat Request (HARQ) feedback mechanism where user equipment sends acknowledgment information back to the base station. This feedback enables the base station to adaptively adjust transmission parameters and retransmit data if needed, improving reliability and coexistence in unlicensed spectrum
2Productivity
If code block groups are used for HARQ feedback in unlicensed spectrum, then spectral efficiency is improved by reducing retransmission overhead, but system complexity increases
Solution Approach 1:
The system segments the transport block into multiple code block groups (CBGs) for independent HARQ feedback. Instead of acknowledging the entire transport block, the base station can selectively retransmit only the failed CBGs, reducing retransmission overhead and improving spectral efficiency in unlicensed spectrum
Solution Approach 2:
The system applies different HARQ feedback strategies to different code block groups based on their individual transmission outcomes. Each CBG can be acknowledged or negative-acknowledged independently, allowing localized retransmission decisions that optimize spectral efficiency while managing complexity
3Object-affected harmful factors
If listen-before-talk procedure is implemented for fair coexistence, then interference with incumbent technologies is reduced, but channel access delay and latency increase
Solution Approach 1:
The system performs LBT sensing for a predetermined time period that is sufficient to detect incumbent transmissions but not excessively long. This partial sensing approach balances fair coexistence with minimizing channel access delay, allowing the system to access unlicensed spectrum efficiently while respecting incumbent users
Data Source
AI summary
Systems and methods of adjusting contention window size (CWS) in a LBT procedure for both UL and DL unlicensed spectrum transmissions are described. The UE makes a HARQ-ACK determination for at least one code block group (CBG) of a transport block (TB) in a reference burst from a base station, determines whether the HARQ-ACK determination for the CBG meets a predetermined number of NACKs, transmits to the base station a single bit HARQ-ACK feedback for the TB that is dependent on whether the predetermined number of NACKs has been met, and receives or determines the adjusted CWS and uses the adjusted CWS for communication with the base station.