Dynamic Contention Window Sizing for 5G Unlicensed Subbands
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Solution Overview
Problem
In wireless communications networks, particularly in 5G and NR systems, determining an optimal contention window size for efficient access to unlicensed frequency bands is challenging, especially for wideband systems, as existing methods do not effectively balance channel access efficiency with friendly coexistence among nodes.
Innovation Solution
A method where a device sends data packets on a reference time unit, receives HARQ-ACKs, and adjusts the contention window size based on the proportion or quantity of ACKs and NACKs, allowing for dynamic adjustment of channel listening parameters to optimize channel access and reduce signaling overheads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the contention window size is increased to reduce collisions and improve channel access efficiency, then channel utilization improves, but the access delay increases and productivity decreases
Solution Approach 1:
The contention window size is dynamically adjusted based on channel conditions and transmission outcomes. The system transitions from static to dynamic CW sizing, allowing the parameter to adapt in real-time to changing network environments, thereby optimizing both access efficiency and delay performance
Solution Approach 2:
The contention window size parameter is modified based on HARQ-ACK feedback and channel state. When transmission succeeds, the CW size is reduced to improve access efficiency; when failures occur or channel conditions deteriorate, the CW size is increased to reduce collisions, achieving a balance between productivity and time loss
2Productivity
If the contention window size is dynamically adjusted for each subband, then channel access efficiency improves, but the device complexity increases
Solution Approach 1:
The frequency band is divided into multiple subbands, each with its own independent contention window size. This segmentation allows granular control of channel access parameters per subband, improving overall channel access efficiency while distributing the management complexity across multiple smaller units rather than one large system
Solution Approach 2:
Each subband is assigned a customized contention window size based on its specific channel conditions and transmission outcomes. This local optimization approach allows different parts of the frequency spectrum to have different CW characteristics, improving productivity while the modular structure keeps device complexity manageable
3Productivity
If wideband data packets are transmitted on unlicensed frequency bands, then data throughput increases, but the difficulty of detecting and measuring channel conditions accurately increases
Solution Approach 1:
The wideband transmission is divided into multiple subbands for independent channel assessment. By segmenting the frequency spectrum, the system can detect and measure channel conditions in smaller, more manageable units, improving measurement accuracy while maintaining overall high data throughput through parallel subband utilization
Solution Approach 2:
The system adjusts transmission parameters including CW size and power allocation based on subband-specific channel quality indicators. This allows accurate detection of channel conditions in each subband and adaptive parameter modification, resolving the contradiction between wideband throughput and measurement accuracy
Data Source
AI summary
Embodiments of this disclosure provide contention window size determining methods and apparatuses. One method includes: sending, by a first device, a data packet that comprises a code block group (CBG), wherein the CBG at least partially overlaps with a first subband and at least partially overlaps with a second subband, receiving, by the first device, a hybrid automatic repeat request-acknowledgement (HARQ-ACK) corresponding to the CBG, and determining, by the first device, a contention window size of the first subband and a contention window size of the second subband based on the HARQ-ACK.