Adaptive Contention Window for mmWave LBT
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Solution Overview
Problem
Current wireless communication systems, particularly in 5G NR, face challenges in channel access procedures, especially in mmWave environments where interference patterns are highly directional, leading to inefficiencies in listen-before-talk (LBT) procedures due to the need for deterministic or random backoff mechanisms that do not effectively manage burst-length-dependent interference.
Innovation Solution
The proposed solution involves adjusting the contention window size based on the burst length of transmissions in LBT procedures, allowing for more accurate clear channel assessment (CCA) and reducing interference by associating the CCA length with the burst length, thereby improving channel access efficiency in both downlink and uplink communications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed or deterministic backoff mechanism is used in LBT procedures, then the channel access procedure is simple to implement, but it cannot effectively manage burst-length-dependent interference leading to reduced reliability
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed backoff mechanism to a dynamic one where the contention window size is adjusted based on the burst length. The system dynamically selects different contention window sizes (e.g., first contention window size for first burst length, second contention window size for second burst length) to optimize channel access reliability for different transmission scenarios while maintaining operational simplicity through automated adaptation.
2Reliability
If a random backoff mechanism with large contention window is used, then collision probability is reduced, but channel access time increases leading to lower productivity
Solution Approach 1:
The patent applies parameter changes by varying the contention window size parameter based on the burst length parameter. For shorter bursts, a smaller contention window is used to enable faster channel access and improve productivity. For longer bursts, a larger contention window is used to reduce collision probability and improve reliability. This dynamic parameter adjustment optimizes both collision avoidance and channel access efficiency across different transmission scenarios.
3Loss of time
If the CCA length is not associated with burst length, then the LBT procedure is faster to execute, but interference management becomes ineffective leading to reduced channel availability
Solution Approach 1:
The patent applies preliminary action by performing the clear channel assessment (CCA) for the entire burst length before the actual data transmission begins. The system determines whether the channel is clear for the full duration of the burst in advance, ensuring that the channel will be available for the entire transmission period. This preliminary CCA action, while requiring time, ensures reliable channel availability and prevents interruptions during data transmission.
Data Source
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AI summary
Aspects are provided which improve LBT by associating contention windows with transmission burst lengths and by allowing contention windows and maximum burst lengths to be adjusted based on interference activity. For downlink, a UE receives a PG for a downlink transmission from a base station indicating a CCA length based on a contention window size associated at least with a burst length for the downlink transmission. The UE performs, after receiving the pre-grant, a CCA based on the CCA length, transmits an APG to the base station when the CCA is successful, and receives the downlink transmission in response to the APG. For uplink, the base station performs a CCA based on a contention window associated at least with a burst length for an uplink transmission, transmits an uplink grant to the UE when the CCA is successful, and receives the uplink transmission in response to the uplink grant.