Clear Channel Assessment Delay Extension for LTE LAA Transmission
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Solution Overview
Problem
Existing LTE systems using Licensed-Assisted Access (LAA) in unlicensed spectrum face challenges with clear channel assessment (CCA) delays, leading to non-standardized reservation signals and inefficiencies in data transmission when CCA is delayed, affecting peak data rates and channel occupancy.
Innovation Solution
Generate a truncated LTE data subframe/slot with PDSCH and CRS content as a reservation signal when CCA is delayed, incorporating masking periods to prevent unexpected decoding and simplify implementation by reusing prepared data frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If clear channel assessment is performed for every transmission opportunity, then collision probability is reduced, but transmission delay increases
Solution Approach 1:
The patent performs clear channel assessment in advance during a CCA extension period before the actual transmission opportunity. This preliminary action allows the system to determine channel availability beforehand, reducing the need for repeated immediate assessments and thereby lowering transmission delay while maintaining collision avoidance through advance channel validation.
Solution Approach 2:
The patent dynamically adjusts the CCA extension duration based on traffic conditions and channel state. When the channel is determined to be clear through preliminary assessment, the system can extend the transmission opportunity without performing additional immediate CCA, adapting the assessment frequency to actual transmission needs and reducing unnecessary delays.
2Loss of time
If CCA extension is implemented, then transmission delay is reduced, but the risk of channel state change increases
Solution Approach 1:
The patent implements periodic clear channel assessments during the CCA extension period rather than relying on a single preliminary assessment. The system performs additional CCA checks at intervals throughout the extended period, ensuring that channel state changes are detected while still allowing most of the extension period to be used for transmission, thus balancing delay reduction with channel state accuracy.
3Speed
If immediate transmission is performed without CCA extension, then channel responsiveness is improved, but transmission opportunity loss increases
Solution Approach 1:
The patent performs a quick preliminary clear channel assessment immediately before the transmission opportunity to maintain channel responsiveness. If the channel is clear, transmission proceeds without delay. If the channel is busy, the system then applies CCA extension to capture additional transmission opportunities, thus balancing immediate responsiveness with overall transmission productivity.
Data Source
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AI summary
A method comprising extending a transmission delay caused by a clear channel assessment check delaying a communication between an access point and a user equipment over an unlicensed transmission link beyond a start of an earliest possible subframe/slot with useful data, the transmission delay being extended till a defined period from a start of a subframe/slot.