LTE Terminal LBT Timing for Shared Spectrum Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
LTE systems are not optimized for operation in non-allocated or shared frequency bands, leading to inefficiencies in communication due to design assumptions based on allocated and non-shared frequency bands.
Innovation Solution
A terminal device equipped with a transmission unit and a CCA check unit that performs LBT before a subframe for PUSCH transmission, determining the start time based on the transmission start time and CCA slot length, improving communication efficiency in shared frequency environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LTE performs transmission in shared frequency bands without LBT, then transmission simplicity is maintained, but transmission efficiency deteriorates due to channel conflicts and interference
Solution Approach 1:
The terminal device performs LBT (Listen Before Talk) before transmitting PUSCH in shared frequency bands. This preliminary channel assessment action checks if the channel is idle before transmission, preventing channel conflicts and interference with other systems (e.g., WLAN) operating in the same band, thereby improving transmission efficiency without requiring complex retransmission protocols
Solution Approach 2:
The invention dynamically adjusts transmission timing based on LBT results. When the channel is busy, transmission is deferred to a later subframe; when idle, transmission proceeds immediately. This dynamic adaptation to channel conditions optimizes transmission efficiency in shared spectra while maintaining relatively simple device implementation through standardized LBT procedures
2Adaptability or versatility
If LTE assumes non-shared frequency band operation, then system design simplicity is maintained, but adaptability deteriorates in shared spectrum environments
Solution Approach 1:
The terminal device is designed to operate universally in both dedicated and shared frequency bands by integrating LBT functionality. The same PUSCH transmission mechanism is used across different band types, with LBT serving as an optional overlay for shared bands. This multi-functionality approach enables frequency band adaptability while maintaining core LTE system design simplicity
Solution Approach 2:
The system adapts to shared frequency bands by changing operational parameters - specifically by enabling LBT procedures and adjusting transmission timing based on channel assessment results. These parameter changes allow the LTE system to function effectively in shared spectra without requiring fundamental architectural modifications, thus improving adaptability with minimal design complexity increase
3Productivity
If LBT is performed at fixed timing intervals, then implementation simplicity is maintained, but transmission efficiency deteriorates due to missed transmission opportunities
Solution Approach 1:
LBT timing is dynamically adjusted based on channel conditions and PUSCH transmission requirements. Instead of fixed intervals, the terminal performs LBT at variable timings - immediately before scheduled transmissions or at flexible intervals when channel opportunities arise. This dynamic timing optimization captures more transmission opportunities in shared bands while maintaining operational simplicity through rule-based timing adjustments
Solution Approach 2:
The terminal performs LBT at optimized timings preceding PUSCH transmissions, determining start time based on PUSCH timing and CCA slot length. This preliminary yet strategically timed channel assessment ensures transmission efficiency by capturing available channel opportunities without requiring continuous monitoring, balancing operational simplicity with improved productivity
Data Source
Figure 1
Figure 2
Figure 3
AI summary
To efficiently control a cell by using a non-allocated frequency band or a shared frequency band. A terminal device includes a transmission unit configured to transmit a PUSCH and a CCA check unit configured to perform LBT before a subframe for which a transmission of the PUSCH is indicated. The terminal device determines start time of the LBT, based on start time of the transmission of the PUSCH, a CCA slot length, and the number of CCA checks. The terminal device includes a reception unit configured to receive a PDCCH. The number of CCA checks is indicated on the PDCCH.