LAA Subframe Reservation Signal for LBT Overhead Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wireless communication systems, particularly in LTE LAA, the Listen-Before-Talk (LBT) procedure incurs unnecessary overhead due to the requirement for UEs to stop transmissions during symbol #2, leading to channel access loss and increased LBT measurements, especially when PUCCH and PUSCH are scheduled in the same or consecutive subframes.
Innovation Solution
Implementing a Time Division Multiplexing (TDM) subframe structure where UEs transmit a reservation signal in unused symbols, allowing efficient TDM between PUCCH and PUSCH, and minimizing LBT measurements by aligning transmission bursts with subframe timing and using a reservation signal to indicate channel occupancy, thereby reducing unnecessary LBT overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UEs stop transmissions during symbol #2 to perform LBT measurements, then channel access reliability is improved, but transmission continuity is worsened and LBT overhead increases
Solution Approach 1:
The patent extracts the LBT measurement requirement from the middle of the subframe transmission by eliminating the need to stop during symbol #2. Through TDM configuration and reservation signal transmission, the LBT procedure is performed only at subframe boundaries, removing the harmful transmission interruption that would otherwise occur during regular subframe operation.
Solution Approach 2:
The patent performs LBT measurements preliminarily at subframe boundaries before transmission bursts begin. By conducting channel access procedures in advance and using reservation signals to indicate upcoming transmissions, the system ensures channel availability is established before data transmission starts, eliminating the need for mid-subframe LBT interruptions.
2Productivity
If TDM is implemented between PUCCH and PUSCH, then resource utilization efficiency is improved, but LBT measurement overhead increases
Solution Approach 1:
The patent merges the LBT measurement requirement with the TDM structure by aligning LBT measurements with subframe boundaries rather than requiring separate measurements for each TDM-switched channel. The reservation signal mechanism combines channel indication with transmission timing, so that a single LBT measurement at the subframe boundary serves both PUCCH and PUSCH transmissions.
3Reliability
If reservation signals are transmitted in unused symbols, then channel occupancy indication is improved, but signal overhead increases
Solution Approach 1:
The patent makes the reservation signal multi-functional by using it both as a channel occupancy indication and as a transmission timing marker. The same reservation signal transmitted in unused symbols serves to indicate that the channel is reserved for upcoming PUCCH or PUSCH transmissions, eliminating the need for separate overhead signals for each function.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
There is provided a method comprising determining, at a user device capable of transmitting at least one subframe, the subframe having a subframe structure comprising at least one first symbol associated with one of physical layer signals and a first channel, and at least one second symbol associated with a second channel, if the respective one of physical layer signals and the first channel is scheduled to be transmitted in the at least one first symbol and, if the respective one of physical layer signals and the first channel is not scheduled to be transmitted in the at least one first symbol, causing transmission of a signal indicating channel occupancy during the at least one first symbol and transmission of the second channel during the at least one second symbol.