Uplink LAA Channel Access Detection for LTE Unlicensed Bands
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In LTE systems operating in unlicensed bands, there is no mechanism for scheduled uplink transmissions to determine the starting point of channel assessment, leading to higher power consumption and reduced chances of channel preemption due to blind channel assessment.
Innovation Solution
A method where the terminal sets the channel assessment time in a subframe after the uplink scheduling instruction is received and before the scheduled transmission, allowing for a specified starting point of load-based channel assessment, which is controlled by the base station through RRC signaling or DCI indications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the terminal performs blind channel assessment without a specified starting point, then the terminal can attempt to access the channel, but the power consumption increases and the probability of channel preemption decreases
Solution Approach 1:
The base station performs channel assessment and makes a scheduling decision in advance before allocating uplink resources to the terminal. The UL grant includes not only resource allocation but also preliminary channel assessment results and timing indicators. This allows the terminal to receive ready-made scheduling information without needing to perform blind channel assessment, thereby reducing power consumption while maintaining reliable channel access.
Solution Approach 2:
The base station acts as an intermediary between the unlicensed channel and the terminal. Instead of letting the terminal directly assess the channel (which causes power consumption and reliability issues), the base station performs the channel assessment and communicates the results to the terminal through the UL grant. This intermediary approach allows the terminal to access the channel based on the base station's assessment, reducing terminal power consumption while improving channel preemption probability through coordinated access.
2Use of energy by moving object
If the terminal waits for base station scheduling instruction before channel assessment, then the terminal can save power, but the channel access delay increases
Solution Approach 1:
The base station performs channel assessment and prepares scheduling decisions in advance, before the terminal needs to access the channel. The UL grant includes timing indicators that tell the terminal exactly when to transmit. This preliminary action by the base station eliminates the need for the terminal to wait or perform delayed assessments, reducing both power consumption and access delay by having everything ready beforehand.
Solution Approach 2:
The base station continuously monitors the channel and maintains ready scheduling decisions, ensuring that when the terminal receives the UL grant, transmission can occur immediately at the indicated time. This continuous preparation by the base station ensures that the terminal's channel access action is continuous and immediate, eliminating gaps and delays while keeping the terminal in a low-power state until scheduled.
3Speed
If the terminal performs channel assessment at any time, then the terminal can access the channel quickly, but the system coordination and fairness with other technologies deteriorate
Solution Approach 1:
The base station provides feedback to the terminal through the UL grant, including channel assessment results, timing indicators, and resource allocation information. This feedback mechanism ensures that the terminal's channel access is coordinated with the base station's overall system management. The terminal accesses the channel quickly at the indicated time, but the access is controlled and coordinated through the feedback loop, maintaining fairness with other technologies and proper system coordination.
Solution Approach 2:
The UL grant mechanism serves multiple functions simultaneously: it allocates uplink resources, provides timing indicators for immediate transmission, conveys channel assessment results, and ensures coordination with the base station's scheduling. This multi-functional approach allows the terminal to access the channel quickly while maintaining system coordination and fairness, as the same mechanism that enables fast access also ensures proper system-wide coordination.
Data Source
Figure 1~2
Figure 3~5
Figure 6~7
AI summary
A channel assessment method, a channel assessment apparatus, a terminal and a base station when a LTE system operates in an unlicensed band are provided, where the method includes: receiving an uplink scheduling instruction transmitted in a subframe n by a base station, where the uplink scheduling instruction is configured to instruct a terminal to transmit uplink data in a subframe n+i by using an allocated resource; and setting channel assessment time in a subframe after the subframe n and before the subframe n+i, so as to detect a clear or busy state of an uplink channel to be occupied by the terminal.