Uplink Control Signaling on Shared Medium
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wireless communication systems, especially in shared communication mediums like the Unlicensed National Information Infrastructure (U-NII) band, there is a challenge in managing uplink control signaling to avoid interference between different Radio Access Technologies (RATs) such as LTE and Wi-Fi, particularly in scenarios where contention for access to the medium is required, leading to potential cross-link interference and inefficient acknowledgment procedures.
Innovation Solution
Implementing a Time Division Duplexing (TDD) frame structure that separates contention-exempt and contention-compliant signaling by introducing a transmission gap period, allowing for selective transmission of uplink control signals based on contention outcomes, and scheduling acknowledgments to occur at predetermined subframes or time intervals after downlink transmissions to minimize interference and optimize channel usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LTE small cell operations are extended into unlicensed frequency bands to increase spectral efficiency and capacity, then spectral efficiency and capacity of the LTE system are improved, but interference with other Radio Access Technologies such as Wi-Fi operating in the same bands occurs
Solution Approach 1:
The uplink subframe is segmented into three distinct periods: transmission gap period, contention-exempt period, and contention-compliant period. This segmentation allows different types of control signals to be transmitted in different time windows, with contention-based access during the transmission gap and contention-exempt access during the contention-exempt period, thereby reducing interference with other RATs while maintaining LTE capacity
Solution Approach 2:
The TDD frame structure implements periodic transmission patterns with regular downlink and uplink subframes. The uplink subframes contain periodic transmission gap periods followed by contention-exempt and contention-compliant periods, creating a rhythmic access pattern that allows LTE to efficiently utilize the unlicensed spectrum while periodically yielding to other RATs, thus reducing overall interference
2Ease of operation
If contention procedures are performed during uplink subframes to access shared communication medium, then access to shared medium is achieved, but transmission latency and collision risk increase
Solution Approach 1:
The contention procedure is performed in advance during the transmission gap period before the actual control signal transmission. This preliminary contention action allows devices to secure medium access rights beforehand, so that subsequent transmissions during the contention-exempt period can proceed without additional contention delays, thereby reducing overall transmission latency
Solution Approach 2:
The transmission gap period acts as an intermediary time window between downlink transmissions and uplink control signal transmissions. During this gap, contention procedures are performed as a mediating step that resolves access rights before the actual data transmission, preventing collisions and reducing latency by avoiding mid-transmission contention
3Object-affected harmful factors
If all uplink control signals are transmitted during contention-compliant periods, then interference with other RATs is reduced, but transmission efficiency and spectral utilization decrease
Solution Approach 1:
Different portions of the uplink subframe are assigned different access characteristics: the transmission gap period uses contention-based access (more interference-friendly), while the contention-exempt period uses priority access (higher efficiency). This local differentiation allows critical control signals to be transmitted efficiently during contention-exempt periods while less time-sensitive signals use contention-compliant periods, achieving both interference reduction and high transmission efficiency
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Disclosed are techniques for accessing a shared communication medium. An aspect includes communicating over the shared communication medium in accordance with a Time Division Duplexing (TDD) frame structure defining a set of downlink subframes and a set of uplink subframes, each uplink subframe being divided into a transmission gap period, a contention-exempt period, and a contention-compliant period, performing a contention procedure for contending for access to the shared communication medium during the transmission gap period, selectively transmitting contention-compliant uplink control signals during the contention-compliant period, and transmitting one or more contention-exempt uplink control signals during the contention-exempt period. An aspect includes receiving a downlink subframe of the shared communication medium and transmitting an acknowledgment of the downlink subframe during an uplink subframe of the shared communication medium, the uplink subframe occurring at least a predetermined number of subframes and/or at least a predetermined amount of time after the downlink subframe.