Uplink Collision Avoidance in Wireless Transmission Time Intervals
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Solution Overview
Problem
In wireless communication systems, collisions between uplink transmissions in a set of transmission time intervals (TTIs) and shortened TTIs (sTTIs) can occur, leading to interference and data loss, especially when UEs are not capable of simultaneous transmission on the same carrier or when transmissions from different UEs coincide.
Innovation Solution
The proposed solution involves identifying overlapping TTIs and sTTIs, where a UE may drop a portion of the transmission in the TTI or schedule transmissions to avoid collisions by not transmitting during coinciding intervals, or by transmitting dropped portions in sTTIs, ensuring that higher priority messages are sent without interfering with lower priority messages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a UE transmits a first message in a set of TTIs of a repetition window to improve reception reliability, then the chance of message reception is improved, but collisions with sTTI transmissions may occur causing interference and data loss
Solution Approach 1:
The base station performs preliminary scheduling of sTTI transmissions to avoid coinciding with TTI repetition windows. By proactively identifying and preventing overlapping time intervals before transmissions occur, the system eliminates collision interference while maintaining both TTI repetition for reliability and sTTI for low-latency communications
Solution Approach 2:
The system dynamically adjusts transmission scheduling based on the coincidence detection between TTI repetition windows and sTTI allocations. When overlap is detected, the base station modifies the scheduling decisions adaptively, either by dropping the lower-priority transmission or rescheduling to a non-overlapping interval, thereby resolving the contradiction between reliability improvement and collision avoidance
2Productivity
If the base station schedules a second message in an sTTI that coincides with TTIs of a repetition window, then sTTI transmission capability is utilized, but collision occurs causing data loss
Solution Approach 1:
The base station implements a feedback mechanism that monitors scheduled transmissions for potential collisions between sTTI and TTI repetition windows. When a coincidence is detected, the system provides feedback to adjust scheduling decisions, either by selecting alternative time intervals or by prioritizing one transmission type over the other, thereby preventing data loss while maintaining high transmission productivity
3Reliability
If the UE drops transmission of a first message in overlapping TTIs to accommodate a higher priority second message, then high priority message transmission is ensured, but the first message transmission is interrupted
Solution Approach 1:
When a collision between sTTI and TTI repetition windows is detected, the system applies a priority-based discarding and recovering mechanism. The lower-priority first message transmission is temporarily discarded in the overlapping interval to accommodate the higher-priority second message, but the system recovers by rescheduling or retransmitting the first message in a non-overlapping TTI interval, thereby ensuring high-priority message delivery while minimizing time loss for the lower-priority message
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. In some wireless communications systems, a base station may configure a user equipment (UE) to transmit a first message in a set of transmission time intervals (TTIs) of a repetition window, and the base station may configure the same UE or a different UE to transmit a second message in a shortened TTI (sTTI). In such systems, if the base station schedules the transmission of the second message in an sTTI that coincides with at least one overlapping TTI in the set of TTIs of the repetition window, the UE may drop at least a portion of the transmission of the first message in the set of TTIs. Alternatively, the base station may avoid scheduling the uplink transmission of the second message in an sTTI that coincides with a TTI in the set of TTIs of the repetition window.