Scheduling Request and ACK/NACK Signal Separation in LTE Uplink
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wireless communication systems, particularly in E-UTRAN (evolved UTRAN) networks, the simultaneous transmission of Scheduling Request (SR) and ACK/NACK signals can lead to errors due to Discontinuous Transmission (DTX) detection failures, resulting in incorrect interpretation of DL resource allocation grants, which affects higher layer protocols and requires slower error recovery with increased signaling overhead.
Innovation Solution
The method involves optimizing the constellation mapping for SR and ACK/NACK signals to maximize separation, using the same constellation points for SR, DTX, and NACK, and configuring separate periodic and aperiodic SR resources to support DTX detection, allowing the UE to transmit ACK/NACK information using different resources based on SR status, thereby minimizing DTX-to-ACK errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If SR and ACK/NACK are transmitted simultaneously using the same resource, then resource utilization is improved, but DTX detection accuracy deteriorates leading to false alarms
Solution Approach 1:
The patent segments the uplink control information by creating separate resources for SR and ACK/NACK transmissions. When SR is detected, the system separates the SR indication from ACK/NACK feedback, allowing independent detection and processing. This segmentation eliminates the interference between SR and ACK/NACK that causes DTX false alarms while maintaining efficient resource utilization through configured grant structures.
Solution Approach 2:
The patent introduces an intermediary detection mechanism that first identifies SR transmissions before processing ACK/NACK feedback. By using SR detection as an intermediate step, the system can determine whether ACK/NACK feedback is present or if the transmission is solely an SR, thereby preventing false DTX detection while maintaining resource efficiency.
2Measurement precision
If DTX detection is performed to identify missed DL grants, then resource allocation accuracy is improved, but false alarms increase leading to incorrect ACK interpretation
Solution Approach 1:
The patent performs preliminary SR detection before attempting DTX detection for ACK/NACK feedback. By first determining whether an SR is present in the uplink transmission, the system can avoid false DTX alarms that would occur if SR energy was misinterpreted as missing ACK/NACK feedback. This preliminary action sequence improves reliability while maintaining detection accuracy.
3Ease of operation
If SR uses unmodulated RS sequences with on/off keying, then SR detection simplicity is improved, but confusion with DTX state increases
Solution Approach 1:
The patent segments the detection process into distinct stages: first detecting SR using the simple on/off keying of unmodulated RS sequences, then separately processing ACK/NACK feedback based on the SR detection result. This segmentation maintains the simplicity of SR detection while eliminating confusion with DTX states, as the system knows whether to expect ACK/NACK feedback or not based on the SR detection outcome.
Data Source
Figure 2
Figure 3
Figure 4
AI summary
A method for signaling between a mobile apparatus (10) and a network node (12) is described. The method includes generating a message that includes a scheduling request. Determining whether a second indication (e.g., an acknowledgment) is to be transmitted in a sub-frame with the first indication is also included. The method includes, in response to a determination that the second indication is not to be included, the message is configured in a first configuration and, in response to a determination that the second indication is to be included, the message also includes the second indication and the message is configured in a second configuration. The first configuration is distinct from the second configuration. The method also includes sending the message, via a wireless transmitter, in the sub-frame. Apparatus and computer-readable media are also described.