Aperiodic SRS Frequency Band Indication in Unlicensed Spectrum
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Solution Overview
Problem
In LTE systems, the traditional aperiodic sounding reference signal (A-SRS) triggering mechanism fails to dynamically schedule SRS transmissions on non-scheduled serving cells in unlicensed spectrum communications, leading to inefficiencies due to unpredictable interference levels and limited control over carrier selection.
Innovation Solution
A method and device for aperiodic SRS scheduling in user equipment and base stations, where higher layer signaling configures unique frequency bands for SRS transmission, allowing flexible scheduling and dynamic frequency selection on unlicensed spectrum, using physical layer signaling to indicate transmitting frequency bands not necessarily associated with the serving cell, and reusing existing DCI formats for compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional A-SRS triggering mechanism is used, then SRS transmission is restricted to scheduled serving cells, but this limits flexibility in unlicensed spectrum where dynamic frequency selection is needed
Solution Approach 1:
The patent segments the SRS configuration by introducing separate configuration indexes for different serving cells. Each serving cell can be independently configured with its own SRS parameters, allowing the base station to trigger SRS on specific cells without scheduling them for data transmission. This segmentation enables flexible SRS transmission on non-scheduled cells while maintaining independent control over each cell's SRS behavior.
Solution Approach 2:
The patent adds a new dimension to the traditional A-SRS triggering mechanism by introducing a serving cell index field in the downlink signaling. This additional dimension allows the base station to indicate not only whether SRS should be transmitted but also on which specific serving cell. This dimensional extension transforms the triggering mechanism from a single-cell constraint to a multi-cell flexible scheduling approach.
2Adaptability or versatility
If SRS is transmitted only on scheduled serving cells, then control over carrier selection is limited, but this prevents dynamic frequency selection on unlicensed spectrum
Solution Approach 1:
The patent applies preliminary action by pre-configuring multiple serving cells with their respective SRS parameters through higher layer signaling before actual SRS transmission. The base station prepares a set of configured serving cells with unique configuration indexes, enabling it to quickly trigger SRS on any pre-configured cell without requiring real-time scheduling decisions. This preliminary configuration enables dynamic frequency selection while maintaining control over carrier selection.
3Adaptability or versatility
If physical layer signaling indicates SRS frequency band independent of scheduled serving cell, then flexibility is improved, but compatibility with existing DCI formats becomes challenging
Solution Approach 1:
The patent achieves universality by designing the downlink signaling to serve multiple functions simultaneously. The same physical downlink control format is used both for scheduling data transmissions and for triggering A-SRS transmissions. By incorporating a serving cell index field and a trigger indicator in the existing DCI structure, the signaling mechanism becomes multi-functional, supporting both traditional scheduling and the new independent SRS frequency band indication without requiring separate signaling formats.
Data Source
AI summary
The present invention provides a UE, a method for an aperiodic SRS in a base station and a device. For a problem of a scheduling restriction of a traditional A-SRS in unlicensed spectrum communication, the present disclosure provides the method and apparatus for the A-SRS, wherein physical-layer signaling is used to indicate a sending frequency band of an SRS to implement flexible scheduling of the aperiodic SRS. As an embodiment, the number of antenna ports of the A-SRS is configured by high-layer signaling identified by a logical cell index. A physical resource occupied by the aperiodic SRS is configured by high-layer signaling identified by a carrier index. The logical cell index at different frameworks may correspond to different physical carriers.