Carrier Indication Fields for Flexible Aperiodic SRS Triggering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In LTE-A systems under carrier aggregation, there is a challenge in applying Physical Downlink Control Channel (PDCCH) from the primary carrier to trigger Aperiodic SRS (ap-SRS) in secondary carriers, which limits the flexibility and efficiency of channel sounding.
Innovation Solution
A user equipment (UE) receives an uplink or downlink grant over a primary carrier, determines the indicated carrier for ap-SRS transmission, and selects UE-specific SRS parameters configured via RRC signaling to transmit ap-SRS on the indicated carrier, using carrier indication fields in DCI formats to enable cross-carrier scheduling and flexible ap-SRS configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If PDCCH from primary carrier is used to trigger ap-SRS in secondary carriers, then cross-carrier scheduling capability is improved, but triggering flexibility and efficiency deteriorate due to lack of proper triggering mechanisms
Solution Approach 1:
The patent segments the triggering mechanism by introducing carrier indication fields (CIF) in DCI formats that specifically identify which secondary carrier should receive the ap-SRS trigger. This segmentation allows the primary carrier's PDCCH to selectively trigger ap-SRS on specific secondary carriers rather than all carriers, resolving the contradiction by enabling cross-carrier scheduling while maintaining triggering flexibility through precise carrier identification.
Solution Approach 2:
The patent introduces an intermediary mechanism where the DCI format acts as a mediator between the PDCCH on the primary carrier and the ap-SRS transmission on secondary carriers. The DCI format contains carrier indication fields that mediate the triggering relationship, allowing flexible and efficient cross-carrier scheduling by specifying exactly which secondary carrier should be triggered.
2Measurement precision
If multiple ap-SRS parameters are configured for different carriers, then sounding precision is improved, but device complexity increases due to multiple parameter sets
Solution Approach 1:
The patent applies universality by designing a unified DCI format structure that can universally trigger ap-SRS on any configured secondary carrier through the carrier indication field. Instead of requiring separate triggering mechanisms for each carrier, the same DCI format with different CIF values serves multiple carriers, reducing device complexity while maintaining the ability to configure carrier-specific ap-SRS parameters for precise channel sounding.
3Measurement precision
If ap-SRS is triggered on multiple carriers simultaneously, then channel estimation accuracy is improved, but signaling overhead increases
Solution Approach 1:
The patent merges the triggering function for multiple carriers into a single DCI format transmission. By combining multiple carrier indications and their corresponding ap-SRS triggers into one unified DCI message on the primary carrier, the system achieves multi-carrier channel estimation simultaneously while minimizing signaling overhead, as all triggers are conveyed in a single signaling event rather than separate signals for each carrier.
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A method of multi-set RRC signaling for ap-SRS configuration is provided to enhance ap- SRS flexibility. An eNB transmits a plurality of sets of UE-specific SRS parameters to a UE via upper layer messaging in a multi-carrier wireless communication system. The eNB also determines triggering information of a selected set of UE-specific SRS parameters and an indicated carrier for the UE. The eNB then transmits an uplink or downlink grant over a primary carrier, the grant comprises triggering information for the UE to send an ap-SRS over the indicated carrier using the selected set of UE-specific SRS parameters. In one embodiment of joint signaling, the plurality of sets of UE-specific SRS parameters are signaled together in a single RRC transmission. In another embodiment of separate signaling, each set of UE-specific SRS parameters is signaled independently.