Multi-Burst A-TRS for SSB-Less Secondary Cell Loop Tracking
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Solution Overview
Problem
In inter-band carrier aggregation scenarios, the absence of synchronization signal blocks (SSBs) in secondary cells leads to reduced reception performance for user equipment (UE) due to the inability to perform automated gain control and time/frequency tracking loops, which are typically reliant on SSBs for synchronization.
Innovation Solution
The implementation of aperiodic tracking reference signals (A-TRS) in SSB-less secondary cells, transmitted in multiple bursts, to facilitate AGC and time/frequency tracking loops before receiving downlink signals, allowing for efficient network energy savings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If periodic SSB transmissions are performed in secondary cells, then synchronization and initial access are maintained, but network energy consumption increases unnecessarily
Solution Approach 1:
The patent replaces continuous periodic SSB transmissions with aperiodic TRS transmissions that occur only when needed. The base station transmits TRS bursts triggered by specific events (e.g., UE requests, scheduling decisions) rather than following a fixed periodic schedule, thereby eliminating unnecessary energy consumption while maintaining synchronization reliability.
Solution Approach 2:
The patent changes the transmission parameters from periodic SSB to aperiodic TRS by modifying the transmission timing, frequency resources, and signal structure. This parameter change allows the system to adapt transmission behavior to actual channel conditions and UE needs, reducing energy waste while preserving synchronization functionality.
2Loss of energy
If SSB transmissions are eliminated in secondary cells, then network energy is saved, but UE reception performance deteriorates due to lack of reference signals for tracking
Solution Approach 1:
The patent introduces TRS (Tracking Reference Signal) as an intermediary element that replaces the synchronization and tracking functions previously provided by SSB. TRS serves as a mediator that enables UE to perform AGC and time/frequency tracking without requiring continuous SSB transmissions, thus preserving reception performance while reducing energy consumption.
Solution Approach 2:
The patent enables the UE to request A-TRS transmissions when needed, allowing the UE to self-manage its synchronization requirements. The UE can autonomously determine when tracking reference signals are necessary based on its reception needs, eliminating the need for the base station to continuously transmit SSB for all UEs.
3Loss of energy
If aperiodic TRS transmissions are used instead of periodic SSB, then energy consumption is reduced, but system complexity increases due to dynamic request and configuration management
Solution Approach 1:
The patent establishes pre-configured TRS resource pools and transmission patterns before actual transmissions occur. The base station and UE agree on available TRS resources, timing structures, and triggering conditions in advance, which simplifies the dynamic management of aperiodic transmissions and reduces the operational complexity despite the flexible transmission scheme.
Data Source
AI summary
Aspects of the present disclosure allow a UE to request, in an anchor carrier on one frequency band, a base station to configure and transmit A-TRS in an SSB-less secondary carrier on a different frequency band. The UE transmits, in a first cell served by the anchor carrier, a request for A-TRS. Based on the request, the UE receives, in a second cell lacking SSB transmissions served by the secondary carrier, the A-TRS based on the request. The base station may also control transmission of the A-TRS in the SSB-less secondary cell based on a timer derived from the request. Using the A-TRS, the UE may apply AGC and time/frequency tracking loop operations prior to receiving a PDSCH in the SSB-less secondary cell, thereby improving reception performance of downlink data transmissions in the secondary carrier. Thus, network energy savings provided by SSB-less secondary carriers may be obtained in inter-band CA.