Adaptive SRS Carrier Switching for LTE Measurement Accuracy
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Solution Overview
Problem
SRS carrier-based switching in LTE networks causes interruptions in reference signals used for critical measurements, such as positioning, which can degrade measurement performance, particularly in scenarios with carrier aggregation and TDD carriers where channel reciprocity is not utilized effectively.
Innovation Solution
Adaptive SRS carrier-based switching mechanisms that minimize interruptions in subframes containing critical signals by dynamically switching SRS transmission between carriers, ensuring that reference time resources are available for measurements, thereby maintaining measurement accuracy and mobility procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If SRS carrier-based switching is performed to support more DL carriers than UL carriers in carrier aggregation scenarios, then the ability to utilize channel reciprocity on TDD carriers is improved, but interruptions in reference signals occur which degrade measurement performance
Solution Approach 1:
The patent implements dynamic SRS carrier-based switching where the UE can switch between different component carriers for SRS transmission based on measurement requirements. This dynamic switching allows the system to adaptively select which carrier to use for SRS transmission, ensuring that measurements on other carriers are not interrupted while still enabling UL feedback for multiple DL carriers.
Solution Approach 2:
The patent segments the SRS transmission across multiple component carriers, allowing different carriers to be used for different purposes. Specifically, the UE can perform measurements on one carrier while transmitting SRS on another carrier, effectively dividing the functionality across multiple carriers to avoid measurement interruptions.
2Productivity
If SRS transmission is switched between carriers to enable UL feedback on more DL carriers, then the network performance is improved, but interruptions occur in subframes containing critical measurement signals
Solution Approach 1:
The patent employs preliminary action by configuring measurement gaps before actual measurements are performed. These measurement gaps are pre-arranged time resources where the UE can perform measurements without being interrupted by SRS switching activities. The network is notified in advance of these gap requirements, allowing proper scheduling coordination.
Solution Approach 2:
The patent introduces measurement gaps as intermediary time resources that mediate between SRS switching operations and measurement requirements. These gaps act as a buffer that allows measurements to occur without conflict with SRS transmission switching, effectively decoupling the two operations in time.
3Adaptability or versatility
If fast carrier switching is implemented to allow SRS transmission on TDD carriers without UL transmission, then channel reciprocity can be utilized, but the complexity of managing SRS switching and measurement coordination increases
Solution Approach 1:
The patent implements feedback mechanisms where the UE reports its SRS switching capabilities and requirements to the network. The network then uses this feedback to configure appropriate measurement gaps and coordinate SRS switching operations. This feedback loop simplifies the complexity by allowing the network to make informed scheduling decisions based on actual UE capabilities and requirements.
Data Source
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AI summary
A method, in a user equipment, for performing one or more radio measurements is provided. The method comprises determining that the user equipment is to perform one or more radio measurements using a first set of reference time resources on at least a first cell operating on a first carrier frequency. The method further comprises adaptively performing reference signal carrier-based switching for transmitting a reference signal on a second cell operating on a second carrier frequency based on the determined first set of reference time resources. A method in a network node is also provided. The method comprises determining that a user equipment is to perform one or more radio measurements using a first set of reference time resources on at least a first cell operating on a first carrier frequency. The method further comprises determining that the user equipment is to adaptively perform reference signal carrier based switching for transmitting a reference signal on a second cell operating on a second carrier frequency based on the determined first set of reference time resources. The method further comprises using a result of the adaptive reference signal carrier based switching for one or more operational tasks.