Carrier Aggregation SRS Switching for TDD Channel Reciprocity
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Solution Overview
Problem
In LTE networks with carrier aggregation, the imbalance between downlink and uplink component carriers leads to challenges in utilizing channel reciprocity for link adaptation and beamforming due to the lack of uplink transmissions on some carriers, resulting in SRS dropping and reduced performance in TDD systems.
Innovation Solution
Implementing SRS carrier-based switching by configuring certain carriers for SRS transmission only, using dedicated SRS subframes and guard periods to minimize collisions with other channels, ensuring SRS transmission priority, and optimizing subframe configurations to enable efficient channel estimation and link adaptation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carrier aggregation is implemented with more downlink component carriers than uplink component carriers, then downlink capacity is improved, but channel reciprocity cannot be utilized for link adaptation on carriers without uplink transmissions
Solution Approach 1:
The patent segments the uplink component carriers into two distinct types: regular uplink carriers that carry both data and SRS transmissions, and SRS-only carriers that are configured exclusively for SRS transmission. This segmentation allows the system to maintain asymmetric carrier aggregation for downlink capacity while ensuring that channel reciprocity can be utilized on specific carriers through dedicated SRS transmission opportunities, thereby resolving the contradiction between downlink capacity and channel estimation accuracy.
2Productivity
If SRS transmission is configured on carriers with other physical channels, then resource utilization is improved, but SRS dropping occurs due to collisions with other channels
Solution Approach 1:
The patent extracts the SRS transmission function from carriers that also carry other physical channels and creates dedicated SRS-only carriers. This extraction eliminates collisions between SRS and other physical channels, ensuring reliable SRS transmission for channel reciprocity-based link adaptation and beamforming, while regular carriers continue to utilize resources efficiently for data transmission.
3Reliability
If SRS transmission priority is ensured through dedicated subframes, then SRS dropping is reduced, but system complexity increases due to additional configuration
Solution Approach 1:
The patent applies local quality by configuring SRS transmission priority and dedicated subframes only on specific SRS-only carriers where channel reciprocity is required, rather than uniformly across all carriers. This localized approach ensures reliable SRS transmission where needed while minimizing the overall system complexity and configuration overhead.
Data Source
AI summary
An apparatus can receive or transmit parameters for a sounding reference signal (SRS) transmission configuration as an uplink (UL)/downlink (DL) configuration of a serving cell. A time division duplex (TDD) operation with a plurality of component carriers (CCs) can be enabled/generated based on the parameters and at least one component carriers being reserved for the UL transmission or having a higher priority than a physical channel transmission such as a physical uplink shared channel (PUSCH) transmission or a physical uplink control channel (PUCCH) transmission.