Aperiodic SRS Triggering via DCI for TDD Carrier Switching

The patent implements periodic SRS transmissions with configurable periods (2, 5, 10, 20, 40, 80, 160, or 320 ms) to balance channel sounding accuracy with resource overhead. The periodic action allows the system to obtain channel quality estimates at regular intervals rather than continuously, reducing SRS overhead while maintaining adequate measurement precision for scheduling decisions.

The patent introduces dynamic triggering mechanisms where the network can activate or deactivate aperiodic SRS transmissions based on current channel conditions and traffic requirements. This dynamic approach allows the system to increase measurement precision only when necessary, rather than maintaining continuous periodic transmissions, thereby reducing overall SRS overhead while preserving the ability to obtain accurate channel estimates when needed.

The patent uses Downlink Control Information (DCI) messages as intermediaries to trigger aperiodic SRS transmissions. The DCI provides a simple binary indicator that tells the wireless device whether to transmit SRS or not, avoiding the need for complex signaling protocols. This intermediary approach enables dynamic resource utilization while keeping the triggering mechanism relatively simple and easy to implement in existing LTE infrastructure.

The patent changes the transmission parameter from continuous periodic SRS to event-triggered aperiodic SRS based on channel conditions and traffic patterns. By changing the triggering parameter from time-based to condition-based, the system improves resource utilization by transmitting SRS only when necessary, while the complexity is managed through predefined triggering conditions rather than complex real-time decision algorithms.

The patent implements periodic SRS transmissions with configurable periods ranging from 2 to 320 milliseconds, allowing the system to achieve adequate channel sounding accuracy at much lower overhead rates compared to every-subframe transmission. The periodic interval can be adjusted based on channel coherence time and traffic requirements, optimizing the trade-off between measurement precision and resource overhead.

The patent applies partial action by transmitting SRS only in selected subframes based on periodic configuration and aperiodic triggering, rather than in every subframe. This partial transmission strategy provides sufficient channel sounding accuracy for scheduling decisions while reducing SRS overhead from the worst-case 7% to typically 1-3% or lower, depending on the periodicity and triggering conditions.