SRS Triggering Mechanism for Unlicensed Band Resource Efficiency
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Solution Overview
Problem
Current wireless communication systems, such as LTE LAA and MulteFire, face inefficiencies in unlicensed band operations due to the lack of mechanisms to control UE to send SRS in multiple UL subframes granted by a single PDCCH, leading to wasted signaling and reduced throughput, especially in high-traffic scenarios.
Innovation Solution
A mechanism is introduced to efficiently trigger UE to send SRS in selected UL subframes within a multi-subframe grant by configuring multiple SRS parameter sets and using dynamic signaling to indicate which subframes to transmit SRS, allowing for flexible and efficient resource usage without increasing control signaling overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the UE sends SRS in each of the multiple granted UL subframes, then the network receives channel sounding information from each subframe, but most of the SRS transmissions are wasted signaling since the channel conditions are coherent across multiple subframes
Solution Approach 1:
The patent extracts only the necessary SRS transmission instances from the multiple granted subframes. By introducing a trigger mechanism that selects specific subframes for SRS transmission, the system removes redundant SRS transmissions while preserving the essential channel sounding function. The network configures multiple SRS parameter sets and triggers transmissions in selected subframes, thereby extracting only the useful measurements and eliminating wasted signaling.
Solution Approach 2:
The patent introduces dynamic control of SRS transmissions through trigger signaling. Instead of fixed periodic SRS transmissions in all granted subframes, the system dynamically selects which subframes require SRS based on current channel conditions and traffic requirements. The network can adaptively trigger SRS in specific subframes using downlink control information, making the SRS transmission pattern flexible and condition-dependent rather than rigid and continuous.
2Loss of energy
If the network abstains from receiving SRS in multiple granted UL subframes, then signaling overhead is reduced, but throughput efficiency decreases due to lack of precise channel soundings for high-traffic UEs
Solution Approach 1:
The patent applies partial action by triggering SRS transmissions in only some of the granted subframes rather than all of them. The network configures multiple SRS parameter sets and selectively triggers transmissions based on traffic conditions. For high-traffic UEs, the network can trigger SRS in specific subframes where channel sounding is most beneficial, applying just enough signaling to maintain throughput efficiency without the excess of triggering in every subframe.
Solution Approach 2:
The patent changes the triggering parameters dynamically based on traffic conditions. By configuring multiple SRS parameter sets with different periodicities and trigger conditions, the system can adapt the SRS transmission pattern to match current network requirements. The trigger signaling allows the network to adjust which parameter sets are active and when transmissions should occur, optimizing the balance between signaling overhead and channel sounding accuracy for different traffic scenarios.
3Adaptability or versatility
If multiple SRS parameter sets are configured with different periodicities, then the network can flexibly control SRS transmissions, but the device complexity increases for managing and triggering multiple parameter sets
Solution Approach 1:
The patent makes the trigger mechanism universal by designing it to handle multiple SRS parameter sets through a unified downlink control information structure. The same trigger signaling mechanism can activate different parameter sets based on current conditions, providing a multi-functional control system. The network can configure multiple parameter sets with different characteristics and use the universal trigger mechanism to select and activate the appropriate set, avoiding the need for separate control mechanisms for each parameter set.
Solution Approach 2:
The patent performs preliminary configuration of multiple SRS parameter sets in advance through higher-layer signaling. All the parameter sets are pre-configured with their respective periodicities, frequencies, and other parameters before actual SRS transmissions begin. This preliminary setup allows the runtime trigger mechanism to simply select from pre-defined options rather than making complex decisions in real-time, reducing the computational burden during active transmission and simplifying the management complexity.
Data Source
Figure 1A~1B
Figure 2~3
Figure 4A
AI summary
When triggering a user equipment (UE) to send a reference signal (SRS) the network configures the UE with multiple parameter sets, each having a timing indication. The UE's resource allocation grants multiple uplink (UL) subframes and identifies/selects one of those parameter sets. The timing indication of the selected set identifies one of the granted UL subframes, in one embodiment by counting only among the allocated/granted shortened UL subframes. This triggers the UE to send SRS in that identified shortened UL subframe. In one embodiment if no UL subframes in the grant are shortened this triggers the UE to send SRS in a subframe previous to all the allocated/granted multiple UL subframes. The same mechanism can be used to trigger feedback reports such as aperiodic channel state information or block ACK/NACK reports, where the different UL signaling being triggered is requested in the network's resource allocation to the UE.