Uplink SRS Triggering for Multi-Antenna Resource Capacity
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Solution Overview
Problem
Existing LTE wireless communication systems face challenges in efficiently configuring and transmitting sounding reference signals (SRS) due to insufficient resources, especially with multiple antennas, leading to increased overhead and capacity issues in LTE-Advanced (LTE-A) scenarios.
Innovation Solution
Methods and apparatus for configuring and transmitting SRS by determining appropriate subframes, transmission combs, and cyclic shifts, including multi-shot SRS transmissions and dynamic resource allocation for multiple antennas, using both higher layer and Layer 1 signaling to manage SRS transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If periodic SRS transmission is used based on semi-static configuration, then SRS transmission is simple to implement, but SRS resources are insufficient to support multiple antennas and cause capacity issues
Solution Approach 1:
The patent introduces dynamic aperiodic SRS transmission that can be triggered on-demand by the network, complementing the static periodic transmission. This allows the system to adapt SRS resource allocation dynamically based on actual channel sounding needs, supporting multiple antennas without requiring permanent resource allocation for each antenna.
Solution Approach 2:
The patent makes existing uplink grant resources serve dual purposes: both for data transmission and for triggering aperiodic SRS transmission. This multi-functionality allows the system to support multiple antennas and increased SRS capacity without adding dedicated triggering mechanisms, resolving the capacity issue while maintaining implementation simplicity.
2Quantity of substance
If aperiodic SRS transmission is introduced to support multiple antennas, then SRS resource capacity increases, but signaling complexity and configuration overhead increase
Solution Approach 1:
The patent reuses existing uplink grant DCI formats and MAC CE structures for triggering aperiodic SRS, rather than creating new signaling protocols. The uplink grant's resource allocation fields are interpreted to also carry SRS triggering information, and existing activation/deactivation mechanisms are leveraged, thereby increasing SRS capacity without proportionally increasing signaling complexity.
Solution Approach 2:
The patent enables the existing uplink grant signaling structure to self-serve the additional function of triggering aperiodic SRS. The same DCI format and MAC CE that control uplink data transmission also control SRS transmission, eliminating the need for separate dedicated triggering signaling and reducing overall system complexity.
3Adaptability or versatility
If multiple triggering mechanisms are used for aperiodic SRS, then SRS transmission flexibility increases, but configuration and management complexity increases
Solution Approach 1:
The patent unifies multiple triggering mechanisms under a common framework where uplink grants, MAC CEs, and PDCCH indicators all ultimately control the same aperiodic SRS transmission resources. This unified approach allows flexible triggering through multiple channels while simplifying configuration management by using consistent resource allocation and activation procedures across all triggering methods.
Data Source
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AI summary
Methods and apparatus for sounding reference signals (SRS) configuration and transmission. The methods include receiving configuration of wireless transmit/receive unit (WTRU) -specific SRS subframes for transmitting SRS and upon receipt of a trigger, transmitting the SRS for a number of antennas. The SRS transmissions may occur in each subframe of a duration of WTRU-specific SRS subframes that start a number of WTRU-specific SRS subframes after a triggering subframe. For multiple SRS transmissions from multiple antennas, cyclic shift multiplexing and different transmission combs may be used. The cyclic shift for an antenna may be determined from a cyclic shift reference value. The cyclic shift determined for each antenna providing a maximum distance between cyclic shifts for the antennas transmitting SRS in a same WTRU-specific subframe. SRS transmissions from multiple antennas in the WTRU-specific subframe may be done in parallel. Methods for handling collisions between SRS and physical channels are presented.