Uplink SRS Comb Hopping for Multi-Antenna Resource Collisions
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Solution Overview
Problem
Existing LTE and LTE-A wireless communication systems face challenges in efficiently managing sounding reference signal (SRS) transmissions, particularly for WTRUs with multiple antennas, due to insufficient resources and lack of clear signaling mechanisms for aperiodic SRS configurations, leading to increased overhead and potential collisions with other channels.
Innovation Solution
Methods for configuring and transmitting SRS include determining cyclic shift multiplexing and transmission combs for multiple antennas, handling collisions with physical uplink channels, and providing dynamic resource allocation through triggers and dedicated signaling to ensure efficient SRS transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If periodic SRS transmission based on semi-static configuration is used, then SRS transmission is simple to implement, but SRS resources are insufficient for WTRUs with multiple antennas and unnecessary transmissions increase overhead
Solution Approach 1:
The patent introduces dynamic aperiodic SRS transmission that can be triggered on-demand by the eNB through DCI signaling, allowing the system to adapt SRS transmission behavior based on actual channel sounding needs rather than following rigid periodic schedules. This dynamic approach enables flexible resource allocation that scales with the number of antennas while transmitting SRS only when required, eliminating unnecessary periodic transmissions.
2Loss of energy
If aperiodic SRS transmission is introduced to reduce overhead, then unnecessary SRS transmissions are reduced, but signaling complexity and resource allocation complexity increase
Solution Approach 1:
The patent extends the existing UL grant DCI format to serve dual purposes: both uplink scheduling and aperiodic SRS triggering. By incorporating SRS triggering functionality into the existing grant structure using flag bits and resource allocation fields, the system avoids creating separate signaling mechanisms, thereby reducing overall signaling complexity while enabling on-demand SRS transmission.
Solution Approach 2:
The patent enables the system to self-manage SRS resource allocation by having the eNB directly trigger and configure aperiodic SRS transmissions through existing DCI formats without requiring additional higher-layer signaling or complex configuration procedures. The WTRU autonomously determines SRS transmission parameters based on the triggered indication, simplifying the overall signaling architecture.
3Productivity
If multiple WTRUs transmit SRS in the same subframe, then resource utilization is efficient, but collisions occur between SRS, PUSCH, and PUCCH transmissions
Solution Approach 1:
The patent segments SRS resources in the frequency domain using transmission combs, where each WTRU is assigned specific comb indices (even or odd subcarriers). This segmentation allows multiple WTRUs to transmit SRS simultaneously in the same subframe on different frequency resources without collision, while maintaining efficient resource utilization across the bandwidth.
Solution Approach 2:
The patent resolves transmission collisions by introducing frequency domain separation through transmission combs as an additional dimension for resource allocation. Instead of only time-division multiplexing SRS transmissions, the system uses frequency-comb based separation to allow simultaneous transmissions from multiple WTRUs without interference, thereby maintaining both high resource utilization and transmission reliability.
Data Source
AI summary
A method for use by a wireless transmit/receive unit (WTRU) for transmitting a sound reference signal (SRS) comprises receiving SRS configuration information. The SRS configuration information comprises an indication to perform transmission comb hopping. The SRS configuration information indicates hopping pattern information for the transmission comb hopping. The method comprises transmitting a first SRS transmission in a first set of resources. The first SRS transmission is transmitted in a first symbol of a slot. The method comprises transmitting a second SRS transmission in a second set of resources based on the indication to perform transmission comb hopping and the hopping pattern information for the transmission comb hopping. The second SRS transmission is transmitted in a second symbol of the slot.