SRS Transmission in Shared Spectrum via Power and Priority
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Solution Overview
Problem
Current Long-Term Evolution (LTE) and LTE-Advanced systems face challenges in transmitting sounding reference signals (SRS) due to power limitations and overlapping transmissions, leading to reduced opportunities for SRS transmission, especially in shared radio frequency spectrum bands where UEs may not win contention for wireless transmissions.
Innovation Solution
The proposed solution involves configuring two or more uplink component carriers (CCs) for UE transmissions, with at least one CC using a shared RF spectrum band, allowing SRS transmission even when power limited, and setting a higher channel priority for SRS in shared RF spectrum bands compared to dedicated RF spectrum bands, enabling more accurate channel quality information for scheduling and transmission parameter setting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a UE transmits SRS in a shared RF spectrum band using conventional LTE/LTE-A techniques, then the UE can obtain channel quality information, but the UE drops SRS transmissions when power limited or when PUSCH/PUCCH transmissions overlap, reducing SRS transmission opportunities
Solution Approach 1:
The patent implements dynamic SRS transmission behavior based on power availability and transmission overlap conditions. The UE dynamically decides whether to transmit SRS by evaluating power headroom and checking for PUSCH/PUCCH overlaps in real-time, allowing flexible adaptation to changing channel and power conditions rather than following fixed transmission patterns
Solution Approach 2:
The patent changes the transmission parameters of SRS based on power availability and overlap conditions. When power is sufficient and no overlaps exist, SRS transmission power and frequency are adjusted to optimize channel quality measurement while managing overall uplink power consumption across multiple component carriers
2Adaptability or versatility
If a UE uses a shared RF spectrum band for uplink transmissions, then spectrum utilization is improved, but the UE may not win contention for wireless transmissions, further reducing SRS transmission opportunities
Solution Approach 1:
The patent performs preliminary checks for power availability and transmission overlaps before attempting SRS transmission in shared spectrum bands. By evaluating conditions in advance and preparing transmission decisions beforehand, the UE can quickly respond to contention outcomes and ensure SRS transmissions occur when possible, improving reliability in competitive spectrum environments
Solution Approach 2:
The patent implements feedback mechanisms where the UE monitors contention outcomes, power consumption, and transmission success in shared spectrum bands, using this information to adjust SRS transmission strategies. The base station also provides feedback on channel quality measurements to refine future SRS transmission timing and power levels
3Loss of information
If the UE transmits multiple uplink channels (SRS, PUSCH, PUCCH) simultaneously, then channel quality information and data transmission are improved, but power limitations cause the UE to drop SRS transmissions
Solution Approach 1:
The patent applies different power allocation and transmission priorities to different uplink channels based on their specific requirements. SRS transmissions receive targeted power allocation when channel quality measurement is critical, while PUSCH and PUCCH transmissions receive appropriate power levels for data and control information, optimizing overall power utilization across multiple functional channels
Solution Approach 2:
The patent implements partial SRS transmission when power is limited, transmitting SRS on a subset of component carriers or at reduced power levels rather than completely dropping SRS transmissions. This partial action ensures some channel quality information is obtained while managing overall power consumption across multiple simultaneous uplink transmissions
Data Source
AI summary
Sounding reference signal (SRS) transmissions in a shared RF spectrum band, alone or in conjunction with a dedicated RF spectrum band, may be transmitted using two or more uplink component carriers (CCs). A UE may identify that the two or more CCs are in a same timing advance group (TAG), and transmit a SRS transmission and a physical uplink shared channel (PUSCH) or physical uplink control channel (PUCCH) transmission during a same uplink symbol. A UE may transmit a SRS based on a minimum configured power in the event that the UE is power limited during a SRS transmission symbol. A channel priority assigned to a CC carrying a SRS transmission in a shared RF spectrum band may be set to a higher channel priority than a channel priority for a similar transmission using a dedicated RF spectrum band.