SRS Placement at Subframe Start for LAA Channel Utilization
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Solution Overview
Problem
The existing LTE system's SRS transmission mechanism is inadequate to meet the requirements of Licensed-Assisted Access using LTE (LAA-LTE) systems, particularly in channel resource utilization and uplink data transmission efficiency.
Innovation Solution
The proposed solution involves user equipment (UE) performing channel detection and sending uplink data with a sounding reference signal (SRS) located at the start of a subframe, based on SRS configuration information received from the base station, using radio resource control (RRC) or physical downlink control signaling (DCI), to improve channel utilization and accuracy in estimating channel quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the existing LTE system's SRS transmission mechanism is used, then the system maintains backward compatibility, but channel resource utilization is insufficient and uplink transmission efficiency is low
Solution Approach 1:
The patent implements dynamic SRS transmission by allowing the base station to flexibly configure SRS transmission parameters (period, subframe offset, frequency offset) based on current channel conditions and traffic requirements. The UE dynamically adjusts SRS transmission timing and frequency resources according to received configuration messages, optimizing channel estimation efficiency for varying uplink transmission needs in LAA systems
Solution Approach 2:
The patent changes key transmission parameters including SRS subframe timing (configurable offset from frame start), frequency offset (relative to uplink data frequency), and transmission periodicity. These parameter adjustments enable adaptive channel estimation resource allocation, improving both channel utilization and uplink transmission efficiency in unlicensed spectrum LAA operations
2Reliability
If channel detection is performed before sending uplink data, then channel access compliance is achieved, but transmission delay increases
Solution Approach 1:
The patent performs channel detection (CCA/LBT) in advance before uplink data transmission on unlicensed carriers. The UE checks channel availability and reserves the channel through preliminary detection, ensuring compliant access to LAA resources before actual data transmission begins, thereby maintaining reliability while managing timing for subsequent SRS and data transmissions
3Productivity
If SRS is located at the start location of the subframe, then channel utilization is improved, but SRS configuration complexity increases
Solution Approach 1:
The patent places SRS specifically at the start location of designated subframes rather than uniformly distributed throughout the frame. This localized positioning optimizes channel estimation for the beginning of transmission bursts where channel conditions are most critical for LAA operations, while the base station manages configuration complexity through centralized parameter signaling to the UE
Data Source
AI summary
A signal transmission method, a signal transmission control method, a user equipment (UE), and a base station, where the signal transmission method includes performing, by UE, channel detection, and sending, by the UE, uplink data when a result of the channel detection is that a channel is available, where the uplink data includes one or more subframes, at least one subframe includes a sounding reference signal (SRS), and the SRS is located at a start location of the subframe. The signal transmission control method includes sending, by a base station, SRS configuration information to the UE using radio resource control (RRC) signaling or physical downlink control signaling (DCI) such that the UE sends an SRS based on the SRS configuration information. Hence, utilization of a channel can be significantly improved.