Uplink Timing Control in Secondary Cells via Segmented Search Spaces
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Solution Overview
Problem
In LTE and LTE-Advanced systems, user equipment (UE) faces challenges in uplink transmission timing control, particularly when using secondary cells (SCells) with varying subcarrier spacing and symbol lengths, leading to increased latency and complexity in setting up RAR windows, as RAR scheduling information is typically transmitted only in the primary cell (PCell).
Innovation Solution
The user equipment is designed to receive and transmit downlink control information, including RAR scheduling information, within the SCell or its TA group, allowing for independent uplink transmission timing control even when resource allocation units differ between cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If RAR scheduling information is transmitted only in the PCell, then the system maintains simplicity in control information transmission, but the latency increases and communication efficiency deteriorates when using SCells with different subcarrier spacing and symbol lengths
Solution Approach 1:
The patent segments the control information transmission by introducing a separate common search space in the SCell for RAR scheduling information, distinct from the PCell's common search space. This allows RAR scheduling to be handled independently in each cell, reducing latency for SCell random access while maintaining the existing PCell control structure.
Solution Approach 2:
The patent adds a new dimension to control information transmission by establishing RAR scheduling capability in the SCell domain, rather than relying solely on the PCell domain. This dimensional expansion allows parallel RAR scheduling operations in both PCell and SCell, reducing overall latency without complicating the fundamental control architecture.
2Reliability
If individual uplink transmission timing control is performed for each cell, then the orthogonality between user equipment is maintained in carrier aggregation, but the device complexity and difficulty of detecting and measuring RAR scheduling information increases
Solution Approach 1:
The patent segments the random access and timing control functions by cell, with each cell (PCell and SCell) having its own common search space for RAR scheduling. This segmentation allows independent timing control for each cell while keeping the detection process standardized within each cell's search space, reducing cross-cell interference and maintaining orthogonality.
Solution Approach 2:
The patent creates equipotential detection conditions by configuring common search spaces with consistent detection mechanisms in both PCell and SCell. This allows user equipment to detect RAR scheduling information using the same procedures in either cell, simplifying the detection process despite individual timing control requirements.
3Productivity
If RAR scheduling information for SCell is transmitted in the PCell's common search space, then the system maintains a unified control structure, but the productivity and communication efficiency decreases due to increased latency
Solution Approach 1:
The patent segments the control information structure by creating separate common search spaces in both PCell and SCell for RAR scheduling. This segmentation enables parallel processing of random access responses in both cells, improving communication efficiency and productivity while maintaining a consistent control mechanism within each cell segment.
Solution Approach 2:
The patent applies universality by making the common search space configuration and detection mechanism applicable to both PCell and SCell. This multi-functionality allows the same control procedures to operate independently in both cells, improving efficiency without requiring cell-specific complex control structures.
Data Source
AI summary
User equipment for communicating with a base station using a secondary cell includes a transmitter that transmits, to the base station, a preamble to start a random access in the secondary cell; a receiver that receives, within a predetermined search space, scheduling information of a random access response to be transmitted, in response to the preamble, from the base station or another base station of a timing advance group including the base station, and that receives a random access response including uplink transmission timing information based on the scheduling information; and a transmission timing controller that controls uplink transmission timing based on the uplink transmission timing information included in the random access response.