Listen-before-talk Configuration for Random Access in Unlicensed Cells
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Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently managing uplink transmissions and random access processes, particularly in carrier aggregation scenarios, where the high PUCCH load on the primary cell can lead to network congestion and increased battery consumption.
Innovation Solution
The implementation of carrier aggregation techniques, including the use of secondary timing advance groups (TAGs) and the configuration of PUCCH groups, allows for the distribution of control signaling across multiple cells, reducing the load on individual cells and improving network efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carrier aggregation is implemented to distribute control signaling across multiple cells, then network capacity and efficiency are improved, but device complexity and configuration difficulty increase
Solution Approach 1:
The patent segments the control signaling load by introducing secondary timing advance groups (TAGs) and PUCCH groups that distribute uplink control information across multiple cells. Instead of concentrating all PUCCH transmissions on the primary cell, the system divides control signaling into multiple groups, each handled by specific cells, thereby reducing the load on any single cell while maintaining overall network capacity.
Solution Approach 2:
The patent adds a new dimension to the random access procedure by introducing a two-step random access mechanism. This adds a new layer to the existing four-step process, allowing devices to complete random access more efficiently by combining message transmission and acknowledgment in fewer steps, thus improving network productivity without proportionally increasing configuration complexity.
2Ease of operation
If PUCCH load is concentrated on the primary cell, then random access procedure is simplified, but network congestion and battery consumption increase
Solution Approach 1:
The patent segments the PUCCH load distribution by creating multiple PUCCH groups associated with different TAGs. Control signaling is distributed across secondary cells based on the TAG configuration, reducing the concentration of PUCCH transmissions on the primary cell. This segmentation reduces network congestion and allows devices to transmit control information more efficiently, lowering battery consumption.
Solution Approach 2:
The patent extracts the PUCCH transmission function from the primary cell and relocates it to secondary cells through the introduction of secondary TAGs. By taking out the control signaling load from the primary cell and placing it in secondary cells, the system reduces primary cell congestion while maintaining simplified random access procedures through the structured TAG-PUCCH group association.
3Productivity
If secondary TAGs are configured to distribute control signaling, then network efficiency is improved, but timing synchronization complexity increases
Solution Approach 1:
The patent segments the timing advance management by creating multiple independent TAGs, each with its own timing advance group. Each TAG can be independently configured and managed, allowing the system to distribute control signaling across multiple cells while maintaining independent timing synchronization for each group. This segmentation approach improves network efficiency by enabling parallel timing management without creating complex inter-dependent synchronization requirements.
Data Source
AI summary
A base station transmits, to a wireless device, at least one radio resource control (RRC) message comprising configuration parameters of an unlicensed cell. The base station transmits a first physical downlink control channel (PDCCH) to initiate a random access procedure on the unlicensed cell. In response to a listen-before-talk (LBT) procedure indicating a clear channel for uplink transmission of a first preamble of the random access procedure, the base station receives the first preamble via a random access channel (RACH) of the unlicensed cell and transmits a second PDCCH for a random access response (RAR). In response to the LBT procedure indicating an LBT failure, the base station receives a second preamble based on a random access resource selection procedure and does not transmit the second PDCCH for the RAR.