Unlicensed Cell Random Access Using LBT and Minimum Bandwidth
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Solution Overview
Problem
The challenge in LTE systems is the limited availability of radio spectrum, which hinders the deployment of LTE-Advanced systems requiring wider bandwidths, and the need for efficient random access procedures in unlicensed bands to ensure fair coexistence with other radio access technologies like Wi-Fi.
Innovation Solution
Carrier aggregation is employed to combine multiple component carriers, and a modified random access procedure is introduced for unlicensed bands, utilizing Listen-Before-Talk (LBT) and regulatory compliance mechanisms to ensure fair coexistence with Wi-Fi and maintain quality of service.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carrier aggregation is used to combine multiple component carriers to achieve wider bandwidth, then the network capacity and data rate are improved, but the device complexity and spectrum management difficulty increase
Solution Approach 1:
The patent segments the wide bandwidth into multiple component carriers (CCs), each operating independently with its own random access resources. This allows the system to achieve wide bandwidth benefits while managing complexity through modular, independent carrier handling rather than treating the entire bandwidth as a single resource pool.
Solution Approach 2:
The patent creates a universal random access framework that works across multiple component carriers with different bandwidths and configurations. The same random access procedure and resource allocation mechanisms can be applied universally to each CC, simplifying device implementation while supporting diverse carrier configurations.
2Speed
If random access procedure is implemented in unlicensed bands without regulatory compliance, then the access speed is improved, but interference with other radio access technologies increases
Solution Approach 1:
The patent implements Listen-Before-Talk (LBT) as a preliminary action before random access preamble transmission in unlicensed bands. The device performs channel sensing to detect ongoing transmissions and defers access until the channel is clear, ensuring fair coexistence with Wi-Fi and other RATs while maintaining efficient random access when the channel is available.
Solution Approach 2:
The patent incorporates feedback mechanisms where the base station provides channel access indicators and the device adjusts its random access behavior based on channel conditions and regulatory requirements. This feedback loop enables dynamic adaptation to unlicensed band conditions, balancing access speed with interference mitigation.
Data Source
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AI summary
The invention relates to a method for performing a random access procedure between a user equipment and a radio base station. The UE is configured with at least one unlicensed cell having an unlicensed cell frequency, via which the UE performs the random access procedure bandwidth. A minimum frequency bandwidth threshold is defined for transmissions via the unlicensed cell. The user equipment selects a random access preamble sequence for the random access procedure. A frequency bandwidth is determined by the UE for transmitting the random access preamble sequence via the unlicensed cell, the determined frequency bandwidth of the random access preamble sequence being at least the minimum frequency bandwidth threshold. The UE then transmits the random access preamble sequence to the radio base station such that at least the determined frequency bandwidth of the unlicensed cell is occupied.