Dynamic LBT Determination for PRACH Transmission in LAA Cells
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Solution Overview
Problem
Current LTE systems face inefficiencies in random access transmission, particularly in the use of unlicensed bands and the determination of uplink LBT procedures for PRACH transmissions, which affect the reliability and efficiency of communication.
Innovation Solution
A terminal and base station apparatus configuration that includes a reception processing unit for receiving DCI format 1C with CC-RNTI scrambled CRC parity bits, a channel measurement unit for performing uplink LBT, and a transmission processing unit for transmitting preambles in LAA cells, where the type of uplink LBT procedure is determined based on the presence of PRACH resources within specific subframes and uplink duration indicated by the DCI format 1C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uplink LBT procedure is performed before PRACH transmission in LAA cell, then channel access reliability is improved, but transmission delay increases due to additional listening time
Solution Approach 1:
The patent applies dynamics by making the LBT procedure optional rather than fixed. The terminal dynamically selects whether to perform LBT based on the subframe type determined from the relationship between uplink subframe number and downlink subframe number. For example, in certain subframe configurations (e.g., when uplink subframe number is even and downlink subframe number is odd), LBT is skipped, while in others it is performed, optimizing the balance between reliability and delay adaptively.
Solution Approach 2:
The patent changes the parameter of LBT execution status based on subframe timing parameters. By calculating the relationship between uplink subframe number and downlink subframe number, the system determines whether the PRACH resource falls within an uplink duration without downlink physical channels. This parameter-based control enables selective LBT execution, reducing unnecessary listening delays while maintaining reliability when needed.
2Productivity
If PRACH resource is allocated in subframe with downlink physical channel, then resource utilization is improved, but interference risk increases
Solution Approach 1:
The patent applies preliminary action by determining the subframe configuration and LBT requirement before PRACH transmission. The terminal calculates the relationship between uplink and downlink subframe numbers in advance to identify whether the PRACH resource is in a subframe without downlink physical channels. This preliminary determination allows the terminal to perform LBT when needed to avoid interference, while skipping LBT when safe, thus managing interference risk proactively.
Solution Approach 2:
The patent uses the subframe timing relationship (calculated from uplink subframe number and downlink subframe number) as an intermediary to mediate between resource allocation and interference avoidance. This intermediary determination indicates whether LBT should be performed, serving as a decision criterion that balances resource utilization with interference prevention without requiring direct coordination between uplink and downlink transmissions.
3Productivity
If LBT procedure type is determined dynamically, then communication efficiency is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the LBT decision process into distinct cases based on subframe timing relationships. The terminal segments the determination into checking whether uplink subframe number and downlink subframe number satisfy specific relationships (e.g., even/odd patterns). This segmentation simplifies the complexity by providing clear, rule-based decision paths rather than requiring complex real-time analysis, making the dynamic determination more manageable.
Data Source
AI summary
Provided is a terminal apparatus configured to receive a PDCCH including DCI format 1C to which CRC parity bits scrambled with a CC-RNTI are added, and to transmit a preamble in an LAA cell, wherein a type of an uplink LBT procedure for a PRACH transmission is determined based on whether or not a PRACH resource to be used for the PRACH transmission is at least included in a subframe in an uplink duration in which no downlink physical channel is received, and a value of the uplink duration is given based at least on an ‘Uplink transmission duration and offset indication’ field included in the DCI format 1C.