PRACH Resource Allocation in LTE Unlicensed TDD Systems
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Solution Overview
Problem
LTE systems operating in unlicensed frequency bands with TDD mode face challenges in dynamic uplink/downlink configurations, leading to inadequate random access capabilities due to lack of flexibility in time-frequency resource allocation and interference with Wi-Fi systems.
Innovation Solution
A resource configuration method that transmits indication information to terminals to dynamically allocate time-frequency resources for PRACH, allowing for flexible subframe changes and optimized random access processes, even with fewer uplink subframes, by indicating the position of the first uplink subframe or UpPTS and configuring six frequency domain resource blocks in each uplink subframe or UpPTS.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fully dynamic uplink/downlink subframe configuration is implemented, then the adaptability to dynamic services and LBT mechanism is improved, but the reliability of random access is worsened due to possible absence of uplink subframes
Solution Approach 1:
The patent configures PRACH resources in advance in specific uplink subframes or UpPTS within a frame structure, ensuring that random access opportunities are pre-established before dynamic subframe changes occur. This preliminary configuration guarantees that even with dynamic uplink/downlink adjustments, terminals always have predetermined uplink resources available for random access, thus maintaining access reliability while allowing service adaptability.
2Device complexity
If traditional fixed TDD uplink/downlink configuration is used, then the device complexity is reduced, but the adaptability to dynamic services and LBT mechanism is worsened
Solution Approach 1:
The patent introduces dynamic uplink/downlink subframe configuration where each subframe can be changed to uplink or downlink at any time based on service requirements and LBT results. This dynamic adjustment mechanism allows the system to adapt to varying traffic patterns and channel conditions while the PRACH resource configuration provides a structured framework that manages the complexity of such dynamic changes.
3Productivity
If downlink subframe conversion to uplink during channel occupation is performed, then the productivity of channel utilization is improved, but the reliability of channel occupation is worsened due to LBT detection and channel loss
Solution Approach 1:
The patent segments the 10ms frame into specific subframes with predetermined functions, designating certain uplink subframes or UpPTS for PRACH resources. This segmentation creates clear boundaries between downlink transmission periods and uplink random access opportunities, allowing efficient channel utilization during downlink while ensuring reliable random access in designated uplink subframes without requiring repeated LBT detections that could cause channel loss.
Data Source
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AI summary
A resource allocation method, device and base station for when an LTE system in an unlicensed frequency band is running in TDD mode a dynamic uplink-downlink configuration, wherein, the method comprises: transmitting to a terminal indication information used to indicate a time-frequency resource occupied by a physical random access channel (PRACH), so as to enable the terminal to initiate a random access process via a corresponding time-frequency resource, wherein the indication information, when indicating a time-domain frequency occupied by the PRACH, only indicates the position of the first subframe occupied by the PRACH, and the first subframe is an uplink subframe or uplink pilot timeslot (UpPTS).