Random Access Preamble Structure for Large Cell Radius
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Solution Overview
Problem
Conventional LTE random access methods struggle with large cell sizes and power-limited environments, particularly in satellite mobile communication networks, where increased cell size leads to uncertainty in uplink timing and reduced data transmission resources due to longer preamble lengths, causing increased receiver complexity and insufficient transmission power.
Innovation Solution
A random access method and preamble structure that adjusts the subcarrier interval and preamble length to compensate for round-trip delay differences, using a cyclic prefix and guard time optimized for satellite systems, allowing for low-complexity frequency domain processing and increased transmission power while maintaining compatibility with conventional LTE.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the cell size is increased to support satellite mobile communication networks, then the coverage area is improved, but the uplink timing uncertainty increases
Solution Approach 1:
The patent changes the subcarrier interval parameter from conventional LTE values to 15 kHz specifically for large cell sizes. This parameter adjustment compensates for the increased uplink timing uncertainty by providing a coarser frequency grid that is more tolerant of timing variations, thereby resolving the contradiction between large coverage area and timing precision
2Duration of action of moving object
If the preamble length is increased to support larger cell sizes, then the round-trip delay coverage is improved, but the data transmission resources are reduced
Solution Approach 1:
The patent introduces dynamic preamble length configuration with multiple formats (0-6) that can be selected based on cell size and propagation delay requirements. This allows the system to use longer preambles only when necessary for large cell sizes, while using shorter preambles for smaller cells, thereby dynamically optimizing the balance between round-trip delay coverage and data transmission resources
3Device complexity
If the subcarrier interval is decreased to reduce receiver complexity, then the processing complexity is reduced, but the frequency resolution is worsened
Solution Approach 1:
The patent sets the subcarrier interval to 15 kHz for large cell sizes, which is coarser than conventional LTE configurations. This parameter change reduces the computational complexity of frequency domain processing and receiver operations while the resulting frequency resolution is sufficient for the intended application scenario of satellite mobile communication
4Reliability
If the transmission power is increased to compensate for path loss, then the link margin is improved, but the terminal power consumption increases
Solution Approach 1:
The patent employs partial action by using longer preambles and adjusted subcarrier intervals only when necessary for large cell sizes and high path loss conditions. For normal conditions, conventional parameters are used, thereby avoiding unnecessary power consumption while maintaining sufficient link margin when required
Data Source
AI summary
A random access method in a mobile communication system, the random access method for supporting random access with a cell size of about 100 kilometers (km) or more and a power limited terminal, and a preamble structure thereof are provided. While a conventional long term evolution (LTE) random access preamble sequence is reused, a difference in a round-trip delay time between terminals in a large cell area may be compensated. Additionally, since higher power transmission is achieved per bandwidth, a higher link margin may be secured. Also, compatibility with resource scheduling of the conventional LTE may be maintained. Random access may be supported in a large cell, and a preamble structure of a satellite mobile communication may be implemented based on terrestrial LTE.