Adaptive Beam Subset Selection for Random Access in Wireless Systems
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Solution Overview
Problem
In wireless communication systems operating at extremely high frequency bands, such as LTE, achieving efficient random access is hindered by increased path loss, which necessitates beamforming with multiple antennas, leading to prolonged network access times for users, especially cell-center users who have better channel quality than cell-boundary users.
Innovation Solution
A method and apparatus for adaptively selecting a beam subset based on channel conditions to optimize random access preamble transmission, allowing the Mobile Station to determine and use beam subsets that satisfy predefined conditions for successful preamble transmission, thereby reducing network access time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If beamforming with multiple antennas is used to compensate for path loss in extremely high frequency bands, then beamforming gain increases, but network access time increases
Solution Approach 1:
The patent segments the complete beam set into multiple beam subsets based on beam directions. The terminal device transmits random access preambles using beams from only one selected subset rather than all beams, dividing the access process into staged attempts across different subsets to reduce overall access time while maintaining necessary beamforming gain.
Solution Approach 2:
The patent introduces dynamic selection of beam subsets based on terminal device conditions. The terminal adaptively chooses which beam subset to use for random access preamble transmission, allowing the system to dynamically adjust between using fewer beams (faster access) or more beams (better gain) based on current channel conditions and terminal capabilities.
2Reliability
If the random access preamble length is designed for cell-boundary users, then detection rate and false alarm rate requirements are met, but cell-center users experience unnecessarily long access times
Solution Approach 1:
The patent applies local quality by allowing different terminal devices to use different beam subsets based on their specific channel conditions. Cell-center users with good channel quality can use smaller beam subsets for faster access, while cell-boundary users with poorer channel quality use larger beam subsets to ensure reliable detection, thus optimizing access time for each user's local condition.
Solution Approach 2:
The patent changes the parameter of beam subset size based on user location and channel conditions. By adjusting which beams are included in the active subset, the system adapts the effective preamble transmission characteristics to match the user's channel quality, enabling cell-center users to achieve faster access without compromising the reliability required for cell-boundary users.
Data Source
AI summary
To adaptively determine a Tx beam subset for random access in a wireless communication system, a method for operating a Mobile Station (MS) includes determining at least one beam subset which satisfies a predefined condition, among a plurality of beam subsets, and transmitting random access preambles using Tx beams of the at least one beam subset. An MS in a wireless communication system includes a controller configured to determine at least one beam subset that satisfies a condition, among a plurality of beam subsets, and a transmitter configured to transmit random access preambles using Transmit (Tx) beams of the at least one beam subset, wherein the plurality of the beam subsets each comprise a plurality of beams radiating to different directions from one another. Other embodiments including a base station and a mobile station are also disclosed.