Random Access Preamble Transmission via Alternative Frequency Resources
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Solution Overview
Problem
Wireless communication systems face inefficiencies in random access procedures due to failed preamble transmissions, particularly at the cell edge or under poor channel conditions, leading to excessive resource usage and reduced connection reliability.
Innovation Solution
A user equipment (UE) transmits a second random access preamble using an alternative frequency resource if no response is received within a specified time frame after the initial attempt, with the alternative resource having a different subcarrier spacing and potentially longer symbol duration, allowing for enhanced robustness and reduced subsequent transmission likelihood.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a UE transmits random access preambles using the same frequency resource for retransmission, then the transmission procedure is simple, but the likelihood of successful reception under poor channel conditions remains low
Solution Approach 1:
The patent changes the frequency resource parameter for preamble retransmission by selecting an alternative frequency resource from a set of configured resources. This parameter change allows the retransmitted preamble to be received under different channel conditions, improving reception reliability when the initial transmission fails due to poor channel conditions.
Solution Approach 2:
The patent introduces a frequency dimension diversity to the random access procedure by configuring multiple frequency resources for preamble transmission. Instead of retransmitting on the same frequency, the UE can switch to a different frequency resource, adding dimensional diversity to overcome frequency-selective fading and improve reception reliability.
2Reliability
If a UE performs multiple retransmissions of random access preambles, then connection establishment reliability improves, but excessive resource usage occurs under poor channel conditions
Solution Approach 1:
The patent changes the frequency resource parameter for each retransmission attempt, selecting from a set of configured frequency resources. This allows the system to improve connection establishment reliability through multiple attempts while managing resource usage by distributing transmissions across different frequency resources rather than persisting on a single failing resource.
Solution Approach 2:
The base station pre-configures a set of alternative frequency resources for preamble transmission before the random access procedure begins. This preliminary action enables the UE to quickly switch to alternative resources when initial transmissions fail, improving reliability without requiring complex real-time resource selection and reducing overall resource usage by avoiding prolonged attempts on failing resources.
3Reliability
If a base station monitors only the original frequency resource for random access preambles, then the monitoring procedure is simple, but preambles transmitted on alternative frequencies are not received
Solution Approach 1:
The base station's frequency resource set is designed to be universal, where each frequency resource in the set can serve as both an initial transmission resource and an alternative retransmission resource. The base station monitors all frequencies in this universal set, enabling it to detect preambles regardless of which specific frequency the UE chooses for transmission, thereby improving detection reliability while maintaining a systematic monitoring approach.
4Reliability
If UEs at cell edge or with poor channel conditions use standard random access procedures, then the procedure is standardized and simple, but successful preamble reception is unlikely
Solution Approach 1:
The patent enables UEs to change the frequency resource parameter when experiencing poor channel conditions or cell edge scenarios. By selecting an alternative frequency resource from a configured set, the UE adapts to different propagation conditions, improving preamble reception success rate for users in challenging locations while maintaining compatibility with standardized procedures.
Solution Approach 2:
The base station pre-configures alternative frequency resources specifically to help UEs in poor channel conditions or cell edge scenarios. This preliminary configuration provides adaptability to edge users without requiring complex real-time channel assessment, allowing them to switch to alternative frequencies that may experience better propagation conditions.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A user equipment (UE) may transmit a first-attempt random access preamble to a base station via a first frequency resource. The first frequency resource may be within a first bandwidth part (BWP), a first component carrier (CC), a first frequency subband, or any combination thereof. If the UE fails to detect a random access response (RAR) for the first-attempt random access preamble within the time period, the UE may transmit a second-attempt random access preamble to the base station. In some examples, the UE may transmit the second-attempt random access preamble via a different, second frequency resource, which may be within a second BWP, a second CC, a second frequency subband, or any combination thereof. The base station may transmit an indication of the second frequency resource to the UE.