Random Access Preamble Repetitions for Wireless Reliability
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Solution Overview
Problem
Wireless communication systems face reliability issues in two-step random access procedures due to unsuccessful transmissions of random access preambles, primarily caused by poor channel conditions and interference, which reduces the likelihood of successful message reception by the network entity.
Innovation Solution
The proposed solution involves configuring user equipment (UE) to transmit multiple repetitions of random access preambles and payloads based on measurements of synchronization signals and received power thresholds, allowing the UE to adjust transmission parameters dynamically to improve reliability, specifically by transmitting on PRACH resources for preambles and PUSCH resources for payloads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a UE transmits a random access preamble in a two-step random access procedure, then the connection establishment is initiated, but the transmission may be unsuccessful due to poor channel conditions and interference
Solution Approach 1:
The network entity provides configuration information in advance, including received power thresholds and repetition parameters, so the UE can prepare appropriate transmission parameters before attempting random access. This preliminary configuration enables the UE to adapt its transmission strategy based on measured signal conditions, improving the likelihood of successful preamble transmission despite poor channel conditions.
Solution Approach 2:
The UE dynamically changes transmission parameters including the number of preamble repetitions, power level, and resource selection based on measured received power of synchronization signals and comparison with thresholds provided by the network. This parameter adaptation allows the UE to optimize transmission reliability under varying channel conditions and interference levels.
2Reliability
If the UE transmits multiple repetitions of random access preambles, then the reliability of message transmission is improved, but the use of time and frequency resources increases
Solution Approach 1:
The system transitions from static random access parameters to dynamic parameter selection. The UE determines the number of repetitions and transmission power based on real-time measurements of synchronization signal received power and network-provided thresholds. This dynamic adaptation allows the system to use more repetitions only when channel conditions warrant it, optimizing the trade-off between reliability and resource consumption.
Solution Approach 2:
The network entity configures multiple parameter sets including different received power thresholds and corresponding repetition numbers. The UE selects appropriate parameters based on measured signal conditions, changing transmission parameters adaptively rather than using fixed repetition counts. This enables efficient resource usage by matching repetition levels to actual channel quality.
3Adaptability or versatility
If the UE determines transmission parameters based on synchronization signal measurements and power thresholds, then the adaptability to channel conditions is improved, but the complexity of the transmission process increases
Solution Approach 1:
The UE autonomously determines its transmission parameters by measuring synchronization signal received power and comparing it with thresholds provided by the network. The UE independently selects the number of repetitions and power level without requiring complex network control or coordination during the random access process. This self-service approach simplifies the overall system complexity while maintaining high adaptability to channel conditions.
Solution Approach 2:
The network entity provides feedback in the form of configured thresholds and parameter recommendations based on network conditions. The UE uses this feedback information to make informed decisions about transmission parameters, creating a feedback loop that improves adaptability without requiring complex real-time interaction during the random access procedure itself.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A user equipment (UE) may receive, from a network entity, one or more synchronization signals of a synchronization signal block (SSB). The UE may receive, from the network entity, a system information message indicating a received power threshold associated with a two-step random access procedure. The UE may transmit, to the network entity in accordance with the two-step random access procedure, a first message (e.g., msgA) of the two-step random access procedure. The first message may include a first number of repetitions of a random access preamble, a second number of repetitions of a random access payload, or both. The UE may determine the first number of repetitions and the second number of repetitions based on measurements of the one or more synchronization signals and the received power threshold indicated by the system information message.