PRACH RA-RNTI Indexing to Prevent Random Access Collisions
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Solution Overview
Problem
The collision of RA-RNTIs occurs when both RACH resources for single and multiple PRACH transmissions are configured at the same time instance, leading to increased latency in RACH procedures due to improper reception of RARs.
Innovation Solution
The method involves determining RA-RNTI based on a first index related to the time domain and a second index related to the frequency domain of the PRACH occasion, using an additional RACH configuration that includes an offset, and employing various methods to distinguish and configure different RACH configurations to prevent RA-RNTI collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If both RACH resources for single and multiple PRACH transmissions are configured at the same time instance, then coverage enhancement is improved, but RA-RNTI collision occurs leading to increased latency
Solution Approach 1:
The patent applies parameter changes by modifying the RA-RNTI calculation parameters. Specifically, it uses different OFDM symbol indices (first index vs. last index) and frequency domain indices to calculate distinct RA-RNTI values for single PRACH transmission and multiple PRACH transmission. This parameter differentiation resolves the collision issue while maintaining both transmission types, thereby improving coverage enhancement without increasing latency.
2Adaptability or versatility
If both RACH resources for single and multiple PRACH transmissions are configured at the same time instance, then transmission flexibility is improved, but RA-RNTI value collision occurs
Solution Approach 1:
The patent applies local quality by making the RA-RNTI calculation method specific to each transmission type. For single PRACH transmission, it uses one set of indices (first OFDM symbol index, first frequency index), while for multiple PRACH transmission, it uses another set (last OFDM symbol index, last frequency index). This localized differentiation ensures unique RA-RNTI values for each transmission scenario, maintaining both flexibility and reliability.
3Reliability
If additional RACH configuration with offset is used to distinguish PRACH occasions, then RA-RNTI collision is prevented, but configuration complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-configuring offset values and index mappings before RACH transmission occurs. The network configures the UE with specific offset parameters and index relationships in advance, so that when PRACH transmission happens, the UE can directly calculate the correct RA-RNTI without complex real-time decisions. This preliminary configuration reduces runtime complexity while ensuring collision-free RA-RNTI generation.
Data Source
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AI summary
A method according to one embodiment of the present disclosure comprises the steps of: receiving a RACH configuration; and transmitting a random access preamble on the basis of an RA-RNTI. The RA-RNTI is determined on the basis of i) a first index related to a time domain of a PRACH occasion and ii) a second index related to a frequency domain of the PRACH occasion. The RACH configuration is based on an additional RACH configuration. The first index or the second index is determined on the basis of the additional RACH configuration.