Two-Step Random Access RNTI Mapping for Collision Avoidance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In the two-step random access procedure of 5G NR, there is a need to determine Radio Network Temporary Identifiers (RNTIs) for the physical uplink shared channel (PUSCH) and physical downlink shared channel (PDSCH) without a received Random Access Response message, and to differentiate between two-step and four-step access procedures to avoid collisions.
Innovation Solution
The terminal device determines a RNTI for the PUSCH in message A based on broadcasted system information, and the network node determines a second RNTI for the PDCCH CRC scrambling in message B, using functions or mappings of the first RNTI, such as hashing or subsets of bits, to differentiate between the two-step and four-step procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a four-step random access procedure is used, then the random access response can be properly received with timing advance, but the procedure takes more time and has more steps
Solution Approach 1:
The patent combines message 1 (PRACH preamble) and message 3 (PUSCH transport block) into a single message A transmission, and combines the random access response (message 2) and contention resolution message (message 4) into a single message B response. This merging reduces the four-step procedure to a two-step procedure, maintaining reliability while reducing time consumption.
Solution Approach 2:
The patent applies preliminary action by including the transport block in message A before receiving the random access response, allowing the UE to transmit data earlier in the procedure. The network also prepares the response message B in advance with both timing advance and contention resolution information, enabling faster processing.
2Adaptability or versatility
If RNTI values are selected from the standard range, then compatibility with existing systems is maintained, but collision risks increase in two-step procedure
Solution Approach 1:
The patent applies local quality by configuring different RNTI selection rules for different messages and procedures. For message A PUSCH, the UE selects from a first set of RNTI values, while for message B PDCCH, the network uses a second set of RNTI values. This differentiation ensures that RNTI collisions between two-step and four-step procedures are avoided, while maintaining compatibility with existing system ranges.
3Device complexity
If timing advance is not provided, then the procedure is simpler, but the cyclic prefix must be very large to accommodate timing variations
Solution Approach 1:
The network provides timing advance information in the message B response message, allowing the UE to adjust its transmission timing before the actual data transmission. This preliminary timing adjustment eliminates the need for excessively large cyclic prefixes while maintaining procedure simplicity.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Various embodiments of the present disclosure provide methods and apparatuses for determining radio network temporary identifier (RNTI) in a two-step random access procedure. A method of a terminal device, comprising: determining a request message for random access, wherein the request message comprises a preamble and a physical uplink shared channel, PUSCH, message and the PUSCH message is determined based on a first radio network temporary identity, RNTI; transmitting the request message; and obtaining a response message for random access based on a second RNTI, wherein the first RNTI and the second RNTI are the same or different.