RNTI Offset for 2-Step and 4-Step RACH Differentiation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing wireless communications networks face challenges in efficiently differentiating between two-step and four-step random access procedures, particularly when multiple devices transmit random access messages on the same slot using frequency division multiplexing, leading to ambiguity in radio network temporary identifiers (RNTIs).
Innovation Solution
The method involves calculating a radio network terminal identifier (RNTI) for communications devices performing a two-step random access process by adding an offset to the index of the first OFDM symbol of the PRACH occasion, ensuring the RNTI is distinct from that used for four-step RACH processes. This offset is used in the MsgB-RNTI equation to differentiate between the two types of random access procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple devices transmit random access messages on the same slot using frequency division multiplexing, then resource utilization is improved, but ambiguity in radio network temporary identifiers occurs
Solution Approach 1:
The patent applies local quality by making the RNTI calculation method specific to the random access type. Two-step RACH uses a different calculation formula (with offset=0) compared to four-step RACH (with offset≠0), allowing each local case to have its own identifier generation rule. This resolves the ambiguity while maintaining frequency division multiplexing capability.
Solution Approach 2:
The patent changes the parameter 'offset' in the RNTI calculation formula based on the random access type. By setting offset=0 for two-step RACH and offset≠0 for four-step RACH, the system generates distinct RNTIs for different access types even when they share the same time slot and frequency resources, thus preventing identifier ambiguity.
2Device complexity
If a unified RNTI calculation method is used for both two-step and four-step RACH, then system complexity is reduced, but differentiation between access types becomes difficult
Solution Approach 1:
The patent segments the RNTI calculation method into two distinct formulas based on random access type. The first formula (for two-step RACH) uses offset=0, while the second formula (for four-step RACH) uses offset≠0. This segmentation allows the system to maintain low complexity by using simple arithmetic operations while achieving effective differentiation between access types.
Data Source
AI summary
A method of operating a communications device in a wireless communications network comprises transmitting a random access message on a wireless access interface, the random access message comprising a selected random access preamble. The method further comprises receiving a resource allocation message comprising an indication of downlink communications resources allocated for the transmission of a random access response message combined with a radio network terminal identifier which identifies the communications device which transmitted the random access message, determining that the resource allocation message identifies the communications device, and in response to determining that the resource allocation message identities the communications device, decoding the signals transmitted using the allocated downlink communications resources.