Two-Step Random Access Contention Resolution via MsgB Segmentation
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Solution Overview
Problem
In the NR radio communication system, contention resolution in the two-step random access procedure is necessary but not effectively addressed, as existing methods do not clearly define how to include information from the Msg2 or Msg4 of a four-step random access procedure in the MsgB of a two-step procedure.
Innovation Solution
User equipment is equipped with a transmitter to send a random access preamble or identifier to a base station, a receiver to obtain a response signal, and a control unit to determine successful contention resolution by matching information in the downlink signal with the user equipment's identifier, using a MAC CE or C-RNTI in the random access response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a two-step random access procedure is implemented to reduce access delay and improve efficiency, then random access speed is improved, but contention resolution capability deteriorates because existing methods do not clearly define how to include information from Msg2 or Msg4 in MsgB
Solution Approach 1:
The patent combines the functions of Msg2 (random access response) and Msg4 (contention resolution message) from the four-step procedure into a single MsgB in the two-step procedure. This merging allows the base station to include both random access response information and contention resolution information in one downlink message, thereby maintaining contention resolution capability while reducing access delay.
Solution Approach 2:
The MsgB in the two-step random access procedure is designed to serve multiple functions simultaneously: it acts as both a random access response (similar to Msg2) and a contention resolution message (similar to Msg4). This multi-functionality allows the two-step procedure to achieve both speed improvement and reliable contention resolution.
2Reliability
If information from Msg2 and Msg4 is integrated into MsgB, then contention resolution is enabled, but message structure complexity increases
Solution Approach 1:
The patent segments the integrated information in MsgB into distinct fields: a random access response field (containing timing advance, uplink grant, and temporary C-RNTI) and a contention resolution field (containing either a UE identifier or a MAC CE). This segmentation allows the complex message to be processed systematically by both the base station and user equipment.
Solution Approach 2:
The patent introduces a MAC CE (Medium Access Control Control Element) as an intermediary structure to carry contention resolution information within MsgB. This standardized intermediary format simplifies the integration of different information types and provides a familiar structure for equipment already designed to process MAC CEs in four-step procedures.
Data Source
AI summary
User equipment includes a transmitter configured to transmit a random access preamble or an identifier of the user equipment to a base station apparatus in a two-step random access procedure, a receiver configured to receive a response signal corresponding to at least one of the random access preamble and the identifier of the user equipment, and a downlink signal based on the response signal, from the base station apparatus, and a control unit configured to determine that a contention resolution is successful when information included in the downlink signal matches a part of or all of the identifier of the user equipment.