Random Access Response Grouping for Smaller PDSCH Transport Blocks
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Solution Overview
Problem
In LTE and NR, the transmission of a large quantity of random access preambles on a same random access occasion (RO) results in a large transport block size (TBS) of the physical downlink shared channel (PDSCH) carrying random access responses (RARs), leading to high modulation order or bit rate and poor demodulation performance.
Innovation Solution
RARs are transmitted based on groups, reducing the transport block size by using downlink control information (DCI) to scramble and indicate RAR groups, allowing flexible scheduling and reducing modulation order or bit rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a relatively large quantity of preambles are multiplexed on a same RO, then the random access capacity is improved, but a relatively large amount of RAR data is transmitted resulting in large TBS and poor demodulation performance
Solution Approach 1:
The patent divides RAR data into multiple RAR groups, where each group contains a subset of the total RAR data. Each RAR group is separately encoded and transmitted on the PDSCH with its own TBS calculation. This segmentation allows the system to maintain high random access capacity (by supporting many preambles) while keeping individual TBS values manageable, thus preserving demodulation performance.
2Productivity
If transmission resources are limited, then resource efficiency is improved, but modulation order or bit rate becomes very high resulting in poor demodulation performance
Solution Approach 1:
By segmenting RAR data into multiple groups transmitted separately, the patent enables efficient use of limited transmission resources while avoiding excessively high modulation orders. Each segment can be transmitted with appropriate modulation and coding parameters, preventing the need for very high bit rates that would degrade demodulation performance.
Solution Approach 2:
The patent introduces dynamic configuration of RAR groups through DCI signaling, allowing the network to adaptively adjust the number and size of RAR groups based on current channel conditions and resource availability. This dynamic approach optimizes resource efficiency while maintaining acceptable demodulation performance under varying transmission constraints.
Data Source
AI summary
Embodiments of this application provide a random access response method and an apparatus. The method includes: RARs associated with one RO are transmitted based on groups, so that a transport block size of RAR data transmitted each time is reduced, and N bits in DCI format 1_0 of CRC are scrambled by using a RA-RNTI to indicate scheduling information of N RAR groups in a PDSCH. Alternatively, DCI format 1_0 of CRC is scrambled by using identifiers of RAR groups, to correspondingly schedule the RAR groups in the PDSCH. According to this application, a problem of a large transport block caused by a large quantity of RARs being transmitted in a PDSCH can be avoided, so that a modulation order or a bit rate is reduced, and demodulation performance of a terminal device is improved.