NTN NPRACH Random Access Responses With OCC Index Matching
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Solution Overview
Problem
In non-terrestrial networks (NTN), the challenge of efficiently multiplexing orthogonal cover codes (OCC) for NPRACH preambles is significant due to long distances and large coverage areas, leading to frequent preamble collisions and inefficient communication capacity.
Innovation Solution
Implementing OCC multiplexing methods such as intra-repetition, inter-repetition, and combined OCC multiplexing, along with indicating the OCC index in NPDCCH DCI format N1, RA-RNTI formula adjustments, and MAC CE to resolve collisions and enhance NPRACH detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If OCC multiplexing is implemented for NPRACH preambles in NTN, then communication capacity and efficiency are improved, but device complexity and signal processing requirements increase
Solution Approach 1:
The patent segments the OCC multiplexing process into distinct components: intra-repetition OCC multiplexing that operates within individual preamble repetitions, and inter-repetition OCC multiplexing that operates across multiple repetitions. This segmentation allows the system to manage complexity by handling OCC operations at different granularities rather than applying a single complex multiplexing scheme to the entire preamble structure.
Solution Approach 2:
The patent introduces OCC multiplexing as an additional dimension for distinguishing NPRACH preambles beyond the traditional preamble index. By adding the OCC index dimension, the system can identify and respond to preambles using a two-dimensional addressing scheme (preamble index + OCC index), thereby increasing communication capacity without requiring additional time-frequency resources.
2Reliability
If OCC multiplexing is used to distinguish NPRACH preambles, then collision frequency is reduced, but the difficulty of detecting and measuring preamble parameters increases
Solution Approach 1:
The patent performs preliminary determination of the OCC index at the base station before generating the random access response. The base station identifies the OCC index used by the UE in the transmitted preamble and incorporates this information into the response message. This preliminary action simplifies the UE's detection task, as the UE can directly compare the indicated OCC index with its transmitted OCC index without performing complex analysis.
Solution Approach 2:
The patent implements a feedback mechanism where the base station echoes back the OCC index to the UE in the random access response. This feedback allows the UE to verify whether the base station correctly identified its preamble transmission, thereby improving detection accuracy and enabling collision resolution through direct comparison of the indicated OCC index with the transmitted OCC index.
3Speed
If multiple OCC multiplexing methods are implemented, then network responsiveness is improved, but device complexity increases
Solution Approach 1:
The patent provides dynamic OCC multiplexing capabilities that can be adapted to different network conditions and coverage requirements. The system supports configurable parameters such as the number of OCC sequences and the specific multiplexing method (intra-repetition, inter-repetition, or combined), allowing the base station to optimize performance for varying signal conditions, coverage enhancement levels, and traffic patterns without requiring separate hardware for each scenario.
Data Source
AI summary
An internet of things (IoT) non-terrestrial network (NTN) device user equipment (UE) is described. The UE includes receiving circuitry configured to receive narrowband physical random access channel (NPRACH) configurations including NPRACH resource configuration, repetition parameters, orthogonal cover code (OCC) multiplexing methods and OCC multiplexing factors. The receiving circuitry is also configured to receive a narrowband physical downlink control channel (NPDCCH) downlink control information (DCI) format N1 and cyclic redundancy check (CRC) scrambled by a random access-radio network temporary identifier (RA-RNTI) for random access response (RAR) in an RA response window. The receiving circuitry is also configured to determine an OCC index indicated in the NPDCCH or the RAR, and compare the determined OCC index with a selected OCC index. Transmitting circuitry is configured to select an NPRACH resource, randomly select an OCC index for an OCC multiplexing and transmit NPRACH preambles.