NPRACH Preamble Multiplexing With OCCs for Higher UE Access Capacity
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Solution Overview
Problem
Existing wireless communications systems face challenges in increasing the capacity of narrowband physical random access channels (NPRACH) in networks, particularly in non-terrestrial networks, limiting the number of user equipment (UEs) that can simultaneously transmit NPRACH preambles.
Innovation Solution
The proposed solution involves multiplexing NPRACH preambles for multiple UEs by applying orthogonal cover codes (OCCs) to sets of symbols within each symbol group, allowing for efficient time-frequency resource utilization and differentiation between UE transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If NPRACH preambles are transmitted by multiple UEs simultaneously, then channel utilization and capacity are improved, but interference between UEs increases and detection difficulty worsens
Solution Approach 1:
The NPRACH preamble transmission resources are segmented into multiple orthogonal cover code sequences. Each UE is assigned a unique OCC sequence to modulate its preamble, dividing the shared time-frequency resources into orthogonal segments that can be independently detected without mutual interference
Solution Approach 2:
The system changes the modulation parameter by applying different orthogonal cover code sequences to different UEs' preambles. This parameter differentiation enables the receiver to distinguish between multiple simultaneous transmissions by correlating with the assigned OCC sequences, thereby improving detection capability in multi-UE scenarios
2Quantity of substance
If the number of NPRACH preambles is increased to support more UEs, then system capacity is improved, but resource conflict and collision probability increase
Solution Approach 1:
The system introduces a new dimension for resource differentiation by applying orthogonal cover code sequences in the code domain. This adds a fourth dimension (code) to the traditional time-frequency-resource allocation, enabling more UEs to share the same time-frequency resources without collision, thereby increasing capacity while maintaining reliability
3Productivity
If orthogonal cover codes are applied to symbol groups, then multiplexing capability is improved, but processing complexity increases
Solution Approach 1:
The orthogonal cover codes are applied selectively to specific symbol groups within the NPRACH preamble structure rather than all symbols. This partial application achieves the necessary multiplexing capability for supporting multiple UEs while limiting the processing complexity to only the essential symbol groups required for random access
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A user equipment (UE) may perform an access procedure for establishing or reestablishing a connection with a network entity. The UE may transmit, as part of the access procedure, one or more repetitions of a narrowband physical random access channel (NPRACH) preamble to the network entity. Each repetition of the one or more repetitions may include a set of symbol groups, and each symbol group of the set of symbol groups may include a set of symbols used by the UE for transmitting the NPRACH preamble. In some examples, the set of symbols may include a subset of symbols to which an OCC is applied. The set of symbols may be multiplexed with one or more other sets of symbols associated with respective preambles of one or more other UEs.