Parallel Preamble Transmission for NOMA Uplink Detectability
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Solution Overview
Problem
In non-orthogonal multiple access (NOMA) systems, the limited number of demodulation reference signals (DMRSs) available for uplink transmission leads to inefficiencies and reduced detectability performance at the base station.
Innovation Solution
User equipment (UEs) implement parallel transmission of preamble sequences with uplink data, splitting data into layers and assigning different signature sequences based on cross-correlation values, to enhance detectability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the system supports a large number of uplink data transmissions using signature sequences, then the quantity of supported UEs increases, but the detectability performance deteriorates due to limited DMRS resources
Solution Approach 1:
The preamble sequence is segmented into multiple segments that are distributed across different data layers. Each segment is modulated independently and transmitted through multiple layers, allowing the base station to reconstruct the complete preamble sequence by combining signals from all layers, thereby maintaining detectability performance while supporting multiple UEs
Solution Approach 2:
The patent transitions from single-layer preamble transmission to multi-layer transmission, adding the layer dimension to the transmission structure. By mapping preamble segments to different spatial layers and utilizing multi-dimensional signal processing at the receiver, the system achieves improved detectability while supporting increased UE capacity
2Reliability
If more DMRSs are allocated to improve detectability, then data detection performance improves, but the system capacity for supporting UEs decreases due to resource constraints
Solution Approach 1:
The patent merges the preamble sequence with data layers by distributing preamble segments across multiple data layers. This combining approach allows the base station to detect preambles even when individual layer signals are weak, improving detection performance without requiring additional dedicated DMRS resources that would reduce system capacity
3Ease of operation
If preamble sequences are transmitted without data layers, then transmission simplicity is maintained, but detectability performance deteriorates in NOMA systems
Solution Approach 1:
The data layers serve dual functions: carrying user data and transmitting preamble sequence segments. This multi-functionality allows the same transmission resources to provide both data communication and detection capabilities, maintaining transmission efficiency while improving detectability in NOMA environments
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. In some systems (e.g., non-orthogonal multiple access (NOMA) systems), a base station may serve a large number of user equipments (UEs) on the uplink. To improve detectability for these uplink transmissions (e.g., if reference signals are not available for the transmissions), the UEs may implement parallel transmissions of preambles with uplink data. A UE may split the uplink data into one or more data layers, and may select one or more preamble layers to transmit superposed with the data layers. These preambles may be sequences known to both the UE and the base station to aid in detectability. The UE may assign different signature sequences to each of these layers based on cross-correlation values (e.g., assigning sequences with higher cross-correlation values to the data layers for improved detectability), and may scramble the layers into a single shared signal for transmission.