Variable Spreading Factor Codes for NOMA Interference Separation
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Solution Overview
Problem
Current wireless communication systems, particularly those using non-orthogonal multiple access (NOMA) in 5G and new radio (NR) standards, face challenges in efficiently managing and separating data layers for multiple users without time, frequency, or spatial domain separation, leading to interference issues that affect spectral efficiency and user connection density.
Innovation Solution
The implementation of a two-stage scrambling technique using variable spreading factor codes for Resource Spread Multiple Access (RSMA) modulated streams, where different scrambling sequences with varying lengths are applied to distinguish between users and layers, enabling efficient interference cancellation and decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If non-orthogonal multiple access (NOMA) is used to increase user connection density, then more users can be supported without time, frequency, or spatial domain separation, but interference between users increases making it difficult to separate and decode data layers
Solution Approach 1:
The patent applies segmentation by dividing the scrambling process into two distinct stages: first scrambling the data layers, then scrambling the resulting signal with a second scrambling sequence. This two-stage segmentation allows the receiver to separately process and cancel interference from different users, resolving the contradiction between supporting more users and managing interference.
Solution Approach 2:
The patent introduces scrambled sequences as intermediary elements that mediate between multiple users sharing the same resources. These scrambling sequences act as unique identifiers and interference management tools, enabling the receiver to distinguish and separate user signals despite the non-orthogonal nature of the access scheme.
2Reliability
If scrambling sequences are used to distinguish between users and layers in NOMA, then user separation is enabled, but the complexity of generating and managing multiple scrambling sequences increases
Solution Approach 1:
The patent applies universality by designing scrambling sequences that serve multiple functions simultaneously: they distinguish between different users, differentiate data layers within the same user, and enable interference cancellation. This multi-functionality reduces the need for separate mechanisms, thereby managing complexity while maintaining reliable user separation.
Solution Approach 2:
The patent employs dynamic scrambling sequence selection where the scrambling sequences are generated based on user-specific parameters such as user identity and layer index. This dynamic generation approach allows flexible adaptation to different numbers of users and layers without requiring fixed, pre-configured sequences, thereby managing complexity through algorithmic flexibility.
3Productivity
If variable spreading factor codes are implemented for different users, then spectral efficiency is improved, but the complexity of codebook management and code assignment increases
Solution Approach 1:
The patent applies parameter changes by varying the spreading factor parameter across different users and data layers. Each user and layer is assigned a specific spreading factor that optimizes the spreading process for that particular signal, improving spectral efficiency through adaptive parameter selection rather than fixed code assignments.
Solution Approach 2:
The patent implements preliminary action by pre-generating codebooks containing spreading codes of various lengths before transmission. These pre-prepared codebooks enable rapid code selection and assignment during operation, reducing real-time processing complexity while maintaining the ability to optimize spectral efficiency through variable spreading factors.
Data Source
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AI summary
Aspects of the present disclosure provide techniques for variable spreading factor codes for non-orthogonal multiple access (NOMA). In an exemplary method, a base station assigns, from a first codebook of N short code sequences of length K, a subset of the short code sequences to a number of user equipments (UEs); receives a signal including uplink data or control signals from two or more of the UEs, wherein a first uplink data or control signal is sent using a first subsequence of one of the assigned short code sequences, and a second uplink data or control signal is sent using a second subsequence of one of the assigned short code sequences or using one of the assigned short code sequences; and decodes each uplink data or control signal in the signal based on the assigned short code sequences and subsequences of the assigned the short code sequences.