Variable Spreading Factor Codes for Dense NOMA Uplink Decoding
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Solution Overview
Problem
Current wireless communication systems, particularly in 5G and new radio (NR) standards, face challenges in efficiently managing multiple access technologies to support increasing mobile broadband demands, requiring improved communication methods between access points and user equipment (UEs) to enhance spectral efficiency and user connection density.
Innovation Solution
The implementation of a method that assigns subsets of short code sequences from a codebook to UEs, using variable spreading factor codes for uplink data or control signals, allowing for simultaneous transmission and decoding of multiple signals without time, frequency, or spatial domain separation, employing a two-stage scrambling technique with different scrambling sequences to distinguish between UEs and layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If orthogonal multiple access technologies (TDMA, FDMA, OFDMA) are used to support multiple users, then system reliability and connection stability are improved, but spectral efficiency and user connection density deteriorate due to resource allocation overhead and orthogonal constraints
Solution Approach 1:
The patent changes the fundamental parameter of code length from fixed to variable. By allowing different code lengths (spreading factors) for different users, the system can dynamically adjust resource allocation without requiring orthogonal separation, thereby improving spectral efficiency while maintaining connection stability through the codebook structure
Solution Approach 2:
The system transitions from static orthogonal resource allocation to dynamic non-orthogonal access. Users can be dynamically assigned different subsets of code sequences from the codebook, allowing flexible adaptation to varying traffic demands and channel conditions, which enhances both spectral efficiency and user connection density
2Measurement precision
If code division multiple access (CDMA) with fixed code sequences is used, then user identification and signal separation are improved, but system adaptability and support for diverse usage scenarios deteriorate
Solution Approach 1:
The codebook is segmented into multiple code sequences of different lengths. Each user can be assigned a specific subset of these sequences, allowing the system to provide precise signal separation for identified users while simultaneously adapting to diverse usage scenarios by selecting appropriate code lengths and subsets for different service requirements
Solution Approach 2:
The codebook structure serves multiple functions: it enables user identification through unique code assignments, provides signal separation through orthogonal or near-orthogonal properties, and supports diverse usage scenarios through variable code length selection. This multi-functional design enhances both measurement precision and system adaptability
3Productivity
If variable spreading factor codes are implemented for non-orthogonal multiple access, then spectral efficiency and user connection density are improved, but signal decoding complexity and computational requirements worsen
Solution Approach 1:
The codebook is pre-designed with specific orthogonal or near-orthogonal properties, and code subsets are pre-assigned to users. This preliminary structuring allows the system to achieve high spectral efficiency through non-orthogonal access while reducing decoding complexity, as the pre-established code properties facilitate more efficient signal separation and user identification during the decoding process
Data Source
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.