Non-orthogonal Coded Multiple Access for Massive Connectivity
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Solution Overview
Problem
Next-generation wireless communication systems face challenges in accommodating explosive data traffic, increasing transfer rates, supporting a large number of connected devices, and achieving low end-to-end latency and high energy efficiency, particularly in contention-based multiple access schemes which suffer from high decoding error rates and complex interference management.
Innovation Solution
The proposed solution involves a contention-based multiple access scheme that uses non-orthogonal coded multiple access (NCMA) with UE-specific non-orthogonal code covers (NCC) to minimize multi-user interference by allocating non-orthogonal codes to each user, enabling efficient resource sharing and interference control through Grassmannian line packing and chordal distance maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If non-orthogonal coded multiple access (NCMA) is used to support massive connectivity and improve frequency usage efficiency, then the number of connected devices and spectral efficiency increase, but multi-user interference and decoding error rates increase
Solution Approach 1:
The patent applies local quality by assigning UE-specific non-orthogonal code covers (NCC) to different user equipments. Each UE receives a unique code cover from a codebook, which provides localized code differentiation. This allows multiple UEs to share the same time-frequency resources while maintaining distinguishable signals through their unique code covers, thereby supporting massive connectivity while managing interference at the user-specific level.
Solution Approach 2:
The patent employs parameter changes by utilizing Grassmannian line packing to optimize the codebook design. The codebook is constructed with specific geometric properties (chordal distance optimization) that change the statistical characteristics of multi-user interference. By carefully designing the code parameters to maximize minimum chordal distance, the system transforms the interference structure from harmful to manageable, reducing decoding error rates while maintaining high user capacity.
2Object-generated harmful factors
If non-orthogonal codes are allocated to each user to minimize multi-user interference, then interference control improves, but system complexity increases due to codebook management and chordal distance calculations
Solution Approach 1:
The patent applies preliminary action by pre-generating and storing optimized codebooks with Grassmannian line packing properties before actual communication occurs. The complex chordal distance optimization and codebook construction are performed in advance, allowing the system to simply look up and assign pre-optimized code covers to UEs during operation. This eliminates the need for real-time complex calculations, reducing system complexity while maintaining interference minimization benefits.
3Loss of time
If grant-free uplink data transmission is implemented to reduce latency, then end-to-end latency decreases, but resource collision and decoding errors increase due to contention-based access
Solution Approach 1:
The patent applies local quality in grant-free transmission by assigning unique UE-specific code covers that provide localized signal differentiation. Even when multiple UEs contend for the same time-frequency resources without grants, their signals remain distinguishable through their unique code covers. This reduces resource collision impact and decoding errors while maintaining the low-latency benefit of grant-free access.
Solution Approach 2:
The patent employs feedback mechanisms where the base station receives uplink data from multiple UEs using the same time-frequency resources, performs multi-user detection based on the known codebooks and UE-specific code covers, and provides feedback for hybrid ARQ (HARQ) processes. This feedback enables the system to handle contention-based access reliably by identifying and correcting decoding errors, thereby reducing resource collision impact while maintaining low latency.
Data Source
AI summary
Provided are a method and an apparatus for transmitting uplink data on the basis of contention in a wireless communication system. Specifically, a terminal receives, from a base station, allocation information for a contention zone in one resource zone. The allocation information includes a configuration field indicating locations and the number of contention zones. The terminal determines whether repetition of uplink data is to be performed, on the basis of downlink channel information. When it is determined that the repetition of uplink data is to be performed, the terminal transmits, to the base station, uplink data through all contention zones indicated by the configuration field. When it is determined that the repetition of uplink data is not to be performed, the terminal transmits, to the base station, uplink data through one contention zone arbitrarily selected from among all the contention zones indicated by the configuration field.