Lattice-Coded Downlink Multiplexing Without SIC Error Propagation
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Solution Overview
Problem
Current NOMA systems face challenges in spectral efficiency and error propagation due to severe interference, especially with large numbers of users, and lack specified coding schemes, which degrades performance.
Innovation Solution
The method involves using finite field linear encoders to form lattice code signals, weighting them with coefficients formed from products of distinct primes, and combining these signals to create a lattice superposition codeword, allowing for effective extraction of individual user signals through modulo lattice operations, while adapting power allocation based on channel conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If orthogonal multiple access (OMA) schemes are used to transmit multiple signals from multiple users, then system-level throughput performance is maintained with simple single-user detection, but spectral efficiency is sacrificed to keep orthogonality among users
Solution Approach 1:
The patent changes the fundamental parameter of signal orthogonality to non-orthogonality, allowing multiple user signals to share the same time-frequency resources. By using lattice code construction with modular arithmetic properties, the system enables signal separation through modulo operations at the receiver, achieving higher spectral efficiency while maintaining reliable detection through the algebraic structure of lattice codes
2Ease of operation
If conventional SIC decoding is adopted in NOMA, then multi-user signal separation is achieved, but performance is significantly degraded due to severe error propagation among different coding layers
Solution Approach 1:
The patent extracts the error propagation problem by using lattice code construction where each user's signal is encoded with a distinct prime number. The modulo operation at the receiver allows direct extraction of each user's signal independent of others, eliminating the sequential dependency and error propagation inherent in conventional SIC decoding
Solution Approach 2:
The lattice code structure acts as an intermediary that transforms the signal separation problem. By embedding user signals in lattice code structures with distinct prime numbers and using modulo operations, the system mediates between the superimposed signals and the individual user decoders, enabling error-free signal extraction without sequential interference cancellation
3Adaptability or versatility
If multiple users are multiplexed in the power-domain with different power allocation coefficients, then users with poorer channel conditions can decode their messages by treating others' information as noise, but the system lacks specified coding schemes leading to degraded performance
Solution Approach 1:
The patent changes the coding scheme parameter from conventional codes to lattice codes with prime number-based construction. This algebraic structure enables the system to maintain adaptability to different channel conditions while achieving superior performance through the mathematical properties of lattice codes and modular arithmetic, which provide inherent error correction and signal separation capabilities
Data Source
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AI summary
A network node, network node method, user equipment, user equipment method and computer program where the method performed at a network node comprises: encoding a plurality of signals destined for a plurality of user equipment using a plurality of linear encoders each configured to generate codewords over finite fields, where each codeword corresponds to a distinct prime which may be determined by the size of finite field of this codeword; mapping each of the plurality of encoded signals into lattice codewords; weighting each of the plurality of lattice codeword signals by multiplying the signals by respective weighting coefficient that are a product of the distinct primes excluding the prime of that lattice codeword; and combining the plurality of weighted lattice signals to form a signal having a lattice code construction and outputting the signal.