Joint Modulation Gray Mapping for NOMA Receiver Complexity
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Solution Overview
Problem
In traditional Non-Orthogonal Multiple Access (NOMA) wireless communication systems, receivers face high complexity due to the need for interference cancellation when decoding signals from UEs in the center of a cell, as they must first detect and cancel signals from UEs on the edge of the cell.
Innovation Solution
A transmitting apparatus and method that jointly modulates encoded signals for multiple UEs using Gray mapping, eliminating the need for interference cancellation by mapping bits such that constellation points satisfy the Gray mapping rule, reducing receiver complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional separate modulation is used for multiple UEs, then the modulation process is simple, but the receiver complexity increases due to required interference cancellation
Solution Approach 1:
The patent merges the modulation processes of multiple UEs into a single joint modulation operation. The modulator maps bits from multiple encoded signals to constellation points simultaneously, creating a unified modulated signal that eliminates the need for separate modulation operations and subsequent interference cancellation at the receiver.
Solution Approach 2:
Instead of the traditional approach where separate modulated signals are superposed and require interference cancellation, the patent inverts the process by jointly modulating multiple encoded signals from the beginning. This reversal of the conventional sequence eliminates the harmful interference issue at the receiver端.
2Device complexity
If joint modulation with Gray mapping is used, then receiver complexity is reduced, but the modulation process becomes more complex
Solution Approach 1:
The patent changes the mapping parameters by applying Gray mapping rules to the joint modulation process. This parameter change ensures that adjacent constellation points differ by only one bit, which simplifies the receiver's decision process and reduces complexity while maintaining a structured modulation approach.
3Measurement precision
If interference cancellation is performed, then signal decoding accuracy is improved, but processing time and complexity increase
Solution Approach 1:
The patent performs preliminary action by applying Gray mapping during the joint modulation process itself. This preliminary structuring of the constellation points ensures that the receiver can directly decode signals without requiring time-consuming interference cancellation operations, thus reducing processing time while maintaining decoding accuracy.
Data Source
AI summary
A transmitting apparatus and a transmitting method are provided. The transmitting apparatus comprises: an encoder configured to encode data for a plurality of user equipments into corresponding encoded signals, respectively; a modulator configured to perform a joint modulation on the encoded signals for the plurality of user equipments to generate modulated signals, wherein the modulator performs the joint modulation by mapping bits of the encoded signals for the plurality of user equipments to a symbol corresponding to each constellation point of a constellation map of the modulated signals so that respective constellation points satisfy a Gray mapping rule; a transmitter configured to transmit the modulated signals.