Constellation Map Segmentation for MUST Demodulation
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Solution Overview
Problem
In multiuser superposition transmission (MUST) schemes, the existing modulation methods fail to maintain high demodulation performance when the power split factor becomes large, leading to overlapping decision regions and degraded performance due to non-orthogonal multiple access (NOMA) and semi-orthogonal multiple access (SOMA) schemes.
Innovation Solution
A method involving a 'bit sequence to constellation points' mapper is introduced to ensure Gray coding compliance, with constellation points being assigned under different power split factors, and the constellation map is divided into sub-regions for bit sequence assignment, allowing for the use of maximum likelihood (ML) or minimum mean square error (MMSE) receivers for demodulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If non-orthogonal multiple access (NOMA) or semi-orthogonal multiple access (SOMA) schemes are used for MUST, then system capacity is improved, but demodulation performance degrades when power split factor becomes large due to overlapping decision regions
Solution Approach 1:
The patent segments the constellation map into multiple sub-regions, with each sub-region assigned to specific bit sequences. This segmentation prevents overlapping decision regions by clearly defining boundaries between different signal representations, thereby maintaining demodulation performance while preserving the high system capacity benefits of non-orthogonal access schemes.
Solution Approach 2:
The patent applies different mapping strategies to different parts of the constellation map. Specifically, bit sequences are assigned to constellation points within specific sub-regions based on local characteristics rather than using a uniform mapping approach. This local quality differentiation ensures that decision regions remain distinct even when power split factors vary, resolving the contradiction between capacity and reliability.
2Ease of manufacture
If existing modulation methods are used in MUST schemes, then implementation is simple, but demodulation performance deteriorates at large power split factors due to non-Gray coding compliance
Solution Approach 1:
The patent introduces a preliminary mapping step that assigns bit sequences to constellation points before modulation. This preliminary action ensures Gray coding compliance is established in advance, so that adjacent constellation points always differ by only one bit. This pre-established mapping structure maintains demodulation accuracy even at large power split factors while keeping the overall implementation relatively simple.
Solution Approach 2:
The patent introduces a bit sequence to constellation point mapper as an intermediary component between the modulator and the channel. This intermediary ensures that the mapping between bits and constellation points adheres to Gray coding principles, thereby improving demodulation accuracy without significantly complicating the overall system architecture. The mapper acts as a mediator that resolves the conflict between simplicity and precision.
Data Source
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AI summary
A method of modulating and demodulating superposed signals for MUST (MultiUser Superposition Transmission) scheme is proposed. A transmitter takes bit sequences intended for multiple receivers under MUST scheme to go through a "bit sequence to constellation points" mapper before entering the modulators to satisfy the Gray coding rule and to achieve high demodulation performance for the receivers. In a first method, each bit sequence is assigned for each constellation point on the constellation map to satisfy one or more conditions under different power split factors. In a second method, the constellation map is divided into sub-regions according to the clustering of the constellation points for bit sequence assignment. A near-UE may use an ML (Maximum Likelihood) receiver for demodulation and decoding the superposed signal. A far-UE may use an ML receiver or an MMSE (Minimum Mean Square Error) receiver for demodulation and decoding the superposed signal.