Constellation Pattern Replication for MIMO Power Control
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Solution Overview
Problem
MIMO communication systems face limitations in achieving high data rates while maintaining low transmit power, as existing techniques require unconstrained energy and result in high peak transmit powers, and there is a need for improved error performance and reduced complexity.
Innovation Solution
A method involving a constellation pattern with replications of a combined constellation, where each replication has a translation offset relative to neighboring ones, allowing for selection of symbols that minimize transmit power while maintaining error performance, using a mirrored constellation approach for decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-equalization with linear precoding is used to improve MIMO performance, then detection performance is improved, but transmit power becomes uncontrolled and peak power increases
Solution Approach 1:
The patent applies parameter changes by introducing a non-linear transformation (modulo operation) on the constellation points. The transmitted symbols are selected from a perturbed constellation where points are shifted based on channel state information, and a modulo operation is applied to constrain the power while maintaining detection performance. This transforms the linear precoding approach into a non-linear scheme that controls peak power.
2Power
If vector perturbation technique is used to constrain transmitted energy, then peak transmit power is reduced, but system complexity increases due to extended symbol set
Solution Approach 1:
The patent extracts the essential function of power constraint from the complex vector perturbation technique by using a simplified modulo operation on the constellation points. Instead of maintaining an extended symbol set with replicated constellations, the invention applies a modulo operation to the precoded symbols, extracting only the necessary power-constraining function while discarding the complexity of managing extended symbol sets.
3Productivity
If higher order constellations are used to increase data rate, then capacity increases, but error performance deteriorates
Solution Approach 1:
The patent applies local quality by adapting the constellation points locally based on channel state information. The precoding process shifts constellation points in the complex plane according to the specific channel conditions, creating locally optimized constellation configurations that maintain adequate Euclidean distances even for higher order modulations. This local adaptation allows higher data rates while preserving error performance.
Data Source
AI summary
A transmitter generates a constellation pattern comprising replications of a first constellation. Each replication has a replication offset relative to a neighbouring replication and alternates between corresponding to the first constellation and an axis mirrored constellation (mirrored around the real and/or imaginary axis). The transmitter selects from the pattern such that a symbol for a data value corresponding to a first constellation point of the first constellation is selected from all replications of this constellation point. The constellation point resulting in the lowest transmit power for a combination of a plurality of antennas may be selected. A receiver receives the selected symbol and provides a folding operation to compensate for replications and mirroring. The replication offset may be lower than the minimum distance between symbols in the first constellation thereby resulting in an improved trade off between transmit power and error probability, e.g. in a Multiple Input Multiple Output system.