Transmitter Spatial Multiplexing DMRS for MU-MIMO
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Solution Overview
Problem
In Non-Linear Precoding (NLP) MU-MIMO systems, the overhead of inserting Demodulation Reference Signals (DMRS) is high due to the need for dedicated radio resources, limiting the efficiency of channel estimation and power management for mobile-station devices.
Innovation Solution
A transmitter apparatus that spatially multiplexes DMRS using a single radio resource, allowing each mobile-station device to perform channel estimation with multiple DMRS, and includes a non-linear precoder that adds a signal integer multiple of a predetermined signal to the DMRS, enabling efficient channel estimation and power optimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dedicated radio resources are allocated for DMRS in NLP MU-MIMO systems, then channel estimation accuracy is improved, but overhead increases and power efficiency deteriorates
Solution Approach 1:
The patent merges multiple DMRS for different mobile stations into a single radio resource by spatially multiplexing them through non-linear precoding. The base station adds perturbation vectors to combine DMRS addressed to different mobile stations, allowing them to be transmitted simultaneously on the same time-frequency resource, thereby reducing overhead while maintaining channel estimation accuracy.
Solution Approach 2:
The patent changes the parameter space by introducing perturbation vectors that are integer multiples of a predetermined signal. This allows the DMRS to be transformed into a different parameter domain where multiple reference signals can coexist without interference, enabling efficient resource utilization and reduced overhead.
2Productivity
If multiple DMRS are transmitted on the same radio resource through spatial multiplexing, then overhead is reduced, but interference between DMRS increases
Solution Approach 1:
The patent converts the potential harm of DMRS interference into a benefit by using non-linear precoding with perturbation vectors. The interference that would normally occur between DMRS on the same resource is transformed into a structured signal that can be easily removed at the receiver through modulo operations, turning a harmful effect into a manageable characteristic.
Solution Approach 2:
The patent introduces perturbation vectors as an intermediary mechanism between multiple DMRS signals. These vectors act as mediators that allow DMRS from different mobile stations to coexist on the same resource without causing harmful interference, as the perturbation structure enables clean separation at the receiver.
3Loss of energy
If non-linear precoding is applied to DMRS, then power efficiency is improved, but channel estimation becomes more complex
Solution Approach 1:
The patent applies preliminary action by pre-structuring the DMRS with known perturbation vectors before transmission. The base station adds perturbation vectors to the DMRS in advance, creating a predictable pattern that the mobile station can reverse through modulo operations, thereby simplifying the overall channel estimation process despite the non-linear precoding.
Data Source
AI summary
A transmitter apparatus to transmit to a plurality of receiver apparatuses a data signal at the same timing and on the same frequency, includes a transmitter unit that transmits a demodulation reference signal addressed to a first receiver apparatus and a demodulation reference signal addressed to a second receiver apparatus different from the first receiver apparatus at the same timing and on the same frequency.