DM-RS Multiplexing Using Cyclic Shift Index
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Solution Overview
Problem
In wireless communication systems, existing technologies face challenges in efficiently multiplexing demodulation reference signals (DM-RS) across multiple layers in MIMO communications, requiring signaling of cyclic shift (CS) values and orthogonal cover codes (OCC) for each layer, which increases signaling overhead and resource consumption.
Innovation Solution
A method and apparatus that derive CS values and OCCs for DM-RS transmission based on a received CS index, allowing for reduced signaling overhead by determining these values and codes for multiple layers using a single CS index, and optionally receiving configured CS values from higher layers, enabling efficient multiplexing without explicit signaling of CS values and OCCs for each layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If explicit signaling of CS values and OCCs is performed for each layer, then orthogonality among layers is maintained, but signaling overhead increases
Solution Approach 1:
A single CS index is used to control multiple layers, where one parameter (CS index) serves multiple functions by determining both the cyclic shift values and orthogonal cover codes for all layers. This universal parameter approach reduces signaling overhead while maintaining the ability to ensure orthogonality across multiple layers through the derived values.
Solution Approach 2:
The patent changes the parameter representation from multiple explicit parameters (individual CS values and OCCs for each layer) to a single parameter (CS index) that generates the necessary values through mathematical relationships. This parameter transformation reduces signaling overhead while preserving the orthogonality function through the derived parameters.
2Productivity
If multiple DM-RS are transmitted over the same time and frequency resources, then throughput is improved, but resource complexity increases
Solution Approach 1:
Multiple DM-RS transmissions are merged into the same time and frequency resources by using different cyclic shift values derived from a single CS index. This combining approach enables simultaneous transmission of multiple layers without requiring additional time-frequency resources, thereby improving throughput while managing complexity through unified parameter control.
3Loss of information
If a single CS index is used to determine CS values and OCCs for multiple layers, then signaling overhead is reduced, but the complexity of deriving these values increases
Solution Approach 1:
The patent establishes predetermined mathematical relationships and formulas for deriving CS values and OCCs from the CS index before actual transmission occurs. These pre-defined derivation rules are stored in the system, allowing the device to automatically compute the necessary parameters without complex real-time calculations, thus reducing derivation complexity while maintaining reduced signaling overhead.
Data Source
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AI summary
Methods and apparatuses are provided for determining cyclic shift (CS) values and/or orthogonal cover codes (OCC) for a plurality of demodulation reference signals (DM-RS) transmitted over multiple layers in multiple-input multiple-output (MIMO) communications. A CS index can be received from a base station in downlink control information (DCI) or similar signaling. Based at least in part on the CS index, CS values for the plurality of DM-RSs can be determined. In addition, OCC can be explicitly signaled or similarly determined from the CS index and/or a configured CS value received from a higher layer. In addition, controlling assignment of CS indices and/or OCC can facilitate providing orthogonality for communications from paired devices in multiuser MIMO.