Uplink DMRS Subordinating Antenna Cyclic Shift
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Solution Overview
Problem
The existing LTE uplink system with a single antenna cannot meet the higher performance requirements of LTE-Advanced, particularly in terms of peak spectrum efficiency, due to limitations in providing demodulation reference signals for multiple transmit antennas.
Innovation Solution
A method is introduced to determine demodulation reference signals (DMRS) for multiple transmit antennas by establishing subordinating relationships between a base transmit antenna and subordinating antennas, maximizing the difference in cyclic shift values, and using a base sequence with cyclic shifts to generate DMRS for each antenna, ensuring backward compatibility with existing LTE protocols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single antenna is used in the uplink of LTE system, then the system complexity is low and backward compatibility is maintained, but the peak spectrum efficiency cannot reach the required 15 bps/Hz for LTE-A
Solution Approach 1:
The patent segments the reference signal design by introducing a base antenna concept and subordinating other antennas to it. Each antenna is assigned a unique cyclic shift value derived from the base antenna's reference signal, allowing multiple antennas to operate with differentiated reference signals while maintaining a structured, manageable design framework.
Solution Approach 2:
The patent creates a universal reference signal generation mechanism where a single base sequence can serve multiple antennas through cyclic shifts. The base antenna's reference signal becomes a template that generates reference signals for all subordinating antennas, enabling one signal design to fulfill multiple antenna functions.
2Productivity
If multiple transmit antennas are introduced to increase spectrum efficiency, then the uplink performance improves, but the system becomes much more complicated and new issues arise in providing demodulation reference signals
Solution Approach 1:
The patent merges the reference signal generation process by having all subordinating antennas derive their reference signals from the base antenna's base sequence. This combining approach reduces the overall complexity compared to designing independent reference signals for each antenna, while still providing the necessary differentiation through cyclic shifts.
Solution Approach 2:
The patent changes the cyclic shift parameter to differentiate reference signals across multiple antennas. By assigning unique cyclic shift values to each antenna based on their antenna indices, the system achieves antenna-specific reference signals without fundamentally changing the base sequence structure, thus managing complexity through parameter variation rather than structural complexity.
3Reliability
If different cyclic shift values are assigned to multiple antennas, then inter-cell interference is reduced and channel estimation is improved, but the complexity of determining and managing cyclic shifts increases
Solution Approach 1:
The patent applies local quality by assigning specific cyclic shift characteristics to each antenna based on its role (base or subordinating) and index. Each antenna receives a cyclic shift value tailored to its position in the antenna array, optimizing local channel estimation quality while maintaining overall system coherence through the hierarchical base-subordinating structure.
Data Source
AI summary
The present invention discloses a method for determining an uplink demodulation reference signal (DMRS), which includes: taking one of multiple transmit antennas in the uplink as a base transmit antenna, taking other transmit antennas as subordinating transmit antennas and setting a DMRS for the base transmit antenna; establishing DMRS subordinating relationships between the base transmit antenna and each of the subordinating transmit antennas; and setting a DMRS for each of the subordinating transmit antennas according to the DMRS of the base transmit antenna and the DMRS subordinating relationship between the base transmit antenna and each of the subordinating transmit antennas. The present invention also provides a user equipment (UE) and an uplink system for providing DMRSs for multiple transmit antennas. The method, UE and system are applicable in both SU-MIMO transmission and MU-MIMO transmission.