DMRS Sharing Across UEs for OTA DPD Compensation
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Solution Overview
Problem
In wireless communications systems, applying digital pre-distortion (DPD) to mitigate non-linear impairments in power amplifiers (PAs) is complex and costly, especially when performed at each transmission antenna, and frequency division multiplexing (FDM) limits access to full demodulation reference signals (DMRS) for user equipments (UEs).
Innovation Solution
A network entity shares a full DMRS pattern with multiple frequency-division multiplexed (FDMed) UEs, allowing them to estimate non-linear impairment compensation function coefficients, which are then averaged and applied by the network entity for downlink transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital pre-distortion is applied at each transmission antenna to mitigate non-linear impairments, then the compensation effectiveness is improved, but the device complexity and cost increase significantly
Solution Approach 1:
The patent introduces an intermediary approach where a single DPD unit processes signals before they are distributed to multiple transmission antennas. Instead of implementing complex DPD circuits at each antenna, the distortion compensation is performed once at a centralized location, then the compensated signals are routed to multiple antennas. This mediator architecture maintains compensation effectiveness while dramatically reducing overall system complexity and cost.
Solution Approach 2:
The patent merges the DPD functionality into a single shared unit that serves multiple transmission antennas. By combining what would otherwise be separate DPD implementations at each antenna into one unified DPD processor, the system achieves the same non-linear impairment compensation for all antennas without multiplying the complexity and cost across multiple independent units.
2Productivity
If frequency division multiplexing is used to allocate frequency resources to multiple UEs, then the system capacity is improved, but the ability to access full demodulation reference signals for non-linear impairment estimation is degraded
Solution Approach 1:
The patent implements a universal DMRS pattern that serves multiple FDMed UEs simultaneously. Instead of allocating separate DMRS patterns to each UE, a single DMRS pattern is designed and transmitted that can be used by multiple UEs for their respective non-linear impairment estimations. This multi-functional DMRS pattern maintains system capacity while ensuring all UEs have access to the full reference signal information they need.
Solution Approach 2:
The patent segments the frequency resources in a way that allows a single DMRS pattern to be effectively shared across multiple UEs. By carefully dividing and allocating frequency subsets while maintaining the integrity of the overall DMRS structure, the system enables multiple UEs to extract the full DMRS pattern information they require for accurate non-linear impairment estimation, even though they are multiplexed in the frequency domain.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. The described techniques relate to improved methods, systems, devices, and apparatuses that support demodulation reference signal sharing across user equipments (UEs) supporting over the air (OTA) digital pre-distortion (DPD). For example, the described techniques provide for demodulation reference signal (DMRS) sharing across UEs supporting OTA DPD. A network entity may share a full DMRS pattern with multiple frequency-division multiplexed (FDMed) UEs. Based on the shared DMRS pattern, the UEs may evaluate the non-linear impairment by estimating non-linearity (NL) compensation function coefficients. Each of the UEs may indicate, to the network entity, their estimated NL compensation function coefficients. The network entity may apply an updated NL compensation function based on the NL compensation function coefficients from the various UEs and transmit a downlink transmission according to the updated NL compensation function.