Massive Array DPD Training for OOB-Compliant Full-Bandwidth Power
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Solution Overview
Problem
Current digital predistortion (DPD) techniques for wireless communication systems face challenges in transmitting signals at higher power levels while maintaining maximum allowable bandwidth without violating out-of-band (OOB) emissions protocols, often requiring significant power back-off which reduces overall signal power.
Innovation Solution
A DPD training procedure is implemented through an iterative process where the transmitter applies DPD to increasing bandwidth subsets, with feedback from the receiver used to adjust coefficients, allowing the system to operate at maximum bandwidth without increasing power back-off, thereby maintaining OOB emissions within regulatory thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If power back-off is applied to decrease OOB emissions below the threshold, then OOB emissions compliance is improved, but a significant reduction in the overall power of the transmitted signal occurs
Solution Approach 1:
The system applies digital predistortion to the transmitted signal before power amplification to pre-compensate for non-linearities that would cause OOB emissions. This preliminary action allows the signal to be amplified to maximum power without exceeding OOB thresholds, as the distortion is corrected in advance through coefficient adjustment based on feedback
2Power
If DPD is applied to the full bandwidth, then transmission power can be maximized, but the complexity of the DPD training process increases
Solution Approach 1:
The full bandwidth is divided into multiple bandwidth subsets that are processed sequentially through iterative DPD training. The system starts with a smaller bandwidth subset, trains the DPD coefficients, then progressively expands to larger subsets until the full bandwidth is achieved. This segmentation reduces the complexity of each training step while ultimately enabling full-bandwidth maximum power transmission
3Object-affected harmful factors
If iterative DPD training is performed with increasing bandwidth subsets, then OOB emissions compliance is maintained at maximum power, but the training time and processing overhead increase
Solution Approach 1:
The DPD training process uses dynamic bandwidth subset expansion where the subset size increases iteratively based on convergence criteria. The system adapts the training progression rate according to the measured performance at each step, allowing faster convergence when conditions permit and slowing down when precision is needed, thus optimizing the trade-off between training time and emission compliance
Data Source
AI summary
This disclosure provides systems, devices, apparatus and methods, including computer programs encoded on storage media, for a DPD training procedure. A base station may transmit, for a plurality of iterations, a signal to at least one UE through a plurality of transmit chains and with application of DPD. The signal transmitted for each iteration may be transmitted with a BW that extends over a plurality of subcarriers and includes pilots extending over a BW subset that increases in subcarrier size for each iteration. The base station may receive, for each iteration, feedback from the at least one UE based on the transmitted signal and apply DPD to each of the plurality of transmit chains based on the feedback. Accordingly, the base station may transmit to one or more UEs through the plurality of transmit chains and with application of the DPD pilot signals that extend over the entire BW.