Block-Based Crest Factor Reduction in Wireless Base Stations
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Solution Overview
Problem
Conventional crest factor reduction (CFR) algorithms in wireless communication systems require real-time, sequential processing of input signal samples, leading to high complexity, cost, and susceptibility to peak regrowth, especially in multi-carrier signals with high peak-to-average power ratios (PAPR), which constraints the efficiency and performance of power amplifiers.
Innovation Solution
A non-sequential, block-based CFR processing method that collects input IQ samples, detects peaks in a block, and applies cancellation waveforms to suppress them, using a single chip digital front end processor to reduce sampling rate and complexity, allowing for efficient peak detection and cancellation without specialized hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If real-time sequential CFR processing is used to detect and suppress peaks, then peak suppression performance is improved, but device complexity and processing cost increase significantly
Solution Approach 1:
The patent divides the continuous signal processing into discrete blocks of N samples. Within each block, peaks are detected and suppressed independently using cancellation waveforms. This segmentation allows the use of simpler batch processing algorithms instead of complex real-time sequential processing, reducing device complexity while maintaining peak suppression performance.
2Reliability
If real-time sequential peak detection and suppression is implemented, then crest factor reduction is achieved, but processing speed and sampling rate requirements increase
Solution Approach 1:
The patent performs peak detection and cancellation waveform generation for entire blocks of samples in advance, before the actual transmission. By preprocessing the signal blocks and storing the cancellation waveforms in memory, the system avoids the need for high-speed real-time processing during transmission, thereby reducing sampling rate requirements and improving processing speed efficiency.
3Measurement precision
If specialized hardware is used for real-time CFR processing, then processing accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent uses digital cancellation waveforms that are generated and stored in memory rather than requiring specialized analog hardware circuits. The cancellation waveforms are computed digitally and applied through standard digital-to-analog converters and summing circuits that are already present in typical communication systems, thereby achieving high processing accuracy without increasing manufacturing cost through specialized hardware.
4Device complexity
If block-based non-sequential processing is used, then computational complexity is reduced, but processing continuity may be affected
Solution Approach 1:
The patent ensures processing continuity by using overlapping blocks where the cancellation window extends beyond the block boundaries. Samples near the edges of blocks are processed together with adjacent blocks, and previously computed cancellation waveforms are reused where applicable. This approach maintains continuous signal processing while allowing the use of computationally efficient block-based non-sequential processing methods.
Data Source
AI summary
A method and apparatus for a radio base station (200) generates a multicarrier communication signal having a reduced crest factor by processing a block of samples (231) with a peak search window (271) to identify and suppress signal peaks exceeding a power threshold value.