Digital Front-End Transition Smoothing for OFDM Block Continuity
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Solution Overview
Problem
Conventional OFDM waveforms in 4G and 5G wireless networks suffer from large out-of-band emissions, leading to harmful interference with adjacent channels, and existing solutions struggle to maintain smooth transitions between OFDM symbols when symbol boundary information is lost during digital pre-distortion and gain adjustments.
Innovation Solution
A transition smoothing method that applies a soft edge pulse-shaping process by appending a ramp-down tail sequence to one block and generating a ramp-up head sequence for the next block, allowing for smooth transitions without requiring symbol boundary information, using a system-on-chip (SoC) with a digital front-end and RF chip configured for multiplexer, nonlinearity compensation, and transition smoothing modules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional OFDM waveforms are used, then wireless communication can be provided, but out-of-band emissions are large causing harmful interference with adjacent channels
Solution Approach 1:
The patent segments the OFDM symbol into multiple blocks (first block, second block, etc.) and applies different processing to each block. Specifically, a ramp-down tail sequence is appended to the first block and a ramp-up head sequence is generated for the second block, allowing independent optimization of each segment to reduce out-of-band emissions while maintaining spectral containment.
Solution Approach 2:
The patent applies preliminary actions by pre-calculating and pre-appending the ramp-down tail sequence to the first block and pre-generating the ramp-up head sequence for the second block before actual transmission. This preliminary processing smooths the transitions between blocks, reducing spectral leakage and out-of-band emissions without requiring complex real-time adjustments.
2Reliability
If digital pre-distortion and gain adjustments are applied, then nonlinearity compensation is achieved, but symbol boundary information is lost making transition smoothing difficult
Solution Approach 1:
The patent implements self-service by having the system automatically generate and apply the ramp-down tail sequence and ramp-up head sequence based on the block structure itself, without requiring external symbol boundary information. The transition smoothing is performed self-contained within the block processing, using the block length and structure to determine the smoothing parameters.
Solution Approach 2:
The patent changes the processing parameters by introducing new parameters (ramp-down tail sequence length, ramp-up head sequence length) that are derived from the block length rather than symbol boundary information. This parameter transformation allows the system to maintain transition smoothing capability while operating without symbol boundary information, as the new parameters are directly computable from the block structure.
3Adaptability or versatility
If transition smoothing is applied without symbol boundary information, then adaptability is improved, but transition continuity between blocks may be compromised
Solution Approach 1:
The patent applies dynamics by making the transition smoothing parameters adaptive to the block structure. The ramp-down tail sequence and ramp-up head sequence are dynamically generated based on the actual block length and content, allowing the system to adapt to different block configurations while maintaining smooth transitions. This dynamic approach ensures continuity is maintained through adaptability rather than fixed assumptions.
Solution Approach 2:
The patent implements feedback mechanisms where the ramp-down tail sequence and ramp-up head sequence are generated based on feedback from the block processing itself. The system uses the actual block length and structure information to determine the smoothing parameters, creating a feedback loop that ensures transition continuity is maintained while adapting to different block configurations without requiring external symbol boundary information.
Data Source
AI summary
Embodiments of apparatus and method for transition smoothing implementation on a stream of data are disclosed. In an example, a system on chip (SoC) for wireless communication includes a digital front-end. The digital front-end is configured to obtain a stream of data having one carrier or multi-carriers. The stream of data is divided into a plurality of blocks. The digital front-end is also configured to adjust a gain of the stream of data based on a predetermined frequency corresponding to a length of each of the plurality of blocks. The digital front-end is also configured to append a ramp-down tail sequence to a first block of the stream of data after a last sample of the first block, and generate a ramp-up head sequence for a second block immediately after the first block, based on a head sequence of the second block.