DFT-s-OFDM Sidelobe Reduction via Boundary Continuity
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Solution Overview
Problem
Conventional techniques for reducing out-of-band emissions in multi-carrier transmissions, such as OFDM, are not applicable to precoded multi-carrier systems, as they unpredictably affect the data due to transformation of correction signals into the time-domain, leading to signal discontinuities and interference.
Innovation Solution
A device and method for generating a transmission block in precoded multi-carrier radio transmissions, where symbol elements are set to fulfill boundary conditions without affecting the data, ensuring continuity across block boundaries by using a subset of symbol elements determined by the boundary condition, allowing for continuous signal transmission and reduced out-of-band emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional correction signal technique is applied to precoded multi-carrier systems, then out-of-band emissions are reduced, but data recovery becomes impossible due to unpredictable transformation into time-domain with large peaks
Solution Approach 1:
The symbol vector is segmented into two disjoint subsets: one subset for data symbols and another subset for correction symbols. This segmentation allows the correction symbols to be specifically designed to reduce out-of-band emissions while the data symbols remain unaffected and recoverable at the receiver.
Solution Approach 2:
Different parts of the symbol vector are assigned different functions: data-carrying symbols in one subset and boundary-condition-satisfying correction symbols in another subset. This local differentiation ensures that the correction symbols locally address the out-of-band emission problem without affecting the global data transmission integrity.
2Object-generated harmful factors
If guard intervals are extended to reduce out-of-band emissions, then emissions are suppressed, but transmission overhead and system complexity increase
Solution Approach 1:
The invention changes the parameter configuration by using a subset of symbol elements for correction purposes. This allows achieving out-of-band emission reduction with shorter filters and guard intervals compared to conventional methods, as the correction is embedded within the symbol structure rather than requiring extended temporal guard periods.
3Object-generated harmful factors
If correction signals are applied to precoded multi-carrier systems, then out-of-band emissions are reduced, but the correction signals transform into time-domain with peaks much larger than data symbols, causing interference
Solution Approach 1:
By segmenting the symbol vector into data symbols and correction symbols in the frequency domain before precoding, the correction symbols maintain controlled amplitude characteristics throughout the transformation process, avoiding the large peak interference problem that occurs when correction signals are applied after time-domain transformation.
Data Source
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AI summary
Goal of the application is providing an alternative to the N-continuous algorithm in frequency domain for sidelobes reduction (OOB) suitable for SC-FDMA. A part of the time domain symbols is used as correction signal to ensure continuity of the signal and its derivatives at symbol boundaries, ie between previous symbol and guard interval (can be Zero Padding or Cyclic Prefix) of current symbol. Said time domain symbols are then FFT precoded, windowed, followed by IFFT and Guard Interval insertion. Also applied to FBMC.