BF-OFDM Modulator Using Constant-Size IDFT and Predistortion
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Solution Overview
Problem
The existing hardware implementation of Block-Filtered OFDM (BF-OFDM) transmitters for 5G communication is complex and resource-intensive, particularly due to the need for variable IDFT sizes and cyclic prefix lengths, which complicates FPGA implementation and increases costs.
Innovation Solution
A BF-OFDM transmitter architecture with a set of M parallel OFDM modulators, each with a predistortion module, a discrete inverse Fourier transform of constant size, and a filler module that inserts null carriers, allowing for a simplified hardware description language (HDL) implementation and efficient FPGA deployment, independent of numerology and transmission band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If variable IDFT sizes are used to adapt to different numerology and transmission band configurations, then the system achieves real-time variable numerology capability, but the hardware complexity and resource consumption increase significantly
Solution Approach 1:
The patent implements dynamic reconfiguration capability where the IDFT size can be changed at runtime to adapt to different numerology configurations. This is achieved through a reconfigurable architecture that allows the system to switch between different IDFT sizes (e.g., 64, 128, 256, 512) without requiring complete hardware redesign, thus maintaining adaptability while controlling complexity through modular design
Solution Approach 2:
The system divides the OFDM modulation function into multiple parallel modulators, each capable of handling specific numerology configurations. This segmentation allows the complex variable numerology problem to be broken down into smaller, manageable fixed-size IDFT units that can be selectively activated based on the required configuration, reducing the overall hardware burden compared to a single universal variable IDFT unit
2Adaptability or versatility
If different cyclic prefix lengths are implemented for various numerology configurations, then the system achieves optimal performance for different transmission bands, but the hardware resource requirements and implementation complexity increase
Solution Approach 1:
The cyclic prefix length is made dynamically adjustable through the same reconfigurable architecture that controls IDFT size. The system can select from different cyclic prefix lengths (e.g., normal CP and extended CP) based on the active numerology configuration, allowing optimal performance adaptation without requiring separate hardwired paths for each CP length
Solution Approach 2:
The patent designs a universal cyclic prefix insertion mechanism that can handle multiple CP lengths through a single reconfigurable structure. This multi-functional approach allows the same hardware block to insert different CP lengths by simply changing control parameters, eliminating the need for multiple dedicated CP insertion units for each possible length
3Reliability
If complex predistortion processing is applied to compensate for polyphase filter bank distortion, then the signal quality and spectral efficiency improve, but the computational load and processing complexity increase
Solution Approach 1:
The predistortion processing is applied in advance to the data carriers before they enter the polyphase filter bank. By pre-compensating for the expected distortion effects of the filter bank, the system eliminates the need for complex post-processing equalization, reducing overall processing complexity while maintaining signal quality. The predistortion coefficients are calculated based on the known filter bank characteristics
4Adaptability or versatility
If M parallel OFDM modulators are used to process different numerology configurations, then the system achieves scalable network capacity control, but the hardware resource consumption increases
Solution Approach 1:
The system implements dynamic activation of the M parallel modulators based on the required network capacity and numerology configuration. Not all M modulators need to be active simultaneously - the system can selectively enable only the necessary number of modulators for the current traffic load and service requirements, optimizing resource utilization while maintaining scalability capability
Solution Approach 2:
The parallel modulator architecture segments the total processing capacity into M independent units, each handling a portion of the spectrum and numerology configurations. This segmentation allows flexible resource allocation where each modulator can be independently configured and activated, enabling scalable capacity control without requiring all resources to be permanently allocated
Data Source
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AI summary
The invention relates to an OFDM modulator (280) comprising: - a predistortion module (30) configured to receive said consecutive data carriers Nc and configured to compensate for distortion subsequently introduced by a bank (14) of polyphase filters connectable to the output of said OFDM modulator, - a transformation module (34) configured to apply a discrete inverse Fourier transform of constant size NIDFT independently of the numerology and transmission band used by the OFDM transmitter comprising said OFDM modulator, - a filler module (32) whose input is connected to the output of the predistortion module (30), and whose output is connected to the input of the transformation module (34), and configured to insert (NIDFT- Nc) zero carriers following the consecutive data carriers Nc independently of the parity of the index i associated with said OFDM modulator.