Frequency-Domain BCET Equalization for Bandwidth-Limited Links
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Bandwidth-constrained communication systems face limitations in achieving high spectral efficiency and reliability due to channel impairments like multipath fading, which traditional modulation formats and error control coding schemes struggle to overcome effectively.
Innovation Solution
The implementation of a bandwidth constrained equalized transport (BCET) system that introduces memory into signals through pulse-shaping filters and employs multidimensional frequency domain processing, including error control coding and iterative decoding, to enhance information rates and system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional modulation formats without memory are used, then the system design is simple, but the spectral efficiency cannot approach the Shannon limit
Solution Approach 1:
The patent changes the fundamental parameter of memory in the system by introducing intentional ISI through pulse-shaping filters. This transforms the system from memoryless to having memory, enabling spectral efficiency to approach the Shannon limit while maintaining manageable complexity through structured design
Solution Approach 2:
The patent replaces traditional time-domain equalization mechanisms with frequency-domain processing using FFT. This substitution simplifies the handling of intentional ISI by transforming the problem into the frequency domain where circular convolution becomes simple multiplication, reducing overall system complexity
2Reliability
If error control codes with redundant information bits are used, then reliability improves, but the information rate decreases
Solution Approach 1:
The patent changes the channel characteristics by introducing controlled ISI through pulse-shaping filters, transforming the channel into one with memory. This allows the development of specialized error control codes that can achieve both high reliability and high information rates by exploiting the structured nature of the intentional interference
Solution Approach 2:
The patent uses iterative decoding where the receiver creates multiple copies of the received signal and processes them through multiple decoding passes. Each iteration refines the estimate of the transmitted symbols, achieving high reliability without permanently losing information rate
3Reliability
If iterative decoding with multiple constituent decoders is used, then performance approaches theoretical bounds, but system complexity increases
Solution Approach 1:
The patent merges the equalization function into the decoding process by using the same constituent decoders to handle both equalization and decoding tasks. This integration reduces overall system complexity compared to having separate equalization and decoding chains, while still achieving performance close to theoretical bounds
Solution Approach 2:
The constituent decoders are designed to perform multiple functions: they act as both equalizers (handling the intentional ISI) and as error control decoders (correcting errors). This multi-functionality reduces the total number of components needed in the system while maintaining high performance
4Productivity
If pulse-shaping filters introduce memory into the signal, then spectral efficiency increases, but the signal becomes more susceptible to channel impairments
Solution Approach 1:
The patent converts the harmful effect of ISI into a beneficial feature by intentionally introducing it through pulse-shaping filters. The structured nature of this intentional ISI allows the receiver to exploit it for gaining spectral efficiency while the error control codes are specifically designed to handle the resulting channel characteristics, turning what would normally be a impairment into an asset
Data Source
AI summary
The present disclosure provides techniques for bandwidth constrained communication systems with frequency domain information processing. A bandwidth constrained equalized transport (BCET) communication system can include a transmitter, a communication channel, and a receiver. The transmitter can include a pulse-shaping filter that intentionally introduces memory into a signal in the form of inter-symbol interference, an error control code (ECC) encoder, a multidimensional fast Fourier transform (FFT) processing block that processes the signal in the frequency domain, and a first interleaver. The receiver can include an information-retrieving equalizer, a deinterleaver with an ECC decoder, and a second interleaver joined in an iterative ECC decoding loop. The communication system can be bandwidth constrained, and the signal can comprise an information rate that is higher than that of a communication system without intentional introduction of the memory at the transmitter.