Parallel OFDM Architecture Reducing Intercarrier Interference
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Solution Overview
Problem
Orthogonal frequency division multiplexing (OFDM) systems are sensitive to frequency offsets, leading to intercarrier interference (ICI) and degraded bit-error-rate (BER) performance due to loss of subcarrier orthogonality, with conventional systems limited to a 4% frequency offset tolerance.
Innovation Solution
A parallel architecture for OFDM communication systems is introduced, utilizing dual inverse and forward fast Fourier transform (FFT) operations in both transmitters and receivers, with a divisional multiplexer and demultiplexer to process signals through separate paths, effectively reducing ICI by combining inverse and forward transformed signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional OFDM systems use single IFFT and FFT operations, then device complexity is reduced, but frequency offset tolerance is limited to 4%
Solution Approach 1:
The patent divides the single OFDM signal into two separate OFDM signals by applying both IFFT and FFT operations to the input data. These two signals are then multiplexed and transmitted through separate channels. At the receiver, the corresponding FFT and IFFT operations are performed separately on each received signal, allowing the system to tolerate frequency offsets up to 20% while maintaining signal integrity.
2Adaptability or versatility
If parallel OFDM architecture with dual IFFT and FFT operations is implemented, then frequency offset tolerance expands to 20%, but device complexity increases
Solution Approach 1:
The patent combines the outputs from two parallel OFDM processing paths (one using IFFT and the other using FFT) through a multiplexer at the transmitter and a demultiplexer at the receiver. This merging approach allows both processed signals to be transmitted and received simultaneously, enabling the system to achieve 20% frequency offset tolerance by leveraging the complementary nature of the two transform operations.
3Reliability
If dual multiplexer and demultiplexer are added for parallel signal processing, then signal-to-intercarrier interference ratio improves, but device complexity increases
Solution Approach 1:
The patent introduces multiplexers and demultiplexers as intermediary components that facilitate the separation and recombination of the two parallel OFDM signal paths. These intermediaries enable the system to process and combine signals from both IFFT and FFT operations without direct interference, thereby improving the signal-to-intercarrier interference ratio while managing the added complexity through structured signal routing.
Data Source
AI summary
A parallel orthogonal frequency division multiplexed (OFDM) communications system includes a transmitter and receiver, the transmitter having a parallel fast Fourier transform (FFT) module operating in parallel to a conventional inverse fast Fourier transform (IFFT) module for providing respective orthogonal outputs received by the receiver. The receiver has a parallel IFFT module and a conventional FFT module for providing respective orthogonal outputs. The respective orthogonal outputs are combined to form a composite signal that provides improved insensitivity to relative frequency offsets and Doppler frequency offsets. The parallel FFT and IFFT modules in the OFDM communication system provides improved signal diversity and performance in the presence of relative frequency offsets and Doppler frequency offsets, and provides improved tracking capability for the receiver with backward compatibility.