OFDM Receiver Narrowband Interference Suppression
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Solution Overview
Problem
Current OFDM communication systems face challenges in suppressing narrowband interference, particularly during data transport, as existing methods either require modifications to the transmitted signal not supported by current standards or fail to account for spectral leakage, leading to significant bit error rates and interference issues.
Innovation Solution
A method for suppressing narrowband interference in OFDM receivers involves estimating parameters of interferers, forming an excision filter, and inserting it into the receiver prior to the discrete Fourier transform, using digital phase lock loops to lock onto interferer frequencies and initialize the filter, which reduces noise from narrowband interferers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If frequency domain techniques are used to suppress narrowband interference, then interference suppression is achieved, but spectral leakage from interference is not accounted for or substantial processing is required to estimate and remove interference from all OFDM frequency bins
Solution Approach 1:
The interference suppression is segmented into two distinct phases: (1) During pilot symbols, detect and estimate interference parameters (frequency, magnitude, phase) using DFT and periodogram analysis; (2) During data transport, apply pre-calculated excision filters to remove identified interferers. This segmentation allows complex interference characterization to be performed only when necessary, reducing overall processing complexity while maintaining effective suppression.
Solution Approach 2:
Interference parameters are estimated and excision filters are pre-calculated during the pilot symbol phase before data transport begins. This preliminary action allows the system to characterize interference once and reuse the information throughout the data transport phase, avoiding repeated complex processing and reducing real-time computational burden.
2Object-affected harmful factors
If pre-coding or spread spectrum techniques are used, then interference suppression is achieved, but modifications to the transmitted OFDM signal are required which are not supported by current OFDM standards
Solution Approach 1:
Instead of modifying the transmitted signal, the invention extracts and removes interference from the received signal by detecting interferer parameters during pilot symbols and applying excision filters during data transport. This extraction approach suppresses interference without requiring any changes to the transmitted OFDM signal structure, ensuring full compatibility with current standards.
Solution Approach 2:
The invention introduces an intermediary excision filter that operates on the received signal between the OFDM receiver and the DFT processor. This intermediary component suppresses narrowband interference without affecting the transmitted signal structure, allowing standard-compliant operation while achieving interference suppression through the mediating filter.
3Measurement precision
If pilot symbol assisted detection is used, then detection and synchronisation are improved, but the system remains susceptible to narrowband interference during data transport phase
Solution Approach 1:
The system uses feedback from the pilot symbol phase where interference parameters are detected and estimated. This feedback information (interferer frequency, magnitude, phase) is then applied during the data transport phase to configure excision filters that actively suppress identified interferers, extending the protection benefit from pilot detection to the entire data reception process.
Solution Approach 2:
An intermediary excision filter is introduced in the signal path during data transport to suppress narrowband interference. This filter acts as a mediator that removes identified interferers from the received signal before further processing, protecting the data transport phase from interference without requiring modifications to the transmitted signal or abandoning pilot-assisted detection.
Data Source
AI summary
A method for suppressing narrowband interference in OFDM receivers is provided including the steps of acquiring a sample of received data, estimating parameters of each of a number of narrowband interferers from the acquired sample of data, forming an excision filter using the estimated parameters and inserting the excision filter into an OFDM receiver.