Hann Windowed OFDM Receiver for Adjacent Channel Interference Mitigation
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Solution Overview
Problem
Current OFDM receiver technologies face limitations in mitigating adjacent channel interference (ACI) without modifying the transmitter, which affects data rates and compatibility with legacy devices, especially in high mobility and vehicular communication scenarios.
Innovation Solution
The implementation of a Hann windowed OFDM receiver that removes the cyclic prefix and applies Fast Fourier Transformation to process OFDM symbols, allowing for improved capacity without disturbing the legacy frame structure, and incorporating techniques like maximum ratio combining with successive interference cancellation to handle induced inter-carrier interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If contemporary OFDM receiver windowing algorithms are used to mitigate ACI, then ACI absorption is reduced, but cyclic extensions are required that are not disturbed by multipath interference, which are unusable unless adopted by a new backward incompatible standard
Solution Approach 1:
The patent changes the windowing function parameter from conventional rectangular or other standard windows to a Hann window function. This parameter change allows the receiver to achieve effective ACI mitigation without requiring modifications to the cyclic extension structure, thereby maintaining backward compatibility with existing standards while improving performance against adjacent channel interference.
Solution Approach 2:
The patent converts the harmful effect of ACI into a manageable problem by using Hann windowing that exploits the structure of the cyclic prefix. Instead of requiring additional protective extensions, the method uses the existing cyclic prefix structure in combination with Hann windowing to achieve ACI rejection, turning the potential harm into a solvable issue without standard changes.
2Object-affected harmful factors
If additional temporal extensions are added to reduce ACI, then ACI mitigation is improved, but throughput is reduced by reducing effective symbol rate and pilot periodicity exceeds coherence time in high mobility scenarios
Solution Approach 1:
The patent changes the windowing approach from requiring extended temporal structures to using Hann windowing on the existing symbol structure. This parameter change in the reception processing allows effective ACI mitigation without adding temporal extensions, thereby preserving the effective symbol rate and maintaining throughput performance even in high mobility scenarios where pilot periodicity must remain within coherence time.
3Adaptability or versatility
If Hann windowing is applied to OFDM symbols without cyclic prefix extensions, then legacy frame structure is preserved and orthogonality with legacy signals is maintained, but ACI mitigation performance must be achieved without additional temporal redundancy
Solution Approach 1:
The patent applies Hann windowing as a processing parameter change at the receiver that works effectively with the standard cyclic prefix structure. This parameter change enables the system to achieve both backward compatibility (maintaining orthogonality with legacy signals) and effective ACI mitigation performance without requiring additional temporal redundancy or modifications to the legacy frame structure.
Solution Approach 2:
The Hann window function acts as an intermediary processing step between the received OFDM symbol and the FFT operation. This intermediary function enables the system to reconcile the conflicting requirements of maintaining legacy compatibility while achieving improved ACI mitigation, serving as a bridge between the existing standard and the performance enhancement goal.
4Device complexity
If conventional receiver algorithms are used, then implementation is simpler, but performance is inadequate with limited cyclic prefix extensions and high ACI conditions
Solution Approach 1:
The patent implements a parameter change in the receiver algorithm by substituting conventional windowing functions with Hann windowing. This change maintains relative simplicity of implementation (comparable to conventional algorithms) while dramatically improving ACI mitigation performance, especially in conditions with limited cyclic prefix extensions. The Hann windowing can be implemented with the same basic computational structure as other windowing functions, avoiding significant complexity increases.
Data Source
AI summary
System and method based upon an OFDM symbol, including a cyclic prefix (CP), that is received after being transmitted over a multiple access channel, wherein the CP is removed, and a Hann window is applied to the symbol. FFT is then applied to the Hann windowed symbol to obtain the frequency domain subcarriers. The pilot symbols are filtered accordingly to obtain Hann windowed pilots to estimate effective channel. Inter-carrier interference is calculated and removed.