Filtered OFDM Waveform Design for Bandwidth Extension
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Solution Overview
Problem
Conventional OFDM carrier aggregation is ill-suited for bandwidth allocations exceeding 20 MHz due to increased computational complexity and inefficient bandwidth utilization, as it requires scalable sampling frequencies and the same numerology for all signals, leading to reduced performance when handling different traffic types and excessive guard bands for interference mitigation.
Innovation Solution
The method employs different numerologies for OFDM-based signals transmitted over various frequency sub-bands, allowing for efficient communication of diverse traffic types by using pulse shaping digital filters to generate filtered OFDM signals with numerologies adapted to the bandwidth of each sub-band, thereby reducing the need for guard bands and improving bandwidth utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional OFDM carrier aggregation uses scalable sampling frequencies and FFT sizes for broader bandwidth allocations, then bandwidth capacity increases, but computational complexity increases
Solution Approach 1:
The patent divides the broad bandwidth into multiple frequency sub-bands, each with its own numerology configuration. This segmentation allows each sub-band to be processed independently with appropriate FFT sizes, reducing overall computational complexity while supporting broad total bandwidth allocations through carrier aggregation
Solution Approach 2:
The patent introduces dynamic numerology configuration where different sub-bands can have different sub-carrier spacings, cyclic prefix lengths, and FFT sizes adapted to their specific bandwidth requirements. This dynamic approach optimizes computational resources by matching processing parameters to actual bandwidth needs rather than using uniform scalable parameters across all carriers
2Ease of operation
If conventional OFDM carrier aggregation uses the same sub-carrier spacings for each aggregated carrier, then system simplicity is maintained, but performance for diverse traffic types deteriorates
Solution Approach 1:
The patent applies different numerology configurations (sub-carrier spacings, cyclic prefix lengths) to different frequency sub-bands based on their specific requirements. This local quality approach allows optimization for different traffic types in different sub-bands while maintaining a unified carrier aggregation framework, balancing system simplicity with traffic adaptability
3Quantity of substance
If conventional OFDM carrier aggregation uses broader bandwidth allocations exceeding 20 MHz, then system capacity increases, but the need for excessive guard bands increases
Solution Approach 1:
The patent changes the numerology parameters (sub-carrier spacing, cyclic prefix length) based on the bandwidth of each frequency sub-band. This parameter adaptation reduces the relative size of guard bands needed for interference mitigation, improving overall bandwidth utilization efficiency while supporting broad total bandwidth allocations through multiple carriers
Data Source
AI summary
Different numerologies may be used to communicate orthogonal frequency division multiplexing (OFDM)-based signals over different frequency sub-bands of a given carrier. This may allow the OFDM-based signals to efficiently support diverse traffic types. In some embodiments, the numerology of OFDM-based signal depends on a bandwidth of the frequency sub-band over which the OFDM-based signals are transmitted. In some embodiments, the OFDM-based signals are filtered OFDM (f-OFDM) signals, and the pulse shaping digital filter used to generate the f-OFDM signals allows the receiver to mitigate interference between adjacent f-OFDM signals upon reception, thereby allowing f-OFDM signals to be communicated over consecutive carriers without relying on a guard band.