Single FFT Signal Chain for Orthogonal NB-IoT Cells
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Solution Overview
Problem
Current Radio Access Network (RAN) solutions for multiple Narrowband Internet of Things (NBIOT) standalone cells require multiple digital filters to avoid interference and use separate signal chains for each cell, leading to high capital expenditures and operational complexity.
Innovation Solution
Aligning subcarriers across multiple NBIOT cells to make them mutually orthogonal, allowing for the use of a single Fast Fourier Transform (FFT) or Inverse FFT (iFFT) for processing, and adjusting guard regions to eliminate the need for digital filters between cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If multiple digital filters are used to avoid interference between consecutive NBIOT standalone cells, then interference between cells is reduced, but device complexity and capital expenditures increase
Solution Approach 1:
The patent changes the frequency parameters of NBIOT cells by introducing raster offsets (e.g., 15 kHz, 30 kHz, 45 kHz) to align subcarriers across cells. This parameter modification ensures orthogonality between cells without requiring digital filters, thereby reducing device complexity while maintaining interference reduction
Solution Approach 2:
Instead of using digital filters to remove interference after signal processing, the patent inverts the approach by pre-aligning subcarriers through frequency parameter changes before signal transmission. This preventive alignment eliminates the need for subsequent filtering operations
2Reliability
If separate signal chains are used for each NBIOT standalone cell, then each cell is processed independently, but device complexity and operational complexity increase
Solution Approach 1:
The patent makes a single FFT/iFFT signal chain universal by aligning subcarriers across multiple NBIOT cells through raster offsets. The same signal chain can process multiple cells independently in terms of logic but shares the same physical processing resources, reducing device complexity while maintaining independent cell processing capability
Solution Approach 2:
The patent merges multiple separate FFT/iFFT signal chains into a single shared signal chain by ensuring orthogonality through frequency parameter alignment. Multiple cells share the same signal processing hardware, reducing complexity while maintaining independent processing through mathematical orthogonality
3Adaptability or versatility
If subcarriers of consecutive NBIOT standalone cells are not aligned, then each cell can be configured independently, but interference occurs between cells
Solution Approach 1:
The patent introduces specific frequency parameter changes (raster offsets of 15 kHz, 30 kHz, 45 kHz) to align subcarriers across cells. These parameter modifications maintain independent cell configuration flexibility while ensuring orthogonality to prevent interference
Data Source
AI summary
A method of processing multiple consecutive Narrowband Internet of Things (NBIOT) cells by a Radio Access Network (RAN) of a mobile network includes one of: a)1) shifting at least one first NBIOT cell relative to an adjacent second NBIOT cell to align all sub carriers of the first and second NBIOT cells to be mutually orthogonal; and a)2) using a first single fast Fourier transform (FFT) or first single inverse fast Fourier transform (iFFT) by the RAN to process both the first and second NBIOT cells; or b1) for a sequence of NBIOT cells, every third NBIOT cell is grouped into a single group, wherein all sub carriers of the NBIOT cells in the single group are mutually orthogonal; and b2) using the first single FFT or the first single iFFT by the RAN to process multiple NBIOT cells in the single group formed from the every third NBIOT cell.