OFDM Data Transmitter Using Null Subcarriers to Prevent Lobe Overlap
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Solution Overview
Problem
The MICS band, used in medical implant communications, faces limitations in data transmission rate due to its restricted frequency band of 300 KHz, which is insufficient for transmitting large amounts of data, such as image information, leading to the need for a wider frequency band to improve transmission efficiency.
Innovation Solution
A data transmitting device and method that utilize Orthogonal Frequency Division Multiplexing (OFDM) to convert serial data symbols into subcarriers using separated sub frequency bands, avoiding occupied frequency channels by inserting null signals and null subcarriers to prevent lobe overlap, thereby allowing data transmission across multiple frequency channels within the MICS band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single frequency channel of 300 KHz is used for data transmission, then interference from other communication systems is reduced, but the data transmission rate is limited and insufficient for large data volumes
Solution Approach 1:
The patent divides the MICS band into 10 frequency channels and further segments each channel into multiple sub-frequency bands. By transmitting data across multiple segmented frequency channels simultaneously using OFDM, the system increases the total bandwidth available for data transmission while maintaining the low-interference characteristics of individual channels.
Solution Approach 2:
The patent transitions from single-dimensional frequency channel usage to multi-dimensional frequency space utilization. By employing OFDM to transmit multiple subcarriers across multiple frequency channels simultaneously, the system effectively adds dimensional capacity to the transmission medium, enabling higher data rates without increasing interference on any single channel.
2Productivity
If multiple frequency channels are used to increase bandwidth, then data transmission rate is improved, but lobe overlap between subcarriers may occur causing interference
Solution Approach 1:
The patent applies different transmission characteristics to different sub-frequency bands. By carefully designing the subcarrier frequency spacing and applying windowing functions to each subcarrier, the system ensures that the spectral lobes of adjacent subcarriers do not overlap excessively in critical regions, thereby reducing inter-carrier interference while maintaining efficient spectrum utilization.
Solution Approach 2:
The patent introduces guard bands and null subcarriers as intermediary elements between data-carrying subcarriers. These intermediary components act as buffers that prevent lobe overlap between adjacent subcarriers, allowing multiple frequency channels to be used simultaneously without causing harmful interference.
3Productivity
If the frequency band is expanded beyond 300 KHz, then transmission rate is improved, but occupied frequency channels may interfere with external communications
Solution Approach 1:
The patent segments the available MICS band into 10 distinct frequency channels and selects multiple non-contiguous channels for simultaneous transmission. This segmentation approach allows the system to aggregate bandwidth from multiple channels while leaving other channels available for external communications, thereby avoiding interference with external systems.
Solution Approach 2:
The patent dynamically adjusts transmission parameters including subcarrier spacing, frequency channel selection, and power distribution across channels. By optimizing these parameters, the system achieves higher transmission rates across multiple channels while maintaining spectral masks that prevent interference with external communications in adjacent frequency bands.
Data Source
AI summary
Disclosed is a data transmitting device which includes an input symbol mapping unit converting serial data symbols to parallel data symbols and generating null signals; and a conversion unit converting the parallel data symbols and the null signals to a plurality of subcarriers and a plurality of null subcarriers using sub frequency bands overlapped with one another, wherein the plurality of subcarriers is transformed using sub frequency bands separated from one another.