Orthogonal Signal Demodulation Using Selective Stream-Block Processing
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Solution Overview
Problem
Conventional OFDM receiver designs face inefficiencies and increased power consumption when handling varying data bandwidths, as they typically demodulate the entire signal to extract a small amount of data, leading to energy wastage and shortened battery life in devices like cellphones and cable modems.
Innovation Solution
The implementation of a receiver system that derives and processes specific stream-blocks of orthogonal subcarriers using a smaller Fast Fourier Transform size, with down conversion and low-pass filtering to isolate and attenuate unwanted subcarriers, allowing only the assigned subcarriers to be transformed and processed, thereby reducing energy consumption and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional OFDM receivers demodulate the entire signal to extract a small amount of data, then complete data extraction is achieved, but energy consumption increases and battery life shortens
Solution Approach 1:
The patent extracts and processes only the necessary stream-blocks containing the receiver's assigned subcarriers from the received OFDM signal, rather than demodulating the entire signal. This is achieved by identifying which stream-blocks contain the receiver's subcarriers and processing only those blocks, thereby reducing energy consumption while maintaining data extraction efficiency.
Solution Approach 2:
The received OFDM signal is divided into multiple stream-blocks, and the receiver processes only the specific stream-blocks that contain its assigned subcarriers. This segmentation allows the receiver to avoid processing unnecessary signal portions, reducing computational load and energy consumption while maintaining complete data extraction for the assigned subcarriers.
2Use of energy by moving object
If receivers process only specific stream-blocks using smaller FFT size, then energy consumption reduces, but signal processing complexity increases
Solution Approach 1:
The patent performs preliminary identification of which stream-blocks contain the receiver's assigned subcarriers before performing FFT processing. This preliminary action allows the receiver to prepare the appropriate stream-blocks for processing and avoid unnecessary computations, reducing both power consumption and processing complexity by working with pre-selected, smaller data sets.
Solution Approach 2:
The receiver dynamically adjusts its processing based on which stream-blocks contain its assigned subcarriers. By adaptively selecting and processing only the necessary stream-blocks with appropriate FFT sizes, the system optimizes the balance between power consumption and processing complexity according to the specific signal conditions and subcarrier assignments.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables receivers to efficiently process only the required data, reducing energy wastage and extending battery life by allowing for dynamic bandwidth allocation and reduced power consumption, especially in low-bandwidth scenarios.
Implementation Method 1
The receiver comprises a converter including an oscillator for down converting the up converted time domain samples. The oscillator provides a frequency that preferably is different from the radio frequency center frequency of the up conversion in the transmitter.
Implementation Method 2
The receiver comprises a low pass filter that filters the down converted time domain samples. The low pass filter passes the one stream-block of subcarriers assigned to the particular data pipe, user or users and attenuates subcarriers that are not the subcarriers in such stream-block.
Data Source
AI summary
A modulation transmission technique comprises placing orthogonal subcarriers across an arbitrary-wide band of frequencies without a fixed pre-defined center frequency. Receivers demodulate only the sub-group of subcarriers in which they are to receive data. Thus a broadcast service with many audio programs could send signals across a wide band and receivers would only demodulate the audio channel that the user or users wanted to hear. This saves energy which is important for battery powered devices. A transform bandwidth smaller than the transform bandwidth of the transmitter is used that encompasses the receivers pass band, plus the 2 transition bands (upper and lower) of the linear filter. This technique maintains orthogonality between subcarriers. The subcarriers in the pass band are utilized and the subcarriers in the transition bands are discarded. The orthogonal subcarriers may include both orthogonal frequency division multiplexed and pulse amplitude modulated signals. A notch filter may be included in the receiver to remove unwanted non-orthogonal signals such as a television signal or other interference.