OFDM Transceiver Subcarrier Allocation for Frequency Diversity
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Solution Overview
Problem
Current OFDM systems face challenges in enhancing system performance and frequency diversity without increasing complexity, particularly in how real and imaginary parts of signals are carried on subcarriers.
Innovation Solution
The proposed solution involves an OFDM transmitting and receiving method where real and imaginary parts of complex signals are modulated onto different subcarriers, with specific allocation strategies such as alternate or separated subcarrier allocation, using complex number multipliers and inverse Fourier transforms to maintain orthogonality and enhance frequency diversity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If real and imaginary parts of complex signals are carried on cosine and sine subcarriers of the same frequency, then the conventional OFDM system can transmit data, but the system performance cannot be improved and frequency diversity cannot be realized
Solution Approach 1:
The patent segments the complex signal into separate real parts and imaginary parts, and assigns them to different subcarriers. Specifically, real parts are modulated onto cosine subcarriers while imaginary parts are modulated onto sine subcarriers at the same frequency, or alternatively assigned to different frequency subcarriers. This segmentation enables frequency diversity without increasing overall system complexity.
Solution Approach 2:
The patent introduces a new dimension for signal allocation by separating real and imaginary parts into different frequency or phase dimensions. Instead of both parts sharing the same carrier, the invention allocates them across multiple dimensions (different subcarriers or different quadrature components), thereby achieving frequency diversity and performance improvement.
2Productivity
If multiple subcarriers are used to transmit signals at lower speeds, then data transmission speed increases, but system complexity increases
Solution Approach 1:
The patent merges the transmission of real and imaginary parts into a unified OFDM framework using single-carrier modulation techniques. By combining BPSK modulation with OFDM and utilizing the orthogonality between sine and cosine subcarriers, the system achieves efficient multi-carrier transmission without proportionally increasing complexity.
Solution Approach 2:
The patent changes the modulation parameters by using real-valued signals modulated onto orthogonal subcarriers instead of traditional complex signals. This parameter change allows the system to achieve higher spectral efficiency and frequency diversity while maintaining manageable computational complexity through simplified modulation schemes.
Data Source
AI summary
An orthogonal frequency division multiplexing (OFDM) receiving apparatus, including a receiving unit, a subcarrier demodulation unit and a signal output processing unit, is provided. The receiving unit is for receiving an RF signal to generate a set of discrete signals. The subcarrier demodulation unit is coupled to the receiving unit, and used for demodulating a set of discrete signals to obtain a complex signal. The signal output processing unit is coupled to the subcarrier demodulation unit, and used for capturing and outputting real parts of the complex signal.