Constant Amplitude Bi-Orthogonal Demodulation for CDMA Systems
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Solution Overview
Problem
Existing CDMA communication systems face challenges in achieving high transmission rates, variable transmission rates, and interference resilience while maintaining low power consumption and affordable power amplifier manufacturing costs, particularly due to issues with signal amplitude variability and orthogonality in multi-code schemes.
Innovation Solution
The apparatus employs constant amplitude coded bi-orthogonal modulation and demodulation, utilizing a serial to parallel converter, constant amplitude encoder, orthogonal code generator, and bi-orthogonal modulation units to generate and correct modulated data with parity bits, ensuring constant amplitude and orthogonality, thereby reducing power consumption and manufacturing costs while maintaining interference resilience and high transmission rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multi-code CDMA scheme is used to increase transmission rate, then data transmission rate is improved, but signal amplitude becomes variable requiring wide linear operation range in power amplifier increasing manufacturing cost
Solution Approach 1:
The patent transforms the variable amplitude signal into a constant amplitude signal by changing the signal representation from amplitude-based to phase-based encoding. The bi-orthogonal modulation maps data bits to specific phases of a carrier wave, ensuring the power amplifier operates within a fixed linear range, thereby reducing manufacturing cost while maintaining high transmission rate through multi-code usage.
Solution Approach 2:
The patent replaces the amplitude modulation mechanism with phase modulation. Instead of varying the amplitude of the carrier wave to encode data, the system varies the phase angles according to bi-orthogonal coding, eliminating the need for power amplifiers with wide linear operation ranges and reducing manufacturing complexity.
2Use of energy by moving object
If constant amplitude coding is applied to reduce power amplifier cost, then power consumption is reduced, but transmission rate and variable transmission rate capability are limited
Solution Approach 1:
The patent segments the data stream into multiple parallel channels, each modulated with a different orthogonal code. By using bi-orthogonal modulation with multiple phases (e.g., 4-phase, 8-phase), the system can transmit multiple bits simultaneously through parallel processing, achieving high transmission rates while maintaining constant amplitude for each individual channel.
Solution Approach 2:
The patent transitions from amplitude-based signal variation to phase-based signal variation, adding a temporal/directional dimension to the modulation. Instead of encoding information in the magnitude of the signal, the system encodes information in the phase angle, allowing multiple data streams to be transmitted simultaneously with constant amplitude through orthogonal phase relationships.
3Productivity
If complex orthogonal modulation like CCK is used to achieve high transmission rate, then data transmission rate is improved, but interference rejection capability and variable transmission rate capability are insufficient
Solution Approach 1:
The patent combines the advantages of orthogonal coding (from codes like Walsh-Hadamard) with bi-orthogonal phase modulation to create a composite modulation scheme. This composite approach integrates the interference rejection capability of orthogonal codes with the constant amplitude and high-rate transmission capabilities of phase modulation, achieving both reliability and productivity simultaneously.
4Use of energy by moving object
If DS/CDMA with Baker codes is used to achieve constant amplitude and low power consumption, then power consumption is reduced, but data transmission rate is low due to frequency spread
Solution Approach 1:
The patent introduces dynamic phase switching based on the data input while maintaining constant amplitude. Unlike static frequency spread schemes, the bi-orthogonal modulation dynamically changes the phase angle according to the encoded data sequence, enabling high transmission rates through rapid phase transitions while keeping the power consumption low due to constant signal amplitude.
Data Source
AI summary
A constant amplitude coded bi-orthogonal demodulator demodulates the received constant amplitude bi-orthogonal modulated data, cancels the parity bits to generate the serial data, detects the occurrence of an error by dividing the demodulated data into a plurality of groups of data, outputs the serial data as demodulated data if an error does not occur, sequentially converts bit polarities of data of groups in which an error occurs if the error detector detects the error, compares distances between the received bi-orthogonal modulated data and the constant amplitude coded bi-orthogonal modulated data, and selects, as demodulated data, data of which corresponding bit polarities are changed according to the comparison results.According to the present invention, power consumption is reduced, a power amplifier can be manufactured at an inexpensive cost, interference robustness can be ensured, and data can be transmitted at a high transmission rate and a variable transmission rate.