Orthogonal Spread-Spectrum Waveform for Non-Contiguous CDMA
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing CDMA systems are limited to using contiguous spectrum, preventing their application in non-contiguous spectrum scenarios and failing to effectively mitigate multi-path distortion effects, which leads to interference and decoding issues.
Innovation Solution
The technology spreads signals over non-contiguous spectrum portions, using a predetermined spectrum with zero components in unavailable regions, allowing CDMA transmission in fragmented spectra while minimizing interference and enabling signal distinction using different spread-spectrum codes, and employing shaping functions to reduce intersymbol interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If direct sequence spread spectrum is used with contiguous spectrum, then the signal can be effectively spread and decoded, but the system cannot operate in non-contiguous or fragmented spectrum scenarios
Solution Approach 1:
The patent segments the spectrum into multiple discrete frequency components rather than using a continuous contiguous spectrum. The spreading signal is constructed by combining multiple frequency components at specific discrete frequencies, allowing the system to operate in non-contiguous or fragmented spectrum scenarios while maintaining signal integrity for reliable decoding.
2Adaptability or versatility
If frequency hopping spread spectrum is used to achieve non-contiguous spectrum, then spectrum flexibility is improved, but the system creates high levels of momentary narrowband interference
Solution Approach 1:
The patent employs periodic action by using a spreading code that periodically varies the phase and amplitude of frequency components. This periodic modulation allows the signal to hop between frequency components in a controlled manner, achieving spectrum flexibility while the periodic structure helps manage interference patterns compared to random frequency hopping.
3Productivity
If multi-path propagation is present with echo paths longer than symbol duration, then signal transmission occurs, but multi-path distortion and intersymbol interference are produced
Solution Approach 1:
The patent transforms the signal processing from the time domain to the frequency domain by using frequency components at discrete frequencies. This dimensional change allows the system to handle multi-path propagation differently, where frequency selective fading at different frequencies can be managed through equalization in the frequency domain, reducing intersymbol interference while maintaining data transmission rate.
Data Source
AI summary
The technology in this application spreads a signal over an available discontinuous spectrum, such as a radio frequency band, so that the spread signal only occupies the non-contiguous spectrum. In this way, CDMA transmission and reception can be used in a fragmented or non-contiguous spectrum that otherwise would not be useable for direct sequence spreading. Spreading over non-contiguous portions of spectrum is preferably performed without producing unacceptable interference in portions of unavailable spectrum located between the allowed spectrum. By avoiding unacceptable interference in portions of unavailable spectrum located between the allowed spectrum, the unavailable spectrum may be used by other users or services.