OQAM CDMA Multicarrier Signal Transmission Without Guard Intervals
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Solution Overview
Problem
Current multi-carrier modulation techniques, such as OFDM and MC-CDMA, face inefficiencies due to the use of guard intervals and poor frequency localization, leading to reduced spectral efficiency and increased interference in mobile and wireless communication systems.
Innovation Solution
The implementation of OQAM/CDMA modulation with complex-valued data transmission using a subset of orthogonal spreading codes, eliminating the need for guard intervals and enhancing spectral efficiency by allowing complex data transmission on the same sub-carrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If OFDM modulation with rectangular shaping is used, then implementation is simple, but frequency localization is poor
Solution Approach 1:
The patent changes the shaping function parameter from rectangular to prototype functions (such as raised cosine or bell-shaped functions) that provide better frequency localization. This parameter change allows the system to achieve improved spectral containment and reduced inter-carrier interference while maintaining the OFDM framework.
2Reliability
If guard intervals are inserted in OFDM to handle multipath, then reliability improves, but spectral efficiency decreases
Solution Approach 1:
The patent extracts and removes the guard interval component from the OFDM structure, replacing it with prototype function shaping that provides inherent multipath resistance through its spectral properties. This extraction eliminates the bandwidth waste associated with guard intervals while maintaining reliability through the frequency localization properties of the prototype functions.
3Productivity
If all available spreading codes are used in MC-CDMA, then capacity increases, but multiple access interference increases
Solution Approach 1:
The patent applies local quality by assigning different prototype functions to different subcarriers or user groups, creating localized spectral properties that reduce interference. This allows the system to maintain high capacity with multiple spreading codes while the localized spectral characteristics of each user's signal reduce multiple access interference through better frequency localization.
Data Source
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AI summary
The invention relates to a method for transmitting a multicarrier spread-spectrum signal formed by a temporal succession of multicarrier symbols, using OQAM modulation and a plurality of inter-orthogonal spreading codes. According to the invention, one such method includes a step comprising the spreading of at least one complex-value data symbol, representative of a source data signal to be transmitted, over a set of sub-carriers of at lesat one multicarrier symbol, each of said sub-carriers modulating a complex value.