Golay-Walsh Sequence Despreading for CDMA Interference
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Solution Overview
Problem
Current spread spectrum modulation techniques, such as those using Golay sequences, face limitations in multicarrier transmission due to the small size of sequence families and poor cross-correlation properties, leading to interference and reduced subscriber capacity in CDMA systems.
Innovation Solution
The method employs Golay-Walsh sequences, which are formed by multiplying Golay sequences with Walsh functions, to improve correlation properties, eliminating sidelobes and maintaining orthogonality, thus enabling efficient de-spreading of data signals without cross-talk and increasing subscriber capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Golay sequences are used for spread spectrum modulation, then cross-correlation properties are improved, but the sequence family size is limited
Solution Approach 1:
The patent combines Golay sequences with Walsh functions to create Golay-Walsh sequences. This merging allows the system to inherit the excellent cross-correlation properties of Golay sequences while utilizing the larger family size and orthogonality characteristics of Walsh functions, thereby resolving the contradiction between correlation performance and sequence availability.
Solution Approach 2:
The invention creates a composite sequence structure by multiplying Golay sequences with Walsh functions. This composite approach integrates the complementary properties of both sequence types, achieving both low cross-correlation values and sufficient sequence family size for practical CDMA systems.
2Quantity of substance
If spreading sequences are used for CDMA transmission, then subscriber capacity is increased, but cross-talk and interference increase
Solution Approach 1:
The patent applies local quality by ensuring that each user in the CDMA system is assigned a unique Golay-Walsh sequence with specific orthogonality properties. This localized assignment of optimized sequences minimizes cross-talk between individual users while maintaining high overall system capacity.
Solution Approach 2:
The invention changes the fundamental parameter of the spreading sequence from traditional PN sequences or simple Walsh functions to Golay-Walsh sequences. This parameter change fundamentally improves the cross-correlation characteristics, allowing more subscribers to share the same frequency band without excessive interference.
3Ease of manufacture
If traditional spreading sequences are used, then system implementation is simple, but sidelobes in correlation function cause interference
Solution Approach 1:
The patent converts the potential harm of complex sequence structures into benefit by utilizing the mathematical properties of Golay sequences. The complementary nature of Golay sequences ensures that sidelobes in the autocorrelation function are eliminated, transforming a potentially problematic feature into an advantage for reducing interference.
Data Source
AI summary
The invention comprises a method for de-spreading of a data signal spread with a spread spectrum sequence. The invention is especially suited for the improvement of correlations of spread data signals after transmission. Therefor it can be integrated as software or hardware module into existing transmission systems. The method comprises the formation of a time-reversed spread data signal from the spread data signal, the formation of a sequence which arises through alternating multiplication of the chips of the spread data signal from the spread data signal, and the sequence of the time-reversed spread data signal, which arises from the time-reversed data signal through alternating multiplication of the chips by +1 and −1, the correlation of the spread data signal with the spread spectrum signal, of the time-reversed spread data signal with the time-reversed spread spectrum signal, of the spread data signal multiplied by the +1, −1 sequence with the spread spectrum sequence multiplied by the +1, −1 sequence and of the time-reversed spread data signal multiplied by the +1, −1 sequence with the time-reversed spread spectrum sequence multiplied by the +1, −1 sequence, and the summation of the four correlations.