Configurable Block CDMA Scheme for Scalable Multi-User Access
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Solution Overview
Problem
Existing CDMA systems become interference limited as the number of users increases, leading to degradation in system performance, despite recent developments in MUI-free techniques like GMC-CDMA, CIBS-CDMA, and SC-FDMA, which face limitations in scalability and complexity.
Innovation Solution
A method that combines the advantages of reduced-complexity SC-FDMA, OFDMA, and self-shift-orthogonal CP-CDMA, utilizing user-specific spreading codes, precoding, and decoding techniques to reduce peak-to-average power ratio and increase robustness, while supporting sub-block processing and multi-input multiple-output (MIMO) systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional CDMA schemes are used to support multiple users simultaneously, then the number of users can be increased, but residual interference increases and system performance degrades
Solution Approach 1:
The patent segments the CDMA system into multiple orthogonal components: orthogonal spreading codes for user separation, orthogonal pilot sequences for channel estimation, and orthogonal data sequences for information transmission. This segmentation maintains orthogonality among users even as the number of users increases, preventing residual interference accumulation.
Solution Approach 2:
The patent changes the parameters of spreading codes and pilot sequences to ensure orthogonality is maintained. By carefully selecting and configuring these parameters (code lengths, sequence structures, orthogonality conditions), the system can support more users without increasing interference, as the orthogonal parameters prevent interference accumulation.
2Object-affected harmful factors
If MUI-free techniques like GMC-CDMA, CIBS-CDMA, and SC-FDMA are used, then multi-user interference is eliminated, but system complexity increases
Solution Approach 1:
The patent merges the advantages of different MUI-free techniques (GMC-CDMA, CIBS-CDMA, SC-FDMA) into a unified framework. By combining orthogonal spreading codes with orthogonal pilot sequences and structured data sequences, the patent achieves MUI-free communication while simplifying the overall system architecture compared to implementing each technique separately.
Solution Approach 2:
The patent creates a universal CDMA framework that can support multiple users with orthogonal codes, pilots, and data sequences simultaneously. This multi-functional approach eliminates MUI while providing a single unified structure that can be applied to various CDMA scenarios, reducing the need for separate complex processing for different techniques.
3Quantity of substance
If the number of users exceeds the maximum allowable number in block CDMA systems, then the system becomes interference limited, but scalability is required
Solution Approach 1:
The patent implements a dynamic user allocation mechanism where orthogonal codes, pilots, and data sequences are assigned based on the current number of active users. The system can dynamically adjust the orthogonal resources available to each user, allowing the network to scale from a small number of users to the maximum supported users without becoming interference-limited, as orthogonality is maintained throughout.
Data Source
AI summary
In an apparatus and method for generating a SC-FDMA signal having a sequence of symbols, a signal is generated by spreading blocks of symbols using a spreading code, then applying an inverse discrete Fourier transform (IDFT) to the symbols, followed by rotating the phase of each symbol, and applying a guard interval in the form of a cyclic prefix (CP), such that the spreading code is selected from sequences having a DFT matrix and Hadamard-Walsh sequence, and whereby the difference between the amounts for rotating the phase of adjacent symbols is constant. The spreading may be changed so as to change the data rate for each transmitter.