CDMA Spreading Factor Selection Threshold
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Solution Overview
Problem
Current methods for selecting code channels and spreading factors in CDMA transmissions, particularly at low spreading factors, lead to increased processing load and symbol interference, outweighing the benefits of lower puncturing, and result in inefficient resource allocation and hardware complexity.
Innovation Solution
A method that determines permissible pairs of code channels and spreading factors based on selection criteria such as hardware limitations, rate matching, and puncturing limits, preferring higher spreading factors below a threshold to balance processing load and puncturing, and optimizing the number of code channels to reduce interference and puncturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If low spreading factors are used to reduce puncturing, then puncturing amount is reduced, but processing load and symbol interference increase
Solution Approach 1:
The patent introduces a threshold spreading factor value that changes the selection criteria for spreading factors. When the spreading factor is below the threshold, higher spreading factors are preferred to reduce processing load, while when above the threshold, lower spreading factors are preferred to reduce puncturing. This parameter-based threshold resolves the contradiction by dynamically adjusting the optimal spreading factor based on system conditions.
2Loss of substance
If low spreading factors are used to reduce puncturing, then puncturing amount is reduced, but symbol interference increases
Solution Approach 1:
The patent uses a threshold spreading factor value to change the selection behavior. By preferring higher spreading factors below the threshold, the system reduces symbol interference while accepting slightly higher puncturing, and only switches to lower spreading factors (which increase interference) when necessary to reduce puncturing significantly, thus balancing the two harmful effects.
3Device complexity
If higher spreading factors are used to reduce processing load, then processing load is reduced, but puncturing amount increases
Solution Approach 1:
The patent establishes a threshold spreading factor value that serves as a decision boundary. When the spreading factor is below this threshold, the system prefers higher spreading factors to reduce processing load. When above the threshold, it prefers lower spreading factors to reduce puncturing. This threshold-based approach resolves the contradiction by finding the optimal balance point.
4Device complexity
If the number of code channels is reduced to lower processing load, then processing load is reduced, but resource allocation efficiency decreases
Solution Approach 1:
The patent makes the number of code channels dynamic rather than fixed. The selection of code channels and spreading factors is adapted based on the threshold spreading factor value and system conditions. This dynamic adjustment allows the system to optimize between processing load and resource allocation efficiency by selecting the appropriate number of code channels for each transmission scenario.
Data Source
AI summary
A set of permissible parameter pairs with the parameters being a number of code channels and an associated spreading factor is determined according to at least one first selection criterion. Then a parameter pair from the set of permissible parameter pairs for the CDMA transmission is selected according to at least one second selection criterion. In this selection process, the spreading factor is used as a second selection criterion with a higher value being preferred over a lower value if both spreading factors are below or equal to a threshold spreading factor value. This accounts for the fact that in a certain regime low spreading factor involve a prohibitively high processing load and lead to increase inter symbol interference.