PHICH Resource Allocation via Dynamic CDM Group Adjustment
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Solution Overview
Problem
In OFDM wireless packet communication systems, efficiently allocating resources for PHICH transmission while maintaining a consistent transmission structure across varying spreading factors (SFs) is challenging, especially when the number of CDM groups changes with SF, leading to resource wastage and interference.
Innovation Solution
A method is proposed to allocate resources and index ACK/NACK signals efficiently by adjusting the number of CDM groups based on the spreading factor, using equations to determine the number of CDM groups and allocating indices such that signals are evenly distributed across channels, maintaining a consistent structure irrespective of the SF.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the number of CDM groups is fixed regardless of spreading factor, then the transmission structure remains consistent, but resource wastage occurs when SF varies
Solution Approach 1:
The patent applies dynamics by making the number of CDM groups variable rather than fixed. The system dynamically adjusts the number of CDM groups based on the spreading factor being used, allowing the resource allocation structure to adapt to different SF values and eliminate resource wastage while maintaining consistent transmission through the mapping equations.
Solution Approach 2:
The patent changes the parameter of CDM group count based on the spreading factor. By establishing a relationship where the number of CDM groups is determined by the SF value (e.g., SF=2 uses 2 CDM groups, SF=4 uses 4 CDM groups), the system optimizes resource utilization for each SF configuration while maintaining structural consistency through the indexing mapping.
2Productivity
If the number of CDM groups changes with spreading factor, then resource allocation efficiency improves, but transmission structure consistency deteriorates
Solution Approach 1:
The patent achieves universality by creating a unified resource allocation framework that works across different spreading factors. The mapping equations and indexing methods are designed to be SF-agnostic, allowing the same basic structure to accommodate variable CDM group counts. This enables the system to maintain structural consistency while adapting the number of CDM groups to match the SF for optimal resource efficiency.
3Reliability
If ACK/NACK signals are multiplexed using CDMA in one time-frequency region, then orthogonality is maintained, but reception performance degrades when channel quality is poor
Solution Approach 1:
The patent applies segmentation by dividing the ACK/NACK signals into multiple CDM groups, where each group occupies a distinct set of resource elements. This segmentation allows the system to maintain orthogonality within each group while providing diversity across groups, so that if one group experiences poor channel conditions, other groups can still be received reliably.
Data Source
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AI summary
A method for allocating a physical hybrid ARQ indicator channel (PHICH) is disclosed. The method includes allocating a CDM group according to a cyclic prefix type in consideration of a ratio of the numbers of necessary CDM groups according to spreading factors, and allocating a PHICH to the allocated CDM group. The PHICH includes an ACK/NACK signal multiplexed by code division multiplexing (CDM). Therefore, resources for PHICH transmission are efficiently allocated and a transmission structure can be maintained irrespective of a spreading factor.