ACK/NACK Frequency-Code Multiplexing for Orthogonality Loss
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional code multiplexing methods for ACK/NACK signals in OFDMA systems face issues with orthogonality loss and inter-channel interference, particularly when UEs have varying receiving power, leading to poor performance of ACK/NACK signals with low power due to interference from signals with high power.
Innovation Solution
A frequency-code combined multiplexing method is introduced, where code multiplexing is applied among UEs with similar ACK/NACK transmitting power and frequency multiplexing is used among UEs with large differences in power, ensuring orthogonality and improved resource utilization by allocating different time-frequency resources based on Modulation and Coding Selection (MCS) levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If code multiplexing is used for ACK/NACK signals, then resource utilization efficiency is improved, but orthogonality is lost and inter-channel interference occurs
Solution Approach 1:
The patent segments UEs into different groups based on their receiving power levels (first group with higher power, second group with lower power). This segmentation allows different multiplexing strategies to be applied to different groups, thereby maintaining orthogonality within each group while improving overall resource utilization efficiency across the system.
Solution Approach 2:
The patent applies different multiplexing qualities to different UE groups: frequency division multiplexing is applied to the first group (higher receiving power) while code division multiplexing is applied to the second group (lower receiving power). This local differentiation resolves the contradiction by optimizing each group's transmission quality according to its specific power characteristics.
2Productivity
If code multiplexing is applied among UEs with varying receiving power, then resource efficiency is improved, but ACK/NACK signals with low power suffer from interference by signals with high power
Solution Approach 1:
The patent segments UEs into two distinct groups based on receiving power thresholds. By separating UEs with varying power levels into different groups, the patent prevents high-power signals from interfering with low-power signals, thereby resolving the interference issue while maintaining resource efficiency through group-specific multiplexing strategies.
Solution Approach 2:
The patent introduces power-level-based grouping as an intermediary mechanism between UEs with different power levels. This intermediary structure (UE groups) prevents direct interference between high-power and low-power signals by assigning them to separate multiplexing domains, thus eliminating the harmful interference effect.
3Reliability
If frequency multiplexing is used, then orthogonality is maintained, but resource utilization efficiency deteriorates
Solution Approach 1:
The patent merges frequency division multiplexing and code division multiplexing into a hybrid approach. Frequency multiplexing is applied to separate UE groups (maintaining orthogonality), while code multiplexing is applied within groups (improving resource efficiency). This combination resolves the contradiction by achieving both orthogonality and high resource utilization efficiency simultaneously.
Solution Approach 2:
The patent dynamically selects the multiplexing method based on UE power characteristics. Instead of using a static multiplexing approach for all UEs, the system dynamically adapts by applying frequency multiplexing to high-power UEs and code multiplexing to low-power UEs, thereby optimizing both orthogonality and resource efficiency according to actual system conditions.
Data Source
AI summary
Disclosed is a method and an apparatus for multiplexing and transmitting/receiving an ACK/NACK resulting from use of a HARQ scheme in an OFDMA system. Frequency and code multiplexing methods are combined with regard to the ACK/NACK to reduce signaling overhead. Frequency multiplexing is conducted by using the MCS level adopted by scheduling channels to improve the ACK/NACK transmitting performance, and code multiplexing is conducted to allocate ACK/NACK resources by using the index of the scheduling channels.