Wireless ACK/NAK Code Hopping for Interference Mitigation
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Solution Overview
Problem
In wireless communication systems, acknowledgement/negative acknowledgement (ACK/NAK) control information transmitted by multiple terminals using the same resources leads to interference between terminals in a cell or between adjacent cells, necessitating efficient code hopping methods to mitigate this interference.
Innovation Solution
The method involves allocating the same frequency-axis sequence and different time-axis sequences to terminals in one slot, and different frequency-axis sequences along with different time-axis sequences in another slot, using a resource index to change terminal groups and achieve orthogonality, thereby reducing interference through code hopping on a symbol block, slot, and time axis code length basis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple terminals use the same time and frequency resources for ACK/NAK transmission, then resource utilization efficiency is improved, but interference between terminals increases
Solution Approach 1:
The patent applies dynamics by making the code allocation dynamic across different slots. Terminals that experienced interference in one slot are automatically allocated different codes in subsequent slots, creating a time-varying code assignment system that adapts to interference conditions and resolves conflicts while maintaining high resource utilization.
Solution Approach 2:
The patent changes the code parameter (spreading code or cyclic shift value) allocated to terminals based on their interference experience. By modifying this parameter dynamically across slots, the system resolves interference while keeping terminals multiplexed on the same time-frequency resources, thus maintaining high resource utilization.
2Adaptability or versatility
If code division multiplexing is used to allow multiple terminals to share resources, then resource sharing capability is improved, but complexity of code allocation and management increases
Solution Approach 1:
The patent segments the code allocation process into independent slot-by-slot decisions. Instead of managing complex long-term code assignments, the system makes simple, localized code allocation decisions for each slot based on recent interference observations, significantly reducing management complexity while maintaining versatile resource sharing.
Solution Approach 2:
The system implements self-service by allowing terminals to automatically adjust their code assignments based on interference feedback. The base station simply observes interference patterns and reallocates codes, eliminating the need for complex centralized code management mechanisms while enabling flexible resource sharing.
3Reliability
If the same frequency-axis sequence is allocated to multiple terminals in one slot, then orthogonality is improved within the slot, but interference occurs between slots
Solution Approach 1:
The patent applies periodic action by systematically varying the frequency-axis sequences allocated to terminals across different slots. This periodic variation ensures that while terminals maintain orthogonality within each slot (using the same sequence), they experience different sequences in subsequent slots, thereby eliminating inter-slot interference through structured time-varying allocation.
Data Source
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AI summary
Provided is a method of forming a signal in a wireless communication system in which a plurality of terminals commonly use time and frequency resources for efficient code hopping. The method includes allocating the same frequency-axis sequence and different time-axis sequences to a plurality of terminals by using a resource index according to a first slot in the first slot; and allocating different frequency-axis sequences and different time-axis sequences to the plurality of terminals by using a resource index according to a second slot in the second slot.