Wireless Network Interference Reduction via Time Offset
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Solution Overview
Problem
In wireless networks, the transmission of Cell-specific Reference Signals (CRS) by one cell interferes with another cell, leading to pessimistic channel measurements and underutilization of network capacity due to interference, as these signals are transmitted in the same resource elements in both cells.
Innovation Solution
Applying a time offset relative to the transmission of scheduling blocks in neighboring cells to distribute the interference of reference signals across multiple resource elements, reducing peak interference and improving signal detection and decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If reference signals are transmitted in the same resource elements in both cells, then network capacity utilization is high, but interference between cells increases leading to pessimistic channel measurements
Solution Approach 1:
The patent applies periodic action by introducing a time offset that shifts reference signal transmissions in alternating subframes between serving and neighboring cells. This periodic shifting pattern ensures that reference signals from different cells do not transmit simultaneously, reducing interference while maintaining high network capacity utilization through coordinated resource allocation.
Solution Approach 2:
The patent implements dynamics by making the reference signal transmission timing adaptive rather than static. The time offset creates a dynamic allocation pattern where resource elements are reassigned between cells based on subframe number, allowing the system to balance capacity utilization and interference reduction flexibly across different time periods.
2Use of energy by moving object
If reference signals are transmitted simultaneously in both cells, then resource efficiency is maximized, but peak interference on individual resource elements increases
Solution Approach 1:
The patent uses periodic action to distribute reference signal transmissions across different time periods. By implementing a time offset pattern that alternates between cells in different subframes, the system maintains high overall resource efficiency while eliminating peak interference conditions that would occur with simultaneous transmissions on the same resource elements.
Solution Approach 2:
The patent applies segmentation by dividing the time domain into different subframes and allocating reference signal transmissions to different segments (subframes) for different cells. This temporal segmentation ensures that while resource efficiency is maintained through full utilization of available resources, peak interference is avoided by ensuring no two cells transmit reference signals simultaneously on the same resource elements.
3Measurement precision
If a time offset is applied to distribute interference, then channel quality estimation accuracy improves, but transmission timing complexity increases
Solution Approach 1:
The patent reduces timing complexity by using a simple periodic pattern for the time offset rather than complex adaptive algorithms. The predetermined relationship between subframe numbers and time offsets creates a regular, easily implementable schedule that improves channel quality estimation accuracy while minimizing the complexity of transmission timing coordination between cells.
Solution Approach 2:
The patent applies self-service by enabling each cell to independently determine its transmission timing based on the predetermined time offset rule and its own subframe number. This eliminates the need for complex centralized coordination or real-time negotiation between cells, simplifying the overall system while maintaining accurate channel quality estimation through interference distribution.
Data Source
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AI summary
A method and a network node (700) serving a first cell in a wireless network, for reducing interference in a second cell caused by transmission of reference signals in the first cell. The network node (700) transmits (7:2) in the first cell a scheduling block where a number of said reference signals are located in predefined resource element positions in the scheduling block, using a time offset relative transmission of a scheduling block in the second cell. Thereby, the impact of interference from a reference signal from one network node will be distributed over several resource elements in the other network node so that the impact in each resource element is reduced, as compared to when all interference from the reference signal hits one single resource element when no time offset is used.