Base Station Frame Timing Offset for LTE Interference Control
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Solution Overview
Problem
In LTE-based cellular systems, dense and unplanned deployments of synchronous LTE small cells, such as femto cells, can lead to interference between synchronization signals and broadcast channel signals, making it difficult for user equipment to detect these signals effectively, and asynchronous operation hampers inter-cell interference coordination methods.
Innovation Solution
Configurable base stations dynamically adjust their frame timings and uplink PRACH communications resources to minimize interference with adjacent base stations while maintaining symbol and subframe level synchronization, allowing for effective inter-cell interference coordination by offsetting frame boundaries and selecting non-overlapping PRACH resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If synchronous operation is used for LTE small cells, then inter-cell interference coordination methods can be effective, but synchronization signals and broadcast channel signals collide between adjacent base stations
Solution Approach 1:
The patent applies dynamics by allowing base stations to dynamically adjust their frame timing offsets based on detected signal conditions. Instead of fixed synchronous or asynchronous operation, the system continuously adapts timing configurations to avoid signal collisions while maintaining coordination effectiveness, resolving the contradiction between reliable interference coordination and harmful signal collisions.
2Object-affected harmful factors
If asynchronous operation is used for LTE small cells, then signal collision between base stations is avoided, but inter-cell interference coordination methods become ineffective
Solution Approach 1:
The patent changes the timing parameter (frame timing offset) of base station operations to resolve the contradiction. By adjusting the timing offset parameter dynamically, the system avoids signal collisions (asynchronous benefit) while maintaining sufficient coordination for interference management (synchronous benefit), thus resolving the contradiction between avoiding signal collision and maintaining coordination effectiveness.
3Object-affected harmful factors
If frame timing is offset between adjacent base stations, then signal collision is reduced, but synchronization between base stations deteriorates
Solution Approach 1:
The patent applies local quality by implementing different synchronization characteristics at different levels: symbol-level and subframe-level synchronization are maintained for stability, while frame-level timing offsets are adjusted locally for each base station to avoid signal collisions. This resolves the contradiction between reducing signal collision and maintaining synchronization stability.
Data Source
AI summary
Methods and apparatus for controlling interference with regard to important control signals, e.g., synchronization signals and broadcast channel signals, are described. A configurable base station monitors for and receives signals from other base stations in its local vicinity and determines the implemented frame timings corresponding to the other deployed base stations. If possible, the configurable base station selects to use a frame timing offset which is different from the frame timing offsets being used by the other base stations. In some embodiments, symbol level and subframe level synchronization are maintained between the base stations; however, frame level synchronization may, and sometimes does vary. Different adjacent base stations may, and sometimes do, intentionally offset their frame boundaries by multiples of a subframe.