Escape Carrier Re-establishment for LTE Interference Mitigation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wireless communication systems, particularly in LTE and LTE-Advanced networks, interference from closed subscriber group femto cells operating in the same frequency band as wide area cells can cause radio link failures due to reduced signal levels, making it difficult for user equipment to maintain connections when entering buildings with non-permitted femto cells, leading to dropped calls or data transmission failures.
Innovation Solution
The implementation of an 'escape carrier' configuration, where certain component carriers are banned by femto stations to create a safe frequency band for macro cell users, and user equipment is pre-informed of this escape carrier to quickly re-establish connections by reducing the timer for declaring a radio link failure and switching to the escape carrier upon interference detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If femto cells operate in the same frequency band as wide area cells to provide local coverage, then local network capacity is improved, but interference to macro cell users increases causing radio link failures
Solution Approach 1:
The frequency spectrum is segmented into two parts: normal component carriers for regular operation and escape carriers reserved for interference mitigation. This segmentation allows femto cells to operate on normal carriers while macro users can escape to dedicated carriers when interfered with, resolving the contradiction between local capacity and interference protection
Solution Approach 2:
Escape carriers act as an intermediary resource that mediates between femto cell operation and macro user protection. When interference occurs, the escape carrier provides an alternative communication path, allowing the system to maintain macro user connections while permitting femto cell operation on other frequencies
2Stability of the object's composition
If user equipment maintains connection on interfered frequency to avoid handover, then connection stability is improved, but call drops increase due to radio link failure
Solution Approach 1:
The system performs preliminary action by pre-configuring escape carriers and providing their frequency information to user equipment before interference occurs. When radio link failure is detected, the UE can immediately switch to the pre-known escape carrier without prolonged connection attempts on the interfered frequency, maintaining stability while preventing call drops
Solution Approach 2:
The system changes the frequency parameter dynamically by switching from normal component carriers to escape carriers when interference is detected. This parameter change allows the connection to maintain stability by moving to a non-interfered frequency rather than persisting on the failed carrier
3Speed
If escape carrier frequency information is provided to user equipment, then connection re-establishment speed is improved, but signaling overhead increases
Solution Approach 1:
The network performs preliminary action by providing escape carrier frequency information during initial connection setup or system information broadcast, before it is needed for re-establishment. This allows the UE to have the frequency information ready in advance, enabling rapid connection recovery without additional signaling overhead during the critical re-establishment phase
Data Source
AI summary
In one exemplary aspect of this invention a method includes receiving at a user equipment from a wide area network access node information identifying at least one predetermined radio frequency carrier; initiating, in response to a presence of an interferer on a radio frequency carrier that is being used for a current connection between the user equipment and the network access node, a connection re-establishment procedure, where the interferer has the potential to cause a radio link failure of the current connection on the radio frequency carrier; and transmitting a connection re-establishment request to the network access node on the predetermined radio frequency carrier. The interferer can be a closed subscriber group network access node that the user equipment is not authorized to gain access to.