WTRU Interference Avoidance in Dense CSG Deployments
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Solution Overview
Problem
In dense deployments of Home Node Bs (HNBs) and Home evolved Node Bs (HeNBs), wireless transmit/receive units (WTRUs) face interference issues when trying to avoid closed subscriber group (CSG) cells, leading to service denial due to excessive reselections or interference from CSG cells, even if the CSG cell is not suitable for the WTRU.
Innovation Solution
The WTRU employs methods to override the priority of non-suitable CSG cell frequencies, perform inter-frequency measurements, and temporarily bar frequencies to find and camp on suitable cells, thereby reducing interference and ensuring service availability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the WTRU obeys the IFRI indication from the CSG cell to avoid interference, then interference from the CSG cell is reduced, but the WTRU experiences excessive cell reselections to other frequencies
Solution Approach 1:
The WTRU dynamically adjusts its behavior based on whether it is in idle or connected mode. In idle mode, it obeys IFRI to avoid interference, while in connected mode, it ignores IFRI to maintain service continuity. This dynamic adaptation resolves the contradiction by applying different strategies in different operational states.
Solution Approach 2:
The system changes the priority parameter of the frequency based on the WTRU's operational state. When in connected mode, the WTRU overrides the default priority settings and maintains camping on the current frequency despite IFRI indications, effectively changing the parameter behavior to prevent excessive reselections.
2Reliability
If the WTRU ignores the IFRI indicator to maintain service on the current frequency, then service continuity is maintained, but the WTRU experiences heavy interference from the CSG cell
Solution Approach 1:
The WTRU dynamically switches between obeying and ignoring IFRI based on its operational state. In connected mode, it ignores IFRI to maintain service, while in idle mode, it obeys IFRI to avoid interference. This dynamic behavior resolves the contradiction by prioritizing service continuity when connected and interference avoidance when idle.
Solution Approach 2:
The WTRU takes preliminary action by maintaining camping on the current frequency before interference becomes problematic. By ignoring IFRI in connected mode, the WTRU proactively prevents service disruption that would otherwise occur due to interference-avoidance reselections.
3Object-affected harmful factors
If the WTRU performs frequent cell reselections to avoid CSG cell interference, then interference is reduced, but service reliability deteriorates due to service denial
Solution Approach 1:
The system dynamically controls reselection behavior based on operational state. In connected mode, the WTRU suppresses reselections to maintain service, while in idle mode, it performs reselections to avoid interference. This resolves the contradiction by applying interference avoidance only when service continuity is not required.
Solution Approach 2:
The WTRU changes the effectiveness of IFRI interpretation based on its operational state. In connected mode, it overrides the IFRI parameter to maintain service, while in idle mode, it respects IFRI to avoid interference. This parameter-based control resolves the contradiction between interference avoidance and service reliability.
Data Source
AI summary
Methods and apparatus are disclosed for avoiding interference from transmissions coming from a home Node B, a home evolved Node B (HeNB) or closed subscriber group (CSG) cells when a wireless transmit receive unit (WTRU) is moving through a dense deployment of CSG cells.