Femtocell Access Control for Interference Mitigation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Access restrictions between femtocell base stations with different closed subscriber groups (CSGs) cause severe interference, preventing user equipment from establishing connections to allowed femtocell base stations due to stronger signals from adjacent non-allowed CSGs.
Innovation Solution
Allow user equipment to access adjacent femtocell base stations with restricted CSGs by temporarily granting access, even if not a member of the CSG, to manage interference, using mechanisms like muted subframes and access control via mobility management entities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If access restriction is enforced for CSG members only, then security and access control are improved, but interference from adjacent non-CSG femtocell base stations increases and connection reliability deteriorates
Solution Approach 1:
The network node acts as an intermediary between the user equipment and the non-CSG femtocell base station. It temporarily extends CSG membership rights to the user equipment, allowing it to access the adjacent femtocell base station without violating the original access restriction policy. This mediator approach resolves the contradiction by enabling interference mitigation while maintaining security control through centralized network authorization.
Solution Approach 2:
The access restriction policy is made dynamic rather than static. The network node temporarily modifies the CSG membership status of user equipment based on real-time interference conditions. When interference from adjacent non-CSG femtocell base stations is detected, the network dynamically extends access rights, and when interference subsides, the restrictions are restored. This dynamic adjustment resolves the contradiction between security and interference mitigation.
2Object-affected harmful factors
If access is granted to non-CSG members, then interference is reduced and connection stability improves, but access control security deteriorates
Solution Approach 1:
The network node serves as an intermediary that controls and manages access to non-CSG femtocell base stations. Instead of allowing unrestricted access, the network node temporarily extends CSG membership rights only to authorized user equipment that experiences interference. This maintains access control security while enabling interference mitigation, as all access decisions are centrally authorized by the network.
Solution Approach 2:
The access control parameters are dynamically changed based on interference conditions. The network node modifies the CSG membership parameter (from non-member to temporary member) for specific user equipment when interference is detected. This parameter change allows selective access granting that maintains security while reducing interference, resolving the contradiction between access control and interference mitigation.
3Ease of operation
If user equipment connects to allowed CSG femtocell base station, then access control is satisfied, but connection quality deteriorates due to severe interference from stronger adjacent signals
Solution Approach 1:
The network node acts as an intermediary that bridges the gap between access control requirements and connection quality needs. It receives interference measurements from user equipment connected to allowed CSG femtocell base stations and temporarily extends CSG membership to enable connection to non-CSG femtocell base stations with better signal quality. This maintains access control compliance through centralized authorization while improving connection quality.
Solution Approach 2:
The CSG membership parameter is dynamically changed from restrictive to permissive based on connection quality measurements. When user equipment reports severe interference while connected to an allowed CSG femtocell base station, the network node changes the access parameter by temporarily extending CSG membership rights, allowing the equipment to switch to a non-CSG femtocell base station with better signal quality, thus resolving the contradiction between access control compliance and connection quality.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The application relates to managing interference at the user equipment caused by femtocell base stations, such as home base stations, home E-UTRAN Node B base stations, and the like, configured with closed subscriber groups by allowing the user equipment to access a femtocell base station which would normally not allow access to the user equipment because the user equipment is not a member of the CSG being served by the femtocell base station. When a user equipment is within range of HeNB serving a CSG cell to which the user equipment is allowed access, referred to as the "allowed HeNB", the user equipment may encounter severe interference from another, adjacent HeNB serving another CSG cell, which the user equipment may not be allowed access to, referred to as the "not allowed HeNB", and which may have a stronger signal in terms of power than the HeNB including the CSG to which access is allowed. Rather than to allow the user equipment (114) to access the allowed HeNB (CSG HeNB 1) to which it is a subscriber by virtue of the CSG, the application proposes to instead allow the user equipment (114) to access the adjacent, not allowed HeNB (CSG HeNB 2) serving the other CSG cell, which the user equipment is not allowed to access by virtue of the user equipment not being a member/subscriber of the other CSG.