Adaptive RLF Declaration in Heterogeneous Wireless Networks
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Solution Overview
Problem
In heterogeneous wireless communication networks, the strategy of connecting devices to the base station with the strongest downlink signal does not necessarily result in the lowest path loss, leading to increased Radio Link Failures (RLF) in the range expansion zone due to significant differences in output power between macro and low-power nodes, which affects downlink signal-to-interference ratio and control signaling.
Innovation Solution
A communication device method that determines whether to relax the conditions for declaring a Radio Link Failure (RLF) based on its location within the expansion zone, using a relaxed rule that is less stringent than the default rule, which includes detecting reference signals from both the serving and neighboring base stations, and considering the implementation of almost blank subframes and network type, to reduce the frequency of RLF declarations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a communication device connects to the base station with the strongest downlink signal, then the downlink signal strength is maximized, but the path loss may not be minimized leading to increased Radio Link Failures
Solution Approach 1:
The patent applies local quality by differentiating the RLF declaration conditions based on the device's location. Devices in expansion zones (where path loss to the low-power node is lower but downlink signal is weaker due to power differences) are subject to relaxed RLF conditions, while devices in normal zones use standard conditions. This localized differentiation resolves the contradiction by acknowledging that signal strength and path loss relationships vary by location.
Solution Approach 2:
The patent implements dynamics by making the RLF declaration parameters adaptive rather than fixed. The system dynamically determines whether to apply relaxed or standard RLF conditions based on real-time assessment of the expansion zone status, allowing the failure detection mechanism to adapt to varying network conditions and location-based characteristics.
2Productivity
If range expansion is implemented to increase low-power node uptake, then uplink data rates and capacity are improved, but downlink signal-to-interference ratio deteriorates due to significant power differences
Solution Approach 1:
The patent applies local quality by identifying expansion zones as a specific local region with distinct characteristics (weaker downlink signal from low-power nodes, higher interference). By targeting RLF condition relaxation specifically to this local zone rather than applying it universally, the system addresses the local quality issue of degraded downlink performance in expansion areas while preserving standard operation in other zones.
Solution Approach 2:
The patent uses the RLF condition relaxation as an intermediary mechanism to mediate between the conflicting requirements of range expansion benefits and downlink signal quality degradation. This intermediary adjustment allows the system to tolerate the reduced signal-to-interference ratio in expansion zones without triggering excessive RLF declarations, thereby enabling range expansion to proceed while maintaining acceptable reliability.
3Reliability
If standard RLF conditions are applied in expansion zones, then false RLF declarations increase, but relaxing conditions may delay failure detection
Solution Approach 1:
The patent applies local quality by tailoring the RLF detection sensitivity to the specific conditions of expansion zones. In these zones where signal fluctuations are more pronounced and path loss characteristics differ, the system uses relaxed conditions that account for these local variations, preventing false declarations while maintaining appropriate detection sensitivity for actual failures.
Solution Approach 2:
The patent implements parameter changes by modifying the RLF declaration thresholds and timing parameters specifically for expansion zone devices. These parameter adjustments (relaxed conditions) are designed to balance two competing needs: avoiding false RLF declarations due to normal signal variations in expansion zones, while still maintaining timely detection of actual radio link failures through adjusted timing and threshold parameters.
Data Source
AI summary
According to one aspect, there is provided a method performed by a communication device for declaring RLF. In some embodiments, the method includes: (1) the communication device establishing a connection with a serving base station; (2) the communication device determining whether to relax a condition for declaring RLF; (3) the communication device using a first rule in declaring an RLF in response to determining that the communication device should not relax the condition; and (4) the communication device using a relaxed rule in declaring an RLF in response to determining that the communication device should relax the condition, wherein the relaxed rule is less stringent than the first rule.