Dual-Mode Relay Node Uplink-Only Service for Interference Mitigation
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Solution Overview
Problem
In cellular communication systems, the uplink/downlink imbalance between macro and relay nodes leads to interference issues, particularly in areas with high traffic or unfavorable radio conditions, where relay nodes with lower transmit power cause cell size discrepancies and increased interference, necessitating effective coordination of cell selection and resource management to mitigate these imbalances.
Innovation Solution
A dual-mode relay node operation is introduced, where UEs close to the relay node are served in both uplink and downlink as per standard protocols, while those in cell extension areas, experiencing better uplink pathloss to the relay, are served only in uplink to reduce interference, with coordinated UL scheduling between macro and relay nodes to manage power imbalances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If relay nodes with lower transmit power are deployed to extend coverage or increase capacity in specific areas, then the impact on macro nodes/network is minimized and interference is limited to relatively small areas, but uplink/downlink imbalance occurs causing cell border misalignment and increased interference
Solution Approach 1:
The patent applies local quality by introducing cell-specific offsets to reference signal received power (RSRP) measurements in the cell selection and mobility decision processes. Different offsets are applied to different cells (macro cell vs. relay cell) to locally adjust the perceived signal strength, thereby aligning uplink and downlink cell borders in specific geographic areas while maintaining the lower transmit power benefit of relay nodes.
Solution Approach 2:
The patent changes the parameter of reference signal received power (RSRP) by introducing cell-specific offsets. This parameter modification allows the system to adjust the effective measurement value used for cell selection and handover decisions, compensating for the transmit power difference between macro and relay nodes and achieving border alignment without increasing relay node power.
2Area of stationary object
If cell range expansion is applied to extend relay cell coverage to match uplink conditions, then UEs with better uplink connection can be served, but downlink interference from macro node increases in the extended area
Solution Approach 1:
The patent applies local quality by implementing differential serving strategies in different geographic zones. In the cell extension area where uplink/downlink imbalance occurs, the system selectively serves UEs only in uplink while excluding them from downlink service, thereby extending relay cell coverage for uplink purposes without allowing downlink interference to macro cell UEs in the same area.
Solution Approach 2:
The patent segments the relay cell service area into two distinct zones: the normal cell area where both uplink and downlink are served, and the cell extension area where only uplink is served. This spatial segmentation allows the system to extend coverage where needed while preventing interference in areas where it would be harmful.
3Ease of operation
If UEs in cell extension area are served in both uplink and downlink by relay node, then complete service is provided, but uplink interference to relay node increases from UEs with better uplink pathloss
Solution Approach 1:
The patent applies local quality by implementing location-dependent serving policies. UEs are evaluated based on their geographic location relative to the cell border, and those identified as being in the cell extension area with uplink/downlink imbalance are selectively served only in uplink. This local differentiation maintains service completeness for legitimate users while eliminating interference from UEs in the imbalance zone.
Solution Approach 2:
The patent introduces the cell-specific offset as an intermediary mechanism that mediates between the conflicting requirements of complete service provision and interference avoidance. By adjusting the effective RSRP measurement through offsets, the system identifies which UEs should be restricted to uplink-only service, thereby indirectly controlling the serving policy without direct intervention.
Data Source
AI summary
Underlay network node and macro base station and methods therein for enabling avoidance of interference in a cell extension area associated with an uplink/downlink imbalance. The underlay network node is assumed to be associated with a cell area A, and a cell extension area B, where the cell extension area B has an uplink/downlink imbalance in relation to a neighboring base station and the network node. The method in the underlay network node involves serving a UE in both uplink and downlink when the UE is located in cell area A. The method further involves serving a UE only in the uplink when the UE is located in cell extension area B, thus enabling avoidance of interference related to communication of a UE located in said cell extension area B.