Relay Node Handover Control in Mobile Communication Systems
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Solution Overview
Problem
In LTE-advanced mobile communication systems, there is no established regulation for handling handover processes when relay nodes are connected, leading to challenges in maintaining communication connectivity during handovers.
Innovation Solution
The system implements a handover process by establishing radio bearers between mobile stations, relay nodes, and radio base stations, using X2-C interfaces and X2AP signals to manage handover requests and acknowledgments, allowing seamless communication even when relay nodes are involved, without requiring significant renovations to the protocol stack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If relay nodes are connected to enable mobile station communication, then communication coverage and flexibility are improved, but handover process regulation is lost
Solution Approach 1:
The patent introduces a relay node as an intermediary between the mobile station and the radio base station. The relay node includes protocol stack functions (PHY, MAC, RLC, PDCP, RRC layers) that mediate communication signals, enabling extended coverage while maintaining standardized handover procedures through the S1 and X2 interfaces between the donor base station and relay node.
Solution Approach 2:
The network is segmented into a donor base station (DeNB) and one or more relay nodes (RN), creating a hierarchical structure. This segmentation allows the handover process to be divided into distinct phases: measurement reporting by the mobile station to the relay node, handover decision by the relay node, and execution through coordinated signaling between relay node and donor base station via S1/X2 interfaces.
2Device complexity
If conventional LTE handover procedures are used without relay node support, then protocol simplicity is maintained, but handover fails when relay nodes are involved
Solution Approach 1:
The relay node is designed with multi-functional capability, implementing a complete protocol stack (PHY, MAC, RLC, PDCP, RRC layers) that allows it to function both as a relay for mobile stations and as a node that can initiate and manage handovers. The relay node can operate in different modes: relaying user data, managing control plane signaling, and coordinating handover procedures through standardized S1 and X2 interfaces.
3Adaptability or versatility
If relay nodes are introduced to extend network coverage, then system versatility is improved, but control signal management becomes complex
Solution Approach 1:
The relay node serves as an intermediary that simplifies control signal management by implementing standardized interfaces (S1 between relay node and core network, X2 between relay node and donor base station). This intermediary role allows control signals to be managed through well-defined protocols rather than requiring complex ad-hoc signaling arrangements.
Solution Approach 2:
The patent adds a new dimensional layer to the network architecture by introducing relay nodes between mobile stations and base stations. This creates a two-tier structure where relay nodes handle local control plane signaling with mobile stations while maintaining backhaul connections to the donor base station, effectively managing complexity through hierarchical organization.
Data Source
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AI summary
A radio base station according to the present invention comprising : a mobile communication system, a first relay node and a first radio base station are connected via a radio bearer, a second relay node and a second radio base station are connected via a radio bearer, and the first radio base station and the second radio base station are connected via a bearer; in which a mobile station is configured so as to conduct a handover process between a first state wherein a radio bearer is established with the first relay node in order to communicate via the first relay node and the first radio base station, and a second state wherein a radio bearer is established with the second relay node in order to communicate via the second relay node and the second radio base station and the mobile station is configured such that in the handover process, control signals involved in the handover process are transmitted and received via the radio bearer between the first relay node and the first radio base station, via the bearer between the first radio base station and the second radio base station, and via the radio bearer between the second relay node and the second radio base station.