Mobile Station EPS Bearer Switching for Small Cell Load Distribution
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Solution Overview
Problem
Current LTE architectures lack a concrete method to minimize the impact on the core network while achieving optimal connectivity, mobility, and increased system capacity through load distribution using small cells or phantom cells.
Innovation Solution
The proposed mobile communication method and mobile station configuration implement an eLA architecture by setting U-plane bearers between the mobile station and a small cell radio base station, while maintaining C-plane bearers with a macro cell, allowing independent PDCP, RLC, and MAC layer functions, and using specific message exchanges to manage EPS bearers and switch routes between macro and small cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a small cell or phantom cell is introduced to increase system capacity and enable load distribution, then productivity is improved, but device complexity increases due to multiple base stations and bearer management
Solution Approach 1:
The patent segments the bearer into two independent parts: C-plane bearer for control signaling and U-plane bearer for user data. This segmentation allows the mobile station to connect to a small cell via U-plane for capacity enhancement while maintaining C-plane connection through macro cell for mobility management, thereby increasing system capacity without proportionally increasing control complexity
Solution Approach 2:
The patent introduces a tunnel mechanism as an intermediary between the mobile station and core network. The tunnel encapsulates user data packets and routes them through appropriate base stations (macro or small cells) based on load conditions, enabling flexible load distribution while abstracting the complexity from the mobile station
2Productivity
If multiple base stations (macro and small cells) are used for load distribution, then productivity increases, but the impact on the core network worsens due to additional signaling and management overhead
Solution Approach 1:
The patent extracts the bearer management complexity from the core network and relocates it to the radio access network. By establishing direct U-plane connections between mobile stations and small cells with local buffering and routing capabilities, the core network is shielded from the complexity of managing multiple base station connections, reducing signaling overhead
3Productivity
If U-plane bearer is established with small cell for capacity enhancement, then productivity is improved, but reliability may worsen due to additional connection points and potential failure modes
Solution Approach 1:
The patent implements prior cushioning by establishing backup paths and using reliable tunneling mechanisms. The U-plane bearer through small cells is designed with fallback options to redirect traffic through macro cells if small cell connections fail, and the tunnel mechanism ensures reliable data delivery through error handling and retransmission protocols
Data Source
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Figure 3(a)~3(b)
AI summary
In a mobile communication method of the invention, when communication of a mobile station (UE) in a "RRC_Connected state" in a cell (#1) under the control of a radio base station (eNB#1) is performed through an EPS bearer formed of a U-plane bearer between the mobile station (UE) and the radio base station (eNB#1) and an S1-U bearer between the radio base station (eNB#1) and a gateway device (S-GW), and if the radio base station (eNB#1) detects that a cell (#10) is located around the mobile station (UE), the radio base station (eNB#1) sends the mobile station (UE) "RRC Connection Reconfiguration" which contains information correlating identification information on the EPS bearer with identification information on the cell (#10).