Heterogeneous Network Cell Selection via CSI-RS Scrambling
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Solution Overview
Problem
In heterogeneous telecommunications networks, there is a need for mechanisms to allow cell-to-UE association in networks with split control-plane and user-plane, as small cells lack macro-cell-like identities, making it difficult for the network to identify the most suitable cell for data channel transmission.
Innovation Solution
The network architecture allows user equipment (UE) to receive control-plane information from macro cells and user-plane information from both macro and small cells, enabling the determination of the most appropriate serving cell through connection requests and responses, with modified random access preambles scrambled with CSI-RS signals for small cells, and inter-base station coordination for cell selection and handover management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If small cells do not have macro-cell-like identities, then energy efficiency is improved by simplifying small cell structure, but cell identification and association become difficult
Solution Approach 1:
The patent introduces a two-stage association mechanism: first, UE associates with macro cell using traditional cell identity; second, UE identifies small cell through CSI-RS reference signals. The macro cell acts as an intermediary that coordinates the association process, allowing small cells to remain energy-efficient without traditional identities while still enabling reliable cell-to-UE association through the combined macro cell identification and small cell CSI-RS identification approach
2Device complexity
If control-plane is solely transmitted by macro cells, then network control and handover procedures are simplified, but user-plane flexibility and data transmission efficiency are reduced
Solution Approach 1:
The patent segments the communication plane into control-plane and user-plane functions. Control-plane (RRC signaling, handover control) is handled exclusively by macro cells, maintaining simplified network control. User-plane (data transmission) is distributed to both macro and small cells, enabling flexible data routing. This segmentation allows small cells to participate in data transmission without requiring full control-plane capabilities, thus maintaining control simplicity while improving data transmission efficiency
Solution Approach 2:
The macro cell serves as an intermediary for control-plane functions while small cells provide user-plane services. The patent enables small cells to transmit user-plane data under the coordination of macro cells, which manage RRC connections and handover procedures. This intermediary relationship allows the network to maintain simplified control-plane management through macro cells while achieving flexible and efficient user-plane data transmission through both macro and small cells
3Loss of information
If standard handover procedures are not triggered, then control-plane signaling is reduced, but cell selection and association mechanisms become insufficient
Solution Approach 1:
The patent replaces the traditional mechanical handover procedure (which requires cell reselection and RRC reconfiguration) with a CSI-RS based cell identification mechanism. Instead of triggering standard handover when moving between small cells, the system uses CSI-RS reference signals to identify and associate with the appropriate small cell while maintaining the existing RRC connection with the macro cell. This substitution reduces control-plane signaling overhead while providing adequate cell selection capability for user-plane data transmission
Data Source
AI summary
There is provided a heterogeneous communications network. The heterogeneous communications network comprises: a macro cell; a small cell provided within the macro cell; and a user equipment provided within the macro cell, wherein the user equipment is operable to receive control-plane information from the macro cell and user-plane information from the macro cell and/or the small cell, and wherein the user equipment is operable to transmit a connection request based on the received control-plane information, the macro cell and/or small cell are operable to determine which of the macro cell and the small cell is to operate as the serving cell for the user equipment based on the connection request, and the determined serving cell is operable to transmit a connection response to the user equipment.