Cell Identifier Allocation for Wireless Network Mobility
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Solution Overview
Problem
The deployment of multiple small cells within a macro cell layer in wireless communications networks leads to challenges such as frequent handovers, increased RRC signalling, and mobility robustness issues, particularly due to interference between macro and small cells, which can result in handover failures and radio link failures when user equipment moves between cells.
Innovation Solution
The implementation of a smart allocation of identifiers based on Channel State Information-Reference Signals (CSI-RS) allows multiple cells to share the same identifier while maintaining independent identification, using CSI-RS for small cell identification and employing phantom cell techniques to manage dual connectivity, thereby reducing handover failures and improving mobility robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple small cells are deployed within a macro cell layer to increase capacity, then network capacity and coverage are improved, but handover frequency and RRC signalling overhead increase
Solution Approach 1:
The patent segments the identifier space by introducing a two-level identification structure: a first identifier (e.g., PCI) that is shared among multiple small cells, and a second identifier (e.g., ECGI or S-GUTI) that provides unique identification. This segmentation allows small cells to be deployed densely for capacity improvement while reducing handover signalling overhead by enabling the use of shorter identifiers during mobility management.
Solution Approach 2:
The patent adds a new dimension to cell identification by introducing a hierarchical identifier structure. Instead of using a single unique identifier for each cell, the system uses a combination of a shared first identifier and a unique second identifier, effectively moving from a one-dimensional to a two-dimensional identification space. This allows multiple small cells to share the same first identifier while maintaining distinguishability through the second identifier.
2Productivity
If small cells are deployed to improve capacity, then traffic offloading capability is enhanced, but mobility robustness and handover failure rate worsen
Solution Approach 1:
The patent introduces a network control node as an intermediary that manages the allocation and coordination of identifiers between macro cells and small cells. This intermediary ensures that identifier allocation is optimized for both capacity and mobility robustness, preventing handover failures by coordinating the use of shared and unique identifiers across the heterogeneous network.
Solution Approach 2:
The patent changes the identification parameters used during handover procedures. By switching from relying solely on unique cell identifiers to using a combination of shared first identifiers and unique second identifiers, the system optimizes handover performance in HetNets. This parameter change reduces identification conflicts and improves handover success rates while maintaining traffic offloading capabilities.
3Measurement precision
If traditional unique identifiers are assigned to each small cell, then cell identification accuracy is maintained, but identifier resource consumption and signalling overhead increase
Solution Approach 1:
The patent merges the identification function across multiple small cells by allowing them to share a common first identifier (e.g., PCI). This merging reduces the total number of unique identifiers needed in the network while maintaining identification accuracy through the complementary use of a unique second identifier (e.g., ECGI) when needed for unambiguous cell distinction.
Solution Approach 2:
The first identifier serves a universal function across multiple small cells, acting as a common reference point for measurements and initial cell identification. This multi-functional identifier reduces the need for numerous unique identifiers, thereby reducing identifier resource consumption while maintaining the ability to accurately identify and differentiate cells when required.
Data Source
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AI summary
Aspects and embodiments provide a method of allocating cell identifiers to a plurality of cells operating in a wireless communications network; a computer program product and a network control node operable to perform that method. The method of allocating cell identifiers to a plurality of cells operating in a wireless communications network in which the plurality of cells are arranged to comprise at least one region of overlapping radio coverage, comprises: selecting an identifier interpretation scheme to be implemented by a control node within said wireless telecommunication network, the identifier interpretation scheme comprising a scheme according to which said control node is operable to distinguish between at least two distinct portions of a cell identifier; allocating an identifier to at least two cells within the wireless telecommunication network and instructing each of the at least two of the plurality of cells to transmit a portion of the identifier in accordance with the selected identifier interpretation scheme to be implemented by the control node. Methods described may substantially simplify performance of cell identification techniques by increasing the number of implicit identifiers available for cell identification whilst keeping low the number of associated measurements.