Two-Index Small Cell Identity for Dense Network Access
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Solution Overview
Problem
In dense small cell deployments, user equipment (UE) faces challenges in distinguishing initial access signals from multiple nodes and preventing frequent handovers, leading to interference and reduced network capacity due to overlapping Physical Cell Identity (PCI) and synchronization signal collisions.
Innovation Solution
A two-index system is introduced for small cell clusters, where a first index is used for individual cell access and identification, and a second index for mobility control, derived from primary/secondary synchronization (PSS/SSS) signals or frequency/time division multiplexing, to orthogonalize PSS/SSS configurations and reduce interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If all nodes transmit the same PSS/SSS signals, then initial access is simplified, but UE cannot distinguish between different nodes leading to synchronization failures
Solution Approach 1:
The Physical Cell Identity (PCI) space is segmented into two distinct indices: a first index derived from PSS/SSS signals for initial access and cell identification, and a second index for mobility control and handover decisions. This segmentation allows UE to initially access any node using the first index while the network uses the second index to manage handovers, resolving the contradiction between access simplicity and node distinction.
Solution Approach 2:
The first index acts as an intermediary that enables UE to access small cells without needing to distinguish between them during initial synchronization. The network then uses the second index as another intermediary to manage mobility and prevent ping-pong effects, separating the access function from the mobility management function.
2Measurement precision
If different PSS/SSS signals are used for small nodes, then node distinction is improved, but PCI collision and interference increase in dense deployments
Solution Approach 1:
By segmenting the PCI into two indices with different functions, the system allows multiple small cells to use the same first index (reducing interference) while the network manages mobility using the second index, eliminating the need for unique PSS/SSS signals at each node.
Solution Approach 2:
The first index serves as a universal identifier that can be shared across multiple small cells for initial access purposes, while the second index provides the differentiation needed for mobility management, allowing the system to achieve node distinction without increasing signal interference.
3Device complexity
If traditional single-index PCI system is used, then cell identification is simple, but frequent handovers occur in dense small cell deployments
Solution Approach 1:
The single PCI index is segmented into two functional indices: the first index maintains simplicity for initial cell identification and access, while the second index provides enhanced mobility control capabilities to prevent frequent handovers in dense small cell environments, resolving the contradiction between system simplicity and handover stability.
Solution Approach 2:
The system dynamically uses the first index for initial access and the second index for mobility management, allowing the identification system to adapt its behavior based on the operational phase, providing both simplicity during access and stability during mobility.
4Productivity
If dense small cell deployment is implemented, then network capacity increases, but signal interference and handover complexity increase
Solution Approach 1:
By segmenting PCI into two indices, the system enables dense small cell deployment where multiple cells can share the same first index (reducing interference) while the network manages handovers using the second index, allowing high capacity deployment without proportional increases in interference and complexity.
Solution Approach 2:
The system changes the parameter structure from a single PCI to a two-index system, fundamentally altering how cells are identified and managed, which enables the network to support dense deployments by decoupling access identification from mobility management parameters.
Data Source
AI summary
A method, system, and computer program product that provides a two-index system for clusters of small cells in a wireless network. A first index is employed for access to and identification of a serving cell within a cluster of small cells. A second index indicates a group of small cells for determining mobility control. The first index may be derived from primary/secondary synchronization signals, or from frequency/time division multiplex signal position. The second index may be indicated in system/master information block signals or predefined as a plurality of small cells identified by the first index for each cell. Determination of physical cell identification is aided by providing a plurality of primary/secondary synchronization (PSS/SSS) signal alternating configurations with indicator, wherein a maximum number of configurations is predefined. Signaling the PSS/SSS configurations by one of broadcast or dedicated signaling, said signaling indicating whether each configuration is one of periodic or aperiodic alternation.