LTE Physical Cell ID Allocation via Frequency Domain Separation
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Solution Overview
Problem
In LTE systems, the distributed method for allocating Physical Cell IDs (PCIs) often fails to select a valid PCI for base stations due to limited available values, leading to potential conflicts and interference among cells.
Innovation Solution
A method for transmitting E-UTRA Absolute Radio Frequency Channel Number (EARFCN) information among base stations via an X2 interface, allowing the formation of a selectable PCI set by removing limited PCIs from the usable list and creating a second reference PCI set based on intersecting usable and first reference PCI sets, enabling random selection of a PCI for the target cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a distributed method is employed to allocate PCI values, then the automatic allocation capability is improved, but the availability of PCI values decreases leading to allocation failure
Solution Approach 1:
The patent introduces a new dimension of frequency information (EARFCN) to the PCI allocation process. By transmitting EARFCN information of neighbour cells via X2 interface and using it as an additional discrimination criterion, the system can allocate the same PCI to cells on different frequencies without interference, effectively expanding the available PCI pool beyond the traditional 504 values.
Solution Approach 2:
The patent changes the parameters used for PCI allocation from only spatial/physical cell identification to include frequency domain parameters (EARFCN). This parameter expansion allows cells with different frequency configurations to share the same PCI, thereby increasing the effective number of available PCIs in the system.
2Area of stationary object
If more eNBs are deployed in the LTE system, then the network coverage is improved, but the PCI allocation failure rate increases due to limited PCI values
Solution Approach 1:
By adding frequency domain information (EARFCN) as an additional dimension for PCI differentiation, the system can support more eNBs within the same geographic area. Cells deployed in dense networks can be assigned the same PCI if they operate on different frequencies, allowing network coverage to expand without proportionally increasing PCI conflicts.
Solution Approach 2:
The patent enables PCI reuse across different frequency layers. A PCI used in one frequency band can be copied and used in another frequency band where it does not cause interference, effectively multiplying the utility of each PCI value and supporting higher eNB density.
3Quantity of substance
If PCI values are reused among neighbour cells, then the PCI availability is improved, but the interference among cells increases
Solution Approach 1:
The patent adds frequency domain separation as an additional dimension to PCI allocation. PCI reuse is permitted only when cells are separated in the frequency domain (different EARFCN values), creating a multi-dimensional allocation space where spatial and frequency separation both contribute to interference avoidance.
Solution Approach 2:
The system changes from single-parameter (PCI only) to multi-parameter (PCI + EARFCN) cell identification. This parameter expansion allows PCI reuse while maintaining interference avoidance by ensuring that cells sharing the same PCI have different frequency configurations, thus eliminating harmful interference.
Data Source
AI summary
The present invention discloses a Physical Cell ID (PCI) allocation method and a base station. The PCI allocation method includes the following steps: a target base station obtains a usable PCI list sent by an Operations And Maintenance (OAM) function entity, and removes limited PCIs of the target cell from the usable PCI list to obtain a selectable PCI set (step S102); the target base station obtains the E-UTRA Absolute Radio Frequency Channel Number (EARFCN) information of neighbor cells of serving cells via an X2 interface message, and obtains a first reference PCI set in a predefined manner, cell EARFCN information in the first reference PCI set is different from that of the target cell of the target base station (step S014); the target base station forms a second reference PCI set based on the intersection of the usable PCI list and the first reference PCI set (step S106); if the selectable PCI set is empty, then a PCI is randomly selected from the second reference PCI set as the target PCI (step S108). The success rate of the PCI allocation for the target cell is improved by the present invention.