LTE Physical Cell Identity Allocation Modulo Cost Optimization
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Solution Overview
Problem
In LTE networks, allocating unique physical-layer cell identifiers (PCI) to base stations is challenging due to inevitable overlap of cells with the same frequency, leading to collisions and poor performance, especially at cell edges, as existing methods fail to efficiently minimize interference between downlink and uplink signals.
Innovation Solution
A method that calculates and allocates PCIs with minimum overall cost by determining mod3 and mod30 costs based on transmission power and Euclidean distances for neighboring base stations, ensuring distinct PCI values under modulo 3 and 30 to avoid collisions and optimize channel synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing PCI allocation methods are used, then cell identification and channel synchronization are achieved, but interference between downlink and uplink signals increases and performance at cell edges deteriorates
Solution Approach 1:
The patent applies parameter changes by considering multiple cost functions with different weights (W1, W2, W3, W4) that correspond to different interference scenarios. The system dynamically adjusts PCI allocation based on varying network conditions by changing which cost function is prioritized, thereby optimizing the balance between downlink and uplink interference minimization.
Solution Approach 2:
The patent implements dynamics by making the PCI allocation process adaptive to changing network conditions. The system continuously evaluates multiple cost functions and adjusts allocations based on real-time measurements of interference and performance metrics, allowing the allocation strategy to evolve with network dynamics.
2Ease of manufacture
If PCI allocation does not consider neighboring base stations, then allocation process is simple, but collisions between downlink and uplink signals increase
Solution Approach 1:
The patent applies preliminary action by evaluating multiple cost functions and determining optimal PCI allocations before actual signal transmission occurs. The system performs preliminary calculations of interference costs based on neighboring base station configurations and finalizes allocations in advance, preventing collisions before they happen.
Solution Approach 2:
The patent implements feedback by measuring actual interference levels and performance metrics after PCI allocation and using these measurements to refine future allocation decisions. The system continuously monitors the impact of allocated PCIs and adjusts subsequent allocations based on observed performance data.
3Ease of operation
If uniform PCI allocation is used, then implementation is straightforward, but performance varies significantly at cell edges
Solution Approach 1:
The patent applies local quality by tailoring PCI allocation decisions to specific local conditions at each base station. Instead of using a uniform allocation strategy, the system evaluates local interference patterns, neighboring base station configurations, and measured performance metrics to determine optimal local allocations, thereby improving performance consistency at cell edges.
Solution Approach 2:
The patent implements segmentation by dividing the PCI allocation problem into multiple independent cost function evaluations. Each cost function corresponds to a specific interference scenario or performance metric, and the system evaluates and segments the allocation space across multiple dimensions before making final decisions.
Data Source
AI summary
A method includes receiving a transmission power, a distance from a source base station, and physical cell identifications (PCIs) under mod3 and mod30. The method includes determining a mod3 cost associated with allocating the PCI to the source base station based on the transmit power and the distance of the corresponding neighboring base station, and determining an overall mod3 cost as a summation of the mod3 costs of the neighboring base stations having the same PCI under mod3. The method also includes determining a mod30 cost associated with allocating the PCI to the source base based on the transmit power and the distance of the corresponding neighboring base station, and determining an overall mod30 cost as a summation of the mod30 costs of the neighboring base stations having the same PCI under mod30. The method further includes allocating the PCI having the minimum overall cost to the base station.