Idle Mode UE Cell Selection With Interference Cancellation
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Solution Overview
Problem
Current wireless communication systems, particularly in LTE technology, face challenges in balancing response time and idle mode power consumption when a UE is camped on a macro or pico cell, with existing methods not effectively managing interference and handoff processes between stronger and weaker cells.
Innovation Solution
The method involves camping on a weaker cell within a cell range expansion region despite a stronger signal from a macro cell, performing interference cancellation at different rates in idle and connected modes, and determining handoff based on signal power and bias values to optimize power consumption and response time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a UE camps on a weaker cell in a cell range expansion region, then the UE can achieve better load balancing and coverage, but the UE experiences higher interference from stronger neighboring cells
Solution Approach 1:
The patent converts the harmful strong interference signal from neighboring macro cells into a beneficial resource by implementing interference cancellation. The UE identifies and subtracts the known interference patterns from stronger cells, transforming what was previously harmful interference into an opportunity for improved signal detection and cell camping decisions in range expansion regions
2Reliability
If the UE performs interference cancellation at a faster rate, then the UE can better handle interference in connected mode, but the UE consumes more power
Solution Approach 1:
The patent implements dynamic interference cancellation rate adjustment based on the UE's operational mode. The system adapts the interference cancellation processing frequency - performing it at a first rate when in idle mode and at a second faster rate when in connected mode - thereby optimizing the balance between interference handling capability and power consumption according to actual network conditions and service requirements
Solution Approach 2:
The patent changes the operational parameter of interference cancellation rate based on the UE's mode state. By adjusting this parameter dynamically between two defined rates corresponding to idle and connected modes, the system optimizes performance while managing power consumption effectively
3Loss of time
If the UE responds quickly to pages by camping on the stronger cell, then the response time is reduced, but the load on the stronger cell increases and coverage in range expansion regions deteriorates
Solution Approach 1:
The patent performs preliminary interference cancellation processing during idle mode before the UE needs to respond to a page. By pre-processing and canceling interference patterns while in idle mode, the UE is prepared to quickly identify and camp on appropriate cells (including weaker cells in range expansion regions) when a page is received, achieving both fast response times and proper load distribution
Data Source
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AI summary
An idle mode UE can RACH to a cell different from the cell paging the UE. The UE can be allocated additional time to respond to all cells in the neighborhood to identify the cell in which to RACH. Interference cancellation can occur at different rates based on whether the UE is in connected mode or idle mode. The time to respond to the page can be a function of a paging cycle. Additionally, a variable bias may promote early handoff to lower power cells and late handoff to high power cells.