Handover Control via Path Loss Conversion in CDMA Systems
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Solution Overview
Problem
In CDMA mobile communication systems, the difference in transmission power of CPICH signals between cells leads to degradation of communication quality due to improper handover target selection, as mobile stations rely on signal power comparisons which are affected by varying path losses.
Innovation Solution
A mobile communication system that includes a base station and a base station controller, where the base station converts and reports the received signal power of CPICH signals from multiple cells based on their transmission power, allowing the controller to accurately determine the best handover target cell by adjusting the reported power values to reflect path losses, thereby reducing the impact of transmission power differences between cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If mobile stations determine handover target based on received CPICH signal power comparison, then handover decision can be made automatically, but improper handover target selection occurs when transmission power of CPICH signals differs among cells
Solution Approach 1:
The patent changes the parameter used for handover decision from raw received CPICH signal power to path loss value. By converting the measurement parameter from received power (which is affected by both path loss and transmission power differences) to path loss (which reflects only channel conditions), the system eliminates the interference of varying transmission powers among cells, enabling accurate automatic handover decisions.
2Ease of operation
If mobile station selects handover target based on highest received CPICH power, then selection process is simple, but path with large loss may be selected when transmission power differs among cells
Solution Approach 1:
The patent transforms the selection criterion from received power magnitude to path loss magnitude. This parameter transformation maintains the simplicity of comparison-based selection while fundamentally improving accuracy, as path loss directly reflects channel quality without being confounded by differences in base station transmission powers.
Solution Approach 2:
The patent replaces the direct received power comparison mechanism with a path loss-based selection mechanism. This substitution changes the underlying measurement principle from comparing absolute power levels (which are transmission-power-dependent) to comparing path loss values (which are transmission-power-independent), thereby resolving the reliability issue.
3Device complexity
If uplink dedicated channel signal is transmitted at common level, then transmission power control is simplified, but received signal quality degrades when path loss is large
Solution Approach 1:
The patent implements feedback through accurate path loss measurement and reporting. By measuring path loss based on CPICH signals and feeding this information back to the network, the system enables the network to make informed decisions about uplink power control and handover, ensuring that signals are transmitted through paths with acceptable quality while maintaining simplified power control at the mobile station.
Data Source
AI summary
When a base station receives a report of signal power of a common pilot channel of each cell received at a mobile station, the base station converts the received signal power in the report on the basis of the transmission power of the common pilot channel of each of the cells. A base station controller determines the cell to which the mobile station is to be connected on the basis of the received signal power of the common pilot channel in each cell.