Inter-Frequency Handoff Selection via Air Interface Quality
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Solution Overview
Problem
Inter-frequency handoff processes in cellular wireless communication systems often result in call drops due to inadequate coverage on the target frequency channel, especially when a subscriber device transitions from a femtocell to a macro network or between base stations with different frequency channels, as the selection of the target frequency channel is based on geographic proximity rather than actual air interface quality.
Innovation Solution
The method involves dynamically selecting a preferred target frequency channel based on reported air interface quality measurements from devices, allowing the RAN to intelligently direct fading devices to scan for the best available channel for handoff, which can be updated periodically or based on time-specific load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the serving base station directs devices to scan for coverage on a target frequency channel based on geographic proximity, then the handoff process is simplified and faster, but the target frequency channel may not provide adequate coverage resulting in call drops
Solution Approach 1:
The system performs preliminary scanning and evaluation of multiple candidate frequency channels before the handoff is actually needed. Devices scan for and report pilot signals on multiple frequency channels in advance, allowing the RAN to identify the best target frequency channel before the fading device needs to handoff, thus avoiding call drops while maintaining fast handoff execution.
Solution Approach 2:
The system implements feedback mechanisms where devices report pilot signal strength measurements from multiple frequency channels back to the RAN. This feedback loop allows the RAN to dynamically determine the optimal target frequency channel based on actual air interface conditions rather than relying solely on pre-configured geographic proximity information.
2Device complexity
If the RAN selects the nearest adjacent base station's frequency channel as the target, then the handoff configuration is simpler, but air interface obstructions or load issues may prevent adequate communication
Solution Approach 1:
The system performs preliminary evaluation of multiple candidate frequency channels by having devices scan and report pilot signals on various channels before handoff is needed. This advance preparation identifies the actual best target channel considering air interface conditions, rather than simply selecting based on pre-configured nearest base station information.
Solution Approach 2:
The system dynamically determines the target frequency channel based on real-time air interface conditions and reported pilot signal strengths, rather than using a static pre-configured target channel. This dynamic selection adapts to changing network conditions such as air interface obstructions and base station load, improving communication reliability.
3Loss of time
If devices scan for coverage on a pre-provisioned target frequency channel, then the scanning process is faster and more efficient, but the provisioned channel may not be the best available option
Solution Approach 1:
The system performs preliminary scanning of multiple candidate frequency channels in advance, having devices report pilot signals on various channels before the actual handoff is needed. This advance scanning identifies the best target frequency channel, so when handoff is required, the device can quickly tune to the pre-identified optimal channel without extensive scanning.
Solution Approach 2:
The system uses feedback from device measurements of pilot signal strength on multiple frequency channels to dynamically determine the best target channel. Devices report their measurements back to the RAN, which uses this feedback to identify the optimal target frequency channel, combining comprehensive evaluation with efficient execution.
Data Source
AI summary
Disclosed is a method and corresponding system to help improve inter-frequency handoff. While a radio access network (RAN) is serving one or more devices, the RAN will receive from the device(s) one or more reports of air interface quality on each of a plurality of potential target frequency channels. Dynamically based on the reported air interface quality information, the RAN will then select a given one of the potential target frequency channels to be a preferred target frequency channel. When a given device is fading from coverage, the RAN will then direct the device to scan for coverage on the preferred target frequency channel that was selected based on the earlier reported measures of air interface quality, so as to facilitate inter-frequency handoff.