Reverse Link Recovery in Cellular Systems
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Solution Overview
Problem
Existing cellular network systems face issues with reverse link power control, leading to frequent call drops due to incorrect demodulation of power control bits and inadequate power management during soft or softer handoffs, resulting in loss of reverse link transmissions.
Innovation Solution
The method involves selectively controlling forward link transmissions to increase the probability of reverse link reacquisition by monitoring reverse link quality and entering a reverse link recovery mode, where forward link transmit power is varied to recover the reverse link, with criteria such as energy-to-noise ratio and frame erasure rate being used to determine recovery success or failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If reverse link transmit power is controlled to minimum acceptable level to reduce interference, then interference within service sector is reduced, but reverse link is lost frequently
Solution Approach 1:
The patent implements dynamic forward link transmit power adjustment during reverse link recovery mode. The base station transitions from normal power control to recovery mode when reverse link quality deteriorates, systematically varying forward link power levels to elicit reverse link responses from mobile stations, thereby dynamically adapting to changing channel conditions and recovering lost reverse links.
Solution Approach 2:
The patent establishes a feedback mechanism where the base station monitors reverse link quality metrics (Ec/Io, frame erasure rate) and initiates reverse link recovery mode when thresholds are exceeded. The systematic variation of forward link power creates observable responses in reverse link transmissions, providing feedback about mobile station status and enabling recovery of lost reverse links.
2Ease of operation
If power control bits are transmitted to control reverse link power, then reverse link transmit power is controlled, but power control bits are incorrectly demodulated leading to wrong power adjustments
Solution Approach 1:
The patent introduces forward link transmit power variation as an intermediary mechanism to indirectly control and verify reverse link status. Instead of relying solely on power control bits that may be incorrectly demodulated, the base station uses systematic forward power adjustments as a mediator to elicit observable reverse link responses, thereby verifying actual mobile station status rather than relying on potentially erroneous power control bit demodulation.
3Adaptability or versatility
If mobile station receives multiple power control bits during soft handoff, then power control is maintained across sectors, but mobile station predisposed to reduce power leading to reverse link loss
Solution Approach 1:
The patent implements a dynamic reverse link recovery mode that activates when reverse link quality deteriorates during handoff operations. The base station systematically varies forward link transmit power across serving sectors, creating observable responses that help determine whether mobile stations are properly maintaining reverse links during soft or softer handoff conditions.
Solution Approach 2:
The patent employs periodic systematic variation of forward link transmit power during reverse link recovery mode. The base station cycles through different power levels in a structured sequence, allowing observation of reverse link responses at each power level. This periodic action helps identify mobile stations that fail to respond appropriately during handoff operations.
Data Source
AI summary
Operation commences with the cellular network infrastructure setting up a forward link and a reverse link with a cellular mobile station. The cellular network infrastructure transmits signals to the cellular mobile station on the forward link and receives signals from the cellular mobile station on the reverse link. The cellular network infrastructure monitors the quality of the reverse link. When the reverse link quality level meets a reverse link lost criteria, the cellular network infrastructure enters reverse link recovery mode of operation in which the transmit power of the forward link is increased in an attempt to recover the reverse link. During the reverse link recovery mode of operation, the cellular network infrastructure may determine that the reverse link quality meets a reverse link recovered criteria. When the reverse link quality meets the reverse link recovery criteria, the cellular network infrastructure exits the reverse link recovery mode of operation for the cellular mobile station and resumes normal power control operations. When the cellular network infrastructure determines that the reverse link recovery mode of operations fail, the cellular network infrastructure ceases forward link transmissions to the cellular mobile station and the call is dropped.