Active Set Management for OFDM Inter-Symbol Interference
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Solution Overview
Problem
Existing methods for configuring and managing an active set in OFDM-based networks face challenges in avoiding inter-symbol interference (ISI) while maintaining performance gains and limiting signaling overhead, particularly in multi-connectivity schemes like Single-Frequency Networks (SFN), where cells with strong signal strength but delayed arrivals cause significant ISI.
Innovation Solution
Implementing new schemes for active set configuration and management that assess and mitigate inter-symbol interference by determining the position of the FFT window based on power delay profiles, allowing cells with significant ISI to be either removed from the active set or have their transmission suppressed, while using existing triggers for adding or replacing cells, thereby optimizing the active set composition to minimize ISI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cells with strong signal strength are added to the active set, then the coverage and mobility performance are improved, but inter-symbol interference increases causing SINR degradation
Solution Approach 1:
The patent converts the harmful effect of delayed signal arrivals causing ISI into a useful mechanism by using the Power Delay Profile (PDP) information to intelligently manage the active set. The PDP measurements, which reveal the delayed arrival times, are transformed into a decision-making tool for adding or removing cells from the active set, thereby converting the harmful delay information into a beneficial control mechanism for maintaining SINR while preserving mobility coverage.
Solution Approach 2:
The patent dynamically changes the active set configuration parameters based on PDP measurements. By monitoring the delay profiles of received signals and comparing them against threshold criteria, the system adjusts the active set composition in real-time, adding cells when their delayed arrivals fall within acceptable ranges and removing them when ISI becomes excessive, thus adapting the system parameters to maintain optimal SINR performance.
2Reliability
If the active set is frequently updated to maintain SINR, then the signal quality is improved, but the signaling overhead increases
Solution Approach 1:
The patent performs preliminary actions by continuously measuring and storing Power Delay Profile information in the background without triggering immediate active set updates. The system accumulates PDP data and only initiates active set modifications when predefined threshold criteria are met, thereby avoiding frequent signaling exchanges while maintaining SINR through proactive monitoring and conditional response.
Solution Approach 2:
The patent implements a feedback mechanism where the terminal reports PDP measurements to the network, and the network uses this feedback to make informed decisions about active set management. This feedback loop allows the system to maintain SINR by responding only when necessary conditions are met, reducing unnecessary signaling overhead while ensuring quality of service through condition-based updates.
Data Source
AI summary
There is provided a method comprising: determining an information on an inter-symbol interference between signals on a same frequency resource and a same time resource from one or more first cells and one or more second cells, wherein an active set of the apparatus comprises at least the one or more second cells, the inter-symbol interference is an estimated inter-symbol interference if at least one of the one or more first cells is not in the active set, and the inter-symbol interference is a measured inter-symbol interference if the active set consists of the one or more first cells and the one or more second cells; and deciding whether or not to inform a network comprising the one or more first cells and the one or more second cells on the information on the inter-symbol interference.