Satellite Base Station Multi-Satellite Diversity Combining
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Solution Overview
Problem
OFDMA air interface in satellite communication systems poses challenges for multi-satellite diversity combining due to the difficulty in finding a single Timing Advance (TA) value that is optimum for all satellite paths, leading to issues with time alignment and path delay equalization.
Innovation Solution
The system employs a satellite base station that estimates and equalizes bipolar delays for each user equipment across diverse satellite paths, allowing for coherent combining of uplink signals using Maximal Ratio Combing (MRC) algorithm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If OFDMA air interface is used for satellite communication, then spectral efficiency and user mobility are improved, but time alignment and path delay equalization become difficult to achieve across diverse satellite paths
Solution Approach 1:
The patent segments the time alignment problem by treating each satellite path independently. Instead of attempting a single universal TA value for all paths, the system calculates separate TA values for each satellite path based on its specific geometry and delay characteristics. This allows OFDMA's spectral efficiency to be maintained while achieving precise time alignment for each path individually.
Solution Approach 2:
The patent implements dynamic TA adjustment where the base station continuously monitors and updates TA values for each satellite path based on current signal conditions. The TA values are not fixed but adapt dynamically to changing propagation conditions, enabling the system to maintain both high spectral efficiency and precise time alignment across diverse satellite geometries.
2Device complexity
If a single Timing Advance (TA) value is used for all satellite paths, then device complexity is reduced, but coherent combining of uplink signals from diverse paths becomes impossible
Solution Approach 1:
The patent applies local quality by assigning different TA values to different satellite paths based on their specific geometric characteristics and delay properties. Each path receives customized TA adjustment tailored to its local conditions, enabling coherent combining while managing complexity through path-specific rather than universal solutions.
Solution Approach 2:
The patent performs preliminary TA calculation and adjustment before the actual signal combining process. The base station pre-computes the appropriate TA values for each satellite path based on known geometry and propagation characteristics, preparing the signals in advance for coherent combining. This preliminary action enables reliable combining without requiring complex real-time adjustments.
3Reliability
If path delay equalization is performed for each user equipment across multiple satellite paths, then uplink sensitivity is improved, but processing complexity at the base station increases
Solution Approach 1:
The patent implements self-service by having the base station automatically calculate and apply TA values for each satellite path without requiring manual intervention or complex user equipment involvement. The base station uses its knowledge of satellite geometry and current signal conditions to autonomously perform delay equalization, improving uplink sensitivity while managing processing complexity through automated algorithms.
Solution Approach 2:
The patent achieves path delay equalization by dynamically changing the TA parameter for each satellite path based on its specific delay characteristics. Instead of using a fixed TA value, the system adjusts the timing parameter adaptively for each path, enabling coherent combining of signals from diverse satellite geometries while keeping the processing approach manageable through parameter-based adjustment rather than complex signal processing.
Data Source
AI summary
A base station including an electronic processor configured to: receive a first signal from a primary satellite, the first signal including a plurality of raw signals from a first user equipment camped on a downlink of the primary satellite; receive a second signal from a diversity satellite, the second signal including at least one of the plurality of raw signals from the first user equipment; store, in a signal sample memory, a copy of the first signal and a copy of the second signal; estimate a bipolar delay for the user equipment; synchronize the copy of the first signal and the copy of the second signal by applying the bipolar delay to the copy of the second signal; and combine the synchronized copies of the first and second signals to generate a plurality of synchronized raw signals for the first user equipment.