Satcom GSM System Latency Normalization and Doppler Compensation
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Solution Overview
Problem
Establishing a GSM terrestrial network in least developed countries is challenging due to the absence of fixed line communication systems and electricity, and existing GSM systems cannot communicate with satellites due to latency and Doppler effect issues.
Innovation Solution
The development of a satcom GSM system that allows a constellation of satellites with large phase array antennas to directly communicate with GSM handsets charged by solar power, without relying on ground-level telecom infrastructure. This involves modifications to the base transceiver station (BTS) software for latency normalization and Doppler compensation, enabling seamless satellite beam handover and communication with commercial unmodified GSM user equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If standard GSM UE communicates with ground-based cell towers, then communication reliability is maintained, but deployment is impossible in areas without fixed line infrastructure and electricity
Solution Approach 1:
The patent introduces a satellite as an intermediary communication node between GSM user equipment and the core network. The satellite relay system enables communication in areas without ground-based infrastructure by mediating the signal transmission through space, thus resolving the contradiction between deployment adaptability and infrastructure requirements
Solution Approach 2:
The patent transitions the communication architecture from a two-dimensional ground-based network to a three-dimensional space-based network. By deploying satellites in orbit, the system eliminates the need for ground infrastructure in remote areas, achieving deployment capability without increasing overall system complexity
2Adaptability or versatility
If GSM UE communicates directly with satellite, then infrastructure independence is achieved, but latency and Doppler effect cause communication failure
Solution Approach 1:
The patent applies preliminary compensation actions for satellite motion effects. The system pre-calculates and compensates for Doppler frequency shifts and timing delays based on satellite ephemeris data before communication occurs, ensuring signal stability and preventing communication failure due to satellite movement
Solution Approach 2:
The patent dynamically adjusts communication parameters such as frequency offset and timing advance based on real-time satellite position and velocity. By changing these parameters in response to satellite motion, the system maintains communication reliability despite the inherent latency and Doppler effects of satellite communication
3Adaptability or versatility
If BTS SW is modified for satellite communication, then satellite beam handover is enabled, but system complexity increases
Solution Approach 1:
The patent segments the satellite communication functionality into modular software components within the BTS. By dividing the complex satellite handover logic into separate, manageable modules, the system enables satellite beam handover capability while keeping the overall software architecture organized and maintainable, thus limiting the increase in effective system complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The satcom GSM system enables voice and data calls between commercial GSM user equipment and the satellite network, providing reliable communication services in areas lacking traditional telecom infrastructure, while maintaining compatibility with standard GSM phones.
Implementation Method 1
a constellation of satellites with large phase array antennas to directly communicate with GSM handsets
Implementation Method 2
the Doppler effect cause by the satellite at the speed of 7 km/sec to 8 km/sec
Data Source
AI summary
A GSM satellite communication system is in communication with a first satellite having a first field of view including a first plurality of cells in which a plurality of active User Equipment (UEs) is located. The plurality of active UEs is in direct communication with the first satellite. The satellite communication system includes a first feeder link and a first tracking antenna configured to communicate with the plurality of active UEs via the first satellite directly serving the first plurality of cells; a first processing device configured to communicate with the plurality of active UEs; and a second processing device configured to normalize delay for a plurality of beam centers of the first plurality of cells, and provide the normalized delay to the first processing device.