Spotbeam Broadcast Networks Using Differential Delay Combining
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Solution Overview
Problem
Satellite broadcast systems face challenges in creating arbitrarily shaped footprints with high antenna gain due to substantial overlap between adjacent beams, necessitating frequency reuse greater than 1, which affects power and spectral efficiency, and lack natural delay diversity for coherent signal combination.
Innovation Solution
Introduce differential delays into bearer signals from adjacent spotbeams to enable constructive signal combination at user equipment, optimizing throughput for broadcast and multicast services.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple small spotbeams are used to create arbitrarily shaped footprints with sharp edges, then coverage precision and interference limitation are improved, but frequency reuse factor must be greater than 1, reducing spectral efficiency
Solution Approach 1:
The patent changes the time domain parameter by introducing differential delays to bearers transmitted in adjacent spotbeams. This transforms the system from requiring frequency domain separation (frequency reuse > 1) to using time domain separation (differential delays), thereby achieving frequency reuse of 1 while maintaining precise arbitrary footprint shapes with sharp edges.
2Use of energy by moving object
If spotbeams are illuminated to minimize satellite power and limit interference, then power efficiency and interference control are improved, but substantial overlap between adjacent beams requires frequency reuse greater than 1
Solution Approach 1:
The patent introduces time domain parameter (differential delay) to resolve the contradiction. By applying different delays to bearers in overlapping spotbeams, the system enables frequency reuse of 1 despite substantial beam overlap, thereby maintaining both power efficiency (through selective spotbeam illumination) and spectral efficiency (through frequency reuse of 1).
Solution Approach 2:
The patent moves the separation mechanism from the frequency dimension (frequency reuse) to the time dimension (differential delays). This dimensional transition allows the system to maintain frequency reuse of 1 while accommodating substantial spotbeam overlap, thus preserving both power and spectral efficiency.
3Productivity
If terrestrial single frequency network techniques are applied to satellite broadcast networks, then power and spectral efficiency are improved, but natural delay diversity is absent, requiring artificial delay introduction
Solution Approach 1:
The patent applies preliminary action by pre-calculating and pre-applying differential delays to bearers before transmission in spotbeams. The network side determines appropriate delay values based on spotbeam geometry and applies them in advance, enabling coherent signal combination at user equipment without requiring complex real-time delay adjustment or feedback mechanisms.
4Object-affected harmful factors
If frequency reuse greater than 1 is used to avoid interference from beam overlap, then interference control is improved, but power and spectral efficiency deteriorate
Solution Approach 1:
The patent changes the separation parameter from frequency to time by introducing differential delays. This allows frequency reuse of 1 (maximizing spectral efficiency) while maintaining interference control through time domain separation. The differential delays ensure that overlapping bearers from adjacent spotbeams do not interfere destructively but can be coherently combined at the receiver.
Data Source
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AI summary
Systems and methods operating a spotbeam satellite network. One example embodiment provides a satellite broadcast system. The system includes an electronic processor communicatively coupled to a satellite, and a user equipment. The electronic processor receives a plurality of bearer signals, each bearing identical broadcast or multicast program information. For each of the plurality of bearer signals, the electronic processor generates one of a plurality of spotbeams for transmission by the satellite within a coverage area. The electronic processor introduces into the bearer signal of each spotbeam of the plurality of spotbeams a differential delay with respect to the bearer signals of each of the other spotbeams of the plurality of spotbeams The user equipment is receives the bearer signals from a plurality of adjacent spotbeams of the plurality of spotbeams. The user equipment constructively utilizes the bearer signals received from the plurality of adjacent spotbeams to decode the program information.