Pulse Position Modulation Scheme for High-Rate Optical Communications
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical communication systems face challenges in maintaining reliable high data rates over long distances and through obstructed channels, particularly due to increased noise and signal bandwidth requirements, which can lead to negative link margins and hardware limitations.
Innovation Solution
A novel Pulse Position Modulation (PPM) scheme with overlapping pulses and amplitude modulation, combined with advanced error correction techniques, is employed to increase raw data rates without altering the signal bandwidth, ensuring robust communication even at low signal-to-noise ratios and through obstructive conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional PPM schemes are used to increase data rate, then raw data rate improves, but signal bandwidth requirements increase leading to hardware limitations and negative link margins
Solution Approach 1:
The patent transitions from conventional 1D PPM to 2D/3D PPM by adding temporal dimension(s). Instead of varying only the position of a single pulse within a slot, the invention uses multiple pulses across multiple time slots with different positions and/or amplitudes, creating a multi-dimensional modulation space that increases data rate without proportionally increasing bandwidth requirements
Solution Approach 2:
The patent embeds multiple pulse structures within each other or within time slots. Multiple pulses are nested within the same or overlapping time intervals, with inner pulses having different positions, amplitudes, or both. This nesting allows multiple data bits to be encoded within the temporal footprint of a single conventional pulse, increasing spectral efficiency
2Productivity
If higher data rates are transmitted over long distances, then productivity improves, but noise increases causing link margin to become negative
Solution Approach 1:
The patent segments the data transmission into multiple discrete pulse events within a modulation symbol. Instead of using a single high-energy pulse, the symbol comprises multiple pulses distributed across time slots, each carrying a portion of the data. This segmentation allows the total energy to be distributed in a way that maintains detectability above noise while increasing the information content per symbol
Solution Approach 2:
The patent changes multiple parameters simultaneously - both temporal position and amplitude (or phase) of pulses are varied to encode data. This multi-parameter modulation allows for more efficient use of the available signal space, achieving higher data rates with the same signal-to-noise ratio requirements by exploiting the joint parameter space rather than relying on a single parameter
3Reliability
If optical channels are obstructed by fog or clouds, then communication reliability deteriorates, but the system should maintain robustness
Solution Approach 1:
The patent incorporates feedback mechanisms where the receiver monitors the quality of received pulses and can request retransmission or adjust decoding parameters. The system uses the knowledge of transmitted pulse patterns and received signal characteristics to dynamically adapt the communication, maintaining reliability despite atmospheric obstructions by identifying and correcting degraded transmissions
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
This approach significantly enhances data transmission rates by up to 337% compared to conventional PPM, maintaining reliable communication without requiring more powerful hardware, and is effective in both clear and obstructed channels.
Implementation Method 1
power Laser sources are used in order to be able to emit optical signals of sufficient energy
Implementation Method 2
the received optical power P OPT is translated into an electrical current I EL at the output of an optical detector, which is proportional to P OPT
Data Source
Figure 1~4
Figure 5~8
Figure 9~10
AI summary
It is an object of the present invention to provide a communications system for communication between two remote terminals, where even at very long distances between these two terminals and/or at very small signal-to-noise ratios a robust communication is possible. The invention achieves the goal set before by suggesting an inventive pulse position modulation scheme and a corresponding optical communications system. Multiple pulses are sent per symbol, the timeslots are made shorter than the pulse duration and after every timeslot in which a pulse is located, several timeslots are left blank. AM modulation of the pulses is also possible. The system and method according to the invention are very well suited for communication with a satellite in deep space, for instance.